,,serial ,,publications ,,of ,,the ,,smithsonian ,,institution ,the emphasis upon publications as a means of diffusing knowledge was expressed by the first ,secretary of the ,smithsonian ,institution4 ,in his formal plan for the ,institution1 ,joseph ,henry articulated a program that included the following statement3 ,it is proposed to publish a series of reports1 giving an account of the new discoveries in science1 and of the changes made from year to year in all branches of knowledge not strictly professional4 ,this keynote of basic research has been adhered to over the years in the issuance of thousands of titles in serial publications under the ,smithsonian imprint1 commencing with ,smithsonian ,contributions to ,knowledge in #ahdh and continuing with the following active series3 ,smithsonian ,annals of ,flight ,smithsonian ,contributions to ,anthropology ,smithsonian ,contributions to ,astrophysics ,smithsonian ,contributions to ,botany ,smithsonian ,contributions to the ,earth ,sciences ,smithsonian ,contributions to ,paleobiology ,smithsonian ,contributions to ,zoology ,smithsonian ,studies in ,history and ,technology ,in these series1 the ,institution publishes original articles and monographs dealing with the research and collections of its several museums and offices and of professional colleagues at other institutions of learning4 ,these papers report newly acquired facts1 synoptic interpretations of data1 or original theory in specialized fields4 ,each publication is distributed by mailing lists to libraries1 laboratories1 institutes1 and interested specialists throughout the world4 ,individual copies may be obtained from the ,smithsonian ,institution ,press as long as stocks are available4 ,s4 ,,dillon ,,ripley ,secretary ,smithsonian ,institution ,the ,wright ,brothers' ,engines ,and ,their ,design ,illustration3 ,kitty ,hawk ,flyer with original ,wright engine poised on launching rail at ,kill ,devil ,hill1 near ,kitty ,hawk1 ,north ,carolina1 #bd ,november #aijc1 the month before the ,wrights achieved man's first powered and controlled flight in a heavier-than-air craft4 ,illustration3 ,reproduction of the first engine1 built by ,pratt ,whitney1 as displayed in ,wright ,brothers ,national ,memorial at ,kitty ,hawk4 ,engine is mounted in a reproduction of the ,wrights' ,flyer built by the ,national ,capital ,section of the ,institute of the ,aeronautical ,sciences 7now the ,american ,institute of ,aeronautics and ,astronautics74 ,engine and plane were donated in #aifc to the ,national ,park ,service ,cape ,hatteras ,national ,seashore4 ,,smithsonian ,,annals ,,of ,,flight 99 ,,number #e ,,smithsonian ,,institution 99 ,,national ,,air ,,and ,,space ,,museum ,the ,wright ,brothers' ,engines ,and ,their ,design ,leonard ,s4 ,hobbs ,,smithsonian ,,institution ,,press ,,city ,,of ,,washington #aiga ,smithsonian ,annals of ,flight ,numbers #a-d constitute volume one of ,smithsonian ,annals of ,flight4 ,subsequent numbers will bear no volume designation1 which has been dropped4 ,the following earlier numbers of ,smithsonian ,annals of ,flight are available from the ,superintendent of ,documents as indicated below3 #a4 ,the ,first ,nonstop ,coast-to-,coast ,flight and the ,historic ,t-#b ,airplane1 by ,louis ,s4 ,casey4 #aifd4 #ij pages1 #dc figures1 appendix1 bibliography4 ,out of print4 #b4 ,the ,first ,airplane ,diesel ,engine3 ,packard ,model ,,dr-#ihj of #aibh1 by ,robert ,b4 ,meyer4 #aifd4 #dh pages1 #cg figures1 appendix1 bibliography4 ,price #fj;c4 #c4 ,the ,liberty ,engine #aiah-aidb1 by ,philip ,s4 ,dickey4 #aifh4 #aaj pages1 #bj figures1 appendix1 bibliography4 ,price #ge;c4 #d4 ,aircraft ,propulsion3 ,a ,review of the ,evolution of ,aircraft ,piston ,engines1 by ,c4 ,fayette ,taylor4 #aiga viii #acd pages1 #gb figures1 appendix1 bibliography of #fja items4 ,price #a4ge4 ,for sale by ,superintendent of ,documents1 ,government ,printing ,office ,washington1 ,d4,c4 #bjdjb--,price #fj cents ,foreword ,in this fifth number of ,smithsonian ,annals of ,flight ,leonard ,s4 ,hobbs analyzes the original ,wright ,kitty ,hawk ,flyer engine from the point of view of an aeronautical engineer whose long experience in the development of aircraft engines gives him unique insight into the problems confronting these remarkable brothers and the ingenious solutions they achieved4 ,his review of these achievements also includes their later vertical #d-;and #f-;cylinder models designed and produced between #aijc and #aiae4 ,the career of ,leonard ,s4 7,luke7 ,hobbs spans the years that saw the maturing of the aircraft piston engine and then the transition from reciprocating power to the gas turbine engine4 ,in #aibj he became a test engineer in the ,power ,plant ,laboratory of the ,army ,air ,service at ,mc,cook ,field in ,dayton1 ,ohio4 ,there1 and later as an engineer with the ,stromberg ,motor ,devices ,corporation1 he specialized in aircraft engine carburetors and developed the basic float-type to the stage of utility where for the first time it provided normal operation during airplane evolutions1 including inverted flight4 ,joining ,pratt ,whitney ,aircraft in #aibg as ,research ,engineer1 ,hobbs advanced to engineering manager in #aice and in #aici took over complete direction of its engineering4 ,he was named vice president for engineering for all of ,united ,aircraft in #aidd1 and was elected vice chairman of ,united ,aircraft in #aief1 serving in that capacity until his retirement in #aieh4 ,he remained a member of the board of directors until #aifh4 ,those years saw the final development of ,pratt ,whitney's extensive line of aircraft piston engines which were utilized by the ,united ,states and foreign air forces in large quantities and were prominent in the establishment of worldwide air transportation4 ,in #aifc ,hobbs was awarded the ,collier ,trophy for having directed the design and development of the ,j#eg turbojet1 the country's first such engine widely used in both military service and air transportation4 ,he was an early fellow of the ,institute of ,aeronautical ,sciences 7later the ,american ,institute of ,aeronautics and ,astronautics71 served for many years on the ,powerplant ,committee of the ,national ,advisory ,committee for ,aeronautics1 and was the recipient of the ,presidential ,certificate of ,merit4 ,,frank ,a4 ,,taylor1 ,acting ,director ,national ,air and ,space ,museum ,march #aigj ,contents ,foreword v ,acknowledgments ix ,the ,beginnings #a ,the ,engine of the ,first ,flight1 #aijc #i ,the ,engines ,with ,which ,they ,mastered the ,art of ,flying #bi ,the ,four-,cylinder ,vertical ,demonstration ,engine and the ,first ,production ,engine #cd ,the ,eight-,cylinder ,racing ,engine #dg ,the ,six-,cylinder ,vertical ,engine #di ,minor ,design ,details and ,performance of the ,wright ,engines #eg ,appendix #fb ,characteristics of the ,wright ,flight ,engines #fb ,the ,wright ,shop ,engine #fd ,bibliography #fi ,index #ga ,acknowledgments ,as is probably usual with most notes such as this1 however short1 before completion the author becomes indebted to so many people that it is not practical to record all the acknowledgments that should be made4 ,this ,i regret extremely1 for ,i am most appreciative of the assistance of the many who responded to my every request4 ,the mere mention of the ,wright name automatically opened almost every door and brought forth complete cooperation4 ,i do not believe that in the history of the country there has been another scientist or engineer as admired and revered as they are4 ,i must1 however1 name a few who gave substantially of their time and effort and without whose help this work would not be as complete as it is4 ,gilmoure ,n4 ,cole1 ,a4 ,l4 ,rockwell1 and the late ,l4 ,morgan ,porter were major contributors1 the latter having made the calculations of the shaking forces1 the volumetric efficiency1 and the connecting rod characteristics of the #aijc engine4 ,louis ,p4 ,christman1 who was responsible for the ,smithsonian drawings of this engine and also supervised the reconstruction of the #aije ,wright airplane1 supplied much information1 including a great deal of the history of the early engines4 ,opie ,chenoweth1 one of the early students of the subject1 was of much assistance2 and ,i am indebted to ,r4 ,v4 ,kerley for the major part of the data on the ,wrights' shop engine4 ,also1 ,i must express my great appreciation to the many organizations that cooperated so fully1 and to all the people of these organizations and institutions who gave their assistance so freely4 ,these include the following3 ,air ,force ,museum1 ,wright-,patterson ,air ,force ,base1 ,ohio ,carillon ,park ,museum1 ,dayton1 ,ohio ,connecticut ,aeronautical ,historical ,association1 ,hebron1 ,connecticut ,fredrick ,c4 ,crawford ,museum1 ,cleveland1 ,ohio ,historical ,department1 ,daimler ,benz ,a4 ,g41 ,stuttgart-,untertuerkheim1 ,west ,germany ,engineers ,club1 ,dayton1 ,ohio ,deutsches ,museum1 ,munich1 ,west ,germany ,educational and ,musical ,arts1 ,inc41 ,dayton1 ,ohio ,henry ,ford ,museum1 ,dearborn1 ,michigan ,franklin ,institute1 ,philadelphia1 ,pennsylvania ,howell ,cheney ,technical ,school1 ,manchester1 ,connecticut ,library of ,congress1 ,washington1 ,d4,c4 ,naval ,air ,systems ,command1 ,u4,s4 ,navy1 ,washington1 ,d4,c4 ,science ,museum1 ,london1 ,england ,victoria and ,albert ,museum1 ,london1 ,england ,in particular1 very extensive contributions were made by the ,smithsonian ,institution and by the ,united ,aircraft ,corporation through its ,library1 through the ,pratt ,whitney ,aircraft ,division's entire ,engineering ,department and its ,marketing and ,product ,support ,departments1 and through ,united ,aircraft ,international4 ,the ,beginnings ,the general history of the flight engines used by the ,wright ,brothers is quite fascinating and fortunately rather well recorded4#a ,the individual interested in obtaining a reasonably complete general story quickly is referred to three of the items listed in the short bibliography on page #fi4 ,the first1 ,the ,papers of ,wilbur and ,orville ,wright1 is a primary source edited by the authority on the ,wright brothers1 ,marvin ,w4 ,mc,farland of the ,library of ,congress2 a compact appendix to volume #b of the ,papers contains most of the essential facts4 ,this source is supplemented by the paper of ,baker#b and the accompanying comments by ,chenoweth1 presented at the ,national ,aeronautics ,meeting of the ,society of ,automotive ,engineers on #ag ,april #aiej4 ,aside from their excellence as history1 these publications are outstanding for the manner in which those responsible demonstrate their competence and complete mastery of the sometimes complex technical part of the ,wright story4 ,footnote #a3 ,an extensive bibliography1 essentially as complete at this time as when it was compiled in the early #aiejs1 is given on pages #abdj-abdb of volume #b of ,the ,papers of ,wilbur and ,orville ,wright1 #aiec4 ,footnote #b3 ,max ,p4 ,baker was a technical adviser to the ,wright estate and as such had complete access to all of the material it contained4 ,the consuming interest of the ,wrights1 of course1 was in flight as such1 and in their thinking the required power unit was of only secondary importance4 ,however1 regardless of their feeling about it1 the unit was an integral part of their objective and1 due to the prevailing circumstances1 they very early found themselves in the aircraft engine business despite their inexperience4 ,this business was carried on very successfully1 against increasingly severe competition1 until ,orville ,wright withdrew from commercial activity and dissolved the ,wright ,company4 ,the time span covered approximately the twelve years from #aijc to #aiae1 during the first five years of which they designed and built for their own use several engines of three different experimental and demonstration designs4 ,in the latter part of the period1 they manufactured and sold engines commercially1 and during this time they marketed three models1 one of which was basically their last demonstration design4 ,a special racing engine was also built and flown during this period4 ,accurate records are not available but altogether1 they produced a total of something probably close to #bjj engines of which they themselves took a small number for their various activities1 including their school and flying exhibition work which at one time accounted for a very substantial part of their business4 ,a similar lack of information concerning their competition1 which expanded rapidly after the ,wright's demonstrations1 makes any comparisons a difficult task4 ,the ,wrights were meticulous about checking the actual performance of their engines but at that time ratings generally were seldom authenticated and even when different engines were tried in the same airplane the results usually were not measured with any accuracy or recorded with any permanency4 ,there is evidence that the competition became effective enough to compel the complete redesign of their engine so that it was essentially a new model4 ,for their initial experimentation the ,wrights regarded gravity as not only their most reliable power source but also the one most economical and readily available1 hence their concentration on gliding4 ,they had correctly diagnosed the basic problem of flight to be that of control1 the matter of the best wing shapes being inherently a simpler one which they would master by experiment1 utilizing at first gravity and later a wind tunnel4 ,consequently1 the acquisition of a powerplant intended for actual flight was considerably deferred4 ,nevertheless1 they were continuously considering the power requirement and its problems4 ,in his ,september #aija lecture to the ,western ,society of ,engineers1 ,wilbur ,wright made two statements3 ,men also know how to build engines and screws of sufficient lightness and power to drive these planes at sustaining speed2 and in conjunction with some figures he quoted of the required power and weight3 ,such an engine is entirely practicable4 ,indeed1 working motors of one-half this weight per horsepower #i pounds per horsepower have been constructed by several different builders4 ,it is quite obvious that with their general knowledge and the experience they had acquired in designing and building a successful shop engine for their own use1 they had no cause to doubt their ability to supply a suitable powerplant when the need arose4 ,after the characteristics of the airframe had been settled1 and the engine requirements delineated in rather detailed form1 they had reached the point of decision on what they termed the motor problem4 ,only one major element had changed greatly since their previous consideration of the matter2 they had arrived at the point where they not only needed a flight engine1 they wanted it quickly4 ,nothing has been found that would indicate how much consideration they had given to forms of power for propulsion other than the choice they had apparently made quite early--the internal-combustion1 four-stroke-cycle piston engine4 ,undoubtedly1 steam was dismissed without being given much1 if any1 thought4 ,on the face of it1 the system was quite impractical for the size and kind of machine they planned2 but it had been chosen by ,maxim for his experiments1#c and some thirty-five or forty years later a serious effort to produce an aviation engine utilizing steam was initiated by ,lockheed4 ,on the other hand internal-combustion two-stroke-cycle piston engines had been built and used successfully in a limited way4 ,and since1 at that time1 it was probably not recognized that the maximum quantity of heat it is possible to dissipate imposed an inherent limitation on the power output of the internal-combustion engine1 the two-stroke-cycle may have appeared to offer a higher output from a given engine size than the four-stroke-cycle could produce4 ,certainly1 it would have seemed to promise much less torque variation for the same output1 something that was of great importance to the ,wrights4 ,against this1 the poor scavenging efficiency of the two-stroke operation1 and most probably its concurrent poor fuel economy1 were always evident2 and1 moreover1 at that time the majority of operating engines were four-stroke-cycle4 ,whatever their reasoning1 they selected for their first powered flight the exact form of prime mover that continued to power the airplane until the advent of the aircraft gas turbine more than forty years later4 ,footnote #c3 ,in the #ahijs the wealthy inventor ,sir ,hiram ,stevens ,maxim conducted an experiment of considerable magnitude with a flying machine that utilized a twin-cylinder compound steam powerplant4 ,it was developed to the flight-test stage4 ,the indicated solution to their problem of obtaining the engine--and the engine that would seem by all odds most reliable--would have been to have a unit produced to their specifications by one of the best of the experienced engine builders1 and to accomplish this1 the most effective method would be to use the equivalent of a bid procedure4 ,this they attempted1 and sent out a letter of inquiry to a fairly large number of manufacturers4 ,although no copy of the letter is available1 it is rather well established that it requested the price of an engine of certain limited specifications which would satisfy their flight requirements1 but beyond this there is little in the record4 ,a more thorough examination of the underlying fundamentals1 however1 discloses many weaknesses in the simple assumptions that made the choice of an experienced builder seem automatic4 ,a maximum requirement limited to only one or two units offered little incentive to a manufacturer already successfully producing in his field1 and the disadvantage of the limited quantity was only accentuated by the basic requirement for a technical performance in excess of any standard of the time4 ,certainly there was no promise of any future quantity business or any other substantial reward4 ,orville ,wright many times stated that they had no desire to produce their own engine1 but it is doubtful that they had any real faith in the buying procedure1 for they made no attempt to follow up their first inquiries or to expand the original list4 ,whatever the reasoning1 their judgment of the situation is obvious2 they spent no time awaiting results from the letter but almost immediately started on the task of designing and building the engine themselves4 ,perhaps the generalities were not as governing as the two specific factors whose immediate importance were determining3 cost and time4 ,the ,wrights no doubt realized that a specially designed1 relatively high performance engine in very limited hand-built quantities would not only be an expensive purchased article but would also take considerable time to build1 even under the most favorable circumstances4 ,so the lack of response to their first approach did not have too much to do with their ultimate decision to undertake this task themselves4 ,the question of the cost of the ,wrights' powerplants is most intriguing1 as is that of their entire accomplishment4 ,no detailed figures of actual engine costs are in the record1 and it is somewhat difficult to imagine just how they managed to conduct an operation requiring so much effort and such material resources1 given the income available from their fairly small bicycle business4 ,the only evidence bearing on this is a statement that the maximum income from this business averaged #c1jjj a year1#d which of course had to cover not only the airplane and engine but all personal and other expenses4 ,yet they always had spare engines and spare parts available2 they seemingly had no trouble acquiring needed materials and supplies1 both simple and complex2 and they apparently never were hindered at any time by lack of cash or credit4 ,the only mention of any concern about money is a statement by ,wilbur ,wright in a letter of #bj ,may #aijh when1 about to sail for ,france for the first public demonstrations1 he wrote3 ,this plan would put it to the touch quickly and also help ward off an approaching financial stringency which has worried me very much for several months4 ,it is a remarkable record in the economical use of money1 considering all they had done up to that time4 ,the myth that they had been aided by the earnings of their