,transcriber's ,notes3 ,underscores 80 before and after a word or phrase indicate italics in the original text4 ,equal signs 80 before and after a word or phrase indicate bold in the original text4 ,small capitals have been converted to ,,solid capitals4 ,illustrations have been moved so they do not break up paragraphs4 ,typographical and punctuation errors have been silently corrected4 ,hoisting ,appliances ,by ,i4,c4,s4 ,,staff ,,hoisting ,parts #c-d #ddg ,published by ,,international ,,textbook ,,company ,,scranton1 ,,pa4 ,hoisting1 ,parts #c and #d3 ,copyright1 #aijf1 by ,,international ,,textbook ,,company4 ,entered at ,stationers' ,hall1 ,london ,all rights reserved ,printed in ,u4 ,s4 ,a4 ,,international ,,textbook ,,press ,scranton1 ,pa4 ,,contents ,,note4--,this book is made up of separate parts1 or sections1 as indicated by their titles1 and the page numbers of each usually begin with #a4 ,in this list of contents the titles of the parts are given in the order in which they appear in the book1 and under each title is a full synopsis of the subjects treated4 ,,hoisting1 ,,part #c ,pages ,hoisting ,appliances #a-dc ,hoist ,indicators #a-e ,column indicators2 ,dial indicators2 ,special indicators4 ,drums and ,reels #f-bj ,cylindrical ,drums #g-h ,conical ,drums #i-af ,hoisting with cylindrical drums2 ,hoisting with conical drums2 ,comparison of cylindrical and conical drums4 ,flat ,rope ,reels #ag-bj ,rope ,wheels #ba-bf ,koepe system2 ,whiting system2 ,modified ,whiting system4 ,rope ,fastenings #bg ,clutches #bh-ca ,jaw clutch2 ,band friction clutches2 ,beekman friction clutch4 ,brakes #cb-dc ,block brake2 ,post brake2 ,strap brake2 ,differential brake2 ,power for brakes2 ,differential lever2 ,power brakes2 ,crank brake4 ,,hoisting1 ,,part #d ,hoisting ,appliances #a-ea ,sheaves #a-e ,cast-iron sheave2 ,wood-lined sheaves2 ,diameter of sheave2 ,rollers and carrying sheaves4 ,cages for ,vertical ,shafts #f-aa ,construction of cage2 ,safety catches2 ,multiple-deck cages4 ,automatic ,dumping ,cages #ab-af ,definition2 ,slope1 or inclined shaft hoisting2 ,slope carriage4 ,skips1 or ,gunboats #ag-bb ,definition2 ,method of loading skips2 ,method of dumping skips2 ,skip cage4 ,buckets #bc ,car ,locks #bc-bd ,cage ,guides #be ,landing ,fans1 or ,keeps #bf-bh ,common forms of fans2 ,hydrostatic fans2 ,pneumatic fans2 ,cage chairs4 ,head-,frames #bi-de ,head-frames in general2 ,types of head-frames2 ,examples of various types2 ,head-frame specification4 ,detaching ,hooks #df-dg ,signaling #dh-ea ,hammer-and-plate signal2 ,electric bells2 ,speaking tubes2 ,pneumatic gong signal2 ,telephones4 ,,hoisting ,serial #hea;,c 7,,part #c7 ,edition #a ,,hoisting ,,appliances ,,hoist ,,indicators #a4 ,the hoist indicator is a mechanism attached to the drum shaft of a hoisting engine to show the hoisting engineer the position of the cage or skip in the shaft throughout the time of hoisting4 ,the use of such indicators is sometimes required by law1 but there is a great diversity of opinion as to the advisability of using them4 ,the objections to them are that they are liable to get out of order1 and that in general the use of any automatic device that tends to relieve the hoisting engineer of responsibility and constant attention to his engine is not to be commended4 ,a hoisting engineer1 however1 depends for his stopping point mainly on a mark made on the rope1 or on the drum1 or on both1 and uses an indicator mostly as a guide for the position of the cage during the hoist4 ,,types ,,of ,,indicators #b4 ,column ,indicators4--,a very simple indicator1 and one that was formerly very commonly used1 is made by inserting a pin into the center of the end of the drum shaft and using this as a miniature drum on which to wind and unwind a chain or cord1 which corresponds to the hoisting rope as the pin corresponds to the drum4 ,this chain or cord is led over a pulley placed at the top of a pair of guides1 representing the shaft1 and carries at its end a weight1 pointer1 or gong1 representing the cage or car1 as shown in ,fig4 #a4 ,illustration3 ,,fig4 #a ,illustration3 ,,fig4 #b ,the different landings in the shaft are marked on the guide2 and as the pointer or gong rises and falls it indicates the position of the cage in the shaft4 ,if a gong is used1 pointer also may be added and the gong so arranged that it will ring at a point some distance before the landing is reached and thus attract the engineer's attention4 ,indicators of this kind1 though cheap and easily constructed1 are not reliable1 for the cord and chain may stretch or they may overlap in winding on the pin1 or may bind in the pulley and thus indicate a wrong position of the cage4 #c4 ,an indicator should have a positive motion and be driven by gearing or by link belts4 ,fig4 #b shows a column indicator that consists of a screw a working inside of a slotted pipe b1 which may be of any length necessary4 ,this screw is revolved by means of the gears c1 which are rotated by the sprocket wheel d4 ,a nut e travels up and down the screw a and the pointer f attached to the nut indicates the position of the cage in the shaft4 ,the pipe standard b is usually painted a dead black and the different levels may be marked on it with chalk or white paint4 ,chalk marks are not safe1 as they may be tampered with and the engineer thus misled4 ,illustration3 ,,fig4 #c ,the pointer a1 ,fig4 #c1 is moved by the rotation of the screw shaft b1 which is revolved by the bevel gears c and d4 ,this indicator also registers the number of hoists by means of the dials e1 for at each hoist the lower end of the pointer a engages a ratchet wheel behind the two dial faces shown and thus registers on the dial4 ,illustration3 ,,fig4 #d #d4 ,dial ,indicators4--,fig4 #d shows a positive-motion indicator that is operated as follows3 ,a worm a on the drum shaft b engages with the worm-wheel c on the small shaft d that is supported by the bearings e4 ,the pointer f is rigidly attached to the shaft d and revolves in front of the properly marked dial g4 #e4 ,fig4 #e shows a dial indicator attached to drum hoists where the speed of rope is constant for each revolution4 ,the wheel a of this indicator may be a worm-wheel working in a worm on the drum shaft1 as described in connection with the indicator shown in ,fig4 #d1 or it may be a sprocket wheel driven by a link belt from a sprocket wheel on a drum1 or it may be a gear-wheel driven directly from another gear-wheel on the drum4 ,the gear-wheels b revolve a vertical shaft c fitted at the upper end with a worm d that drives the worm-wheel e placed on the end of the pointer spindle4 ,the different levels from which hoisting is to be done may be painted on the dial1 or better1 they may be placed on movable targets that are clamped to the dial and can thus be moved as occasion requires4 ,illustration3 ,,fig4 #e ,,example4--,an indicator is desired for a shaft #hjj feet deep at which the drum of the hoisting engine to be used is #aj feet in diameter2 what ratio of gearing must be used so that the pointer will make one revolution during the hoist8 ,,solution4--,the circumference of the drum is #ca4db ft4 7,d #aj #c4adaf #ca4daf ft472 hence1 the revolutions per hoist are #hjj #ca4db #be4df revolutions4 ,then1 if the pointer is to make one revolution per hoist1 the ratio of the gearing will be #be4df to #a4 ,ans4 #f4 ,special ,indicators4--,one fault of nearly all indicators is that they give a regular movement throughout the winding1 and the space over which the pointer travels is too small to enable the engineer to land the cage accurately4 ,indicators have been made with a differential motion to the pointer1 the motion being greater at the time of landing and less during the middle of the hoist4 ,they are also made with two pointers1 one operating like the dial indicator above described and the other remaining stationary during all the hoist but the last few feet1 when it moves around its circle4 ,illustration3 7a7 7b7 ,,fig4 #f #g4 ,where flat ropes are used or where round ropes wind on a conical drum1 the length of rope wound or unwound is different for each turn of the drum4 ,with all the indicators thus far described1 while the speed with which the indicator moves is proportional to the speed at which the drum and the drum shaft revolve1 it is not proportional to the speed of the rope when winding and unwinding on a conical drum or on a flat rope reel4 ,fig4 #f 7a7 and 7b7 shows two views of a compensating dial indicator4 ,by means of the spiral form of sheave c1 the hand d is made to move equal distances around the disk e for equal distances of cage movement in the shaft4 ,the rope f passes about the spiral sheave and one end is attached at the small end g of the spiral1 while the other end is fastened to the periphery of the sheave h1 which takes its motion from the drum shaft or crank-shaft of the hoisting engine by means of the bevel gear i4 ,consequently1 while the sheave h has a regular motion dependent directly on the revolution of the hoisting drum1 the pointer d moves irregularly1 depending on the position of the spiral sheave c2 that is1 whether a small or large diameter of the spiral is presented to the rope4 ,the rope j carrying the counterweight k is attached to a small circular drum l that is on the same shaft as the spiral sheave4 ,the purpose of this cord and counterweight is to keep the indicator line f taut and to bring the indicator back to position as the cord f unwinds from the sheave h4 #h4 ,in order that the pointer may not stand at exactly the same point on the dial when the cage is at the top and at the bottom1 and so that the engineer may be able to distinguish between the top and the bottom positions of the cage by the pointer1 the ratio of the gearing is usually increased by allowing one or two extra teeth on the worm-wheel4 ,in the example in ,art4 #e1 assume a ratio of #bg3 #a2 that is1 if a worm-gear is used1 the worm-wheel will have #bg teeth4 ,if the pitch of the teeth is inch1 the circumference of the pitch circle will be #bg #bj4be inches and the diameter #f4dd inches4 ,the pitch of the worm will1 of course1 be the same as that of the wheel1 and its diameter will be whatever is necessary to give sufficient strength outside of the shaft1 since it bears no relation to the ratio of the gearing4 ,,drums ,,and ,,reels #i4 ,the drum1 or reel1 of a hoisting engine is the part on which the rope winds4 ,it is either keyed fast to the engine shaft or is connected to the shaft by means of a clutch1 the shaft being made extra heavy to carry the strain due to the weight of the drum and the pull of the rope4 ,,cylindrical ,,drums #aj4 ,the outer part1 or shell1 of a drum a1 ,fig4 #g1 is supported on rims b1 and these rims are connected by arms or spiders c with the hubs d4 ,the brake rings e are for the band brakes1 of which there may be one or two4 ,the part a may be lagged with strips of wood bolted to the rims b1 the heads of the bolts being countersunk4 ,fig4 #h shows the detailed dimensions of a drum #h feet in diameter having a #d-;foot face designed to carry heavy loads and a large amount of rope4 ,the shell is of boiler plate and the spiders of cast-steel4 ,illustration3 ,,fig4 #g #aa4 ,the shell may be cast in one piece for small drums or built up in sections for large drums1 as in ,figs4 #g and #h4 ,the shell may have a smooth surface1 ,fig4 #h1 or it may have grooves1 ,fig4 #g1 for the rope to lie in as it is wound on the drum4 ,on an iron drum without grooves1 the rope will chafe sidewise2 and furthermore if the rope winds on a hard flat surface it bears here and there on a single wire and tends to flatten1 causing internal wear between the wires2 while1 in the case of a rope winding in a groove1 it is supported on about one-quarter of its circumference1 bringing many more wires to bear on the drum and dividing the pressure between them4 ,a wooden-lagged drum causes less wear on a rope than an ungrooved iron-shell drum1 as grooves are gradually worn in the lagging1 but is not so good as a grooved iron drum4 ,it is not good practice to allow a rope to wind on itself1 and the drum should be long enough to take the full length of the rope required for the hoist4 ,at least two turns of the rope should be on the drum when the load is at the bottom1 as the friction between the rope and drum thus greatly lessens the strain coming on the rope at the point where it is fastened to the drum4 ,allowance for two or three additional turns of the rope should also be made so that the cage may be hoisted above the landing4 ,illustration3 ,,fig4 #h ,the shell usually has a flange at each end1 as shown in ,figs4 #g and #h1 but it may have a flange at one end only1 or may be without flanges entirely4 ,if1 however1 the flanges are not used1 the drum must be extra long to prevent the rope running off the end4 ,if the drum is very long1 a third spider is added midway between the other two to stiffen it against collapse4 ,,example4--,find the length of a drum #f feet #c inches in diameter necessary to hold #a1jjj feet of #a-;inch wire-rope4 ,,solution4--,the diameter from center to center of the rope when wound on the drum is #f ft4 #c in4 plus #a in41 or #f ft4 #d in41 which is equal to #ai4if ft4 7approximately #bj ft47 of circumference4 ,then1 to wind #a1jjj ft4 will require 1_/ #ej turns on the drum4 ,allowing two turns of the rope to protect the fastening and three turns in case of overwinding1 gives fifty-five turns to be allowed for on the drum4 ,if the drum is of iron with grooves turned in it1 in4 must be left between adjacent parts of the rope1 or #a in4 from the center of one turn to the center of the next4 ,then1 #ee #a #hb in4 plus in4 at each end #hd in41 or #g ft4 for the length of the drum between the flanges4 ,ans4 ,if the drum has wooden lagging1 clearance need not be allowed between two adjacent coils of rope1 as in this case the rope winds against itself and so takes up only #a in4 ,it will then be #ee #a in4 #fh in41 or #e ft4 #h in4 long 7say #e