sister ,katherine as a school teacher was demolished long ago4 ,footnote #d3 ,fred ,c4 ,kelly1 ,miracle at ,kitty ,hawk1 #aiea4 ,the decision to build the engine themselves added one more requirement1 and possibly to some extent a restriction1 to the design4 ,they undoubtedly desired to machine as much of the engine as possible in their own shop1 and the very limited equipment they had would affect the variety of features and constructions that could be utilized1 although experienced machine shops with sophisticated equipment were available in ,dayton and it is obvious that the ,wrights intended to1 and did1 utilize these when necessary4 ,the use of their own equipment1 of course1 guaranteed that the parts they could handle themselves would be more expeditiously produced4 ,they commenced work on the design and construction shortly before ,christmas in #aijb4 ,the subject of drawings of the engine is interesting1 not only as history but also because it presents several mysteries4 ,taylor#e stated1 ,we didn't make any drawings4 ,one of us would sketch out the part we were talking about on a piece of scrap paper 444 ,obviously somewhere in the operation some dimensions were added1 for the design in many places required quite accurate machining4 ,orville ,wright's diary of #aijd has the entry1 ,took old engine apart to get measurements for making new engine4 ,finally1 no ,wright drawings of the original engine have been seen by anyone connected with the history or with the ,wright estate4 ,in the estate were two drawings 7now at the ,franklin ,institute71 on heavy brown wrapping paper1 relating to one of the two very similar later engines built in #aijd2 one is of a cylinder and connecting rod1 the other is an end view of the engine4 ,thus even if the very ingenious drafting board now in the ,wright ,museum at ,carillon ,park was available at the time there is no indication that it was used to produce what could properly be called drawings of the first engine4 ,footnote #e3 ,charles ,e4 ,taylor 7,charley ,taylor to the many who knew him7 was in effect the superintendent of and also the only employee to work in the original small machine shop4 ,a most versatile and efficient mechanic and machine operator1 he made many parts for all of the early engines1 and in the manner of the experimental machinist1 worked mainly from sketches4 ,he also had charge of the bicycle shop and its business in the absence of the ,wrights4 ,there are in existence1 however1 two complete sets of drawings1 both of which purport to represent the #aijc flight engine4 ,one set was made in ,england for the ,science ,museum in the two years #aibh and #aici4 ,the #aibh drawings were made on receipt of the engine1 which was not disassembled1 but in #aici the engine was removed from the airplane1 disassembled1 the original #aibh drawings were corrected and added to1 and the whole was made into one very complete and usable set4 ,the other set was prepared in ,dayton1 ,ohio1 for ,educational and ,musical ,arts1 ,inc41#f and was donated to the ,smithsonian ,institution4 ,this latter set was started under the direction of ,orville ,wright1 who died shortly after the work had been commenced4 ,footnote #f3 ,this is a charitable agency set up by the late ,colonel and ,mrs4 ,e4 ,a4 ,deeds primarily for the purpose of building and supporting the ,deeds ,carillon and the ,carillon ,park ,museum in ,dayton1 ,ohio4 ,the two sets of drawings1 that is1 the one of the ,science ,museum and that made in ,dayton for the ,smithsonian ,institution1 cannot be reconciled in the matter of details4 ,hardly any single dimension is exactly the same and essentially every part differs in some respect4 ,many of the forms of construction differ and even the firing order of the two engines is not the same1 so that in effect the drawings show two different engines4 ,illustration3 ,figure #a4--;,first flight engine1 #aijc1 valve side4 7,photo courtesy ,science ,museum1 ,london47 ,the primary trouble is1 of course1 that the exact engine which flew in #aijc is no longer in existence1 and since no original drawings of it exist1 there is considerable doubt about its details4 ,the engine had its crankcase broken in an accident to the airframe 7this was caused by a strong wind gust immediately following the last of the first series of flights at ,kitty ,hawk71 and when it was brought back to ,dayton it was for some inexplicable reason completely laid aside1 even though it presumably contained many usable parts4 ,when the engine was disassembled to obtain measurements for constructing the #aijd engines1 again apparently no drawings were made4 ,in ,february #aijf ,orville ,wright wrote that all the parts of the engine were still in existence except the crankcase2 but shortly after this the crankshaft and flywheel were loaned for exhibition purposes and were never recovered4 ,in #aibf the engine was reassembled for an exhibition and in #aibh it was again reassembled for shipment to ,england4 ,the only parts of this particular engine whose complete history is definitely known are the crankshaft and flywheel1 which were taken from the #aijd-aije flight engine4 ,this latter engine1 now in the restored #aije airplane in the ,carillon ,park ,museum in ,dayton1 does not contain a crankshaft1 and in its place incorporates a length of round bar stock4 ,illustration3 ,figure #b4--;,first flight engine1 #aijc1 underside and flywheel end4 7,photo courtesy ,science ,museum1 ,london47 ,in late #aidg work on the ,educational and ,musical ,arts drawings was initiated under the direction of ,louis ,p4 ,christman and carried through to completion by him4 ,christman has stated that ,orville ,wright was critical of the ,science ,museum drawings but just what he thought incorrect is not known4 ,whatever his reasons1 he did encourage ,christman to undertake the major task of duplication4 ,christman worked directly with ,orville ,wright for a period of six weeks and had access to all the records and parts the ,wrights had preserved4 ,the resultant drawings are also very complete and1 regardless of the differences between these two primary sets1 both give a sufficiently accurate picture of the first engine for all purposes except that of exact reproduction in every detail4 ,there exists a still unsolved puzzle in connection with what seems to be yet another set of drawings of the first engine4 ,in ,december #aidc1 in writing to the ,science ,museum telling of his decision to have the airplane and engine brought back to the ,united ,states1 ,orville ,wright stated1 ,i have complete and accurate drawings of the engine4 ,i shall be glad to furnish them if you decide to make a replica4#g ,no trace of these particular drawings can be found in any of the museums1 institutions1 or other repositories that normally should have acquired them and the executors of ,orville ,wright's estate have no record or knowledge of them4 ,the date of his letter is four years before the ,dayton drawings were commenced2 and when ,christman was working on these with ,orville ,wright they had copies of the ,science ,museum drawings1 with complete knowledge of their origin1 yet ,christman has no knowledge of the drawings referred to in ,orville's letter to the ,museum4 ,finally1 the evidence is quite conclusive that there were no reproducible or permanent drawings made at the time the first engine was constructed1 and1 of course1 the reconstructed engine itself was sent to ,england in #aibh and not returned to this country until #aidh4h ,footnote #g3 ,the ,science ,museum expressed a desire to have these but never received them4 ,there is a reference to them in a letter to the ,museum from the executors of his estate dated #bj ,february #aidh1 but is seems rather obvious from the text that by this time the drawings mentioned by ,orville ,wright in his #aidc letter had become confused with those being prepared by ,christman for the ,smithsonian ,institution4 ,the ,science ,museum did have constructed from its own drawings a very fine replica which is completely operable at this time4 ,footnote #h3 ,there is a third set of drawings prepared by the ,ford ,motor ,company also marked as being of the #aijc engine and these are rather well distributed in various museums and institutions4 ,what this set is based on has been impossible to determine but it is indicated from the existence of actual engines and parts and the probable date of their preparation 7no date is given on the drawings themselves7 that they were copied from drawings previously made1 and therefore add nothing to them4 ,the ,orville ,wright-,henry ,ford friendship originated rather late1 considering ,ford's avid interest in history and mechanical things4 ,this tardiness could possibly have been the result of ,wright coolness--a coolness caused by a report1 at the time the validity of the ,wright patents was being so strongly contested1 that ,ford had advised some of those opposing the ,wrights to persevere and to obtain the services of his patent counsel who had been successful in overturning the ,selden automobile patent4 ,if this barrier ever existed it was surmounted1 and ,ford spent much effort and went to considerable expense to collect the ,wright home and machine shop for his ,dearborn museum4 ,the shop equipment apparently had been widely scattered and its retrieval was a major task4 ,it is most likely that the drawings resulted from someone's effort to follow out an order to produce a set of ,ford drawings of the original engine4 ,a small scale model of the #aijc flight engine1 constructed under the supervision of ,charles ,taylor1 is contained in the ,dearborn ,museum4 ,the ,engine of the ,first ,flight1 #aijc ,in commencing the design of the first engine1 the first important decision arrived at was that of the number and size of the cylinders to be employed and the form in which they would be combined1 although it is unlikely that this presented any serious problem4 ,in a similar situation ,manly1 when he was working on the engine for the ,langley ,aerodrome1#i was somewhat perturbed because he did not have access to the most advanced technical knowledge1 since the automobile people who were at that time the leaders in the development of the internal combustion engine1 tended for competitive reasons to be rather secretive about their latest advancements and designs4 ,but although the standard textbooks may not have been very helpful to him1 there were available such volumes as ,w4 ,worby ,beaumont's ,motor ,vehicles and ,motors which contained in considerable detail descriptions and illustrations of the best of the current automobile engines4 ,the situations of ,manly and the ,wrights differed1 however1 in that whereas the ,wrights' objective was certainly a technical performance considerably above the existing average1 ,manly's goal was that of something so far beyond this average as to have been considered by many impossible4 ,importantly1 the ,wrights had their own experience with their shop engine and a good basic general knowledge of the size of engine that would be necessary to meet their requirements4 ,footnote #i3 ,charles ,l4 ,manly was engaged in the development of the engine for the ,langley ,aerodrome4 ,see also footnote to ,table on page #fb4 ,engine roughness was of primary concern to them4 ,in the #aijb description of the engine they sent to various manufacturers1 they had stated3 444 and the engine would be free from vibration4 ,even though their requirement for a smooth engine was much more urgent than merely to avoid the effect of roughness on the airplane frame1 they were faced1 before they made their first powered flight1 with the basic problem with which the airplane has had to contend for over three-quarters of its present life span3 that is1 it was necessary to utilize an explosion engine in a structure which1 because of weight limitations1 had to be made the lightest and hence frailest that could possibly be devised and yet serve its primary purpose4 ,however great the difficulty may have appeared1 in the long view1 the fault was certainly a relatively minor one in the overall development of the internal combustion engine--that wonderful invention without which their life work would probably never have been so completely successful while they lived1 and which1 even aside from its partnership with the airplane1 has so profoundly affected the nature of the world in which we live4 ,it seems quite obvious that to the ,wrights vibration1 or roughness1 was predominantly if not entirely caused by the explosion forces1 and they were either not completely aware of the effects of the other vibratory forces or they chose to neglect them4 ,although crankshaft counterweights had been in use as far back as the middle #ahjjs1 the ,wrights never incorporated them in any of their engines2 and despite the inherent shaking force in the #d-;inline arrangement1 they continued to use it for many years4 ,the choice of four cylinders was obviously made in order to get1 for smoothness1 what in that day was a lot of small cylinders2 and this was sound judgment4 ,furthermore1 although the majority of automobiles at that time had engines with fewer than four cylinders1 for those that did the inline form was standard and well proven1 and1 in fact1 ,daimler was then operating engines of this general design at powers several times the minimum the ,wrights had determined necessary for their purpose4 ,what fixed the exact cylinder size1 that is1 the square #dx#d-;in4 form1 is not recorded1 nor is it obvious by supposition4 ,baker says it was for high displacement and low weight1 but these qualities are also greatly affected by many other factors4 ,the total displacement of just over #bjj cu in4 was on the generous side1 given the horsepower they had determined was necessary1 but here again the ,wrights were undoubtedly making the conservative allowances afterwards proven habitual1 to be justified later by greatly increased power requirements and corresponding outputs4 ,the ,mean ,effective ,pressure 7,,mep71 based on their indicated goal of #h hp1 would be a very modest #cf psi at the speed of #hgj rpm at which they first tested the engine1 and only #ca psi at the reasonably conservative speed of #ajjj rpm4 ,the #dx#d-;in4 dimension would provide a cylinder large enough so that the engine was not penalized in the matter of weight and yet small enough to essentially guarantee its successful operation1 as cylinders of considerably larger bore were being utilized in automobiles4 ,that their original choice was an excellent one is rather well supported by the fact that in all the different models and sizes of engines they eventually designed and built1 they never found it necessary to go to cylinders very much larger than this4 ,illustration3 ,figure #c4--;,first flight engine1 #aijc1 installed in the ,kitty ,hawk airplane1 as exhibited in the ,science ,museum4 7,photo courtesy the ,science ,museum1 ,london47 ,a second basic determination which was made either concurrently or even possibly in advance of that of the general form and size was in the matter of the type of cylinder cooling to adopt4 ,based on current practice that had proven practical1 there were three possibilities1 all of which were in use in automobiles3 air1 water1 or a combination of the two4 ,it is an interesting commentary that ,fernand ,forest's#aj proposed #cb-;cylinder aircraft engine of #ahhh was to be air-cooled1 that ,santos-,dumont utilized an air-cooled ,clement engine in his dirigible flights of #aijc1 and that the ,wrights had chosen air cooling for their shop engine4 ,with the promise of simplicity and elimination of the radiator1 water and piping1 it would seem1 offhand1 that this would be the ,wrights' choice for their airplane2 but they were probably governed by the fact that not only was the water-cooled type predominant in automobile practice1 but that the units giving the best and highest performance in general service were all water cooled4 ,in their subsequent practice they never departed from this original decision1 although ,wilbur ,wright's notebook of #aijd-aijg contains an undated weight estimate by detailed parts for an #h-;cylinder air-cooled engine4 ,unfortunately1 the proposed power output is not recorded1 so their conception of the relative weight of the air-cooled form is not disclosed4 ,footnote #aj3 ,fernand ,forest1 ,les ,bateaux ,automobiles1 #aijf4 ,one of the most important decisions relating to the powerplant--one which was probably made long before they became committed to the design itself--was a determination of the method of transmission of power to the propeller1 or propellers4 ,a lingering impression exists that the utilization of a chain drive for this purpose was a natural inheritance from their bicycle background4 ,no doubt this experience greatly simplified the task of adaptation but a merely cursory examination shows that even if they had never had any connection with bicycles1 the chain drive was a logical solution1 considering every important element of the problem4 ,the vast majority of automobiles of the time were chain driven1 and chains and sprockets capable of handling a wide range of power were completely developed and available4 ,further1 at that time they had no accurate knowledge of desirable or limiting propeller and engine speeds4 ,the chain drive offered a very simple and inexpensive method of providing for a completely flexible range of speed ratios4 ,the other two possibilities were both undesirable3 the first1 a simple direct-driven single propeller connected to the crankshaft1 provided essentially no flexibility whatsoever in experimentally varying engine or propeller speed ratios1 it added an out-of-balance engine torque force to the problem of airplane control1 and1 finally1 it dictated that the pilot would be in the propeller slipstream or the airflow to it2 the second1 drive shafts and gearing for dual propellers1 would have been very heavy and expensive1 and most probably would have required a long-time development1 with every experimental change in speed ratios requiring a complete change in gears4 ,again1 their original choice was so correct that it lasted them through essentially all their active flying years4 ,the very substantial advantages of the chain drive were not1 however1 obtained at no cost4 ,torque variations in the engine would tend to cause a whipping action in the chain1 so that it was vulnerable to rough running caused by misfiring cylinders and1 with the right timing and magnitude of normal regular variations1 the action could result in destructive forces in the transmission system4 ,this was the basic reason for the ,wrights' great fear of engine vibration1 which confined them to the use of small cylinders and made a fairly heavy flywheel necessary on all their engines4 ,when they were requested to install an ,austro-,daimler engine in one of their airplanes1 they designed a flexible coupling which was interposed between the engine and the propeller drive and this was considered so successful that it was applied to the flywheel of some engines of their last model1 the #f-gj1 which had been giving trouble in this regard4#aa ,footnote #aa3 ,grover ,loening1 letter of #aj ,april #aifc1 to the ,smithsonian ,institution4 ,although flat1 angled1 and vertical engines had all been operated successfully1 the best and most modern automotive engines of the time were vertical1 so their choice of a horizontal position was probably dictated either by considerations of drag or their desire to provide a sizable mounting base for the engine1 or both4 ,there is no record of their ever having investigated the matter of the drag of the engine1 either alone or in combination with the wing4 ,the merit of a vertical versus a horizontal position of the engine was not analogous to that of the pilot1 which they had studied1 and where the prone position undoubtedly reduced the resistance4 ,having decided on the general makeup of their engine1 the next major decision was that of just what form the principal parts should take1 the most important of these being the cylinders and crankcase4 ,even at this fairly early date in the history of the internal combustion engine various successful arrangements and combinations were in existence4 ,individual cylinder construction was by far the most used1 quite probably due to its case