ft4 #i in474 ,ans4 ,,conical ,,drums #ab4 ,in hoisting in balance from deep shafts with cylindrical drums1 if no tail-rope is used1 or in hoisting from a single shaft with an unbalanced cage1 the hoisting engine is not loaded equally at different points of the hoist owing to the gradually changing weight of the unbalanced rope4 ,the following illustrations will further explain this4 #ac4 ,hoisting ,with a ,cylindrical ,drum4--,suppose that1 from a single-compartment vertical shaft #a1jjj feet deep1 it is required to hoist each trip a load1 including friction1 of #aa1jjj pounds made up as follows3 ,,pounds ,weight of material #d1jjj ,weight of car #c1jjj ,weight of cage #c1jjj ,friction1 #aj per cent4 #a1jjj ------ ,total #aa1jjj ,if a #a-;inch cast-steel rope weighing #c pounds per foot is used1 winding about a drum #g feet in diameter1 the weight of rope is then #c #a1jjj #c1jjj pounds and the load on the rope1 when the cage is at the bottom1 is #aa1jjj #c1jjj #ad1jjj pounds1 while at the top the load on the rope is only #aa1jjj pounds4 ,the moment of the load at the bottom is then the load #ad1jjj multiplied by the radius #c1 or #ad1jjj #c #di1jjj foot-pounds2 and at the top1 #aa1jjj #c #ch1ejj foot-pounds4 ,this shows that the load against the engine is much greater at the beginning than at the end of the hoist4 #ad4 ,take now a double-compartment vertical shaft of the same depth as in ,art4 #ac and assume the same amount of material hoisted at a trip1 in the same mine car and on the same cage2 but that an empty car and cage are lowered in one compartment while the loaded car and cage are hoisted in the other4 ,the two cars and the two cages will balance each other1 and the loads will be as follows3 ,at the beginning of the hoist1 when the loaded car and cage are at the bottom1 the gross load is #ad1jjj pounds1 made up as follows3 ,,pounds ,weight of material #d1jjj ,weight of mine car #c1jjj ,weight of cage #c1jjj ,friction1 #aj per cent4 of above #a1jjj ,weight of rope #c1jjj ------ ,total #ad1jjj ,multiplying this by the radius of the drum1 the gross turning moment is #ad1jjj pounds #c feet #di1jjj foot-pounds1 as before1 but there is a counterbalancing load of #f1jjj pounds1 made up as follows3 ,,pounds ,weight of mine car #c1jjj ,weight of cage #c1jjj ----- ,total #f1jjj ,less friction1 #aj per cent4 #fjj ----- #e1djj ,this means a counterbalancing load moment of #e1djj pounds #c feet #ah1ijj foot-pounds4 ,the net load moment to be overcome by the engine at the beginning of the hoist is1 therefore1 #di1jjj-ah1ijj #cj1ajj foot-pounds4 ,at the end of the hoist there is a gross load on the loaded side of #aa1jjj pounds1 made up as follows3 ,,pounds ,weight of material #d1jjj ,weight of mine car #c1jjj ,weight of cage #c1jjj ,friction1 #aj per cent4 #a1jjj ------ ,total #aa1jjj ,this is equal to a gross load moment of #aa1jjj pounds #c feet #ch1ejj foot-pounds1 but there is a counterbalancing load of #h1ajj pounds1 made up as follows3 ,,pounds ,weight of mine car #c1jjj ,weight of cage #c1jjj ,weight of rope #c1jjj ----- ,total #i1jjj ,less friction1 #aj per cent4 of #f1jjj #fjj ----- #h1djj ,this is equal to a counterbalancing load moment of #h1djj pounds #c feet #bi1djj foot-pounds1 and leaves a net load moment against the engine of #ch1ejj-bi1djj #i1ajj foot-pounds4 ,in other words1 the load moment that the engine has to overcome varies from #cj1ajj foot-pounds at the beginning of the hoist to #i1ajj foot-pounds at the end of the hoist4 #ae4 ,hoisting ,with ,conical ,drums4--,conical drums are designed to make the work of the engine as nearly uniform as possible throughout the hoist4 ,to accomplish this1 when the cage is at the bottom of the shaft1 and the load is therefore heaviest1 the rope winds on that part of the drum having the smallest diameter4 ,as hoisting continues1 the rope winds on a gradually increasing diameter of drum1 and when the cage is at the top of the hoist1 and the load therefore least1 the rope is winding on that part of the drum having the greatest diameter2 in this way1 the moment of the load at every point of the hoist is approximately the same4 ,the great difference in the loads at different parts of the hoist is due mainly to the variation in the weight of the rope hanging from the drum2 hence1 the less the weight of the rope in proportion to the total load on the engine1 the more nearly uniform is the load on the engine4 ,illustration3 ,,fig4 #i #af4 ,fig4 #i 7a7 shows the condition at the beginning of the hoist when conical drums are used4 ,cage a is at the bottom and carries a loaded car2 cage b is at the top and carries an empty car4 ,the net moment that the engine must overcome is the sum of the weight of the material to be hoisted1 weight of the cage and car at a1 and the weight of the rope attached to a1 multiplied by the small radius r of the drum1 minus the weight of the car and cage at b1 multiplied by the large radius ,r of the drum4 ,fig4 #i 7b7 shows the condition of things at the end of the hoist1 when the cage a is at the top and cage b at the bottom4 ,the loaded car and cage a1 whose rope in ,fig4 #i 7a7 was winding on the smallest diameter of the drum1 is now at the top and the rope is winding on the largest diameter of the drum4 ,the cage b with the empty car is now at the bottom and the rope is unwinding from the smallest diameter of the drum4 ,the net moment that the engine must overcome in this position is equal to the sum of the weight of the material hoisted1 the weight of the cage a and the car1 multiplied by the larger radius ,r of the drum1 minus the sum of the weights of the cage b1 the car1 and the rope1 multiplied by the small radius r of the drum4 #ag4 ,if the moment of the load against the engine at the beginning of the hoist is to equal that at the end of the hoist1 it is possible to determine what relative diameters of drum will produce such an effect1 as follows3 ,let ,w weight of material hoisted2 ,w weight of cage and car2 ,w weight of rope2 ,r large radius of drum2 r small radius of drum4 ,the load moment may be calculated by including friction as of the total weight hoisted1 except the weight of the rope1 as shown in ,art4 #ad2 or the friction may be disregarded without serious error4 ,then1 under the conditions shown in ,fig4 #i 7a71 and disregarding friction1 ,load moment 7,w,w,w7r - ,w,r 7#a7 and under the conditions shown in ,fig4 #i7;b71 ,load moment 7,w ,w7,r - 7,w ,w7r 7#b7 ,placing formula #a formula #b1 7,w,w7,r - 7,w,w7r 7,w,w,w7r - ,w,r1 and 7,w #b,w #b,w7 ,r r ------------------- 7#c7 7,w #b,w7 ,since the diameter of a drum is generally given instead of the radius1 it follows that if ,d larger diameter1 d smaller diameter1 and then1 since ,d #b,r and d #br1 formula #c may be written 7,w #b,w #b,w7 ,d d ---------------------- 7#d7 7,w #b,w7 ,formula #d gives only approximate results1 which are1 however1 sufficiently accurate for the mine superintendent's use1 and for this reason friction has been omitted1 as it would make the formula much more complex4 ,it may be expressed as a rule as follows3 ,rule4--,to find the large diameter of a conical drum1 multiply the small diameter by the sum of the weight of the material to be hoisted1 twice the weight of the cage and car1 and twice the weight of the rope2 divide this product by the sum of the weight of the material1 and twice the weight of the cage and car4 ,illustration3 ,,fig4 #aj ,applying this rule to the problem given in ,art4 #ad and omitting friction1 #g7d1jjj #ab1jjj #f1jjj7 ,d ------------------------- #i4f feet 7#d1jjj #ab1jjj7 ,the drum would then be #g feet in diameter at the small end and #i feet #g inches at the larger end4 #ah4 ,fig4 #aj shows a special form of combined conical and cylindrical drum designed for hoisting a total balanced load of #be tons through a vertical height of #eej feet4 ,fig4 #aa shows a combined conical and cylindrical drum2 an unusual feature is the rope reel shown at each end of the drum1 which permits of properly storing a few hundred feet of extra rope1 allowing the rope to be lengthened1 when needed1 without splicing4 ,illustration3 ,,fig4 #aa #ai4 ,comparison of ,cylindrical and ,conical ,drums4 ,the disadvantages of the cylindrical drum lie entirely in the fact that the load on the engines is variable1 but it is possible to overcome this disadvantage by adding a tail-rope to the cages to balance the weight of the rope4 ,this system gives its best results where hoisting is done from one level only1 but in deep hoisting it is impracticable because of the extra weight added and because of possible excessive swaying of the rope4 ,the conical drum has two strong points in its favor3 first1 the load on the engine may be nearly equalized during the entire hoisting period2 and1 second1 the starting of the engines with the load requires less power4 ,the disadvantages of the conical drum are as follows3 ,to maintain a certain average speed of hoisting1 the speed toward the end of the hoist is of necessity higher than the average and comes at a time when a slowing up should be taking place1 so that more care must be exercised when making the landing4 ,to prevent the rope from being drawn out of the grooves1 the latter must be made deep and with a large pitch1 thereby increasing the width of the face or length of the drum4 ,in making a landing1 when the rope is on the conical face1 the rope must be kept taut1 as any slackness will permit the rope to leave the groove1 with the result that all the rope will pile up in the bottom grooves of the drum allowing the cage to drop into the mine1 unless it is resting on the chairs4 ,if there are several levels to be hoisted from1 the equalizing of the load on the engines can only be realized for one level2 for all other levels this advantage will be lost4 ,for large depths1 conical drums become very long and require correspondingly long leads from head-frame to drum4 ,to hold the same amount of rope1 conical drums are heavier than cylindrical ones1 and as a result1 the power required in starting the load is somewhat increased owing to the greater inertia of the rotating parts4 ,some of these disadvantages have been overcome by making a combination of cone and cylindrical drums4 ,the drums are so designed that the landing takes place only when the rope is on the cylindrical portion of the drum4 ,for deep hoisting1 the greater diameter of the drum and its length must be inconveniently large if the load is equalized4 ,the length and diameter can be reduced by making one-half of the drum cylindrical and by having the rope from each end wind on the same cylindrical portion of the drum4 ,in all cases1 however1 these modifications are made at the expense of the equalization of the load on the engines1 and it is not possible to obtain the latter without including some serious disadvantage4 ,there are certain objections to both cylindrical and conical drums3 their great size and weight1 for large hoists1 make them very expensive2 their width necessitates placing the engines far apart1 which adds to the cost of the engines1 foundations1 and buildings2 the great weight of the drums is also objectionable1 because it forms a large part of the mass to be put in motion and brought to rest at each hoist4 ,,flat ,,rope ,,reels #bj4 ,to overcome the objections to conical and cylindrical drums1 several other systems of hoisting have been tried1 among them being one that uses a reel1 ,fig4 #ab1 and a flat rope4 ,the hub a is increased in diameter1 above what is necessary for strength1 to such a size as is suitable to wind the rope on4 ,it is then cored out from the inside1 so as not to contain too great a mass of metal4 ,illustration3 ,,fig4 #ab ,the arms b of the reel extend radially from the hub to confine the rope laterally when it is all wound on the drum4 ,these arms are connected at their outer ends by a continuous flange c1 which flange is flared out1 as shown at d1 so as to take in the rope easily1 if it is deflected at all sidewise4 ,in the larger-sized reels1 the arms are bolted to the hub1 and often the outer rim connecting the arms is omitted4 ,hardwood lining was formerly used on the arms under the impression that the wear on the rope would be less than with bare iron arms1 but sand and grit become embedded in the wood and grind the rope4 ,polished iron arms with rounded corners and lubricated with oil or tar are best4 ,the end of the rope is fastened in a pocket e provided for it in the hub4 ,the rope winds on itself1 so that the diameter of the reel increases as the hoist is made and as the load due to the weight of the rope decreases4 ,this serves to equalize the load due to the rope in the same manner as the conical drum4 ,two reels are generally put on the same shaft1 and while one is hoisting from one compartment of the shaft the other is lowering into another compartment4 ,the periphery of the hub where the rope winds should not be round but of gradually increasing radius1 for if a flat rope be wrapped about a round hub the rope will have to abruptly mount itself at the end of the first revolution and so on for every revolution4 ,the radius of the hub should increase at such a rate as to raise the rope an amount equal to its thickness in the first wrap1 so that it will wind on itself without jar at the point of attachment1 as well as on succeeding wraps4 #ba4 ,in ,america1 it is customary to wind on reels of small diameter1 that is1 starting at #c or #e feet and increasing to #h or #ab feet2 but several large plants have been built with reels starting at #h feet and increasing to #ai feet4 ,in ,england1 reels have been made starting at #af feet and increasing to #bj or #bb feet4 ,such large reels are easier on the rope but require large engines1 as hoisting in balance is used to only a slight extent4 ,the large reel is easy on the rope1 both from the fact that it bends the rope but little and also gives less pressure on the bottom wraps1 as each wrap adds to the pressure4 ,these reels are driven by means of plain jaw or friction clutches4 ,the wear of a flat rope is excessive and the rope itself costs more than a round rope of the same strength1 does not last as long1 and requires more care and attention4 #bb4 ,calculating ,size of ,flat ,rope and ,reel4--,the calculation of the size of a flat rope for given work is not so simple as that of a round rope1 as there is a variable factor in the width and thickness of the rope that must be taken into account4 ,to illustrate the method of calculation1 suppose that it is required to hoist #e1jjj pounds of material in a #c1jjj-pound skip from a vertical two-compartment shaft #b1jjj feet deep under conditions requiring a factor of safety of about #i for the rope4 ,the determination of the size of the rope and the small and large diameters of the reels must proceed together4 ,the latter calculations are performed in much the same manner as for conical drums4 ,referring to ,table relating to flat wire ropes in ,hoisting1 ,part #b1 it is found that a flat steel rope #f inches by inch in size and with a breaking strength of #aej1jjj pounds weighs #e4a pounds per foot2 hence1 #b1jjj feet of it weighs #b1jjj #e4a #aj1bjj pounds4 ,the total load on the rope will then be #ai1jjj pounds1 made up as follows3 ,,pounds ,weight of material #e1jjj ,weight of skip #c1jjj ,friction1 #aj per cent4 #hjj ,weight of rope #aj1bjj ------ ,total #ai1jjj ,this rope gives a factor of safety of #aej1jjj_/ai1jjj #g4h1 which is not quite enough when figured from the dead load without that due to acceleration4 ,an #h rope with a breaking strength of #bjj1jjj pounds weighs #f4i pounds per foot2 hence1 #b1jjj feet of it weighs #b1jjj #f4i #ac1hjj pounds4 ,the load on the rope will then be #bb1fjj pounds1 made up as follows3 ,,pounds ,weight of material #e1jjj ,weight of skip #c1jjj ,friction1 #aj per cent4 #hjj ,weight of rope #ac1hjj ------ ,total #bb1fjj #bjj1jjj ,this rope gives a factor of safety of -------- #h4h4 #bb1fjj ,substituting the foregoing weights of material1 skip1 and rope in formula #d1 in ,art4 #ag1 gives 7#e1jjj #f1jjj #bg1fjj7 ,d d ------------------------ 4 7#e1jjj #f1jjj7 ,hence1 the equation of moments is ,d #c4e;d4 ,in other words1 the large diameter1 or that of the last coil of rope1 should be #c4e times the small diameter1 or that of the reel hub4 #bc4 ,fig4 #ac represents a coil of flat rope whose greater diameter ,d and smaller diameter d are to be determined4 ,the area of the hub about which the rope is to coil is 77d1 while the area included by the outer coil of rope is 77,d hence1 the area of annular space occupied by the rope is 77,d - 77d 777,d - d74 ,such values for ,d and d must be chosen that the equation of moments in ,art4 #bb is satisfied1 while the area 777,d-d7 must correspond to the space occupied by the given rope when rolled4 ,illustration3 ,,fig4 #ac ,,illustration4--#b1jjj feet of rope inch thick requires #b1jjj #ab ---------- #ab1jjj #b square inches in which to be coiled4 ,to satisfy the equation of moments1 ,d must equal #c4e d2 hence1 to satisfy both these conditions 777#c4e;d7 - d #ab1jjj2 d #cg inches1 or #c feet #a inch2 ,d #cg #c4e #abi4e inches1 or #aj feet #i inches4 ,the dimensions of the reel will then be3 diameter of hub #c feet #a inch2 width between flanges1 #h inches1 allowing inch on each side of the rope for clearance2 diameter of the flanges where they flare1 #aj feet #i inches4 ,,rope ,,wheels ,illustration3 ,,fig4 #ad #bd4 ,koepe ,system4--,in its lightest form1 a drum requires a large amount of power to set it in motion1 which power is absorbed by the brake and lost when it is brought to rest again4 ,furthermore1 with deep shafts requiring long drums1 the fleet1 or angle that the rope makes with the head-sheave due to its traveling from one end of the drum to the other1 is not only a disadvantage and possible cause of accident1 but it is a source of wear4 ,to overcome these objections and also the great cost of large cylindrical or conical drums1 the ,koepe system of hoisting1 shown in ,fig4 #ad1 was devised by ,mr4 ,frederick ,koepe4 ,a single grooved driving sheave a is used in place of a drum4 ,the winding rope b passes from one cage ,a up over a head-sheave1 thence around the sheave a and back over another head-sheave1 and down to a second cage ,b2 it encircles a little over half the periphery of the driving sheave and is driven by the friction between the sheave and rope4 ,a balance rope c beneath the cages and passing around the sheave d gives an endless-rope arrangement with the cages fixed at the proper points4 ,the driving sheave is stronger than an ordinary carrying sheave1 as it has to do the driving and is usually lined with hardwood1 which is grooved to receive the winding rope1 the depth of the groove being generally equal to twice the diameter of the rope4 ,instead of being placed parallel1 the head-sheaves are placed at an angle with each other1 each pointing to the groove in the driving sheave1 thus reducing the side friction of the rope on the sheaves4 ,the system has been in successful operation since #ahgg1 and experiments made on it have determined that1 with a rope passing only one-half turn around the drum sheave1 the coefficient of adhesion with clean ropes is about 4#c4 ,if the ropes are oiled1 the adhesion becomes less1 and sometimes slippage occurs1 producing not only wear of the driving sheave lining but giving an incorrect reading of the hoist indicator and thus possibly producing overwinding1 unless the position of the cage is indicated by marks on the rope1 or unless the engineer can see the cage4 ,at the end of the hoist1 if the upper cage is allowed to rest on the keep1 its weight and the weight of the tail-rope are taken from the hoisting rope1 and there is then not enough pull on the hoisting rope to produce sufficient friction with the drum sheave to start the next hoist4 ,to prevent this trouble1 the keeps are dispensed with1 or the rope is made continuous and independent of the cage4 ,to do this1 crossheads are placed above and below each cage and connected by ropes or chains outside of the cages4 ,the bridle chains are then hung from the top crosshead1 and when the cage rests on the keeps1 the weight of the winding and tail-ropes remains on the driving sheaves4 #be4 ,advantages and ,disadvantages of the ,koepe ,system4--,with this system1 only one driving sheave is necessary for the operation of two compartments1 and it is light1 inexpensive to build1 and very narrow1 admitting of a short sheave shaft and small foundations4 ,this system permits a perfect balance of rope and cage1 so that the work to be done by the engine is uniform1 except for the acceleration1 and consists only in lifting the material and overcoming the friction4 ,there is no fleeting of the rope between the driving sheaves and the head-sheaves4 ,the system has the following disadvantages1 which prevent its being used to any considerable extent3 ,liability to slippage of the rope on the drum2 if the rope breaks1 both cages may fall to the bottom2 hoisting from different levels cannot be well done1 for1 since the cages are at fixed distances from each other1 the length of the rope is such that when one cage ,a is at the top1 the other cage ,b is at the bottom4 ,if hoisting is to be done from the bottom1 this is satisfactory1 but if hoisting is to be done from some upper level1 cage ,b1 which is at the bottom1 must be hoisted to that level to be loaded before it can go to the top4 ,then1 when cage ,b goes to the top with its load1 cage ,a must go to the bottom1 wait there while cage ,b is being unloaded1 and then be hoisted to the upper level to receive its load4 ,for each trip1 therefore1 the time required for a cage to go from the bottom to the upper level and be loaded is lost2 and two movements of the engines are necessary for a hoist instead of one4 #bf4 ,the ,whiting ,system4--,this is a system of hoisting with round ropes1 in which two rope wheels placed tandem are used in place of cylindrical or conical drums4 ,as shown in ,fig4 #ae1 for a two-compartment shaft the rope passes from one cage a up over a head-sheave c1 down under a guide sheave d1 and is then wound three times about the rope wheels e and f1 to secure a good hold1 then around a fleet sheave g1 and back under another guide sheave h1 up over another head-sheave i1 and down to the other cage b4 ,when the system is to be used for a single-compartment shaft1 one end of the rope carries the cage and the other end carries a balance weight1 which is run up and down in a corner of the shaft4 ,a balance rope below the cages1 as shown1 is generally used1 though it is not essential to the working of the system1 as it is in the ,koepe system4 ,when sinking a shaft1 a balance rope cannot be used as it interferes with the work at the bottom of the shaft4 ,illustration3 ,,fig4 #ae ,the drums or wheels e1 f are light1 inexpensive1 and narrow1 thus permitting short sheave shafts and small foundations4 ,they are lined with hardwood blocks1 each lining having three rope grooves turned in it4 ,the main wheel e is driven by a hoisting engine1 which may be either first or second motion4 ,the following wheel f is coupled to the main wheel by a pair of parallel rods1 one on each side1 like the drivers of a locomotive4 ,as the rope wraps about the wheels e1 f three times1 there are six semi-circumferences of driving contact with the rope1 as compared with the one semi-circumference in the ,koepe system1 and there is no slipping of the rope on the wheels4 ,the following wheel f is best tilted or inclined from the vertical an amount equal1 in the diameter of the wheels1 to the pitch of the rope on the wheel1 so that the rope may not run out of its groove and may run straight from one wheel to the other without any chafing between the ropes and the sides of the grooves4 ,the capacity of the wheels e1 f is unlimited1 while grooved cylindrical drums1 conical drums1 and reels will hold only the fixed length of rope for which they are designed4 ,as shown by the dotted lines1 the fleet sheave g is arranged to travel backwards and forwards1 in order to change the working length of the rope from time to time to provide for an increased depth of shaft1 and for the changes in the length of rope due to stretching and when the ends are cut off to resocket the rope4 ,the fleet sheave g is moved a distance equal to half the change in the length of rope4 #bg4 ,hoisting from intermediate levels can be readily done with the ,whiting system2 for instance1 if the cage a is at the top and cage b at the bottom1 and hoisting is to be done from some upper level1 it is only necessary to run the fleet sheave g out1 and thus shorten the working length of the rope until cage b comes up to the upper level4 ,it can then be loaded and go to the top4 ,while cage b goes to the top1 cage a descends to the same level1 where it can be loaded while cage b is being unloaded1 and can then go directly to the top without any of the lost time1 as is the case in the ,koepe system4 ,the system permits a perfect balance of rope and cage1 so that the work to be done by the engines is uniform1 except for the acceleration1 and consists only in lifting the material and overcoming the friction4 ,there is no fleeting of the rope1 so the rope wheels can be placed as close to the shaft as may be desired4 #bh4 ,this system was tried as early as #ahfb in ,eastern ,pennsylvania1 but it was not used extensively because hoisting from great depths was not necessary1 since1 for depths of less than #a1jjj feet1 cylindrical and conical drums are quite satisfactory4 ,in the ,lake ,superior copper region1 there are now three ,whiting hoists1 two of which are probably the largest hoisting plants in the world4 ,each plant consists of a pair of triple-expansion1 vertical1 inverted-beam engines1 driving direct a pair of #ai-;foot drums4 ,the high-pressure cylinders are #bj inches in diameter1 the intermediate cylinders #cb inches1 and the low-pressure cylinders #ej inches1 and all six of them have a #gb-;inch stroke4 ,the rope used is a #b-;inch plow-steel rope and hoists #aj tons of material at a trip1 in one case from a depth of #d1ihj feet1 the deepest shaft in the world4 ,several plants on the ,whiting system have been built in ,england1 and two or more are working in ,south ,africa4 #bi4 ,modified ,whiting ,system4--,a modification of the ,whiting system is sometimes used in which a large drum keyed to the crank-shaft replaces the small tandem drums1 and even the slight probability of the rope slipping in the ,whiting system is thus obviated4 ,one rope is fastened to one end of the drum1 and the other rope to the other end in such a way that while one is winding on the other will be winding off the drum4 ,one rope passes directly to the head-sheave while the other passes first around a fleet sheave1 similar to that used for the ,whiting system1 but preferably placed horizontal1 and thence to the head-sheave4 ,this system possesses the same advantages as the ,whiting system except that the depth of hoist is limited by the size of the drum1 and that there is a fleet of the rope4 ,up to the limiting depth1 as determined by the size of the drum1 this system can be used with equal economy for any depth4 ,this hoist1 as well as the ,whiting1 is therefore especially suitable for a place where one mining company operates several mines1 for it enables the company to select one size for all their permanent work1 with all the advantages that come from duplicate machinery4 ,,rope ,,fastenings ,illustration3 ,,fig4 #af #cj4 ,a common method of fastening a rope to a drum1 ,fig4 #af 7a71 is to pass the rope through a hole in the drum rim and then around the shaft1 clamping the end to the rope between the shaft and shell1 as shown4 ,care should be taken to make the radius of curvature of the hole at a as large as possible so that the rope will not be bent any sharper than is necessary4 ,when an iron drum is used1 the thickness of the rim does not afford enough depth in which to bend the rope and it