of manufacture and adaptability to change4 ,since #d-;cylinder engines were just coming into general use 7a few production engines of this type had been utilized as early as #ahih71 there were few examples of en-bloc or one-piece construction4 ,the original ,german ,daimler ,company undoubtedly was at this time the leader in the development of high-output internal-combustion engines1 and in #aijb1 as an example of what was possible1 had placed in service one that possibly approximated #dj hp1 which was an ,,mep of #gj psi4 7,almost without exception1 quoted power figures of this period were not demonstrated quantities but were based on a formula1 of which the only two factors were displacement and rpm47 ,the cylinders of this ,daimler engine were cast iron1 the cylinder barrel1 head1 and water jacket being cast in one piece4 ,the upper part of the barrel and the cylinder head were jacketed1 but1 surprisingly1 the bottom #fj percent of the barrel had no cooling4 ,the cylinders were cast in pairs and bolted to a two-piece aluminum case split at the line of the crankshaft4 ,ignition was make-and-break and the inlet valves were mechanically actuated4 ,displacement was #dac cu in4 and the rpm was #ajej4 ,although a few examples of integral crankcase and water jacket combinations were in use1 the ,wrights were being somewhat radical when they decided to incorporate all four cylinders in the one-piece construction1 particularly since they also proposed to include the entire crankcase and not just one part of it4 ,it was undoubtedly the most important decision that they were required to make on all the various construction details1 and probably the one given the most study and investigation4 ,many factors were involved1 but fundamentally everything went back to their three basic requirements3 suitability1 time1 and cost4 ,there was no obvious reason why the construction would not work1 and it eliminated a very large number of individual parts and the required time for procuring1 machining1 and joining them4 ,probably one very strong argument was the advanced state of the casting art1 one of the oldest of the mechanical arts in existence and one the ,wrights used in many places1 even though other processes were available4 ,what no doubt weighed heavily was that ,dayton had some first-class foundries4 ,the casting1 though intricate and not machinable in their own shop1 could be easily handled in one that was well outfitted4 ,the pattern was fairly complex but apparently not enough to delay the project or cause excessive cost4 ,illustration3 ,figure #d4--;,first flight engine1 #aijc1 left side and rear views1 with dimensions4 7,drawing courtesy ,howell ,cheney ,technical ,school47 ,,left ,,side ,,view4 ,illustration3 ,,rear ,,view ,the selection of aluminum for the material was an integral part of the basic design decision4 ,despite the excellence and accuracy of the castings that could be obtained1 there was nevertheless a minimum dimension beyond which wall thickness could not be reduced2 and the use of either one of the two other proven materials1 cast iron or bronze1 would have made the body1 as they called it1 prohibitively heavy4 ,the use of aluminum was not entirely novel at this time1 as it had been utilized in many automobile engine parts1 particularly crankcases2 but its incorporation in this rather uncommon combination represented a bold step4 ,there was no choice in the matter of the alloy to be used1 the only proven one available was an #h percent copper #ib percent aluminum combination4 ,by means of the proper webs1 brackets and bosses1 the crankcase would also carry the crankshaft1 the rocker arms and bearings1 and the intake manifold4 ,the open section of the case at the top was covered with a screw-fastened thin sheet of cold-rolled steel4 ,the main bearing bosses were split at a #de deg4 angle for ease of assembly4 ,the engine support and fastening were provided by four feet1 or lugs1 cast integral on the bottom corners of the case1 and by accompanying bolts 7,figure #b74 ,although the crankcase continued to be pretty much the body of the internal combustion aircraft engine throughout its life1 the ,wrights managed to incorporate in this original part a major portion of the overall engine1 and certainly far more than had ever previously been included4 ,the design of the cylinder barrel presented fairly simple problems involving not much more than those of keeping the sections as thin as possible and devising means of fastening it and of keeping the water jacket tight4 ,they saved considerable weight by making the barrel quite short1 so that in operation a large part of the piston extended below the bottom of it2 but this could be accepted1 as there were no rings below the piston pin 7,figure #f74 ,the barrel material1 a good grade of cast iron1 was an almost automatic choice4 ,in connection with these seemingly predetermined decisions1 however1 it should be remembered that their goal was an engine which would work without long-time development1 and that1 with no previous experience in lightweight construction to guide them they were nevertheless compelled to meet a weight limit1 so that the thickness of every wall and flange and the length of every thread was important4 ,with the separate cylinder barrel they were now almost committed to a three-piece cylinder4 ,it would have been possible to combine the barrel and head in a one-piece casting and then devise a method of attachment1 but this would have been more complex and certainly heavier4 ,for housing the valves1 what was in effect a separate cylindrical1 or tubular1 box was decided upon4 ,this would lie across the top of the cylinder proper at right angles to the cylinder axis1 and the two valves would be carried in the two ends of this box4 ,the cylinder barrel would be brought in at its head end to form a portion of the cylinder head and then extended along its axis in the form of a fairly large boss1 a mating boss being provided on one side of the valve box4 ,the cylinder barrel would then be threaded into the valve box and the whole tightened or fastened to the crankcase by means of two sets of threads1 one at each end of the barrel proper4 ,this meant that three joints had to be made tight with only two sets of threads4 ,this was accomplished by accurate machining and possibly even hand fitting in combination with a rather thick gasket at the head end1 one flat of which bore against two different surfaces4 ,this can be seen in ,figure #f1 where the circular flange on the valve box contacts both the crankcase and the cylinder barrel4 ,altogether it was a simple1 light1 and ingenious solution to a rather complex problem4 ,at this point the question arises3 ,why was the engine layout such that the exhaust took place close to the operator's ears8 ,it would have been possible1 starting with the original design1 to turn the engine around so that the exhaust was on the other side4 ,this would have little effect on the location of the center of gravity1 and the two main drive chains would then have been of more equal length4 ,however1 of the many factors involved1 probably one of the principal considerations in arriving at their final decision was the location of the spark-advance control1 which was in effect the only control they had of engine output1 except for complete shutoff4 ,in their design this was immediately adjacent to the operator2 with a turned-around engine1 an extension control mechanism of some sort would have been required4 ,the noise of the exhaust apparently became of some concern to them1 as ,orville's diary in early #aijd contains an entry with a sketch labeled ,design for ,muffler for ,engine1 but there is no further comment4 ,the problem of keeping joints tight1 and for that matter the entire construction itself1 were both greatly simplified by their decision to water-jacket only a part of the cylinder head proper1 and the valve box not at all4 ,this was undoubtedly the correct decision for their immediate purpose1 as again they were effecting savings in time1 cost1 complexity1 and weight4 ,there is nothing in the record1 however1 to show why they continued this practice long after they had advanced to much greater power outputs and longer flight times4 ,their own statements show that they were well aware of the effect of the very hot cylinder head on power output and they must also have realized its influence on exhaust-valve temperature4 ,the cylinder assembly was made somewhat more complicated by their desire to oil the piston and cylinder by means of holes near the crankshaft end in what was1 with the engine in the horizontal position1 the upper side of the cylinder barrel4 ,this complication was no doubt taken care of by not drilling the holes until a tight assembly had been made by screwing the barrel into place1 and by marking the desired location on the barrel4 ,since this position was determined by a metal-to-metal jam fit of the crankcase and cylinder barrel flange1 the barrel would reassemble with the holes in very nearly the same relative position after disassembly4 ,with the valve box1 or housing1 cylindrical1 the task of locking and fastening the intake and exhaust valve guides and seats in place was easy4 ,the guide was made integral with and in the center of one end of a circular cage1 the other end of which contained the valve seat 7see ,figure #e74 ,four sections were cut out of the circular wall of the cage so that in effect the seat and guide were joined by four narrow legs1 the spaces between which provided passages for the flow of the cylinder gases4 ,these cages were then dropped into the ends of the valve boxes until they came up against machined shoulders and were held in place by internal ring nuts screwed into the valve box4 ,the intake manifold or passage was placed over the intake valves so that the intake charge flowed directly into and through the valve cage around the open valve and into the cylinder4 ,the exhaust gas1 after flowing through the passages in the valve cage1 was discharged directly to the atmosphere through a series of holes machined in one side of the valve box4 ,illustration3 ,figure #e4--;,first flight engine1 #aijc1 assembly4 7,phantom cutaway by ,j4 ,h4 ,clark1 with key1 courtesy ,aeroplane47 ,,key #a and #b4 ,bearing caps in one piece with plate #c4 #c4 ,plated screwed over hole #d in crankcase end4 #d4 ,key-shaped hole as hole #e in intermediate ribs4 #f4 ,inter-bearings cap 7white-metal lined7 and screwed to inter-rib halves #g4 #h4 ,splash-drip feed to bearings4 #i4 ,return to pump from each compartment of crankcase base 7sump7 via gallery #aj and pipe to pump #aa underneath jacket4 #ab4 ,oil feed from pump via rubber tube #ac4 #ac4 ,drip feeds to cylinders and pistons4 #ad4 ,gear drive to pump4 #ae4 ,big-end nuts1 lock-strip1 and shims4 #af4 ,gudgeon-pin lock4 #ag4 ,piston-ring retainer pegs4 #ah4 ,cylinder liner screwing into jacket4 #ai4 ,open-ended can admits air4 #bj4 ,fuel supply4 #ba4 7,hot7 side of water jacket makes surface carburetter4 #bb4 ,sparking plug 7comprising positive electrode #bc and spark-producing make-and-break #bd74 #be4 ,lever attached to lever #bf via bearing #bg screwed into chamber neck #bh4 #bf4 ,levers with mainspring #bi and inter-spring #cj1 and rocked by cam #ca4 #ca4 ,cam with another alongside 7for adjacent cylinder74 #cb4 ,positive busbar feed to all four cylinders4 #cc4 ,assembly retaining-rings4 #cd4 ,sealing disc4 #ce4 ,exhaust outlet ports4 #cf4 ,camshaft right along on underside of jacket and also driving oil pump #aa via #ad4 #cg4 ,spring-loaded sliding pinion drives make-and-break shaft #ch through peg in inclined slot #ci4 #dj4 ,cam to push pinion #cg along and so alter its angular relation with shaft #ch 7to vary timing74 #da4 ,exhaust-valve cams bear on rollers #db mounted in end of rocker-arms #dc4 #dd4 ,generator floating coils4 #de4 ,friction-drive off flywheel4 #df4 ,sight-feed lubricator 7on stationary sleeve74 #dg4 ,hardwood chain tensioner4 ,the intake and exhaust valves were identical and of two-piece construction1 with the stems screwed tightly into and through the heads and the protruding ends then peened over4 ,this construction was not novel1 having had much usage behind it1 and it continued for a long time in both automobile and aircraft practice4 ,one-piece cast and forged valves were available but here again it was a choice of the quick1 cheap1 and proven answer4 ,the entire valve system1 including guides and seats1 was of cast iron1 a favorite material of the ,wrights1 except for the valve stems1 which were1 at different times1 of various carbon steels4 ,ordinary cold-rolled apparently was used in those of the original engine1 but in later engines this was changed to a high-carbon steel4 ,the piston design presented no difficulty4 ,in some measure this was due to the remarkable similarity that seems to have existed among all the different engines of the time in the construction of this particular part1 for1 although there were some major variations1 it was1 in fact1 almost as if some standard had been adopted4 ,pistons all were of cast iron and comparatively quite long 7it was a number of years before they evolved into the short ones of modern practice72 they were almost invariably equipped with three wide piston rings between the piston pin and the head2 and1 although there were in existence a few pistons with four rings1 no oil wiper or other ring seems to have been placed below the piston pin4 ,the ,wrights' piston was typical of the time1 with the rings pinned in the grooves to prevent turning and the piston pin locked in the piston with a setscrew4 ,in designing this first engine they were1 however1 apparently somewhat unsure about this latter feature1 as they provided the rod with a split little end and a clamping bolt 7see ,figure #f71 so that the pin could be held in the rod if desired2 but no examples of this use have been encountered4 ,the ,wrights' selection of an automatic or suction-operated inlet valve was entirely logical4 ,mechanically operated inlet valves were in use and their history went back many years1 but the great majority of the engines of that time still had the automatic type1 and with this construction one complete set of valve-operating mechanisms was eliminated4 ,they were well aware of the loss of volumetric efficiency inherent in this valve1 and apparently went to some pains to obtain from it the best performance possible4 ,speaking of the first engine1 ,orville ,wright wrote1 ,since putting in heavier springs to actuate the valves on our engine we have increased its power to nearly #af hp and at the same time reduced the amount of gasoline consumed per hour to about one-half of what it was4#ab ,footnote #ab3 ,assuming a rich mixture1 consumption of all the air1 and an airbrake thermal efficiency of #bd4ej for the original engine1 the approximate volumetric efficiency of the cylinder is calculated to have been just under #dj4 ,why they continued with this form on their later engines is a question a little more difficult to answer1 as they were then seeking more and more power and were building larger engines4 ,the advantages of simplicity and a reduced number of parts still existed1 but there also was a sizable power increase to be had which possibly would have more than balanced off the increased cost and weight4 ,they did not utilize mechanical operation until after a major redesign of their last engine model4 ,very possibly the answer lies in the phenomenon of fuel detonation4 ,this was only beginning to be understood in the late #aibjs1 and it is quite evident from their writings that they had little knowledge of what made a good fuel in this respect4 ,it is fairly certain1 however1 that they did know of the existence of cylinder knock1 or detonation1 and particularly that the compression ratio had a major effect on it4 ,the ratios they utilized on their different engines varied considerably1 ranging from what1 for that time1 was medium to what was relatively high4 ,the original flight engine had a compression ratio of #d4d3a4 ,the last of their service engines had a compression ratio about twenty percent under that of the previous series--a clear indication that they considered that they had previously gone too high4 ,quite possibly they concluded that increasing the amount of the cylinder charge seemed to bring on detonation1 and that the complication of the mechanical inlet valve was therefore not warranted4 ,illustration3 ,figure #f4--;,first flight engine1 #aijc1 cross section4 7,drawing courtesy ,science ,museum1 ,london47 ,the camshaft for the exhaust valves 7#aja1 ,figure #f71 was chain driven from the crankshaft and was carried along the bottom of the crankcase in three babbit-lined bearings in bearing boxes or lugs cast integral with the case4 ,both the driving chain and the sprockets were standard bicycle parts1 and a number of bicycle thread standards and other items of bicycle practice were incorporated in several places in the engine1 easing their construction task4 ,the shaft itself1 of mild carbon steel1 was hollow and on each side of an end bearing sweated-on washers provided shoulders to locate it longitudinally4 ,its location adjacent to the valves1 with the cam operating directly on the rocker arm1 eliminated push rods and attendant parts1 a major economy4 ,the cams were machined as separate parts and then sweated onto the shaft4 ,their shape shows the principal concern in the design to have been obtaining maximum valve capacity--that is1 a quite rapid opening with a long dwell4 ,this apparent desire to get rid of the exhaust gas quickly is manifested again in the alacrity with which they adopted a piston-controlled exhaust port immediately they had really mastered flight and were contemplating more powerful and more durable engines4 ,this maximum-capacity theory of valve operation1 with its neglect of acceleration forces and seating velocities1 may well have been at least partially if not largely the cause of their exhaust-valve troubles and the seemingly disproportionate amount of development they devoted to this part1 as reported by ,chenoweth1 although it is also true that the exhaust valve continued to present a problem in the aircraft piston engine for a great many years after1 even with the most scientific of cam designs4 ,the rocker arm 7#ajb1 ,figure #f7 is probably the best example of a small part which met all of their many specific requirements with an extreme of simplicity4 ,it consisted of two identical side pieces1 or walls1 of sheet steel shaped to the desired side contour of the assembly1 in which were drilled three holes1 one in each end1 to carry the roller axles1 and the third in the approximate middle for the rocker axle shaft proper4 ,this consisted of a piece of solid rod positioned by cotter pins in each end outside the side walls 7see ,figure #e74 ,the assembly was made by riveting over the ends of the roller axles so that the walls were held tightly against the shoulders on the axles1 thus providing the correct clearance for the rollers4 ,the construction was so light and serviceable that it was essentially carried over to the last engine the ,wrights ever built4 ,the basic intake manifold 7see ,figure #e7 consisted of a very low flat box of sheet steel which ran across the tops of the valve boxes and was directly connected to the top of each of them so that the cages1 and thus the valves1 were open to the interior of the manifold4 ,through an opening in the side toward the engine the manifold was connected to a flat induction chamber 7#ba1 ,figure #e7 which served to vaporize the fuel and mix it with the incoming air4 ,this chamber was formed by screw-fastening a piece of sheet steel to vertical ribs cast integral with the crankcase1 the crankcase wall itself thus forming the bottom of the chamber4 ,a beaded sheet-steel cylinder resembling a can 7#gc1 ,figure #f7 but open at both ends was fastened upright to the top of this chamber4 ,in the absence of anything else1 this can could be called the carburetor1 as a fuel supply line entered the cylinder near the top and discharged the fuel into the incoming air stream1 both the fuel and air then going directly into the mixing chamber4 ,the can was attached near one corner of the chamber1 and vertical baffles1 also cast integral with the case1 were so located