is necessary to build in a pocket for the purpose1 as shown at ,fig4 #af 7b74 ,it is well to make both sides of this pocket with a long radius to avoid damaging the rope in case all the rope is accidentally unwound and the drum backed so as to bring the rope against the other side of the pocket4 ,,clutches #ca4 ,it is often desired to have the drum of a hoisting engine run loosely on the engine shaft1 so that it may run independently of the engine4 ,with such loose-running drums1 the engine generally runs only in the direction required to hoist the load1 while the cage is lowered entirely by means of the brake4 ,in this way1 one engine provided with several drums may be used for hoisting from several shafts or from several levels in the same shaft at the same time4 ,such a loose-running drum is connected to the engine shaft when a load is to be hoisted by means of a clutch1 of which there are two forms commonly used for hoisting machinery3 jaw or piston clutches and friction clutches4 ,illustration3 ,,fig4 #ag #cb4 ,jaw ,clutch4--,fig4 #ag shows a jaw clutch1 one-half a of which is shown ready to be bolted to a drum or flat rope reel1 which is loose on the shaft b4 ,the other half c of the clutch is moved back so that the jaws d are not in contact with the jaws e on the part a4 ,the half c slides freely on a feather key f1 which is driven tightly into a deep key seat in the shaft b2 a collar g1 fitting loosely in a groove in the hub of c1 is provided with trunnions h on each side2 levers i connect these trunnions with the lever j attached to a suitable handle1 by means of which the clutch is made to slide endwise on the shaft so that the jaws d engage or disengage the jaws e and thus connect or disconnect the drum or reel from the clutch4 ,there are generally four or six jaws d that engage the same number of jaws e on the drum1 and it is necessary to have little or no play between d and e when the clutch is connected or there will be too much shock4 ,the clutch is about #b feet in diameter1 and the jaws are #c or #d inches deep for the average #bj #dh first-motion hoisting engine4 ,instead of the clutch being fastened to the shaft by feather keys1 the shaft may be hexagonal where the clutch slides on it and the clutch is machined to match4 ,jaw clutches are made of either cast-iron or cast-steel1 and should be in halves1 for convenience of repair1 and securely bolted together4 ,illustration3 ,,fig4 #ah #cc4 ,band ,friction ,clutches4--,fig4 #ah shows a band friction clutch that is attached to and revolves with the shaft a4 ,the winding drum runs loosely on the same shaft and has a driving-band ring or seat b on one end2 when the ring c of the clutch is tightened by means of the mechanism shown1 the clutch and driving band become practically one piece and the drum revolves with the clutch4 ,the clutch is constructed as follows3 ,the driving disk d keyed to the driving shaft a is connected to one end of the ring c by a fixed arm e1 which is bolted firmly to the disk d and revolves with it2 a movable arm f that connects with the other end of the band c turns on the pin g4 ,when the band c is loose1 it can revolve about the seat b without touching it1 but the band can be tightened and made to clamp b either when revolving or standing still1 as follows3 ,the sliding sleeve h may be caused to slide about #f inches along the hub of the disk d by levers 7not shown7 that take hold of trunnions i on a ring on the sliding sleeve2 this sleeve is connected to the movable arm f by a link j1 and when the sleeve is on the end of the hub the link stands at an angle of about #fj with the shaft2 by sliding the sleeve toward the disk d1 the link is made to move the arm f about #a inches at its outer end and to thus tighten the driving-band c1 so that it grips the ring b4 ,the adjusting nuts k take up the wear of the wooden blocks with which the ring c is lined4 ,band lifters l hold the band clear of the ring when it is loose4 ,the clutch shown is built to run in the direction indicated by the arrow1 but such clutches may be built to run in either direction2 they should always be run in the direction for which they are designed1 so that the load may always come on the fixed arm4 ,if the band be tightened slowly1 there will be no sudden start or jerk on the rope1 as the slip of the band will prevent the entire force of the grip taking effect at once2 and after the drum reaches full speed1 there is little or no slipping of the driving-band4 ,it is best to keep the band only just tight enough to do the work1 for should the car get off the track1 or be overwound1 or should a cage stick in the shaft for any reason1 the band will slip and thus become a safety appliance1 and not strain or break the rope1 shaft timbering1 or machinery1 as would be the case if a positive clutch1 ,fig4 #ag1 were used4 #cd4 ,the ,beekman ,friction ,clutch4--,a simple friction clutch is shown in ,fig4 #ai1 in which a is a section of the drum shell4 ,the wooden blocks b bolted to the side of the gear-wheel c are made of suitable shape to conform to the ,v-shaped groove d in the side of the drum4 ,the steel spring e between the two steel washers f1 f disengages the clutch1 as soon as the pressure is relieved1 by reversing the motion of the lever g and screw h from the opposite end of the drum4 ,when the lever g is turned1 the screw h is forced against the end of the pin i1 which1 in turn1 presses the cross-key j against the collar k1 forcing the drum against the blocks b and frictionally engaging the gear-wheel c4 ,this drum shaft is prevented from moving endwise by means of the collar l and the grooves m in the babbitted pillow-block4 ,the wide bearings of the drum on its shaft are lubricated by means of the pipes n4 ,illustration3 ,,fig4 #ai ,a clutch is often used to change the length of the hoisting rope when hoisting from two or more lifts or levels4 ,in this case the shaft carries two drums1 one of which is fixed to the shaft1 while the other is provided with a friction clutch4 ,when it is desired to change the length of the rope1 the cage attached to the loose drum is brought to1 say1 the upper landing4 ,the cages both resting on the wings1 the clutch is loosened and the other cage attached to the fixed drum is now brought to the desired level1 when the clutch is again tightened and hoisting proceeds4 ,the change is made in #b or #c minutes4 ,,brakes #ce4 ,a brake is a device by means of which the motion of a hoisting drum may be retarded or stopped4 ,this is accomplished by friction of the brake against the circumference of the brake wheel4 ,there are three types of brakes1 known as block brakes1 post brakes1 and strap brakes4 ,illustration3 ,,fig4 #bj #cf4 ,the ,block ,brake4--,the block brake1 ,fig4 #bj1 consists of one or more wooden blocks or shoes b attached to a lever having a fulcrum at d1 and connected by a rod to the lever c4 ,block brakes are objected to mainly because they throw a great load on the journals of the drum when they are applied2 they cannot be relied on when there is a heavy load on the drum1 and they require the application of great force to the lever c for a given braking power4 ,they are1 however1 cheap and easily applied to a drum1 and the shoe is readily replaced when worn4 #cg4 ,the ,post ,brake4--,the post brake1 ,fig4 #ba1 is composed practically of two block brakes applied at two places on the drum diametrically opposite each other1 thus equalizing the pressure on the journals4 ,the blocks are generally somewhat longer than in the block brake1 or about one-quarter of the circumference of the drum on each side4 ,in ,fig4 #ba1 a is the drum2 b are wooden brake blocks2 c are the posts which in the brake shown are of massive1 built-up1 steel construction2 d are the fulcrums on the plates e1 which plates are adjustable by means of the nuts f2 by means of these nuts1 the fulcrums may be brought closer together as the wooden blocks b wear away2 g is a tension rod generally furnished with a turnbuckle to adjust its length as the wooden blocks wear away4 ,power is applied at the end of the bent lever h1 as shown by the arrow4 ,illustration3 ,,fig4 #ba ,the stops i are adjusted so that the blocks b on each side are equally distant from the drum when the brake is off4 ,the fulcrums d should be some distance below the drum and brake ring1 for if they are too near the drum it will be difficult to swing the lower end of the wooden blocks far enough to clear the drum4 ,illustration3 ,,fig4 #bb #ch4 ,improved ,post ,brake4--,in order to have an equal clearance at top and bottom1 and to have a more powerful leverage than in the ordinary post brake1 the posts may be made movable at both top and bottom1 ,fig4 #bb4 ,the tops of the posts a a are moved1 as in ,fig4 #ba1 by the tension rod b and the lever c1 the latter being connected by rod d to lever e4 ,this lever is pivoted at f and motion is transmitted to the fulcrums j by the link g1 the lever h1 and the tension rod i4 ,the back post a is supported by the uprights k1 which are pivoted at l and swing backwards and forwards like a parallel ruler4 ,the front post a is supported by the single upright m1 pivoted at n4 ,the setscrews o regulate the motion of the bottom of the posts so as to give equal clearance to the bottom and top of the posts4 ,an objection to both the block and the post brake is the fact that1 if the drum surface to which the brake is applied is not perfectly round1 the resistance of the brake will not be uniform when applied while the drum is in motion4 #ci4 ,the ,strap ,brake4--,a strap brake consists of a wrought-iron band or strap that partly encircles the drum and is connected at its free ends to levers with which the band may be tightened on the brake wheel and the drum thus firmly held4 ,the iron or steel band either lies directly against the wooden lagging of the drum or on wooden blocks bolted to the drum2 or else it has bolted to it a lining of wooden blocks that bear on the drum when the band is tightened4 ,the most efficient forms of strap brakes are those in which the strap or straps are in contact with #bgj or more of the circumference of the drum4 ,the greater the arc of contact1 the more securely is the drum held by the brake4 ,a single strap is sometimes used1 but this is only satisfactory with small drums1 say #h feet or less in diameter2 on large drums two straps are generally used1 each extending half way around the drum4 ,the levers for transmitting the power from the hand lever or treadle to the brake strap are variously arranged4 ,in some cases1 the force is multiplied by several short levers2 in others1 by one long lever4 ,the treadle or foot-lever1 however1 has been replaced almost entirely by the hand lever4 ,illustration3 ,,fig4 #bc #dj4 ,the simplest form of strap brake1 ,fig4 #bc1 consists of a single strap a1 with one end anchored at b and the free end attached to the brake lever c4 ,this brake acts on the same principle as the block brake and is open to the objection that it brings an undue load on the journals1 but it is more efficient and holds the drum more firmly under a heavy load than a block brake4 ,illustration3 7a7 7b7 7c7 ,,fig4 #bd ,block brakes are usually run dry1 but in band brakes and post brakes with ample surfaces and proper leverage the wood may be occasionally slightly oiled with black oil1 which greatly adds to the durability of the blocks without unduly lessening the power of the brake4 #da4 ,a two-strap brake is shown in ,fig4 #bd4 ,one end of each strap a1 b is fastened to the pedestal c by either of the methods shown in ,fig4 #bd 7a71 7b71 and 7c74 ,in the method shown in ,fig4 #bd 7a7 and 7b71 the forgings d1 d1 drawn out to the form of bolts1 are riveted to the ends of the straps and passed through a casting c that is secured to the foundation4 ,the object in giving one bolt to one strap and two bolts to the other strap is to allow the straps to pass each other and yet have their lines of action intersect4 ,the bolts are fastened to c by four nuts on each bolt1 i4 e41 two principal nuts and two locknuts4 ,this gives a means of adjustment in the length of the strap to take up the wear4 ,a second method of securing or anchoring the back ends of the straps is shown at 7c74 ,in this case1 a wrought-iron angular piece is riveted to each strap1 and these pieces are passed over the bolt e that takes the place of the casting of the former arrangement4 ,nuts are used1 as shown1 to adjust the straps for wear4 ,the bolt should be short and stiff1 so as to be well able to stand up to its work when the drum is moving or tending to move in the direction shown by the arrow4 ,when the brake is applied1 the friction between the brake strap and the circumference of the brake wheel produces a great strain on the pedestal c1 which must be securely anchored4 ,the front ends of the straps are worked into eyes1 as shown at f1 and by these eyes and suitable pins passing through them the ends are fastened to the brake lever g4 ,this lever is supported on and rotates about a pin h1 so that when the braking force is applied at i1 in the direction of the arrow1 the brake lever rotates1 pulling down on strap a and up on strap b2 and1 if the straps are held firmly at the back end1 the more force that is applied at i the tighter will the drum be gripped by a and b4 ,the ends of the straps should be brought in as close to the drum as is practicable1 both front and back1 so as to give the greatest amount of contact between the drum and the straps and to get the best effect from the force applied4 ,the springs j are used with straps that are not stiff enough to clear the drum when the brake is released4 #db4 ,the rotation of the drum may assist or retard the action of the lever in applying the drop brake4 ,for instance1 if1 in ,fig4 #bc1 the drum revolves in the direction indicated by the arrow1 the pull of the drum at the brake strap is in the same direction as the pull of the lever when applying the brake and the action of the lever is then assisted by the motion