that the incoming mixture was forced to circulate over the entire area of exposed crankcase inside the chamber before it reached the outlet to the manifold proper1 the hot surface vaporizing that part of the fuel still liquid4 ,illustration3 ,figure #g4--;,first flight engine1 #aijc3 cylinder1 valve box1 and gear mechanism2 below1 miscellaneous parts4 7,photos courtesy ,science ,museum1 ,london1 and ,louis ,p4 ,christman47 ,fuel was gravity fed to the can through copper and rubber tubing from a tank fastened to a strut1 several feet above the engine4 ,of the two valves placed in the fuel line1 one was a simple on-off shutoff cock and the other a type whose opening could be regulated4 ,the latter was adjusted to supply the correct amount of fuel under the desired flight operating condition2 the shutoff cock was used for starting and stopping4 ,the rate of fuel supply to the engine would decrease as the level in the fuel tank dropped1 but as the head being utilized was a matter of several feet and the height of the supply tank a matter of inches1 the fuel-air ratio was still maintained well within the range that would ignite and burn properly in the contemplated one-power condition of their flight operation4 ,this arrangement is one of the best of the many illustrations of how by the use of foresight and ingenuity the ,wrights met the challenge of a complex requirement with a simple device1 for while carburetors were not in the perfected stage later attained1 quite good ones that would both control power output and supply a fairly constant fuel-air mixture over a range of operating conditions were available1 but they were complex1 heavy1 and expensive4 ,the arrangement1 moreover1 secured at no cost a good vaporizer1 or modern hot spot4 ,in their subsequent engines they took the control of the fuel metering away from the regulating valve and gravity tank combination and substituted an engine-driven fuel pump which provided a fuel supply bearing a fairly close relationship to engine speed4 ,the reasons behind selection of the type of ignition used1 and the considerations entering into the decision1 are open to speculation1 as are those concerning many other elements that eventually made up the engine4 ,both the high-tension spark plug and low-tension make-and-break systems had been in wide use for many years1 with the latter constituting the majority in #aijb4 ,both were serviceable and therefore acceptable1 and both required a magneto4 ,the art of the spark plug was in a sense esoteric 7to a certain extent it so remains to this day71 but the spark-plug system did involve a much simpler combination of parts3 in addition to the plug and magneto there would be needed only a timer1 or distributor1 together with coils and points1 or some substitute arrangement4 ,the make-and-break system1 on the other hand1 required for each cylinder what was physically the equivalent of a spark plug1 that is1 a moving arm and contact point inside the cylinder1 a spring-loaded snap mechanism to break the contact outside the cylinder1 and a camshaft and cams to actuate the breaker mechanism at the proper time4 ,furthermore1 as the ,wrights applied it1 the system required dry cells and a coil for starting1 although these did not accompany the engine in flight4 ,and finally there was the problem of keeping tight the joint where the oscillating shaft required to operate the moving point in the spark plug entered the cylinder4 ,this is one of the few occasions1 if not the only one1 when the ,wrights chose the more complex solution in connection with a major part--in this particular case1 one with far more bits and pieces4 ,however1 it did carry with it some quite major advantages4 ,the common spark plug1 always subject to fouling or failure to function because of a decreased gap1 was not very reliable over a lengthy period1 and was undoubtedly much more so in those days when control of the amount of oil inside the cylinder was not at all exact4 ,make-and-break points1 on the other hand1 were unaffected by excess oil in the cylinder4 ,because of this resistance to fouling1 the system was particularly suitable for use with the compression-release method of power control which they later utilized1 although they probably could not have been looking that far ahead at the time they chose it4 ,high-tension current has always1 and rightfully so1 been thought of as a troublemaker in service2 in ,beaumont's #aijj edition of ,motor ,vehicles and ,motors1 which seems to have been technically the best volume of its time1 the editor predicted that low-tension make-and-break ignition would ultimately supersede all other methods4 ,and finally1 the large number of small parts required for the make-and-break system could all be made in the ,wright ,brothers' shop or easily procured1 and in the end this was probably the factor1 plus reliability1 that determined the decision which1 all things considered1 was the correct one4 ,there was nothing exceptional about the exact form the ,wrights devised4 ,it displayed the usual refined simplicity 7the cams were made of a single small piece of strip steel bent to shape and clamped to the ignition camshaft with a simple self-locking screw71 and lightness4 ,the ignition camshaft 7#ch1 ,figure #e71 a piece of small-diameter bar stock1 was located on the same side as the exhaust valve camshaft1 approximately midway between it and the valve boxes1 and was operated by the exhaust camshaft through spur gearing4 ,that the ,wrights were thinking of something beyond mere hops or short flights is shown by the fact that the ignition points were platinum-faced1 whereas even soft iron would have been satisfactory for the duration of all their flying for many years4 ,the control of the spark timing was effected by advancing or retarding the ignition camshaft in relation to the exhaust valve camshaft4 ,the spur gear 7#cg1 ,figure #e7 driving the ignition camshaft had its hub on one side extended out to provide what was in effect a sleeve around the camshaft integral with the gear4 ,the gear and integral sleeve were slidable on the shaft and the sleeve at one place 7#ci1 ,figure #e7 was completely slotted through to the shaft at an angle of #de deg4 to the longitudinal axis of the shaft4 ,the shaft was driven by a pin tightly fitted in it and extending into the slot4 ,the fore-and-aft position of the sleeve on the shaft was determined by a lever-operated cam 7#dj1 ,figure #e7 on one side and a spring on the other4 ,the movement of the sleeve along the shaft would cause the shaft to rotate in relation to it because of the angle of the slot1 thus providing the desired variation in timing of the spark4 ,the magneto was a purchased item driven by means of a friction wheel contacting the flywheel1 and several different makes were used later1 but the original is indicated to have been a ,miller-,knoblock 7see ,figure #e74 ,the connecting rod is another example of how1 seemingly without trouble1 they were able to meet the basic requirements they had set for themselves4 ,it consisted of a piece of seamless steel tubing with each end fastened into a phosphor-bronze casting1 these castings comprising the big and little ends1 drilled through to make the bearings 7,see ,figures #e and #f74 ,it was strong1 stiff and light4#ac ,forged rods were in rather wide use at the time and at least one existing engine even had a forged ,i-beam section design that was tapered down from big to little end4 ,the ,wrights' rod was obtained in little more time than it took to make the simple patterns for the two ends4 ,the weight was easily controlled1 no bearing liners were necessary1 and a very minimum of machining was required4 ,concerning the big-end material1 there exists a contradiction in the records3 ,baker1 whose data are generally most accurate1 states that these were babbited1 but this must be in error1 as the existing engine has straight bronze castings without babbiting1 and there is no record1 or drawing1 or other indication of the bearings having been otherwise4 ,footnote #ac3 ,a rather thorough stress analysis of the rod shows it to compare very favorably with modern practice4 ,in the absence of an indicator card for the #aijc engine1 if a maximum gas pressure of five times the ,,mep is assumed1 the yield-tension factor of safety is measurably higher than that of two designs of piston engines still in wide service1 and the column factor of safety only slightly less4 ,the shear stresses in the brazed and threaded joints are so low as to be negligible4 ,different methods of assembling the rod were used4 ,at one time the tube ends were screwed into the bronze castings and pinned1 and at another the ends were pinned and soldered4 ,there is an indication that at one time soldering and threads were used in combination4 ,one of the many conflicts between the two primary sets of drawings exists at this point4 ,the ,smithsonian drawings show the use at each end of adapters between the rod and end castings1 the adapters being first screwed into the castings and pinned and then brazed to the inside of the tube4 ,the ,science ,museum drawings show the tube section threaded and screwed into the castings4 ,the direct screw assembly method called for accurate machining and hand fitting in order to make the ends of the tubing jam against the bottom of the threaded holes in the castings1 and at the same time have the end bearings properly lined up4 ,the weakness of the basic design patently lies in the joints4 ,it is an attempt to utilize what was probably in the beginning a combination five-piece assembly and later three1 in a very highly stressed part where the load was reversing4 ,it gave them considerable trouble from time to time1 particularly in the #d-;cylinder vertical engines1 and was abandoned for a forged ,i-beam section type in their last engine model2 but it was nevertheless the ideal solution for their first engine4 ,the crankshaft was made from a solid block of relatively high carbon steel which1 aside from its bulk and the major amount of machining required1 presented no special problems4 ,it was heat-treated to a machinable hardness before being worked on1 but was not further tempered4 ,the design was an orthodox straight pin and cheek combination and1 as previously noted1 there were no counterweights to complicate the machining or assembly4 ,a sizable bearing was provided on each side of each crank of the shaft1 which helped reduce the stiffness requirement4 ,their only serious design consideration was to maintain the desired strength and still keep within weight limitations4 ,a fundamental that every professional designer knows is that it is with this particular sort of part that weight gets out of control2 even an additional #a_/af in41 if added in a few places1 can balloon the weight4 ,with their usual foresight and planning1 the ,wrights carefully checked and recorded the weight of each part as it was finished1 but even this does not quite explain how these two individuals1 inexperienced in multicylinder engines--much less in extra-light construction--could1 in two months1 bring through an engine which was both operable and somewhat lighter than their specification4 ,in one matter it would seem that they were quite fortunate4 ,the records are not complete1 but with one exception there is no indication of any chronic or even occasional crankshaft failure4 ,this would seem to show that it apparently never happened that any of their designs came out such that the frequency of a vibrating force of any magnitude occurred at the natural frequency of the shaft4 ,much later1 when this type of vibration became understood1 it was found virtually impossible1 with power outputs of any magnitude1 to design an undampened shaft1 within the space and weight limitations existing in an ordinary engine1 strong enough to withstand the stress generated when the frequency of the imposed vibration approximated the natural frequency of the shaft4 ,the vibratory forces were mostly relatively small in their engines1 so that forced vibration probably was not encountered1 and the operating speed range of the engines was so limited that the natural frequency always fell outside this range4 ,the flywheel was about the least complex of any of their engine parts and required little studied consideration1 although they did have to balance its weight against the magnitude of the explosion forces which would reach the power transmission chains1 with their complete lack of rigidity1 a problem about which they were particularly concerned4 ,the flywheel was made of cast iron and was both keyed to and shrunk on the shaft4 ,some doubt still exists about the exact method of lubricating the first engine4 ,the unit presently in the airplane has a gear-type oil pump driven by the crankshaft through a worm gear and cross shaft1 and the ,appendix to the ,papers states that it was lubricated by a small pump2 nevertheless ,baker says1 after careful research1 that despite this evidence1 it was not4 ,also1 the drawings prepared by ,christman 7they were commenced under the supervision of ,orville ,wright7 do not show the oil pump4 ,in ,march #aije ,wilbur ,wright wrote to ,chanute1 ,however we have added oiling and feeding devices to the engine 4442 but this could possibly have referred to something other than an oil pump4 ,but even if a pump was not included originally1 its presence in the present engine is easily explained4 ,breakage of the crankcase casting caused the retirement of this engine1 which was not rebuilt until much later1 and the pattern for this part had no doubt long since been altered to incorporate a pump4 ,it was therefore easier in rebuilding to include than to omit the pump1 even though this required the addition of a cross shaft and worm gear combination4 ,on later engines1 when the pump was used1 oil was carried to a small pipe1 running along the inside of the case1 which had four small drill holes so located as to throw the oil in a jet on the higher1 thrust-loaded side of each cylinder4 ,the rods had a sharp scupper on the outside of the big end so placed as also to throw the oil on this same thrust face4 ,some scuppers were drilled through to carry oil to the rod bearing and some were not4 ,the first engine was finished and assembled in ,february #aijc and given its first operating test on #bb ,february4 ,the ,wrights were quite pleased with its operation1 and particularly with its smoothness4 ,their father1 ,bishop ,wright1 was the recorder of their satisfaction over its initial performance1 but what he noted was probably the afterglow of the ineffable feeling of deep satisfaction that is the reward that comes to every maker of a new engine when it first comes to life and then throbs4 ,they obtained #ac hp originally3 later figures went as high as almost #af1 but as different engine speeds were utilized it is rather difficult to settle on any single power figure4 ,the most realistic is probably that given in the ,papers as having been attained later1 after an accurate check had been made of the power required to turn a set of propellers at a given rpm4 ,this came out at approximately #ab hp1 the design goal having been #h4 ,following exactly the procedure that exists to this day1 the engine went through an extended development period1 and it was the end of ,september #aijc before it was taken1 with the airplane1 to ,kitty ,hawk where the historic flights1 which have had such a profound effect on the lives of all men1 were made on #ag ,december #aijc4 ,the ,engines ,with ,which ,they ,mastered ,the ,art of ,flying ,two more engines of this first general design were built but they differed somewhat from each other as well as from the original4 ,together with a third #h-;cylinder engine these were begun right after the first of the year in #aijd1 shortly after the ,wrights' return from ,kitty ,hawk4 ,in planning the #h-;cylinder engine they were again only being forehanded1 but considerably so1 in providing more power for increased airplane performance beyond that which might possibly be obtained from the #d-;cylinder units4 ,progress with the #d-;cylinder engines was such that they fairly quickly concluded that the #h-;cylinder size would not be necessary1 and it was abandoned before completion4 ,exactly how far it was carried is not known4 ,the record contains only a single note covering the final scrapping of the parts that had been completed2 and apparently there were no drawings1 so that even its intended appearance is not known with any exactness4 ,it was probably a #ij deg4 ,v-type using their original basic cylinder construction4 ,the changes carried through in the two #d-;cylinder engines were not major4 ,the water-cooled area of the cylinder barrel was increased by nearly ten percent but the head remained only partially cooled4 ,in hindsight1 this consistent avoidance of complete cylinder-head cooling presents the one most inexplicable of the more important design decisions they made1 as it does not appear logical4 ,in the original engine1 where the factors of time and simplicity were of paramount importance1 this made sense1 but now they were contemplating considerably increased power requirements1 knowing the effect of temperature on both the cylinder and the weight of cylinder charge1 and knowing that valve failure was one of their most troublesome service problems4 ,nor does it seem that they could have been avoiding complete cylinder cooling through fear of the slightly increased complexity or the difficulty of keeping the water connections and joints tight1 for they had faced a much more severe problem in their first engine1 where their basic design required that three joints be kept tight with only two sets of threads1 and had rather easily mastered it2 so there must have been some much more major but not easily discernible factor which governed1 for they still continued to use the poorly cooled head1 even carrying it over to their next engine series4 ,very probably they did not know the effect on detonation of a high-temperature fuel-charge4 ,one of the new engines was intended for use in their future experimental flying and has become known as ,no4 #b4 ,it had a bore of #d-a_/h in41 incorporated an oil pump1 and at some time shortly after its construction a fuel pump was added4 ,the fuel pump was undoubtedly intended to provide a metering system responsive to engine speed and possibly also to eliminate the small inherent variation in flow of the original gravity system4 ,this engine incorporated a cylinder compression release device not on the original4 ,the exact reason or reasons for the application of the compression release have not been determined1 although the record shows it to have been utilized for several different purposes under different operating conditions4 ,whatever the motivation for its initial application1 it was apparently useful1 as it was retained in one form or another in subsequent engine models up to the last #f-;cylinder design4 ,essentially it was a manually controlled mechanism whereby all the exhaust valves could be held open as long as desired1 thus preventing any normal charge intake or compression in the cylinder4 ,its one certain and common use was to facilitate starting1 the open exhaust valves easing the task of turning the engine over by hand and making priming easy4 ,in flight1 its operation had the effect of completely shutting off the power4 ,the propellers would then windmill and keep the engine revolving4 ,one advantage stated for this method of operation was that when power was required and the control released1 the engine would be at fairly high speed1 so that full power was delivered immediately fuel reached the engine4 ,it is also reported to have been used both in making normal landings and in emergencies1 when an instant power shutdown was desired4 ,although it is not clear whether the fuel shutoff cock was intended to be manipulated when the compression release was used for any of these reasons1 over the many years of its availability1 undoubtedly at one time or another every conceivable combination of operating conditions of the various elements was tried4 ,because of the pumping power required with at least one valve open during every stroke1 the windmilling speed of the engine was probably less than with any other method of completely stopping power output1 but whether