of the drum4 ,on the other hand1 if the drum is revolving in the opposite direction1 it opposes the action of the lever and a greater force must be applied to the lever to overcome this opposing pull of the drum4 ,hence1 in the case of strap brakes1 if possible1 that end should be anchored which will cause the revolution of the drum to assist the lever in applying the brake and throw the strain on the anchor bolt instead of on the lever4 ,illustration3 ,,fig4 #be #dc4 ,if a brake is required to work with the drum running in either direction1 there are several ways of bringing the strain due to the load on the anchorage in whichever way the drum runs4 ,one of the simplest of these is shown in ,fig4 #be1 where a is a drum with a strap brake b embracing nearly the entire circumference2 c is a lever bar that is attached to the ends of the brake strap by pins d and e1 which work in the slots f in the iron anchor plates g4 ,one anchor plate is on each side of the lever1 and both are bolted to the foundation4 ,if the band is kept of the proper length1 then1 no matter which way the drum is turning1 the pull of the drum will come on the anchorage1 and the pull on the lever need be only sufficient to take up the slack end of the band4 ,to illustrate3 ,if the drum is turning in the direction indicated by the arrow1 the pin e holding the lower end of the band will be on the bottom of its slot and the pin d will be free in its slot and engaged in tightening the slack end of the band through the motion of the lever c4 ,were the drum running the other way1 the pin d connected with the upper half of the band would move to the upper end of its slot and take the main load1 while the pin e at the lower end of the band would only have to take up the slack4 ,the outer1 or long1 end of the lever moves downwards in all cases to tighten the band4 ,provision must be made to lift the band clear of the drum when slack1 but no anchorage other than at g should be attempted4 ,illustration3 ,,fig4 #bf #dd4 ,the ,differential ,brake4--,the differential brake has both ends of the brake strap attached to short lever arms operated by the brake lever1 but these arms are of different lengths and are so arranged that as the longer arm tightens the brake strap the shorter arm yields and loosens the strap4 ,the tightening1 however1 is more than the loosening or yielding and1 as a result1 the brake band is tightened about the brake wheel4 ,the form of the lever arm is immaterial so long as the differential principle is retained1 that is1 that the shorter arm yields when the longer pulls1 when the brake is thrown into action4 ,this principle is illustrated in ,fig4 #bf4 ,in this brake1 no provision is made for anchoring either end of the brake strap1 but the entire load is thrown on the lever arms a and b4 ,these lever arms are connected with the arm c1 which revolves on the same shaft d and is operated by the reach rod e4 ,the revolution of the drum is thus resisted by the shaft d4 ,this brake is self-acting when the drum revolves so as to pull on the shorter arm1 as indicated by the arrows2 that is1 the motion of the drum helps to set the brake when the latter is once applied4 ,when1 however1 the drum revolves in the opposite direction1 the action of the brake is opposed1 instead of being assisted1 by the motion of the drum4 ,as a consequence1 this particular form of brake is not adapted to hoisting drums that revolve in opposite directions at each alternate hoist4 ,differential brakes are not generally used4 ,illustration3 ,,fig4 #bg #de4 ,power for ,brakes4--,for small drums and light loads1 the brakes are usually applied by hand power through suitable lever connections4 ,the force that a man can exert can be multiplied indefinitely by levers and combinations of levers2 but while the force is multiplied1 the distance through which it can act is divided in the same ratio4 ,a certain amount of motion is required to free the brake band from the drum1 when the brake is off2 this1 then1 limits the leverage that a man can use4 ,suppose1 for instance1 that with a strap brake the band moves from the drum inch1 thus increasing the diameter #a inch1 or the circumference about #c inches4 ,then1 supposing that a man can exert his force to advantage through #c feet1 or #cf inches1 the available leverage is _/ #ab4 ,that is1 if a man can pull #ej pounds on his hand lever1 he can exert #ej #ab #fjj pounds circumferentially on the brake band1 with simple levers4 ,if any form of differential levers is used1 the ratio by which the force applied at the hand lever can be increased will be considerably larger4 ,a diagram will explain this more clearly4 #df4 ,in ,fig4 #bg1 a is the hand lever1 with a fulcrum at b and a pin at c by which it takes hold of a reach rod or connection d4 ,this rod is connected to the end h of the brake lever e1 which is connected by pins at f1 g to the brake bands4 ,if the leverage of the hand lever a is made #f to #a1 that is1 if ab #f ----- --- 1 cb #a and a force of #ej pounds is applied at a1 a pull of #cjj pounds will be exerted at the pin c and1 consequently1 along the rod d to the end of the brake lever e4 ,then1 if the brake lever is made with a ratio of #d to #a1 that is1 if eh #d eh ----- --- ---- 1 eg #a ef a pull of #cjj pounds #d #a1bjj pounds will be exerted at the pin f or g4 ,this total pull must be divided equally between the arms eg and ef1 giving #fjj pounds pull on each4 ,according to the principle of the lever1 the distances through which these forces act are inversely proportional to the forces acting4 ,it is assumed that the brakeman can exert the force of #ej pounds through #cf inches2 if this is the motion of the end of the hand lever a1 one-sixth of this1 or #f inches1 will be the motion at c and1 therefore1 at h2 one-fourth of #f inches or #a inches will be the motion at f and g2 that is1 f will increase its half of the brake band #a inches in circumference1 and g will do likewise with its half1 making the total circumference #c inches more1 or the diameter #a inch more1 and thereby moving the band away from the drum inch radially4 ,the levers are all shown in mid-position to make the figure more simple1 but the relative leverages remain the same at all points in the motion4 ,this is an example of simple levers1 but the force applied at the hand lever may be increased in a much greater ratio by the use of a device known as a differential lever4 ,illustration3 ,,fig4 #bh #dg4 ,the ,differential ,lever4--,the principle of the operation of the differential lever with which a constantly increasing force can be applied to the brake strap is illustrated in ,fig4 #bh4 ,let a o represent a straight lever whose fulcrum is at o2 and let the reach rod be attached at e4 ,in this position1 if a o #f ------ --- 1 e o #a the effective lever is #f to #a4 ,if1 now1 the lever is moved through #cj to the position b o1 the force applied at a moves through the distance a b1 and the reach rod through the horizontal distance k f1 so that the effective leverage is increased a small amount e k and the ratio of the arms becomes a o ------- 4 k o ,when the lever is moved another #cj to the position c o1 the reach rod moves a distance i g1 which is less than k f1 so that the effective leverage is increased by the amount k l and the ratio of the arms becomes a o ------ 4 l o ,again1 moving the lever #cj more to the position d o1 the reach rod moves through the still shorter distance j h1 which is less than i g1 and the effective leverage becomes very great4 ,it is evident from this that the farther the lever is moved toward d the greater becomes the effective leverage4 ,in practice1 it would be impossible to move the lever through the entire quadrant to advantage1 and there would also be more movement of the reach rod at the beginning of the stroke and less at the end than is needed to produce the desired effect4 ,illustration3 ,,fig4 #bi ,from the principle just given1 it is plain that1 if p o1 ,fig4 #bh1 represents a brake lever with the reach rod attached at q1 a smaller pull will be exerted on the brake band if the lever is moved to the position b o than would be exerted if a lever were moved through the same angle from b o to d o4 ,the movement from p o to b o is a convenient and easy one for the engineer to make1 while the movement from b o to d o is inconvenient4 ,to overcome the inconvenience and still to obtain the advantage of this latter movement1 the differential lever shown in ,fig4 #bi is used4 ,by means of an arm placed on the lever1 the point of attaching the reach rod is at l instead of p2 hence1 when the handle r b is moved to the position s b1 the point l moves to m1 thus securing a greater and gradually increasing pull with the easier movement of the handle4 ,a differential lever may be advantageously used in connection with any band or post brake and on a drum running in either direction4 ,such levers are considered by many preferable to the differential brake4 #dh4 ,power ,brakes4--,large drums and heavily loaded drums cannot be controlled by hand-power brakes1 and in such a case some other form of power1 such as steam1 compressed air1 or water1 must be used4 ,illustration3 ,,fig4 #cj ,fig4 #cj shows1 in outline1 how such power is applied4 ,the movements of the hand lever ,a1 instead of being directly communicated to the lever operating the brake1 merely control the valve v connected with the cylinder a4 ,by means of this valve1 steam1 compressed air1 or water is admitted to either end of the cylinder and this moves the piston in the direction necessary to apply or release the brake4 ,there are a number of varieties of such power brakes1 differing in structural details1 but the action of all is essentially the same4 ,with steam or air power1 the brake would be applied with its full force almost instantaneously1 thus subjecting the various parts of the mechanism to very severe and objectionable strains1 unless the valves were modified so as to regulate the admission of the steam or air4 ,one method of controlling this action is the use of a valve that requires a long travel to give it a full opening4 ,such a valve can be opened a little1 so as to allow the steam to leak through and thereby increase the pressure in the cylinder gradually4 ,as the motion is difficult to regulate1 a better method is by means of a floating valve1 described in ,hoisting1 ,part #a4 #di4 ,crank ,brake4--,in addition to the brake applied to the drum and intended for use mainly in emergencies1 many hoisting engines are also fitted with a strap brake applied to the crank-disk4 ,in some states1 crank-brakes are required by law4 ,in order to give a large bearing surface1 the crank-disk is made very large4 ,,hoisting 7,,part #d7 ,serial #hea;,d ,edition #a ,,hoisting ,,appliances ,,sheaves #a4 ,sheaves are grooved iron or steel wheels used to carry or guide a rope4 ,the general method of mounting them on a frame for hoisting light loads is shown in ,fig4 #a4 ,the journal boxes are so constructed as to be easily taken apart for inspection or repair4 ,for hoisting heavy loads1 the timbers must be braced1 as is explained under the heading ,head-,frames in this ,section4 ,sheaves are of two styles--those composed entirely of cast-iron and those with cast-iron hubs and rims and wrought-iron or soft-steel arms or spokes4 ,illustration3 ,,fig4 #a #b4 ,the cast-iron sheave1 ,fig4 #b1 has arms with a cross-section1 as shown at a b1 and with the flanges of the arms tapering from the hub to the rim2 that is1 d is greater than c and f is greater than e4 ,the bottom of the groove g in the rim should be a circular arc1 whose radius is a little larger than that of the rope used over the sheave1 to allow for the angling of the rope due to its fleeting on the drum4 ,the flanges h are made quite deep to prevent the rope jumping off4 ,this sheave is cheaper than a combined cast-iron and wrought-iron or steel sheave1 and for many purposes it is entirely satisfactory4 ,its great weight is an objection1 because it adds to the weight on the journals and also offers considerable resistance to being set in motion and stopped4 ,illustration3 ,,fig4 #b ,if a sheave is merely used to carry the rope or to deflect it only a little1 the contact and pressure between the rope and the sheave is small2 consequently1 the power of the rope to turn the sheave will be slight4 ,in such a case1 when the rope starts or stops quickly1 as it usually does in modern hoisting plants1 the heavier the sheave the more will it lag behind the rope and the greater will be the wear on the rope due to slipping4 #c4 ,the sheave with a cast-iron hub and rim and wrought-iron or soft-steel spokes1 ,fig4 #c1 is an excellent and extensively used sheave1 especially the larger diameters4 ,the spokes are screwed into the hub and rim and are carried to the right and to the left of the hub alternately1 as shown in ,fig4 #c 7b71 so as to take hold of the opposite ends of the hub1 thereby giving stiffness to the sheave against any side stress4 ,illustration3 ,,fig4 #c ,with a sheave having cast-iron arms1 the load from the rope is transmitted to the shaft by a compressive stress through the arms directly under the load2 that is1 if a rope runs over the sheave1 ,fig4 #b1 putting a load on it from j to k1 this load will be transmitted as a compressive stress through the arms l and m to the hub and the shaft4 ,of course1 a part of this load is carried around the rim to the lower arms and is supported by them in tension1 but these lower arms are not considered in designing the sheave because cast-iron is of comparatively little value in tension1 whereas it is of great value in compression4 ,in the case of the sheave with wrought-iron arms1 or spokes1 ,fig4 #c1 the load is transmitted around the rim to the side opposite its point of application and is carried from there to the hub and shaft by the tension of the spokes2 in fact1 from the method of construction1 the spokes in this sheave act only by tension4 ,the sheave is strong and rigid1 and much lighter than a cast-iron sheave of the same strength1 so that there is less wear between it and the rope due to any slipping action when it is started or stopped4 ,illustration3 ,,fig4 #d ,illustration3 ,,fig4 #e #d4 ,sometimes1 the spokes1 instead of being radial as in ,fig4 #c1 are made tangent at the center of the wheel1 ,fig4 #d1 to an imaginary circle1 which is about #b inches in diameter for a #aj-;foot sheave4 ,alternate pairs of spokes are made tangent to the opposite sides of the circle1 so that they pull against each other1 and this makes the sheave rigid in both directions4 ,that is1 spoke ,a is tangent to the right side of the tangent circle and ,a to the left side1 while spoke ,b is tangent to the right side of the circle and ,b to the left side4 ,the pair ,b ,b is joined to one end of the hub1 while the pair ,a ,a is joined to the other end1 thus giving lateral stiffness to the sheave4 ,this arranges the spokes in groups of four1 so that the total number must be some multiple of four4 ,the tangential direction of the spokes is often necessary in very large sheaves carrying heavy loads1 because with such a sheave it requires considerable force to turn the shaft in its bearings1 and while radial spokes act only as long levers in turning the shaft1 with tangential spokes there is also a direct pull to do it4 #e4 ,wood-,lined ,sheaves4--,the rims of all sheaves are made either solid or with wooden lining1 as shown in section in ,fig4 #e4 ,one flange a of the rim is a separate piece that is held on by bolts b4 ,the wooden lining is in the form of blocks placed with the grain of the wood running radially and held securely by clamping together the two flanges with bolts1 as shown4 ,with such a sheave1 there is much less wear on the rope than there is with one that has a plain cast-iron rim4 ,the wear of the sheave proper is also avoided1 because as the blocks wear down they are taken out and replaced by new ones4 #f4 ,diameter of ,sheave4--,the size of a sheave about which a rope bends is determined generally by the size of the rope to be used1 as explained under ,wire ,ropes in ,hoisting1 ,part #b2 but1 if the rope is simply to be supported in a straight line1 the space available for setting the sheave and its cost and weight usually determine the size used4 ,the minimum allowable diameter of sheave should not be used unless it is necessary to do so1 for the larger the sheave the less will be the wear of the rope due to the bending1 and the longer the life of the rope1 but the cost of the sheave1 which increases with the size1 puts a limit in the other direction4 #g4 ,rollers and ,carrying ,sheaves4--,wooden or iron rollers are sometimes used for rope carriers or guides1 instead of light sheaves1 when the rope has merely to be supported and there is no bending of the rope1 excepting the slight amount due to the sagging between the rollers4 ,the diameter of the rollers is of little importance in such cases so far as the rope is concerned4 ,if they are for use on a slope to keep the rope from dragging on the ground1 they must be small1 because the cars must run over them1 and mine cars are usually made low because of restricted headroom in the mine4 ,rollers and carrying sheaves are fully described and illustrated in ,haulage4 ,if a hoisting rope changes its course from a straight line1 even if the deflection is only a small amount1 a roller is not advisable and a sheave should be used1 if possible4 ,,cages ,,cages ,,for ,,vertical ,,shafts #h4 ,a cage is a carriage used for hoisting mine cars and their contents1 men1 timber1 etc41 in both vertical and inclined shafts4 ,cages are built of wood strengthened with iron or steel1 or entirely of iron or steel4 ,illustration3 ,,fig4 #f #i4 ,the cage shown in ,fig4 #f is much used in the anthracite region of ,pennsylvania4 ,it is made largely of oak strengthened with iron and the size varies to suit the shaft1 being sometimes as large as #f feet wide by #ab feet long4 ,the general construction of the cage is evident from the figure1 but several appliances that should be common to all cages in some form or other require detailed explanation4 ,a covering a1 called a bonnet1 protects persons on the cage from objects falling down the shaft1 and is required by law in some ,states4 ,this bonnet is made of steel plate with flanges or angle irons to stiffen it1 and is usually inclined4 ,to prevent objects of moderate size from wedging between the edge of the bonnet and the shaft lining1 the former is sometimes made shorter than the cage1 so that a space of about a foot is left between its lower edge and the shaft lining4 ,a short bonnet of this character does not1 however1 fully protect persons on the cage4 ,the upper part of the bonnet is fastened to the upper cross-bar of the cage by two hinges and is held up by rods b that are attached to the bonnet and have sockets at their lower ends1 which fit over pins bolted to the uprights of the cage4 ,by raising the rods from the pins the bonnet can be lowered so that pipes or long timbers may be lowered on the cage4 #aj4 ,safety catches are intended to prevent a cage falling in case the hoisting rope breaks4 ,a common form1 shown at c1 ,fig4 #f1 and in detail in ,fig4 #g1 consists of a pair of toothed cams j1 ,fig4 #g1 fastened on each side of the cage near the shaft guides4 ,the drawbar b to which the rope is attached extends through the top cross-piece of the cage and through the cylinder d1 at the bottom of which is a plate c supplied with lugs for the rods f that connect it with the levers g4 ,inside the cylinder are three powerful rubber springs1 which are in compression so long as the cage hangs from the rope1 but are extended if the rope breaks1 drawing the rods f down and with them the ends of the levers g to which they are attached2 and1 since the levers are pivoted1 their other ends are moved upwards and with them the rods k4 ,the cams j are each attached to one end of the rods k in such a manner that as the rods move upwards they rotate the cams inwards until they come in contact with the shaft guides4 ,the teeth of the cams grasp the wooden shaft guides and stop the descent of the cage4 ,the cams are provided with projections a and l that strike the guide and thus prevent the cams turning entirely around4 ,fig4 #g 7a7 shows the springs extended and the dogs j just about to grasp the shaft guides1 while ,fig4 #g 7c7 shows the position of the dogs when the springs are compressed as they are when hoisting4 ,at e in cylinder d1 ,fig4 #g 7b71 there are slots for the lugs of plate c to move up and down as the spring is compressed or extended4 ,instead of rubber springs1 helical steel springs are sometimes used1 and with a somewhat different design flat steel springs are used4 ,illustration3 7a7 7b7 7c7 ,,fig4 #g ,illustration3 ,,fig4 #h ,the cams1 or dogs1 may be placed at any point along the upright post of the cage1 and in some cases two sets of cams are used on each side1 one set at the top and another in the middle1 both sets being connected by rods so that they work together4 ,practical tests of these catches1 made by allowing the cage to drop1 show that they are1 as a rule1 very efficient devices4 ,the cams usually take hold at once1 the cage dropping only a few inches1 or1 at most1 a few feet if the guides are dry and free from oil4 ,when the guides are very greasy or wet1 the cage may drop several feet before the cams take a firm hold and stop it1 and with ice-covered guides1 instances are given where the cage has fallen #ae feet before the cams ploughed their way through the ice and took firm hold of the guides2 but in so doing the momentum the cage acquired was so great that the guides were destroyed4 ,fortunately for the utility of safety catches1 ropes are usually broken while a loaded cage is being raised1 and the cage has an upward momentum2 if a rope breaks when the cage is descending at a speed of #cj or #dj feet a second1 its momentum is so great that either the catches or guides break4 ,the catches generally hold and either the guides or cage suffer more or less injury under such circumstances4 ,instead of being placed near the top of the cage the dogs are frequently placed near the center1 or near the bottom2 in some cases two sets of dogs have been used1 one set being at the top and the other at the bottom4 ,instead of being cam-shaped with a number of small teeth on the rim of the cam1 as shown in ,fig4 #g1 the dogs are now frequently made consisting of one or more strong straight teeth on each side of the guide4 ,these teeth are operated similarly to those shown in ,fig4 #g1 and are driven into the guides if the rope breaks1 thus holding the cage more firmly than the cam-shaped guides1 particularly where the guides are wet4 ,,table ,i ,platform ,guides ---------------------------------------- -,safe ,load ,weight ,width ,length ,size ,distance ,between ,pounds ,pounds ---------- ,feet ,inches --------------- ,feet,inches ,feet ,inches ---------------------------------------- ---------------- #d #c #f #f #f #d #f #e1jjj #b1jjj #f #aj #f #aj #f #c #h1jjj #c1hjj #aa4 ,the ,heavy ,steel ,cage4--,the cage that is shown in ,fig4 #h is made of iron and steel except the wood flooring1 which is laid in two courses1 one lengthwise and one diagonal4 ,the joints should not be driven too tightly1 as the wood is likely to swell4 ,the track is bolted to the floor1 or deck1 of the cage4 ,the cast-steel safety dogs are operated by steel springs a1 coiled about the bars b1 which are connected to the drawbar c by chains1 as shown4 ,the drawbar drops if the rope breaks and thus assists the action of the springs a4 ,this cage is in use at both coal and iron mines1 and is built to suit any size of shaft and guides4 ,standard sizes are given in ,table ,i4 #ab4 ,the ,light ,steel ,cage4--,fig4 #i shows a light steel cage much used at gold and silver mines4 ,it has a spring drawbar and steel safety dogs1 operated by steel springs1 as in ,fig4 #h1 but the floor is of steel grating in order to give as little air pressure as possible against the cage4 ,the openings a in the side frames are provided so that through them the nuts can be tightened on the bolts that hold the shaft guides4 ,the cage is provided with bails b that swing down over each end of a car to hold it on the cage4 ,illustration3 ,,fig4 #i #ac4 ,multiple-,deck ,cages4--,cages are sometimes built that have two or more decks or platforms one above the other1 thus giving greater hoisting capacity to a shaft4 ,a two-deck1 safety1 hoisting cage is shown in ,fig4 #aj4 ,the upper deck is heavier than in a single-deck cage of similar construction4 ,the lower deck is suspended from the upper deck by means of pins so that it may be removed at any time4 ,a double-deck cage may be used by first changing the car on the upper deck and then bringing the lower deck to the track level and changing the other car4 ,time can be saved by having two track levels1 both at the loading and landing stations1 enabling both decks to be loaded and unloaded at the same time4 ,illustration3 ,,fig4 #aj ,multiple-deck cages have been mainly used at ore mines in ,america and very few coal mines have been equipped with them4 ,cages are also built to accommodate two cars placed either side by side or end to end4 ,illustration3 ,,fig4 #aa ,,automatic ,,dumping ,,cages #ad4 ,a dumping cage is a cage so constructed that at the proper place it can be automatically tipped sufficiently to dump the contents of a car that is on it and will then right itself for the down trip1 thus avoiding the necessity of removing the car from the cage1 and saving time at the head4 ,the construction of the cage is such that the car is held firmly in place while dumping4 ,the principle of the self-dumping cage is illustrated in ,fig4 #aa1 the cage being shown in its highest and lowest positions4 ,the cage is made in two parts a and b4 ,the fixed frames b slide on the guides k and have attached to them the safety catches and hoisting gear4 ,the movable part a is united to the frame b by the hinge c4 ,the platform d1 on which the car rests1 is fastened to the movable part a by the support e and further secured by the braces f4 ,at the top of a is attached the wheel g that runs along the rail h1 keeping a in an upright position until it reaches the dumping place i4 ,here the rail h is bent as shown and the wheel g is made to follow it by means of the guide j4 ,this throws the top of a over so as to incline the platform and dump the car that is on it4 ,on lowering1 the cage rights itself when g passes below the point i4 ,the part b is kept in a vertical position by means of shoes that slide on the main guides k4 ,it is possible to dispense with the guide rail h by attaching a flange to the top of a at the back1 to slide on the main guide k4 ,this flange should be shorter than the shoe on b4 ,the main guide is cut away at the point where this flange comes when the wheel g enters the curved guide j1 leaving an opening just large enough to allow the flange on a to pass through4 ,the shoe on b1 being longer1 completely spans the space and cannot pass through1 but makes b move straight up on the main guides4 ,the bottom of the cage in ,fig4 #aa has an interrupted track1 and at the bottom of the shaft the track is also interrupted1 as shown in the plan at the bottom of the figure1 but in such a way that when the cage is resting at the bottom this portion of the track n projects up through the bottom of the cage and makes a continuous track4 ,when the cage is raised the wheels of the car drop into the spaces n in the cage bottom1 thus preventing the car from running off the cage during hoisting or dumping4 #ae4 ,slope1 or ,inclined-,shaft1 ,hoisting4--,in a slope1 or inclined shaft1 the mine cars are attached directly to the hoisting rope and hoisted singly or in trains for inclinations less than #ce1 at which inclination the material will begin to fall from the top of the car4 ,for steeper slopes1 it is customary to use a slope cage or