this difference was large enough to be noticeable1 or was even considered1 is doubtful4 ,since a simple ignition switch was all that was required to stop the power output1 regardless of whether a fuel-control valve or a spark-advance control was used1 it must be concluded that the primary function of the compression release was to facilitate starting1 and any other useful result was something obtained at no cost4 ,the compression release was later generally abandoned1 and until the advent of the mechanical starter during the #aibjs1 starting an engine by pulling the propeller through could be a difficult task4 ,with the ,wrights' demonstrated belief that frugality was a first principle of design1 it is hardly conceivable that they would have accepted for any other reason the complication of the compression-release mechanism if a simple ignition switch would have sufficed4 ,the compression-release mechanism was kept relatively simple1 considering what it was required to accomplish4 ,a small non-revolving shaft was located directly under the rocker arm rollers that actuated the exhaust valves4 ,four slidable stops were placed on this shaft1 each in the proper location1 so that at one extreme of their travel they would be directly underneath the rocker roller and at the other extreme completely in the clear4 ,they were positioned along the shaft by a spring forcing them in one direction against a shoulder integral with the shaft1 and the shaft was slidable in its bearings1 its position being determined by a manually controlled lever4 ,when the lever was moved in one direction the spring pressure then imposed on the stops would cause each of them to move under the corresponding rocker roller as the exhaust valve opened1 thus holding the exhaust valve in the open position4 ,when the shaft was moved in the other direction the collar on the shaft would mechanically move the stop from underneath the roller1 allowing the valve to return to normal operation4 ,illustration3 ,figure #h4--;,development engine ,no4 #c1 #aijd-aijf1 showing auxiliary exhaust port1 separate one-piece water-jacket block4 7,photo by author47 ,if the #aijc engine is the most significant of all that the ,wrights built and flew1 then certainly the ,no4 #b unit was the most useful1 for it was their sole power source during all their flying of #aijd and #aije and1 as they affirmed1 it was during this period that they perfected the art1 progressing from a short straightaway flight of #ei seconds to a flight controllable in all directions with the duration limited only by the fuel supply4 ,it is to be greatly regretted that no complete log or record was kept of this engine4 ,the ,wrights again exhibited their engineering mastery of a novel basic situation when1 starting out to make flight a practical thing1 they provided engine ,no4 #c to be used for experimental purposes4 ,in so doing they initiated a system which continues to be fundamental in the art of providing serviceable aircraft engines to this day--one that is expensive and time consuming1 but for which no substitute has yet been found4 ,their two objectives were3 improvement in performance and improvement in reliability1 and the engine was operated rather continuously from early #aijd until well into #aijf4 ,unfortunately1 again1 no complete record exists of the many changes made and the ideas tested1 although occasional notes are scattered through the diaries and notebooks4 ,in its present form--it is on exhibition at the ,engineers ,club in ,dayton1 ,ohio--the ,no4 #c engine embodies one feature which became standard construction on all the ,wright #d-;cylinder models4 ,this was the addition of a number of holes in a line part way around the circumference of the cylinder barrel so that they were uncovered by the piston at the end of its stroke toward the shaft1 thus becoming exhaust ports 7see ,figure #i74 ,this arrangement1 although not entirely novel1 was just beginning to come into use1 and in its original form the ports exhausted into a separate chamber1 which in turn was evacuated by means of a mechanically operated valve1 so that two exhaust valves were needed per cylinder4 ,elimination of this chamber and the valve arrangement is typical of the ,wrights' simplifying procedure1 and it would seem that they were among the very first to use this form4#ad ,footnote #ad3 ,rankin ,kennedy1 ,flying ,machines--,practice and ,design1 #aiji4 ,the primary purpose of the scheme was to reduce1 by this early release and consequent pressure and temperature drop1 the temperature of the exhaust gases passing the exhaust valve1 this valve being one of their main sources of mechanical trouble4 ,it is probable that with the automatic intake valves being used there was also a slight effect in the direction of increasing the inlet charge1 although with the small area of the ports and the short time of opening1 the amount of this was certainly minor4 ,with the original one-piece crankcase and cylinder jacket construction1 the incorporation of this auxiliary porting was not easy1 but this difficulty was overcome in the development engine by making different castings for the crankcase itself and for the cylinder jacket and separating them by several inches1 so that room was provided between the two for the ports4 ,this engine demonstrated the most power of any of the flat #ds1 eventually reaching an output of approximately #be hp1 which was even somewhat more than that developed by the slightly larger #d-a_/h-;in4-bore flight engine1 with which #ba hp was not exceeded4 ,indicative of the development that had taken place1 the performance of the ,no4 #c engine was twice the utilized output of the original engine of the same size1 an increase that was accomplished in a period of less than three years4 ,the ,wrights were only twice charged with having plagiarized others' work1 a somewhat unusual record in view of their successes1 and both times apparently entirely without foundation4 ,a statement was published that the #aijc flight engine was a reworked ,pope ,toledo automobile unit1 and it was repeated in an ,english lecture on the ,wright brothers4 ,this was adequately refuted by ,mc,farland but additionally1 it must be noted1 there was no ,pope ,toledo company or car when the ,wright engine was built4 ,this company1 an outgrowth of another which had previously manufactured one-and two-cylinder automobiles1 was formed1 or reformed1 and a ,pope license arrangement entered into during the year #aijc4 ,the other incident was connected with ,whitehead's activities and designs4 ,whitehead was an early experimenter in flying1 about the time of the ,wrights1 whose rather extraordinary claims of successful flight were published in the #aija-aijc period but received little attention until very much later4 ,his first engines were designed by a clever engineer1 ,anton ,pruckner1 who left at the end of #aija1 after which ,whitehead himself became solely responsible for them4 ,it was stated that the ,wrights visited the ,whitehead plant in ,bridgeport1 ,connecticut1 and that ,wilbur remained for several days1 spending his time in their machine shop4 ,this was not only categorically denied by ,orville ,wright when he heard of it but it is quite obvious that the #aijc or any other of the ,wright engine designs bears little resemblance to ,pruckner's work4 ,in fact1 its principal design features are just the opposite of ,pruckner's1 who utilized vertical cylinders1 the #b-stroke cycle1 and air-cooling1 which ,whitehead at some point changed to water-cooling4#ae ,footnote #ae3 ,considerable doubt surrounds ,whitehead's actual flight accomplishments1 but ,pruckner's engines were certainly used1 as several were sold to early pioneers1 including ,charles ,wittemann4 ,it is probable that the specific power output was not very great1 for the air-cooled art of this time was not very advanced and ,pruckner had a rather poor fin design4 ,but the change to water cooling eliminated this trouble1 and the engines were most simple1 should have been relatively quite light1 and with enough development could probably have been made into sufficiently satisfactory flying units for that period4 ,the ,four-,cylinder ,vertical ,demonstration ,engine and the ,first ,production ,engine ,in #aijf1 while still doing general development work on the flat experimental engine1 the ,wrights started two new engines1 and for the first time the brothers engaged in separate efforts4 ,one was a modification of the old ones by ,wilbur and the other1 an entirely new pattern by ,orville4 ,there is no record of any of the features of ,wilbur's project or what was done in connection with it4 ,two months after the experimental operation of the two designs began1 an entry in ,wilbur's diary gives some weight and performance figures for the #d x #d rebuilt horizontal1 and since ,orville's design was vertical the data clearly refer to ,wilbur's2 but since the output is given only in test-fan rpm it does not serve to indicate what had been accomplished and there is no further mention of it4 ,orville's design became the most used of any model they produced4 ,it saw them through the years from #aijf to #aiaa or #aiab1 which included the crucial ,european and ,united ,states ,army demonstrations1 and more engines of this model were manufactured than any of their others including their later #f-;cylinder4 ,although its ancestry is traceable to the original #aijc engine1 the design form1 particularly the external configuration1 was considerably altered4 ,along with many individual parts it retained the basic conception of four medium-size cylinders positioned in line and driving the propellers through two sprocket wheels4 ,from the general tenor of the record it would seem1 despite there being no specific indication1 that from this time on ,orville served as the leader in engine design1 although this occurred with no effect whatsoever on their finely balanced1 exactly equal partnership which endured until ,wilbur's death in #aiab4 ,the first major change from the #aijc design1 putting the engine in an upright instead of flat position1 was probably done primarily to provide for a minimum variation in the location of the center of gravity with and without a passenger4 ,whether or not it had any influence1 the vertical cylinder arrangement was becoming predominant in automobile powerplants by this time1 and the ,wright engines now began to resemble this prevailing form of the internal combustion engine--a basic form that1 in a wide variety of uses1 was to endure for a long time4 ,over the years1 the ,wrights seem to have made many changes in the engine3 the bore was varied at different times1 rod assembly methods were altered1 and rod ends were changed from bronze to steel4 ,chenoweth states that on later engines an oil-control ring was added on the bottom of the piston1 necessitating a considerable increase in the length of the cylinder barrel4 ,this arrangement could not have been considered successful1 as it apparently was applied to only a limited number of units and was not carried over to the later #f-;cylinder engine model4 ,there was much experimentation with cam shapes and most probably variations of these got into production4 ,with the crankcase1 they did not go all the way to the modern two-piece form but instead retained the one-piece construction4 ,assembly was effected through the ends and a detachable plate was provided on one side for access to the interior4 ,it is clear that they regarded this ability to get at the interior of the case without major disassembly as a valuable characteristic1 and later featured it in their sales literature4 ,they were apparently willing to accept the resultant weakening of the case and continued the construction through their last engine model4 ,the integrally cast cylinder water jackets were abandoned and the top of the crankcase was machined flat to provide a mounting deck for individual cylinders4 ,the use of aluminum alloy was continued1 and the interior of the case was provided with strengthening webs of considerable thickness1 together with supporting ribs4 ,the cam shaft was supported directly in the case4 ,the individual cylinder design was of extreme simplicity1 a single iron casting embodying everything except the water jacket4 ,the valves seated directly on the cast-iron cylinder head and the guides and ports were all contained in an integral boss on top of the head4 ,the exhaust valve location on the side of the engine opposite the pilot was a decided advantage over that of the #aijc design1 where the exhaust was toward the pilot4 ,a four-cornered flange near the bottom of the cylinder provided for fastening it to the crankcase1 and a threaded hole in the top of the head received a vertical eyebolt which served as the rocker-arm support4 ,the cylinder was machined all over2 two flanges1 one at the bottom and the other about two-thirds of the way down provided the surfaces against which the water jacket was shrunk4 ,the jacket was an aluminum casting incorporating the necessary bosses and double shrunk on the barrel2 that is1 the jacket itself was shrunk on the cylinder-barrel flanges and then steel rings were shrunk on the ends of the jacket over the flanges4 ,the jacket thickness was reduced by machining at the ends1 making a semigroove into which the steel shrink rings fitted4 ,these rings insured the maintenance of a tight joint despite the tendency of the aluminum jacket to expand away from the cast-iron barrel4 ,illustration3 ,figure #i4--d-;,cylinder vertical engine3 a1 magneto side2 b1 valve port side with intake manifold removed2 c1 flywheel end of engine at ,carillon ,park ,museum1 ,dayton1 ,ohio2 d1 magneto side with crankcase cover removed4 7,photos3 a1 ,smithsonian ,a-#cggc2 b1 d1 ,pratt ,whitney ,d-#aejjc1 #aejjg2 c1 by ,a4 ,l4 ,rockwell47 ,why the one-piece crankcase and cylinder jacket combination of the #aijc engine was abandoned for the individual cylinder construction can only be surmised4 ,the difference in weight was probably slight1 as the inherent weight advantage of the original crankcase casting was largely offset by the relatively heavy valve boxes1 and the difference in the total amount of machining required1 because of the separate valve boxes1 cages1 and attaching parts1 also was probably slight4 ,although the crankcase had shown itself to be structurally weak1 this could have been cared for by proper strengthening4 ,the #aijc design did have some fundamental disadvantages3 it required a fairly complex pattern and expensive casting1 plus some difficult machining1 part of which had to be very accurate in order to maintain both gas and water joints tight2 and the failure of any one cylinder that affected the jacket meant a complete crankcase replacement4 ,it seems probable that a change was initially made mandatory by their intention to utilize the ported exhaust feature1 the value of which they had proved in the experimental engine4 ,the separate one-piece water jacket construction they had arrived at in this engine was available1 but once the decision to change was made1 the individual cylinder with its shrunk-on jacket had much to commend it--simplicity1 cost1 ease of manufacture and assembly and attachment1 and serviceability4 ,the advantages of the auxiliary1 or ported1 exhaust were not obtained without cost1 however1 as the water jacket around the barrel could not very easily be extended below the ports4 ,thus1 even though the water was carried as high as possible on the upper end1 a large portion of the barrel was left uncooled1 and the lack of cooling at the lower end1 in conjunction with the uncooled portion of the head1 meant that only approximately half the entire cylinder surface was cooled directly4 ,the piston was generally the same as in the #aijc engine1 except that six radial ribs were added on the under side of the head1 tapering from maximum thickness at the center to nothing near the wall4 ,they were probably incorporated as an added path for heat to flow from the center of the piston toward the outside1 as their shape was not the best use of material for strength4 ,the piston pin was locked in the piston by the usual set screw1 but here no provision was made for the alternate practice of clamping the rod on the pin4 ,this piston-pin setscrew construction had become a standard arrangement in automobile practice4 ,the piston rings were the normal wide design of that time1 with what would now be considered a low unit pressure4 ,quite early in the life of this engine model the practice was initiated of incorporating shallow grooves in the surface of the more highly loaded thrust face of the piston below the piston pin to provide additional lubrication4 ,this development apparently proceeded haphazardly4 ,figure #aj;c shows three of the pistons from an engine of low serial number--the first of this model to be delivered to the ,u4,s4 ,navy--and it will be noted that one has no grooves1 another has one1 and the other has three4 ,the eventual standardized arrangement provided three of these grooves1 approximately #a_/af in4 wide1 extending halfway around the piston1 and1 although the depth was only a few thousandths of an inch1 the amount of oil carried in them was apparently sufficient to assist in the lubrication of the face1 as they were used in both the #d-;and #f-;cylinder engines4 ,each cylinder was fastened to the crankcase by four nuts on studs driven into the aluminum case4 ,valves and rocker arms were similar to those of the early engines1 the automatic inlet valve being retained4 ,the continued use of the two-piece valve is not notable1 even though one-piece forgings were available and in use at this time2 the automobile continued for many years to use this construction4 ,the camshaft was placed at the bottom of the engine1 inside the crankcase1 and the rocker arms were actuated by pushrods which were operated by hinged cam followers4 ,the pushrod was fastened in the rocker by a pin1 about which it operated1 through its upper end and was positioned near the bottom by a guide in the crankcase deck4 ,the lower end of the rod bore directly on the flat upper surface of the cam follower1 and valve clearance adjustment was obtained by grinding this end4 ,the camshaft and magneto were driven by the crankshaft through a three-member train of spur gears 7see ,figures #i1 #aj and #aa74 ,the built-up construction of the connecting rod was carried over from the first engine1 and in the beginning apparently the same materials were used1 except that the big end was babbited4 ,later the rod ends were changed from bronze to steel4 ,the big end incorporated a small pointed scupper on one side for lubrication1 as with the original1 and this was sometimes drilled to feed a groove which carried oil to the rod bearing1 but where the drilling was omitted1 the only function the scupper then could perform was1 as in the original engine1 to throw a small amount of oil on the cylinder wall4 ,the crankshaft and flywheel were similar in design to those on the #aijc engine1 except that the sharp corners at the top and bottom of the crank cheeks were machined off to save weight 7see ,figure #aj;f74 ,an oil pump and a fuel pump were mounted side by side in bosses cast on the valve side of the crankcase2 they were driven from the camshaft by worm gears and small shafts crossing the case4 ,illustration3 ,figure #aj4--d-;,cylinder vertical engine3 a1 cylinder assembly with valve mechanism parts2 b1 cylinder disassembled1 and parts2 c1 pistons and connecting rods2 d1 bottom side of piston2 e1 crankshaft1 flywheel and crankcase end closure2 f1 crankcase1 with compression release parts4 7,pratt ,whitney photos ,d-#adiif1 #aejja1 #adiih1 #adiid1 #adiii1 #adihi1 respectively47 ,the camshaft construction was considerably altered from the #aijc design4 ,although the reason is not entirely clear1 one indication suggests that breakage or distortion of the shaft may have been encountered3 whereas in the #aijc engine there had been no relationship between the location of the cams and the camshaft bearings1 in this engine the exhaust valves were carefully positioned so that all cams were located very close to the supporting bearings in the crankcase4 ,also1 the camshaft was solid1 although it would seem that the original hollow shaft construction could have provided equal stiffness