carriage on which the mine car is hoisted1 or else to dump one or more cars of the material into a gunboat1 or skip1 at the bottom of the slope or at some landing along the slope1 and to then hoist the gunboat1 or skip4 ,fig4 #ab shows a cage for use in a slope or steeply inclined shaft4 ,it is made of steel with timber platform and differs from a vertical shaft cage mainly in having its upper frame inclined and in running on four wheels a1 b4 ,these wheels usually run on timber guides1 so that the safety dogs c will take hold of the guide in case the rope breaks4 ,for slopes of variable inclination1 the platform d may be made adjustable by means of a hand lever so as to be always level4 ,illustration3 ,,fig4 #ab #af4 ,a slope carriage is a frame so constructed that when rails are placed on the top and a mine car run on them the car will be practically horizontal4 ,the carriage is mounted on wheels and axles in order to follow the slope tracks1 and is supplied with a drawbar1 or with hooks1 as shown in ,fig4 #ac1 for attachment to the hoisting rope4 ,these carriages are sometimes built to run on a slope track of the same gauge as the mine cars1 but to insure stability they have generally a broader gauge4 ,the headroom necessary is governed not so much by the form of the carriage as by the length of the car and the inclination of the seam4 ,this height is less when the cars are placed on the carriage with their length across the slope than when they are run on lengthwise2 but this arrangement increases the width of the slope4 ,when the inclination is very steep1 the wheels are sometimes placed on the sides of the carriage and above its center of gravity and run between two tracks or guides1 on each side of the slope4 ,illustration3 ,,fig4 #ac ,the carriage1 ,fig4 #ac1 is for use on slopes of a uniform inclination4 ,it is made almost entirely of heavy timber1 is stiff and simple of construction1 and is easy to repair4 ,its details will be readily understood from the illustrations1 except perhaps1 the device for locking the car to prevent its running off during the hoist4 ,the middle portion of the platform a having a piece of the car track on it1 may move vertically up or down4 ,as shown in the side elevation1 it is resting on the horizontal timbers b of the carriage in a position ready for hoisting4 ,at the end of the hoist1 when the cage settles on the keeps c1 shown in the end elevation1 this platform reaches them first and is supported by them while the rest of the carriage descends still farther until the timbers d rest on the keeps also4 ,the track on the platform a is then at the same level as that on d1 and the car can be run off and replaced by another4 ,when the empty car is on1 the carriage is lifted from the keeps1 but the platform a remains until the timbers b pick it up1 when the keeps are swung back out of the way and the carriage is lowered4 ,slope carriages usually have the tracks running crosswise so that the car is pushed on from the side instead of from the end4 ,,skips1 ,,or ,,gunboats #ag4 ,skips are self-dumping cars used for hoisting material from shafts or slopes4 ,in a vertical shaft1 they run in guide tracks2 but in a slope they have wheels and run on a track like a car4 ,in the anthracite region of ,pennsylvania1 skips are called gunboats4 ,as the skip is not detached from the hoisting rope1 time is saved at the top over that needed to unhook and hook the cars to the rope or to remove and place the cars on the cage4 ,but since dumping the material into the skip and again on the surface produces considerable fine material1 skips1 or gunboats1 are seldom used for any material1 such as coal1 that is often lessened in value by being broken4 ,the skip1 or gunboat1 shown in ,fig4 #ad is closed along the top a and open at the end b1 which is cut at about the angle of the slope in which it is to be used1 so as to remain practically level during the hoist4 ,it is made of sheet iron1 the bottom1 sides1 and top being stiffened by angle or ,t irons1 and the back stiffened and protected by #c-;inch planks1 backed by #c #f timbers4 ,the wheels of a skip are fixed on the axles1 which run in journal boxes1 thus insuring smoother running than is obtained with loose wheels4 ,the details of the journal bearings1 as shown in ,fig4 #ae1 consist of three castings1 the bracket a1 which is bolted or riveted to the gunboat1 a pivot casting b1 and the bearing proper c4 ,the bearing c rests on the axle and carries1 by means of trunnions d1 the pivot casting b1 on the top of which is placed a rubber cushion e to lessen the shocks between the casting and the bracket4 ,illustration3 ,,fig4 #ad ,illustration3 ,,fig4 #ae #ah4 ,method of ,loading ,skips4--,in ,fig4 #af1 a skip a is shown in a slope standing immediately below a level where a car b is ready to have its load dumped into the skip4 ,instead of dumping the mine car directly into the skip1 a bin is frequently provided at the level station1 or landing1 into which the mine cars are dumped and from which the material is loaded into the skip through suitable chutes4 ,the use of such bins makes the hoisting of material largely independent of the working conditions on the levels and the hoisting can be more systematically and satisfactorily carried on4 ,illustration3 ,,fig4 #af ,illustration3 ,,fig4 #ag ,if the material comes to the slope as shown in ,fig4 #ag1 it is necessary to let down a bridge a1 on which the car runs1 in order to reach the skip4 ,after the car is dumped1 the bridge is lifted out of the way into the dotted position1 so as to leave the slope unobstructed4 #ai4 ,method of ,dumping ,skips4 ,to dump a skip at the surface1 the tracks are extended above the slope mouth1 as shown in ,figs4 #ah and #ai1 and are arranged so that the material may be dumped directly into a bin or into cars as desired4 ,in the arrangement shown in ,fig4 #ah1 the front wheel of the skip strikes a stop a and1 since the bail of the skip is pivoted far down toward the lower end1 as the rope continues to pull1 the rear of the skip is raised and the material is dumped4 ,the objection to this method is that if the rope is slightly overwound the skip is pulled off the track and does not then right itself on the track when the rope is released4 ,illustration3 ,,fig4 #ah ,in the ,lake ,superior iron and copper region1 many of the dumps are built as shown in ,fig4 #ai4 ,in this dump1 the rails of the main track a are curved as shown at b2 a short distance back of the beginning of this curve1 another track c begins outside the track a and runs in a straight line parallel to the inclination of the hoist4 ,the track c is of a wider gauge than a1 and the rear wheels of the skip have a wider tread than the front1 so that they will run on c while the front wheels take the curved track until they strike the stop d4 ,the rear of the skip will thus be raised and the material dumped4 ,there are but two tracks in the main part of the slope4 ,illustration3 ,,fig4 #ai ,illustration3 ,,fig4 #bj ,illustration3 ,,fig4 #ba ,in the method illustrated in ,fig4 #bj1 the rear and front wheels have the same tread1 but the rear axle is longer than the front and has rollers a on each side4 ,these strike the track b1 and while the front wheels follow the curved track c these rollers run on the track b and thus raise the rear end of the skip4 #bj4 ,skip ,cage4--,where a self-dumping skip is to be used in a vertical or highly inclined shaft and it is desired to use safety catches1 the skip a is mounted in a cage or frame b1 ,fig4 #ba1 similar to the self-dumping cage1 ,fig4 #aa4 ,the skip being pivoted at c one side of the center1 and resting on the frame of the cage1 tends to remain upright until it reaches the dump2 but for safety it is sometimes locked in place by the latch d1 which hooks over the pin e4 ,when near the top1 the roller f on the end of the latch d comes in contact with a bar that depresses the roller and thus unhooks the latch4 ,the roller g enters and travels along the guide rails h1 tipping the skip4 ,there are two rollers g1 one on either side of the skip4 ,the nose i is temporarily caught on the roller j1 thus stopping the movement of the skip sidewise and away from the upright guide4 ,,buckets #ba4 ,buckets1 such as are used for hoisting material during shaft sinking1 are continued in use after mining begins when the amount of material to be hoisted is small4 ,,car ,,locks #bb4 ,several methods of keeping the car on the cage have already been illustrated3 by chains1 ,fig4 #h2 by bails1 ,figs4 #i1 #aj1 and #ab2 by omitting sections of the rail under the car wheels1 ,fig4 #aa2 and by dropping a portion of the platform1 ,fig4 #ac4 ,a very common way is merely to put a pin through the hole in the drawbar and into the floor of the cage4 ,another common device consists of a brake block that fits between the wheels and can be thrown in from the side by a lever when the car is in place4 ,another device consists of a yoke1 which1 by means of a lever1 is raised when the car is in place so that it passes about the axle and thus holds the car4 ,a device frequently used on self-dumping cages is shown in ,fig4 #bb4 ,illustration3 ,,fig4 #bb ,the curved bars a of iron1 which just fit around the car wheels as shown1 are attached to the loose bars b1 on the ends of which are the weights c4 ,when the cage is at the bottom1 these weights strike on a cross-piece and are raised to the position shown by the dotted lines1 throwing out the bars b1 as shown by the dotted line1 thus releasing the wheels4 ,the devices shown in ,figs4 #aa1 #ac1 and #bb do not come into action until the cage leaves the landing and the cars must1 therefore1 be watched until that time4 ,,cage ,,guides #bc4 ,guides are used in all vertical shafts of any considerable depth and in many highly inclined shafts to keep the cage from swinging about and striking the sides of the shaft4 ,they are made of wooden rails1 iron rails1 or wire ropes4 ,in ,american mines1 timber guides predominate1 although some iron ones are used1 and for small shafts at ore mines wire-rope guides are common4 ,in ,english mines1 wire ropes1 called conductors1 are very largely used4 ,this difference in practice is probably due to the fact that in ,english mines the shafts are usually round and the cages are rectangular4 ,in such a shaft1 the wire-rope conductors hang from the head-frame without any cross-bracing1 but they require a strong support1 as both the weight of the ropes and the strain to give the necessary tension come on the head-frame4 ,when both the shaft and the cage are rectangular1 as in most ,american mines1 timber guides are easily put in and they offer a good surface for the safety catches to grip4 ,illustration3 ,,fig4 #bc ,wooden guides are always rectangular in cross-section and in the ,united ,states are usually made of yellow pine or other long-grained wood that does not splinter easily2 in some localities1 oak or some of the other harder woods are used4 ,there is no fixed size for cage guides1 but #d #d1 #f #h1 #h #aj1 and #d #aa timbers are frequently used4 ,the guides are firmly fastened to the shaft buntons with lagscrews or with bolts countersunk into the guide so as to be clear of the shoes1 and1 to secure safety with speed in hoisting1 the ends of the guides must be put together with joints that are not liable to displacement and that offer no projections to the shoes in passing4 ,the buntons to which the guides are secured must be so firmly fastened that they cannot get out of place1 and the guides must be set as nearly as possible in a straight line1 because if they are crooked the cage is thrown back and forth as it travels along them and this not only increases the strain on the hoisting rope and engine1 but sooner or later loosens and misplaces the guide4 ,fig4 #bc shows a plan of a cage with the bunton ,a1 guides ,b1 and cage shoes ,c in their normal positions4 ,,landing ,,fans ,,or ,,keeps #bd4 ,in order to take the strain off the hoisting rope while a cage or skip is being loaded or unloaded1 a mechanism to support the cage is placed at the top and at any level of the mine where loading is done1 excepting at the bottom level where all that is usually required are the cross-timbers for the cage to rest on4 ,these supports have different names in various localities1 being known as fans1 keeps1 cage rests1 landing dogs1 landing chairs1 wings1 etc4 ,their use increases the safety of caging4 #be4 ,a common form of keeps is shown in ,fig4 #bd4 ,the cage a rests on four square bars of iron b1 one under each corner of the cage4 ,these bars have an eye or hub at the lower end and are keyed to the shafts d1 which rest in cast-steel boxes4 ,the levers e and f1 which are also keyed to the ends of the shafts d1 are connected by a rod g4 ,chains h prevent the fans from moving too far under the cage4 ,when the cage is to be lowered1 it is first lifted clear of the fans and the lever e is moved into the dotted position1 thus moving the fans b out of the way and permitting the cage to be lowered4 ,the inside of the fans have no projections1 and the operating mechanism is such that no harm would come if they were left in the shaft and a hoist were made1 as the cage would open out the fans and pass through them without any trouble4 ,if1 however1 the fans are not drawn back at all the headings in the shaft when the cage is lowered1 great damage results when the cage strikes the projecting fans4 ,to avoid the possibility of such an accident1 fans have been devised that fall back out of line of the shaft as soon as the weight of the cage is removed from them4 ,illustration3 ,,fig4 #bd #bf4 ,hydrostatic ,fans4--,most fans in use are built on the same principle as those just described1 although the details of their construction may vary4 ,an objection that can be raised against them is that1 with large cages and heavy loads1 the jar caused by letting the cage down on such a rigid support is very hard on the cage4 ,all cages1 particularly heavy ones1 suffer much more