with less weight4 ,the final decision was possibly determined by the practicality that there existed no standard tubing even approximating the size and wall thickness desired4 ,there still was no carburetor1 a gear pump metering the fuel in the same manner as on the #aijd-aije engine4 ,basically1 the intake charge was fed to the cylinders by a round gallery manifold running alongside the engine4 ,this was split internally by a baffle extending almost from end to end1 so that the fuel mixture entering the manifold on one side of the baffle was compelled to travel to the two ends before it could return to the inside cylinder1 this feature being a copy of their #aijc general intake arrangement4 ,apparently various shapes and positions of entrance pipes with which to spray the fuel into the manifold were used2 and the injection arrangement seems also to have been varied at different times4 ,the fuel pump was not necessarily always used1 as the engine in some of the illustrations did not incorporate one1 the fuel apparently being fed by gravity1 as on the original engine4 ,chenoweth describes an arrangement in which exhaust heat was applied to the inlet manifold to assist the fuel vaporization process1 but it is believed that this was one of the many changes made in the engine during its lifetime and not necessarily a standard feature4 ,a water circulation pump was provided1 driven directly by the crankshaft through a two-arm universal joint intended to care for any misalignment between the shaft and the pump4 ,the water was piped to a horizontal manifold running along the cylinders just below the intake manifold1 and a similar manifold on the other side of the engine collected it for delivery to the radiator4 ,it is a little difficult to understand why it was not introduced at the bottom of the water jackets4 ,the crankcase was a relatively strong and well proportioned structure with three heavy strengthening ribs running from side to side1 its only weakness being the one open side4 ,a sheet-iron sump was fastened to the bottom by screws and it would appear from its design1 method of attachment1 and location of the engine mounting pads that this was added some time after the crankcase had been designed2 but if so it was apparently retrofitted1 as engines with quite low serial numbers have this part4 ,the ignition was by high-tension magneto and spark plug and this decision to change from the make-and-break system was undoubtedly the correct one1 just as adoption of the other form originally was logical under the circumstances that existed then4 ,the high-tension system was simpler and had now collected more service experience4 ,the magneto was driven through the camshaft gear1 and a shelf1 or bracket1 cast as an integral part of the case1 was provided for mounting it4 ,the spark advance control was in the magneto and1 since spark timing was the only means of regulating the engine power and speed1 a wide range of adjustment was provided4 ,the engine had the controllable compression release which had been added to the ,no4 #b and ,no4 #c flat engines1 although mechanically it was considerably altered from the original design4 ,instead of the movable stop operating directly on the rocker roller to hold the exhaust valve open1 it was located underneath a collar on the pushrod4 ,this stop was hinged to the crankcase and actuated by a small rod running along and supported by the crankcase deck4 ,longitudinal movement of this rod in one direction would1 by spring pressure on each stop1 push them underneath the collars as the exhaust valves were successively opened4 ,a reverse movement of the rod would release them 7see ,figure #aj;f74 ,why they retained the method of manually operating the compression release1 which was the same as had been used in the #aijd-aije engine1 is not quite clear4 ,that is1 the mechanism was put into operation by pulling a wire running from the pilot to a lever actuating the cam which moved the control rod4 ,when normal valve operation was subsequently desired1 the pilot was compelled to reach with his hand and operate the lever manually1 whereas a second wire or push-pull mechanism would have obviated the necessity for both the awkward manual operation of the lever and the gear guard which was added to protect the pilot's hand1 the lever being located close to the camshaft gear4 ,the #d-;cylinder vertical engine was a considerable improvement over the previous designs4 ,they had obtained a power increase of about #dj percent1 with a weight decrease of #aj percent1 and now had an engine whose design was almost standard form for good internal combustion engines for years to come4 ,in fact1 had they split the crankcase at the crankshaft center line and operated the inlet valves mechanically1 they would have had what could be termed a truly modern design4 ,they needed more cylinder cooling1 both barrel and head1 particularly the latter1 and an opened-up induction system for maximum power output1 but this was not what they were yet striving for4 ,they had directly stated that they were much more interested in reliability than light weight4 ,this engine model was the only one of the ,wright designs to be licensed and produced abroad1 being manufactured in ,germany by the ,neue ,automobil-,gesellschaft and by ,bariquand et ,marre in ,france4 ,the latter was much more prominent and their engines were used in several early ,european airplanes4 ,illustration3 ,figure #aa4--d-;,cylinder vertical engine assembly1 ,bariquand et ,marre version4 7,drawing courtesy ,bristol ,siddeley ,engines1 ,ltd47 ,illustration3 ,,the ,,wright ,,brothers ,,aero ,,engine ,the ,french manufacturer1 without altering the basic design1 made a number of changes of detail which seem to have greatly annoyed ,wilbur ,wright1 although some of them could probably be listed as improvements1 based on several features of later standard design4 ,one consisted of an alteration in the position of the fuel and oil pumps1 the latter being lowered to the level of the sump4 ,the crankcase was drilled to provide forced-feed lubrication to the connecting rod big end and crankshaft main bearings4 ,strengthening ribs were added to the pistons running from the upper side of the pin bosses to the piston wall1 and the crankcase studs holding down the cylinders were replaced with bolts having their heads inside the case4 ,the hinged cam follower was omitted and the pushrod bore directly on the cam through a roller in its end4 ,the magneto was moved toward the rear of the engine a considerable distance and an ignition timing control device was introduced between it and its driving gear4 ,instead of the magneto being mounted directly on the special bracket integral with the crankcase1 a wooden board running from front to rear of the engine was used and this was fastened to the two engine support pads1 the magneto bracket being omitted entirely4 ,despite his criticism of the ,french motor and the quality of its manufacture1 ,wilbur was compelled to install one in his own exhibition airplane during his early ,french demonstrations at ,le ,mans after rod failure had broken his spare crankcase1 and much of his subsequent demonstration flying was made with the ,french product4 ,the ,eight-,cylinder ,racing ,engine ,by #aiji regular and special air meets and races were being held and various competitions for trophies conducted4 ,among these the ,gordon ,bennett ,cup ,race for many years was considered a major event4 ,for the #aiaj competition it was decided to enter a ,wright machine and1 since this was a race with speed the sole objective1 the available #d-;cylinder engine1 even in a version pushed to its maximum output1 was deemed too small4 ,they built for it a special #h-;cylinder unit in a #ij deg4,v form4 ,they were thus resorting to one of their #aijd concepts--modifying and enlarging a version known and proved in use--as the proper method of most quickly increasing output4 ,unfortunately again1 there are essentially no detailed drawings available1 so that the design cannot be studied4#af ,footnote #af3 ,a drawing of the camshaft is held by ,the ,franklin ,institute4 ,only one engine is historically recorded as having been built1 although in view of the ,wrights' record of foresight and preparation it is almost certain that at least one spare unit1 assembled or in parts1 was provided4 ,in any case1 the airplane--it was called the ,baby ,grand ,racer--and engine were wrecked just before the race1 and no physical parts were retained1 so that the sole descriptions come from external photographs1 memory1 and hearsay4 ,mc,farland thinks that possibly ,orville ,wright1 particularly1 was somewhat discomfited over the accident that eliminated the machine1 as he had previously flown it quite successfully at a speed substantially higher than that of the ultimate winner1 and he wanted to get it out of sight and mind as quickly as possible4 ,the ,air ,force ,museum at ,wright ,field1 ,dayton1 ,ohio1 has an incomplete set of drawings of a #ij deg4,v1 #h-;cylinder ,wright engine1 but it is quite obvious from the basic design and individual features1 as well as from at least one date on the drawings1 that this conception is of a considerably later vintage than that of the ,baby ,grand ,racer4 ,the racing engine was in essence a combination of two of the standard #ds on a redesigned crankcase utilizing as many of the #d-;cylinder engine parts as possible4 ,the rods were reported to have been placed side by side1 and the regular #d-;cylinder crankshaft1 with alterations to accommodate the rods1 was utilized4 ,a single cam operated all the exhaust valves4 ,it was compact and light1 its only fundamental disadvantage being the inherent unbalance of the #ij deg4,v-#h4 ,the arrangement provided a much higher powered unit in the cheapest and quickest manner1 and one that could be expected to operate satisfactorily with the least development4 ,the ,six-,cylinder ,vertical ,engines ,shortly after the construction of the #h-;cylinder engine the ,wrights were again faced with the ever-recurrent problem of providing a higher powered standard production engine for their airplanes1 which were now being produced in some numbers4 ,by this time1 #aiaa1 there had been a relatively tremendous growth in both flying and automotive use of the internal combustion engine and as a result many kinds and sizes had been produced and utilized1 so that numerous choices were presented to them4 ,but if they were both to make use of their past experience and retain the simplicity they had always striven for1 the more practical possibilities narrowed down to three3 they could increase the cylinder size in the #d-;cylinder combination1 or they could go either to #f or #h cylinders in the approximate size they had previously used4 ,illustration3 ,figure #ab4--,original #f-;cylinder engine3 a1 push-rod side2 b1 valve-port side2 c1 crankcase with sump removed4 7,photos3 ,smithsonian ,a-#cggc;,a1 #deeih2 ,pratt ,whitney ,d-#aejae1 respectively47 ,the #d-;in4 cylinder in combination with a #e-;in4 stroke would provide in four cylinders about the displacement they wanted4 ,strokes of #f in4 were not uncommon and cylinders of #f-;in4 bore had been very successfully utilized in high-output automobile racing engines many years before this1 so there was seemingly no reason to doubt that the #e-;in4 cylinder could be made to operate satisfactorily1 but it is not difficult to imagine the ,wrights' thoughts concerning the roughness of an engine with cylinders of this diameter4 ,the question of the grade of available fuel may possibly have entered into their decision to some extent1 but it seems far more likely that roughness1 their perennial concern1 was the predominant reason for not staying with the more simple #d-;cylinder form 7as we have seen1 roughness to them meant the effect of the cylinder explosion forces74 ,actually1 of course1 they never went larger than a #d-c_/h-;in4 cylinder bore1 and later aircraft engine experience would seem generally to confirm their judgment1 for with the piston engine it has always been much more difficult to make the larger bores operate satisfactorily at any given specific output4 ,while the #ij deg4,v1 #h-;cylinder arrangement would have enabled them to utilize a great number of the #d-;cylinder-engine parts1 it would have given them a somewhat larger engine than was their apparent desire1 unless they reduced the cylinder size4 ,and while they had had some limited experience in building and operating this kind of engine1 and twice had chosen it when seeking more power1 both of these choices were greatly influenced by the desire to obtain quickly an engine of higher power4 ,it is also possible that something in their experience with the ,v-#h moved them away from it2 the unbalanced shaking force inherent in the arrangement may well have become evident to them4 ,what probably also helped them to their final conclusion was the fundamental consideration that the ,v-#h provided two extra cylinders which were not really needed4 ,the eventual selection of the #f-;cylinder was a slight compromise4 ,in order to get the desired output the cylinder displacement was increased1 but this was done by lengthening the stroke--the first time this had been altered since the original design4 ,the increase 7from #d to #d-a_/b in47 was only #a_/b in41 and the bore1 the more important influence on fuel performance1 was kept the same4 ,overall1 the choice was quite logical4 ,they were utilizing the in-line construction upon which almost all of their now considerable experience had been based1 and the sizes of and requirements for parts also conformed to this experience4 ,they could1 in fact1 use many of the same parts4 ,the natural balance of the #f-;cylinder arrangement gave them a very smooth engine1 and had they stiffened the shaft and counter-weighted the cranks1 they would have produced the smoothest engine that could have been built at that time4 ,in the literature are two references to a ,wright #f-;cylinder engine constructed around the cylinders of the vertical #d4 ,one of these is in ,angle's ,airplane ,engine ,encyclopedia1 published in #aiba1 and the other is in ,aerosphere #aici1 published in #aidj4 ,the wording of the latter is essentially identical with that of the former2 it seems a reasonable conclusion that it is a copy4 ,although it is possible that such an engine was built at some time1 just as the #h-;cylinder racing engine was cobbled up out of parts from the #d-;cylinder vertical1 no other record1 no engines1 and no illustrations have been found4 ,it is thus quite certain that no significant quantity was ever manufactured or utilized4 ,the crankcase was considerably changed from that of the vertical #d1 and was now in two pieces1 with the split on the crankshaft center line4 ,however1 the shaft was not supported by the lower half of the case1 as eventually became standard practice1 but by bearing caps bolted to the ends of the upper case and1 in between1 to heavy ribs running across the upper case between the cylinders4 ,the lower half of the case thus received none of the dynamic or explosion loads1 and1 serving only to support the engine and to provide for its mounting1 was lightly ribbed4 ,in it were incorporated integral-boss standpipe oil drains which discharged into a bolted-on sump4 ,the upper half of the case was again left open on one side1 giving the desired access to the interior1 and1 additionally1 the design was altered to provide a method of camshaft assembly that was much simpler than that of the vertical #d 7see p4 #db74 ,the cylinder was also greatly altered from that of the vertical #d4 ,it was made in three parts1 a piece of seamless steel tubing being shrunk on a cast-iron barrel to form the water jacket1 with a cast-iron cylinder head shrunk on the upper end of the barrel4 ,this construction compelled the use of long studs running from the cylinder head to the case for fastening down the cylinder 7see ,figures #ab;a-c74 ,for the first time the cylinder heads were water-cooled1 cored passages being provided1 and more barrel surface was jacketed than previously1 although a considerable area at the bottom was still left uncooled1 obviously by direct intent1 as the ported exhaust arrangement was no longer employed4 ,also for the first time one-piece forged valves were used1 but just when these were incorporated is not certain and1 surprisingly1 they were applied to the inlet only1 the exhaust valve being continued in the previous two-piece screwed and riveted construction4 ,the reasoning behind this is not evident4 ,if a satisfactory two-piece exhaust valve had finally been developed it would be logical to carry it over to the new design2 but exhaust valves normally being much more troublesome1 it would seem that a good exhaust valve would make an even better inlet valve and1 in the quantities utilized1 the two-piece design should have been much cheaper4 ,in the original #f-;cylinder engine the inlet valves operated automatically as in all previous models1 but at the time of a later extensive redesign 7#aiac7 this was changed to mechanical actuation1 and the succeeding engines incorporated this feature4 ,all the valve-actuating mechanism was similar to that of the vertical #d1 and the engine had the usual compression-release mechanism1 the detail design being carried over directly from the #d-;cylinder4 ,design of the piston followed their previous practice1 with wide rings above the pin and shallow grooves below the pin on the thrust face1 and with the pin fastened in the piston by a set screw4 ,the piston had four ribs underneath the head 7see ,figure #ac;b7 radiating from the center and with the two over the pin bosses incorporating strengthening webs running down and joining the bosses4 ,the piston length was reduced by #a in41 thus giving a much less clumsy appearance and1 with other minor alterations1 a weight saving of #dj percent 7see ,figures #ac;b and c74 ,the rods were for the first time made of ,i-section forgings1 a major departure1 machined on the sides and hand finished at the ends1 with a babbit lining in the big end1 the piston pin bearing remaining steel on steel4 ,illustration3 ,figure #ac4--,original #f-;cylinder engine3 a1 cylinder assembly and valve parts2 b1 bottom side of piston2 c1 piston1 piston pin and connecting rod2 d1 valve mechanism2 e1 crankshaft and flywheel4 7,pratt ,whitney photos ,d-#aejab1 #aejag1 #aejac1 #aejah1 respectively47 ,at least two different general carburetion and induction systems were utilized1 possibly three4 ,one1 and most probably the original1 consisted of a duplicate of the injection pump of the #d-;cylinder fitted to a manifold which ran the length of the engine1 with three takeoffs1 each of which then split into two1 one for each cylinder4 ,of this arrangement they tried at least two variations involving changes in the location and method of injecting the fuel into the manifold2 and there seems to have been an intermediate manifold arrangement1 using fuel-pump injection at the middle of the straight side1 or gallery1 manifold1 which was fed additional air at both ends through short auxiliary inlet pipes4 ,this would indicate that with the original arrangement1 the end cylinders were receiving too rich a mixture1 when the fuel in the manifold was not properly vaporized4 ,although the exhaust was on the same side of the engine as the inlet system1 no attempt was made to heat the incoming charge at any point in its travel4 ,an entirely different system adopted at the time of the complete redesign in #aiac consisted of two float-feed ,zenith carburetors each feeding a conventional three-outlet manifold4 ,this carburetor was one of the first of the plain-tube type1 that is1 with the airflow through a straight venturi without any spring-loaded or auxiliary air valves1 and was the simplest that could be devised4 ,when properly fitted to the engine1 it gave a quite good approximation of the correct fuel and air mixture ratio over the speed-load running range1 although it is considerably more than doubtful that this was maintained at altitude1 as is stated in one of the best descriptions of the engine published at the time the carburetors were applied4 ,the compression ratio of this engine was lowered by almost #bj percent from that of the vertical #d4 ,this1 in combination with the low bore-to-stroke ratio1 the unheated charge1 and the later mechanically operated inlet valve1 indicates that the ,wrights were now attempting for the first time to secure from an engine something approaching the maximum output of which it was capable4 ,as the engine originally came out1 it continued to utilize only one spark plug in each cylinder4 ,the high-tension magneto had a wide range of spark advance adjustment1 which again provided the only control of the engine when equipped with the original fuel pump injection4 ,the location of the valves and pushrods was similar to that in the #d1 so that the cams were immediately adjacent to the camshaft bearings1 which were carried in the crankcase ends and in the heavy webs4 ,the camshaft was gear-driven and the cam shape was similar to that of the last #ds1 with a quite rapid opening and closing and a long dwell1 leaving the valve opening accelerations and seating velocities still quite high4 ,the crankshaft was a continuation of their basic design of rather light construction1 particularly in the webs4 ,the cheeks were even thinner 7by #a_/d in47 than those of the #d although the width was increased by #a_/h in4 7see ,figure #ac;e74 ,for the first time they went to a forging1 the rough contour type of the time1 and utilized a chrome-nickel alloy steel4 ,lubrication was by means of the usual gear pump1 and the piston and rod bearings continued to be splash-fed4 ,the rod big-end bearing carried a small sharp undrilled boss at the point where1 on the other engines1 had been located scuppers whose purpose was apparently still to throw lubricating oil on the cylinder wall carrying the more highly loaded side of the piston4 ,the rod big-end bearing was lubricated by a hole on the top of the big-end boss catching some of the crankcase splash1 which was then carried to the bearing by a groove4 ,when the #f-;cylinder engine was completely redesigned in #aiac this led to the introduction in late fall of that year of a new model called the #f-fj1 the #fj designating the rating in horsepower4 ,there is little in the ,wright records to show why such a radical revision was thought necessary1 but the general history of the period gives a rather clear indication4 ,the competition had caught up to the ,wrights in powerplants4 ,other engines were being installed in ,wright airplanes1 and ,navy log books show these other engines being used interchangeably with those of the ,wrights4 ,most of the descriptions of the new model published at the time it was introduced concentrate on the addition of the two carburetors and the mechanical operation of the inlet valves1 but these were only two of many major changes4 ,the cylinder was completely revised1 the intake being moved to the camshaft side of the engine from its position adjacent to the exhaust1 so that the two ports were now on opposite sides of the cylinder4 ,by proper positioning of the rocker-arm supports and choice of their length and angles1 all valves were made operable from a single camshaft4 ,the shrunk-on steel water jacket cylinder was retained1 but the water connections were repositioned so that the water entered at the bottom and came out at the top of the cylinder4 ,over the life of the #f-;cylinder engine several different valve types were used but the published specifications for the model #f-fj called for cast iron heads--the old two-piece construction4 ,the piston pins were case hardened and ground and the crankshaft pins and journals were heat treated and ground4 ,the fuel and oil pumps were removed from the side of the crankcase and a different ignition system was applied1 although still of the high-tension spark-plug type which by this time had become general practice on all so-called high-speed internal-combustion engines4 ,a second threaded spark-plug hole was provided in the cylinder head and despite its more common use for other purposes1 it is evident that the intention was to provide two-plug ignition4 ,it is doubtful that at the specific output of this engine any power difference would be found between one-and two-plug operation1 so that the objective was clearly to provide a reserve unit in case of plug failure4 ,however1 it was also used for the installation of a priming cock for starting and because of the prevalence of single-wire ignition systems on existing and illustrated engines1 it seems to have been used mostly in this manner1 even though dual-ignition systems later became an unvarying standard for aircraft engines4 ,viewed externally1 the only part of the engine that appears the same as the original #f is the small lower portion of the crankcase2 but what is more visually striking is the beauty of the new lines and extreme cleanness of the exterior design 7see ,figures #ad and #ae74 ,many of their individual parts had shown the beauty of the sparse design of pure utility but it was now in evidence in the whole4 ,despite the proven practical value of their other models1 this is the only one that can be called a good-looking engine1 instantly appealing to the aesthetic sense1 even though the vertical #d is not an ugly engine4 ,the appearance of their final effort1 in a field they were originally reluctant to enter and concerning which they always deprecated the results of their own work1 was a thing of which a technically trained professional engine designer could be proud4 ,the #f-fj was continued in production and development until it became the #f-gj1 and indications are that it eventually approached an output of #hj horsepower4 ,illustration3 ,figure #ad4--f-;,cylinder #f-fj and #f-gj engine1 right rear intake side4 7,pratt ,whitney photo47 ,illustration3 ,figure #ae4--f-;,cylinder #f-gj engine1 incorporating flexible flywheel drive1 exhaust side4 7,smithsonian photo ,a-#edcha47 ,minor ,design ,details and ,performance of the ,wright ,engines ,in the ,wright brothers' various models were many minor design items which altogether required a great deal of consideration1 but which did not materially affect overall engine performance4 ,the results generally could all be classed as good practice2 however1 one of these utilized in the #d-;cylinder vertical engine was rather unorthodox and consisted of offsetting the cylinders with relation to the crankshaft4 ,this arrangement1 which can be seen in the drawing 7,figure #aa7 was apparently an attempt to reduce the maximum side load on the piston during the power stroke1 but since the peak gas loading usually occurs at about #aj to #ae percent of the power stroke1 this probably did not have much effect1 and it was not carried over to the #f-;cylinder design4 ,all engine bearings were of the plain sleeve type and1 except for the bronze and steel bearings in the connecting rod1 were of babbit4 ,the advantages of babbit for bearings were discovered very early in the development of the mechanical arts1 and apparently the ,wrights never encountered a bearing loading sufficiently high to cause a structural breakdown in this relatively weak material4 ,valve openings show no variation through the successive production engines1 although the ,wrights most probably experimented with different amounts4 ,the #aijc engine and the vertical #d-;and #f-;cylinder all had lifts of #e_/af in41 but the valve-seat angles varied somewhat2 the records show included angles of #aaj deg4 to #ij deg4--not a large difference4 ,the valve-operating mechanism was the same from the first vertical #d onward4 ,the high side thrust caused by the cam shape required for the very rapid valve opening they chose was1 no doubt1 the reason for the use of the hinged cam follower1 and since the same general cam design was used in their last engine1 the #f-;cylinder1 the same method of operation which had apparently proved very serviceable was continued4 ,how satisfactory was the considerably simpler substitute used in the ,bariquand et ,marre version of the #d-;cylinder engine is not known4 ,possibly it was one of the alterations in the ,wrights' design that ,wilbur ,wright objected to1 although in principle it more closely conforms to the later fairly standard combination valve tappet and roller construction3 ,the available drawings do indicate1 however1 that the cam of the ,bariquand et ,marre engine was also altered to give a considerably less abrupt valve opening than the ,wright design1 so that there was less side thrust4 ,for the ,wright #f-;cylinder engine their #d-;cylinder cam was slightly altered to provide a rounding off near the top of the lobe1 thus providing some reduction in the velocity before maximum opening was reached4 ,all their cam designs indicate a somewhat greater fear of the effect of seating velocities than of opening accelerations4 ,since the range of cylinder diameters utilized did not vary greatly1 the valve sizes were correspondingly fairly uniform4 ,the diameter of the valves for the original #d-;in4-bore cylinder was #b in41 while that for the #d-c_/h-;in4 bore used in the #f-;cylinder engine was actually slightly smaller1 #a-g_/h in4 ,possibly the ,wrights clung too long to the automatic inlet valve1 although it did serve them well2 but possibly1 as has been previously noted1 there were valid reasons for continuing its use despite the inherently low volumetric efficiency this entailed4 ,the inherent weakness in the joints of the three-piece connecting rod has been pointed out1 but aside from this1 the design was excellent1 for all the materials and manufacturing methods required were readily available1 and structurally it was very sound4 ,tubular rods were still in use in aircraft engines in the #aibjs4 ,the ,wrights had a surprisingly thorough grasp of the metallurgy of the time1 and their choice of materials could hardly have been improved upon4 ,generally they relied upon the more simple and commonly used metals even though more sophisticated and technically better alloys and combinations were available4#ag ,case hardening was in widespread use in this period but their only utilization of it was in some parts of the drive chains purchased completely assembled and in the piston pins of their last engine4 ,the treatment of the crankshafts of all their engines except the final #f-;cylinder was typical of their uncomplicated procedure3 the particular material was chosen on the basis of many years of experience with it1 hardening was a very simple process1 and the expedient of carrying this to a point just below the non-machinable range gave them bearing surfaces that were sufficiently hard1 yet at the same time it eliminated the possibility--present in a heat-treating operation--of warping the finished piece4 ,footnote #ag3 ,baker states that the first crankshaft was made from a slab of armor plate and if this is correct the alloy was a rather complex one of approximately 4#cj-4ce carbon1 4#cj-4hj manganese1 4#aj silicon1 4#jd phosphorus1 4#jb sulphur1 #c4be-c4ej nickel1 #j4jj-a4ij chromium2 however1 all the rest of the evidence1 including ,orville ,wright's statement to ,dr4 ,gough1 would seem to show that it was made of what was called tool steel 7approximately #a4j carbon74 ,in the entire #aijc engine only five basic materials--excepting those in the purchased magneto and the platinum facing on the ignition-system firing points--were used3 steel1 cast iron1 aluminum1 phosphor bronze1 and babbit4 ,the steels were all plain carbon types with the exception of the sheet manifold1 which contained manganese1 and no doubt this was used because the sheet available came in a standard alloy of the time4 ,overall1 the ,wright engines performed well1 and in every case met or exceeded the existing requirements4 ,even though aircraft engines then were simpler than they became later and the design-development time much shorter1 their performance stands as remarkable4 ,as a result1 the ,wrights never lacked for a suitable powerplant despite the rapid growth in airplane size and performance1 and the continual demand for increased power and endurance4 ,few service records dating from before #aiaa1 when the military services started keeping log books1 have been found4 ,some of those for the period toward the end of their active era have been preserved1 but for that momentous period spanning the first few years when the ,wrights had the only engines in actual continuous flight operation1 there seems to be essentially nothing--perhaps because there were no standard development methods or routines to follow1 no requirements to be met with respect to pre-flight demonstrations or the keeping of service records4 ,beginning in #aijd1 however1 and continuing as long as they were actively in business1 they apparently had in progress work on one or more developmental or experimental engines4 ,this policy1 in combination with the basic simplicity of design of these engines1 accounted in large measure for their ability to conduct both demonstrations and routine flying essentially whenever they chose4 ,time between engine overhauls obviously varied4 ,in mid #aijf an engine was rebuilt after running about #ab hours4 ,this is comparatively quite a good performance1 particularly when it is remembered that essentially all the running was at full power output4 ,it was considerably after #aibj before the ,liberty engine was redesigned and developed to the stage where it was capable of operating #ajj hours between overhauls1 even though it was being used at cruising1 or less than full1 power for most of this time4 ,the ,wrights of course met with troubles and failures1 but it is difficult1 from the limited information available1 to evaluate these and judge their relative severity4 ,lubrication seems to have been a rather constant problem1 particularly in the early years4 ,although some bearing lubrication troubles were encountered from time to time1 this was not of major proportions1 and they never had to resort to force-feed lubrication of the main or rod big-end bearings4 ,the piston and cylinder-barrel bearing surfaces seem to have given them the most trouble by far1 and examination of almost any used early ,wright engine will usually show one or more pistons with evidence of scuffing in varying degrees1 and this is also apparent in the photographs in the record4 ,this is a little difficult to understand inasmuch as most of the time they had the very favorable operating condition of cast iron on cast iron4 ,many references to piston seizure or incipient seizure1 indicated by a loss of power1 occur1 and this trouble may have been aggravated by the very small piston clearances utilized4 ,why these small clearances were continued is also not readily explainable1 except that with no combination of true oil-scraper rings1 which was the basic reason why the final form of aviation piston engine was able to reach its unbelievably low oil consumptions1 their large and rather weak compression rings were probably not doing an adequate job of oil control1 and they were attempting to overcome this with a quite tight piston fit4#ah ,in any event1 they did encounter scuffing or seizing pistons and cylinder over-oiling at the same time4 ,as late as #d ,may #aijh in the ,wright ,papers there appears the notation3 ,the only important change has been in the oiling4 ,the engine now feeds entirely by splash4444 ,footnote #ah3 ,their intended piston ring tension is not known4 ,measurements of samples from the #d-;and #f-;cylinder vertical engines vary greatly1 ranging from less than #a_/b lb per sq in4 to almost #a-a_/d lb4 ,the validity of these data is very questionable as they apply to parts with unknown length of service and amount of wear4 ,it seems quite certain1 however1 that even when new the unit tension figure with their wide rings was only a small fraction of that of the modern aircraft piston engine4 ,their troubles tended to concentrate in the cylinder-piston combination1 as has been true of almost all piston engines4 ,references to broken cylinders are frequent4 ,these were quite obviously cylinder barrels1 as replacement was common1 and this again is not readily explainable4 ,the material itself1 according to ,orville ,wright1 had a very high tensile strength1 and in the #aijc engine more than ample material was provided1 as the barrel all the way down to well below the attachment to the case was #g_/cb in4 thick4 ,the exact location of the point of failure was never recorded1 but in its design are many square corners serving as points of stress concentration4 ,also1 of course1 no method was then available for determining a faulty casting1 except by visual observation of imperfections on the surface1 and this was probably the more common cause4 ,it is interesting1 however1 that the engine finally assembled in #aibh for installation in the #aijc airplane sent to ,england has a cracked cylinder barrel1 the crack originating at a sharp corner in the slot provided at the bottom of the barrel for screwing it in place4 ,valve failures were also a continuing problem1 and ,chenoweth reports that a large proportion of the operating time of the #aijd-aijf development engine was concentrated on attempts to remedy this trouble4 ,none of their cams1 including those of the #f-;cylinder engine1 evidence any attempt to effect a major reduction in seating velocities4 ,united ,states ,navy log books of #aiab and #aiac record many instances of inlet valves broken at the weld1 indicating that some of the earlier #f-;cylinder engines were fitted with valves of welded construction4 ,for the engineer particularly1 the fascination of the ,wrights' engine story lies in its delineation of the essentially perfect engineering achievement by the classic definition of engineering--to utilize the available art and science to accomplish the desired end with a minimum expenditure of time1 energy1 and material4 ,light weight and operability were the guiding considerations2 these could be obtained only through constant striving for the utmost simplicity4 ,always modest1 the ,wrights seem to have been even more so in connection with their engine accomplishments4 ,although the analogy is somewhat inexact1 the situation is reminiscent of the truism often heard in the aircraft propulsion business--few people know the name of ,paul ,revere's horse4 ,yet1 as ,mc,farland has pointed out1 ,the engine was in fact far from their meanest achievement4 ,with hardly any experience in this field and only a meagerly equipped machine shop1 they designed and assembled an internal combustion engine that exceeded the specifications they had laid down as necessary for flight and had it operating in a period of about two months elapsed time4 ,the basic form they evolved during this unequalled performance carried them through two years of such successful evolutionary flight development that their flying progressed from a hop to mastery of the art4 ,and the overall record of their powerplants shows them to have been remarkably reliable in view of the state of the internal combustion engine at that time4 ,appendix ,characteristics of the ,wright ,flight ,engines ---------------------------------------- --------------------------------- #aijc #aijd-aije #aijh-aiaa #aiaa-aiae ,first flight ,experimental ,demonstrations service enginea flights and service ---------------------------------------- --------------------------------- ,cyl4_/,form #d_/;flat #d_/;flat #d_/vertical #f_/vertical ,bore and stroke 7in47 #dx#d #d-a_/hx#d #d-c_/hx#d #d-c_/hx#d-a_/b ,displacement 7cu4 in47 #bja #bad #bdj #djf ,horsepower #h4be-af #ae-ba #bh-db #ej-ge ,,rpm #fgj-abjj #ajgj-acfj #acbe-aejj #adjj-aefj ,,mep #di-ec #eb-eg #gj-hg #gj-id ,weight 7lb7 #adj-ahj #afj-agj #afj-ahj #bfe-cjj ---------------------------------------- --------------------------------- ,footnote a3 ,concurrently with the ,wrights' first engine work1 ,manly was developing the engine for the ,langley ,aerodrome1 and a comparison of the ,wrights' engine development with that of ,manly is immediately suggested1 but no meaningful comparison of the two efforts can be drawn4 ,beyond the objective of producing a power unit to accomplish human flight and the fact that all three individuals were superb mechanics1 the two efforts had nothing in common4 ,the ,wrights' goal was an operable and reasonably lightweight unit to be obtained quickly and cheaply4 ,manly's task was to obtain what was for the time an inordinately light engine and1 although the originally specified power was considerably greater than that of the ,wrights1 it was still reasonable even though ,manly himself apparently increased it on the assumption that ,langley would need more power than he thought4 ,the cost and time required were very much greater than the ,wrights expended4 ,he ended up with an engine of extraordinary performance for its time1 containing many features utilized in much later important service engines4 ,his weight per horsepower was not improved upon for many years4 ,the ,wrights' engine proved its practicability in actual service4 ,the ,manly engine never had this opportunity but its successful ground tests indicated an equal potential in this respect4 ,a description of the ,langley-,manly engine and the history of its development is contained in ,smithsonian ,annals of ,flight number #f1 ,langley's ,aero ,engine of #aijc1 by ,robert ,b4 ,meyer 7xi#aic pages1 #dd figures2 ,smithsonian ,institution ,press1 #aiga7 ,it is not possible to state the exact quantities of each engine that the ,wrights produced up to the time that their factory ceased operation in #aiae4 ,chenoweth gives an estimate1 based on the recollection of their test foreman1 of #ajj vertical #ds and #ej #fs4 ,my estimate 7see page #b7 places the total of all engines at close to #bjj4 ,original ,wright-built engines of all four of these basic designs are in existence1 although they are rather widely scattered4 ,the ,smithsonian's ,national ,air and ,space ,museum has examples of them all1 including1 of course1 the unique first-flight engine4 ,their condition varies1 but many are operable1 or could easily be made so4 ,among the best are the first-flight engine and the last vertical #f1 at the ,smithsonian1 the first vertical #f1 at the ,united ,states ,air ,force ,museum1 and the vertical #d1 at the ,carillon ,park ,museum4 ,the ,wrights were constantly experimenting and altering1 and this in connection with the lack of complete records makes it almost impossible to state with any certainty specific performances of individual engines at given times4 ,weights sometimes included accessories and at others did not4 ,often they were of the complete powerplant unit1 including radiator and water and fuel1 with no clarification4 ,in the table1 performance is given in ranges which are thought to be the most representative of those actually utilized4 ,occasionally performances were attained even beyond the ranges given4 ,for example1 the #dx#d-;in4 flat development engine eventually demonstrated #be hp at an ,,mep of approximately #fe psi4 ,one important figure--the horsepower actually utilized during the first flight--is quite accurately known4 ,in #aijd the #aijd-aije flight engine1 after having been calibrated by their prony-brake test-fan method1 was used to turn the #aijc flight propellers1 and ,orville ,wright calculated this power to be #ab4je bhp by comparing the calibrated engine results with those obtained with the flight engine at ,kitty ,hawk when tested under similar conditions4 ,however1 since the tests were conducted in still air with the engine stationary1 this did not exactly represent the flight condition4 ,no doubt the rotational speed of the engine and propellers increased somewhat with the forward velocity of the airplane so that unless the power-rpm curve of the engine was flat1 the actual horsepower utilized was probably a small amount greater than ,orville's figures4 ,the lowest power figure shown for this engine is that of its first operation4 ,no fuel consumption figures are given1 primarily because no comprehensive data have been found4 ,this is most probably because in the early flight years1 when the ,wrights were so meticulously measuring and recording technical information on the important factors affecting their work1 the flights were of such short duration that fuel economy was of very minor importance4 ,after success had been achieved1 they ceased to keep detailed records on very much except their first interest--the flying machine itself--and when the time of longer flights arrived1 the fuel consumption that resulted from their best engine design efforts was simply accepted4 ,the range obtained became mostly a matter of aerodynamic design and weight carried4 ,orville ,wright quotes an early figure of brake thermal efficiency for the #aijc engine that gives a specific fuel consumption of 4#ehj lb of fuel per bhp_/hr based on an estimate of the heating value of the fuel they had4 ,this seems low1 considering the compression ratio and probable leakage past their rather weak piston rings1 but it is possible4 ,in an undated entry1 presumably in #aije1 ,orville ,wright's notebook covered fuel consumption in terms of miles of flight2 one of the stated assumptions in the entry is1 ,one horsepower consumes 4#fj pounds per horsepower hour--still quite good for the existing conditions4 ,published figures for the #f-fj engine centered around 4#fg lb_/hp hr for combined fuel and oil consumption4 ,the ,wright ,shop ,engine ,despite the fact that the ,wright shop engine was not a flight unit1 it is interesting both because it was a well designed stationary powerplant with several exceedingly ingenious features1 and because its complete success was doubtless a major factor in the ,wrights' decision to design and build their own first flight engine4 ,put in service in their small shop in the fall of #aija1 it was utilized in the construction of engine and airframe parts during the vital years from #aijb through #aijh and1 in addition1 it provided the sole means of determining the power output of all of their early flight engines4 ,by means of a prony brake1 its power output was carefully measured and from this the amount of power required for it to turn certain fans or test clubs was determined4 ,these were then fitted to the flight engines and the power developed calculated from the speed at which the engines under test would turn the calibrated clubs4 ,although a somewhat complex method of using power per explosion of the shop engine was made necessary by the basic governor control of the engine1 the final figures calculated by means of the propeller cube law seem to have been surprisingly accurate4#ai ,restored under the personal direction of ,charles ,taylor1 it is in the ,henry ,ford ,museum in ,dearborn1 ,michigan1 together with the shop machinery it operated4 ,footnote #ai3 ,the ,papers of ,wilbur and ,orville ,wright1 volume #b1 ,appendix4 ,the engine was a single cylinder1 #d-stroke-cycle hot-tube ignition type4 ,the cylinder1 of cast iron quite finely and completely finned for its day1 was air-cooled1 or rather1 air-radiated1 as there was no forced circulation of air over it1 the atmosphere surrounding the engine simply soaking up the dissipated heat4 ,although this was possibly a desirable adjunct in winter1 inside the small shop in ,dayton1 the temperature there in summer must have been quite high at times4 ,the operating fuel was city illuminating gas1 which was also utilized to heat1 by means of a burner1 the ignition tube4 ,this part was of copper1 with one completely closed end positioned directly in the burner flame2 the other end was open and connected the interior of the tube to the combustion chamber4 ,the inlet valve was of the usual automatic type while the exhaust valve was mechanically operated4 ,the fuel gas flow was controlled by a separate valve mechanically connected to the inlet valve so that the opening of the inlet valve also opened the gas valve1 and gas and air were carried into the cylinder together4 ,illustration3 ,figure #af4--,shop engine1 #aija1 showing governor and exhaust valve cam4 7,photo courtesy ,r4 ,v4 ,kerley47 ,the engine was of normal stationary powerplant design1 having a heavy base and two heavy flywheels1 one on each side of the crank4 ,these were necessary to ensure reasonably uniform rotational speed1 as1 in addition to having only one cylinder1 the governing was of the hit-and-miss type4 ,it had a #fx#g-;in4 bore and stroke and would develop slightly over #c hp at what was apparently its normal operating speed of #ddg rpm1 which gives an ,,mep of #bg psi4 ,the engine is noteworthy not only for its very successful operation but also because it incorporated two quite ingenious features4 ,one was the speed-governing mechanism4 ,as in the usual hit-and-miss operation1 the engine speed was maintained at a constant value1 the output then being determined by the number of power strokes necessary to accomplish this4 ,the governor proper was a cylindrical weight free to slide along its axis on a shaft fastened longitudinally to a spoke of one of the flywheels4 ,a spring forced it toward the center of the wheel1 while centrifugal force pulled it toward the rim against the spring pressure4 ,after each opening of the valve the exhaust-valve actuating lever was automatically locked in the valve-open position by a spring-loaded pawl1 or catch4 ,the lever had attached to it a small side extension1 or bar1 which1 when properly forced1 would release the catch and free the actuating lever4 ,this bar was so positioned as to be contacted by the governor weight when the engine speed was of the desired value or lower1 thus maintaining regular valve operation2 but an excessive speed would move the governor weight toward the rim and the exhaust valve would then be held in the open position during the inlet stroke1 so no cylinder charge would be ingested4 ,since the ignition was not mechanically timed1 the firing of the charge was dependent only on the compression of the inlet charge in the cylinder1 so it made no difference whether the governor caused the engine to cease firing for an odd or even number of revolutions1 even though the engine was operating on a #d-stroke cycle at all times4 ,illustration3 ,figure #ag4--,shop engine1 #aija1 showing operation of exhaust valve cam4 7,pratt ,whitney drawing47 ,the exhaust valve operating cam was even more ingenious4 ,to obtain operation on a #d-stroke cycle and still avoid the addition of a half-speed camshaft1 a cam traveling at crankshaft speed was made to operate the exhaust valve every other revolution 7see ,figure #ag74 ,it consisted of a very slim quarter-moon outline fastened to a disc on the crankshaft by a single bearing bolt through its middle which served as the pivot about which it moved4 ,just enough clearance was provided between the inside of the quarter-moon and the crankshaft to allow the passage of the cam-follower roller4 ,the quarter-moon1 statically balanced and free to move about its pivot1 basically had two positions4 ,in one the leading edge was touching the shaft 7,figure #ag;b71 so that when the cam came to the cam follower1 the follower was forced to go over the top of the cam1 thus opening the exhaust valve4 ,when the cam pivot point had passed the roller1 the pressure of the exhaust valve spring forced the following edge of the cam into contact with the shaft and this movement1 which separated the leading edge of the cam from the shaft1 provided sufficient space between it and the shaft for the roller to enter 7,figure #ag;c74 ,thus1 when the leading edge of the cam next reached the roller1 the roller1 being held against the crankshaft by the valve spring pressure 7,figure #ag;d71 entered the space between the cam and the shaft and there was no actuation of the valve4 ,in exiting from the space1 it raised the trailing edge of the cam1 forcing the leading edge against the shaft 7,figure #ag;a7 so that at the next meeting a normal valve opening would take place4 ,the cam was maintained by friction alone in the position in which it was set by the roller1 but since the amount of this could be adjusted to any value1 it could be easily maintained sufficient to offset the small centrifugal force tending to put the cam in a neutral position4#bj ,footnote #bj3 ,the ,wrights apparently never applied for an engine patent of any kind4 ,this no doubt grew out of their attitude of regarding the engine as an accessory and deprecating their work in this field4 ,a reasonably complete patent search indicates that this particular cam device has never been patented1 although a much more complex arrangement accomplishing the same purpose was patented in #aijj1 and a patent application on a cam-actuating mechanism substantially identical to that of the ,wrights and intended for use in a golf practice apparatus is pending at the present time4 ,bibliography ,,angle1 ,,glenn ,d4 ,wright4 ,pages #eba-ebc in ,airplane ,engine ,encyclopedia1 an ,alphabetically ,arranged ,compilation of ,all ,available ,data on the ,world's ,airplane ,engines4 ,dayton1 ,ohio3 ,the ,otterbein ,press1 #aiba4 ,,baker1 ,,max ,p4 ,the ,wright ,brothers as ,aeronautical ,engineers4 ,annual ,report of 444 the ,smithsonian ,institution 444 for the ,year ,ended ,june #cj1 #aiej1 pages #bji-bbc1 #d figures1 #i plates4 ,,beaumount1 ,,william ,,worby4 ,motor ,vehicles and ,motors3 ,their ,design1 ,construction1 and ,working by ,steam1 ,oil1 and ,electricity4 #b volumes4 ,philadelphia3 ,j4 ,b4 ,lippincott1 #aija-aijb4 ,,chenoweth1 ,,opie4 ,power ,plants ,built by the ,wright ,brothers4 ,s4,a4,e4 ,quarterly ,transactions 7,january #aiea71 #e3ad-ag4 ,,forest1 ,,fernand4 ,les ,bateaux automobiles4 ,paris3 ,h4 ,dunod et ,e4 ,pinat1 ,editeurs1 #aijf4 ,,gough1 ,,dr4 ,h4 ,j4 ,materials of ,aircraft ,construction4 ,journal of the ,royal ,aeronautical ,society 7,november #aich71 #db3ibb-ajcb4 ,illustrated4 ,,kelly1 ,,fred ,c4 ,miracle at ,kitty ,hawk2 the ,letters of ,wilbur and ,orville ,wright4 ,new ,york3 ,farrar1 ,straus and ,young1 #aiea4 ---------- ,the ,wright ,brothers1 a ,biography ,authorized by ,orville ,wright4 ,new ,york3 ,harcourt1 ,brace ,co41 #aidc4 ,,kennedy1 ,,rankin4 ,flying ,machines3 ,practice and ,design4 ,their ,principles1 ,construction and ,working4 #aeh pages4 ,london3 ,technical ,publishing ,co41 ,ltd41 #aiji4 ,,lawrance1 ,,charles ,l4 ,the ,development of the ,aeroplane ,engine in the ,united ,states4 ,pages #dji-dbi in ,international ,civil ,aeronautics ,conference1 ,washington1 ,d4,c41 #ab-ad ,december #aibh1 ,papers ,submitted by the ,delegates for ,consideration by the ,conference4 ,washington3 ,government ,printing ,office1 #aibh4 ,,mcfarland1 ,,marvin ,w4 ,the ,papers of ,wilbur and ,orville ,wright4 #b volumes4 ,new ,york3 ,mc,graw ,hill ,book ,co41 #aiec4 ,,renstrom1 ,,arthur ,g4 ,wilbur and ,orville ,wright3 ,a ,bibliography ,commemorating the ,hundredth ,anniversary of the ,birth of ,wilbur ,wright1 ,april #af1 #ahfg4 ,washington1 ,d4,c43 ,the ,library of ,congress ,government ,printing ,office1 #aifh4 ,contains #bjee entries4 ,the #f-;,cylinder #fj-;,horsepower ,wright ,motor4 ,aeronautics 7,november #aiac71 #ac7e73agg-agi4 ,wright ,brothers4 ,pages #hbi-hcj in ,aerosphere #aici1 ,including ,world's ,aircraft ,engines1 with ,aircraft ,directory1 ,glenn ,d4 ,angle1 editor4 ,new ,york3 ,aircraft ,publishers1 #aidj4 ,index ,angle1 ,glenn ,d41 #ea ,baby ,grand ,racer1 #dg ,baker1 ,max ,p4 #a1 #aj1 #bf1 #bh ,bariquand et ,marre1 #dc1 #dd-de1 #eg-eh ,beaumount1 ,william ,worby1 #i1 #be ,bristol ,siddeley ,engines1 ,ltd41 #dd-de ,carillon ,park ,museum1 ,dayton1 ,ohio1 ix1 #en1 #g1 #cg ,chanute1 ,octave1 #bh ,chenoweth1 ,opie1 ix1 #bb1 #ce1 #db1 #fc ,christman1 ,louis ,p41 ix1 #g1 #h1 #bh ,cole1 ,gilmoure ,n41 ix ,clarke1 ,j4 ,h41 #ah ,daimler-,benz ,a4 ,g41 ix1 #aj1 #ac ,engineers ,club1 ,dayton1 ,ohio1 ix1 #cb ,ford1 ,henry1 #h ,ford1 ,henry1 ,museum1 ,dearborn1 ,michigan1 #h1 #fd ,forest1 ,fernand1 #aa ,franklin ,institute1 ,philadelphia1 ,pennsylvania1 ix1 #dg ,gough1 ,dr4 ,h4 ,j41 #ehn ,howell ,cheney ,technical ,school1 ,manchester1 ,connecticut1 x1 #ad1 #ae ,kelly1 ,fred ,c1 #dn ,kerley1 ,r4 ,v41 ix1 #fe ,kitty ,hawk ,flyer1 ii1 #c ,langley ,samuel ,p4 ,aerodrome1 #i1 #fb ,loening1 ,grover ,c1 #acn ,manly1 ,charles ,l41 #i1 #fb ,maxim1 ,sir ,hiram ,stevens1 #c ,mc,farland1 ,marvin ,w41 #a1 #cc1 #dg1 #fa ,miller-,knoblock ,manufacturing ,co41 ,south ,bend1 ,indiana1 #bf ,national ,park ,service1 ,cape ,hatteras ,national ,seashore1 ii1 ix ,neue ,automobil-,gesellschaft1 #dc ,porter1 ,l4 ,morgan1 ix ,pratt ,whitney ,aircraft ,corp41 v1 x1 #cg1 #dj-da1 #di1 #eb1 #ec1 #fg ,pruckner1 ,anton1 #cc ,rockwell1 ,a4 ,l41 ix1 #cg ,santos-,dumont1 ,alberto1 #aa ,science ,museum1 ,london1 x1 #e1 #f1 #g1 #h1 #aa1 #ba1 #bc1 #bf ,taylor1 ,charles ,e41 #e1 #fd ,united ,aircraft ,corp41 v1 x ,western ,society of ,engineers1 #b ,whitehead1 ,gustave1 #cc ,wittemann1 ,charles1 #ccn ,wright1 ,bishop ,milton 7father71 #bh ,wright1 ,katherine 7sister71 #d ,zenith carburetor1 #eb 99,u4,s4 ,,government ,,printing ,,office3 #aiga--cig-gfd ,publication in ,smithsonian ,annals of ,flight ,manuscript for serial publications are accepted by the ,smithsonian ,institution ,press1 subject to substantive review1 only through departments of the various ,smithsonian museums4 ,non-,smithsonian authors should address inquiries to the appropriate department4 ,if submission is invited1 the following format requirements of the ,press will govern the preparation of copy4 ,copy must be typewritten1 double-spaced1 on one side of standard white bond paper1 with #a-a_/b top and left margins1 submitted in ribbon copy with a carbon or duplicate1 and accompanied by the original artwork4 ,duplicate copies of all material1 including illustrations1 should be retained by the author4 ,there may be several paragraphs to a page1 but each page should begin with a new paragraph4 ,number all pages consecutively1 including title page1 abstract1 text1 literature cited1 legends1 and tables4 ,a manuscript should consist of at least thirty pages1 including typescript and illustrations4 ,the title should be complete and clear for easy indexing by abstracting services4 ,include an abstract as an introductory part of the text1 followed by an identification of the author that includes his professional mailing address4 ,a table of contents is optional4 ,an index1 if required1 may be supplied by the author when he returns page proof4 ,headings are to be used discriminately and must be typed with extra space above and below4 ,for matters of general style 7including bibliography and footnotes or notes7 follow ,a ,manual of ,style1 #abth edition1 ,university of ,chicago ,press1 #aifi4 ,for more detailed treatment on footnotes and bibliography see ,citation ,style ,manual prepared for ,,mht publications 7,october #aifc74 ,use the modern order of citing dates3 #bi ,february #aigb4 ,simple tabulations in the text 7e4g41 columns of data7 may carry headings or not1 but they should not contain rules4 ,formal tables must be submitted as pages separate from the text1 and each table1 no matter how large1 should be pasted up as a single sheet of copy4 ,use the metric system instead of 7or in addition to7 the ,english system4 ,illustrations 7line drawings1 maps1 photographs1 shaded drawings7 can be intermixed throughout the printed text4 ,they must be clearly numbered in sequence1 as they are to appear in the text4 ,they will be termed ,figures and should be numbered consecutively2 if a group of figures is treated as a single figure1 however1 the individual components should be indicated by lowercase italic letters on the illustration1 in the legend1 and in text references3 ,figure #i;b4 ,type 7double spaced7 all legends on a page or pages separate from the text and not attached to the artwork4 ,in the bibliography spell out book1 journal1 and article titles1 using initial caps with all words except minor terms such as and1 of1 the4 7,for capitalization of foreign language titles1 follow the national practice of the language47 ,underscore 7for italics7 book and journal titles4 ,use the parentheses-colon system3 #aj7b73e-i for volume1 number1 and page citations4 ,notes and footnotes1 accompanying a manuscript1 are to be typed consecutively1 double-spaced1 and on sheets separate from the text4 ,in typing the notes the number should be typed on the line and followed by a period4 ,the footnote number should be typed slightly above the line and should follow any punctuation mark except a dash4 ,for free copies of his own paper1 a ,smithsonian author should indicate his requirements on ,form #cf 7submitted to the ,press with the manuscript74 ,a non-,smithsonian author will receive fifty free copies2 order forms for quantities above this amount with instructions for payment will be supplied when page proof is forwarded4