wear from being landed too suddenly than from the strains of hoisting4 ,for this reason1 it is advisable to make the upper parts as light as compatible with strength and the side pieces stronger than needed for the actual strains to which they are subjected4 ,hydraulic fans1 ,fig4 #be1 have successfully overcome this trouble4 ,the cylinder shown is one of four on which the cage rests4 ,the eye at the lower end fits on a bar by means of which the cylinders are moved backwards and forwards similar to the motion of the fans b1 ,fig4 #bd4 ,in ,fig4 #be 7a71 the cage is shown as about to rest on the jaw a4 ,as the cage settles1 it pushes the plunger b downwards1 but this action is resisted by oil in the cylinder at c4 ,at first1 this resistance is very slight1 because the ,v-shaped grooves d in the plunger1 which are of considerable size at the end of the plunger1 allow the oil to escape freely into the upper chamber e4 ,these grooves1 however1 taper down to nothing1 so that the flow of oil through them decreases until none can pass except by leakage around the plunger4 ,this allows the plunger with its load to settle slowly to the bottom1 as shown in ,fig4 #be 7b74 ,illustration3 7a7 7b7 ,,fig4 #be ,if now the cage is lifted and the weight thus removed from the jaw a1 the spring g pushes the plunger b outwards and allows the oil to run from e back into c4 #bg4 ,pneumatic ,fans4--,a pneumatic fan1 shown in section in ,fig4 #bf1 is one in which the shock of the landing is partially relieved by a cushion of compressed air4 ,the fan is keyed at the bottom to the shaft a that rotates it1 as in ,fig4 #bd4 ,the cylinder b contains the plunger c1 which is kept at the top limit of its motion by the spring d4 ,when the cage lands in the jaw e1 the plunger descends1 compressing the air in the cylinder b4 ,the air escapes slowly through the _/-inch hole f1 thus allowing the cage to settle into place with very little shock4 ,these fans should be made of wrought-iron or cast-steel so as not to be easily broken4 ,illustration3 ,,fig4 #bf #bh4 ,cage ,chairs4--,in the case of a cage required to stop at a large number of levels1 it is expensive to provide fans at each level1 and to obviate this a strong steel bar or dog may be used under each corner of the cage1 all four bars being connected to a lever on the cage1 by means of which they can be thrown out at will so as to rest on supports provided at each level4 ,fig4 #bg shows ,gray's patent cage chair1 which operates on this principle4 ,the sliding bars a are connected by the cross-bars b1 which are pivoted at the center and operated by the bar c through the links d4 ,by moving the lever e into the position shown1 the bars a are thrown out so as to rest in notches or on wall plates in the shaft4 ,the springs f1 through the cross-bars b1 force the sliding bars a back under the cage when the lever e is released4 ,,head-,,frames #bi4 ,a head-frame of wood1 iron1 or steel is built over a shaft or slope mouth to carry the sheaves over which the hoisting ropes are conducted from the mine to the drum of the hoisting engine2 it also usually carries the upper portion of the cage guides or1 in the case of a slope1 the tracks for cars4 ,illustration ,illustration3 ,,fig4 #bg ,a head-frame must be strong enough to bear the strain brought on it due to the total load hoisted and the pull of the engine in hoisting this load2 it must also be rigid in construction to withstand the severe vibration and shock to which it is subjected on account of the rapid hoisting and the jar due to the landing of the cages4 ,illustration3 ,,fig4 #bh ,the amount and direction of stresses that a head-frame must resist are usually determined by applying the parallelogram of forces as follows3 ,fig4 #bh is a simple head-frame at a slope2 a is the drum of the hoisting engine with the rope coming from its upper side and running over the head-sheave b down to the slope cage c4 ,assuming that the angles e1 f made by the two portions of the rope with the horizontal are equal1 and that the pull on each part of the rope is #bj1jjj pounds1 to determine the amount and direction of the resultant of the two rope pulls1 proceed as follows3 ,extend the rope lines to the point of intersection g and from there lay off the two lines g h and g k1 to some definite scale1 representing the pull of the rope4 ,if a scale of #b1jjj pounds to inch is taken 7 inch #b1jjj pounds71 g h and g k will each be #a inch long4 ,complete the parallelogram by drawing h l parallel to g k and k l parallel to g h4 ,the diagonal g l represents the direction and amount of the force acting on the head-frame due to the pull of the two portions of the rope4 ,the diagonal1 by measurement1 is #a inches or _/ inches long1 and since each tenth inch equals #b1jjj pounds1 the stress on the head-frame in the line of the diagonal g l is #b1jjj #ae #cj1jjj pounds4 ,the figure also shows that the direction of this force is vertical1 hence there is no tendency for the frame to be pulled over to either side and1 theoretically1 side bracing is not needed4 ,illustration3 ,,fig4 #bi #cj4 ,consider now the case of a vertical shaft1 ,fig4 #bi1 in which1 as before1 a is the drum1 b the head-sheave1 c the cage1 and d the head-frame1 and assume the same pull of #bj1jjj pounds on each part of the rope4 ,as before1 extend the lines of the rope1 which are the lines of force along which the pulls due to the engine and the load act1 until they intersect at g4 ,from this point lay off on these lines distances representing the stresses in the rope to any scale4 ,using the same scale as before1 inch #b1jjj pounds1 the lines g h and g k representing the two forces will be each #a inch long4 ,completing the parallelogram by drawing h l parallel to g k1 and k l parallel to g h1 and drawing the diagonal g l through g1 the resultant1 g l _/ inches1 represents a stress of #ch1jjj pounds4 ,the direction of the resultant is also determined1 being in the line of the diagonal g l4 ,if the head-frame shown in ,fig4 #bh were used for this case1 it would be overturned by this resultant force1 unless the leg on the opposite side of the shaft from the engine were securely anchored1 so an inclined brace m is added to resist this overturning action4 ,the resultant of all forces acting on the head-frame should generally fall within the structure if the greatest stability is to be secured1 but when this cannot be done it is necessary to resist the overturning pull by anchoring the head-frame to its foundations much more securely than is the case where the resultant falls within the structure4 ,the direction of the resultant force may be obtained by drawing a line through the intersection of the lines of action of the forces at g and the center of the head-sheave b1 as may be seen in ,figs4 #bh and #bi4 ,illustration3 ,,fig4 #cj #ca4 ,in ,figs4 #bh and #bi1 the pull of one hoisting rope running from the top of the drum was considered1 but in most cases it is necessary to consider the pull from two hoisting ropes1 one running from the top and one from the bottom of the drum f1 as shown in ,fig4 #cj4 a b and a b represent the directions of action of the two forces acting on the hoisting ropes1 while the two vertical forces a c and a c acting down the shaft are approximately equal to the two forces acting toward the drum4 ,there are1 therefore1 two resultants a d and a d1 the directions of which are determined by lines from a and a through the center of the sheave e4 ,the amounts of these resultant forces can be determined by the parallelogram of forces as shown in ,figs4 #bh and #bi4 ,a resultant that is a mean between a d and a d1 both in position and amount1 is sometimes taken1 or the greater value as determined from a d or a d and the greatest inclination as given by a d may be used1 as being the worst theoretical conditions to which the frame may be subjected4 ,a head-frame usually has a vertical post approximately parallel to the vertical pull of the rope in the shaft1 and an inclined member g h approximately parallel to the resultant determined by the parallelogram of forces4 ,if g h1 ,fig4 #cj1 is parallel to the resultant1 the vertical leg h i is under no strain and merely supports the end of g h4 ,if the resultant falls between g h and h i1 both of these legs will be under compression4 ,if the resultant falls outside of g h1 the leg g h will be under compression and h i will be under tension4 ,the head frame will be most stable when the resultant falls between g h and h i1 but this cannot always be accomplished in building the frame on account of the conditions at the head of the shaft2 nor is it always advisable to do so from structural considerations4 #cb4 ,since wood is much better adapted to withstand compressive than tensile stresses and since steel is adapted to withstand either tensile or compressive stresses1 it is much more important that the members of timber frame conform as closely as possible to the theoretical line worked out in ,figs4 #bh1 #bi1 and #cj than in the case of a steel frame4 ,take1 for instance1 the case shown in ,fig4 #ca1 where for some local reason it is impossible to put an inclined strut in or near the line of the resultant stress to withstand the pull that tends to overturn the head-frame4 ,in a steel structure1 a can very easily be made a tension member by anchoring its lower end to a heavy foundation4 ,this resists the tendency to overturn and makes a very stable structure4 ,in practice1 braces can generally be located parallel to the line of resultant strain1 ,fig4 #bi1 or outside this line1 as shown in ,fig4 #cj1 so that the strain due to the pull of the rope will come mainly on the inclined brace and not on the upright4 ,to distribute the stress on the foot of the different parts of the frame1 an inclined brace is usually set farther from the shaft than the parallelogram of forces locates it1 and so placed that about two-thirds of the strain due to the pull of the rope comes on the brace and one-third on the upright parts of the frame4 ,in order to give the frame a more stable base and because the base must be larger than the top of the frame to bring the foundations back from the shaft mouth1 usually the members h i are also slightly inclined4 ,illustration3 ,,fig4 #ca ,wherever permanency of head-frames is required1 if steel is obtainable at a price at all comparable with wood1 steel structures are being used1 as timber frames rot4 ,,types ,,of ,,head-,,frames #cc4 ,there are three types of head-frame construction--the ,a type1 the square type without an inclined brace1 and the square type with an inclined brace4 #cd4 ,a ,type of ,head-,frame4--,fig4 #cb shows the construction of a triangular1 or ,a-shaped1 head-frame of which 7a7 is a side elevation and 7b7 an end view4 ,this particular frame is largely used at anthracite mines1 but the type is one quite commonly used for timber frames1 though the details of construction vary in different localities4 ,the height of the frame is from #cj to #ej feet1 and with direct-acting engines this height should be sufficient to allow a play of at least two-thirds of a revolution between the cage landing and the overwinding point4 ,the posts a are parallel to the hoisting rope b as it hangs down the shaft and the inclined brace c1 which resists any thrust that would tend to rotate the head-frame1 is parallel to the resultant pull of the two parts of this rope b2 the inclined braces d stiffen the frame and help support the cross-timbers m that support the cage guides e4 ,the sills f are made of three pieces of timber #h inches by #ad inches in cross-section4 ,the posts a rest in cast-iron shoes g that are firmly bolted to the posts and sills4 ,the inclined braces c1 d are fitted with cast-iron shoes h1 i4 ,the post a and the two braces c1 d are held in place at the top of the frame by the casting j1 which also supports the pillow-block k4 ,the posts a and the brace c are made up of two pieces of timber each #h inches by #ad inches in cross-section4 ,the brace d consists of one piece of timber #h inches by #ad inches in cross-section4 ,the transverse braces l consist of two pieces of timber #f inches by #ad inches in cross-section1 bolted through the timbers a and c4 ,the supports m for the guides are single pieces of #h #h timber4 ,the center post1 as shown in ,fig4 #cb 7b71 is braced by the two pieces n1 o1 which are supported by two timbers p1 q bolted to the two outside posts4 ,the posts a and the inclined braces c are further braced by the tie-rods r1 s1 t1 and u1 all of which are fitted with turnbuckles1 as shown at v4 ,the different posts are firmly bolted together1 the bolts being fitted with cast-iron washers4 ,illustration3 7a7 7b7 ,,fig4 #cb ,illustration3 ,,fig4 #cc ,fig4 #cc shows the construction of the ordinary timber gallows frame used at many ore mines4 ,fig4 #cd shows a steel ,a frame1 of which the principal dimensions are as follows3 height to sheave center #dh feet2 base #cc feet #aj inches by #ef feet4 ,legs a and b are made of laced channels1 as are also the central upright posts and cross-braces4 ,the forward inclined legs are made of ,i beams4 ,the weight of the frame is #ih1jjj pounds without the sheaves4 ,the advantages claimed for this type of design are that it gives a very strongly braced frame while using a minimum of material4 ,also1 in cases of overwinding1 the cage goes over the top of the frame without injury to the frame1 and should men be overwound they would fall only the height of the frame instead of being crushed against the top4 #ce4 ,square ,type ,without ,inclined ,brace4--,fig4 #ce shows a steel frame in which the tendency to be overturned by the pull of the rope is resisted by a nearly vertical tension leg as explained in ,art4 #cb4 ,each leg of the frame is built of channel bars connected by lattice bracing1 as shown1 and the legs are stiffened by horizontal channel cross-bars similarly braced and also by diagonal tie-rods1 provided with turnbuckles4 ,illustration3 ,,fig4 #ce ,illustration3 ,,fig4 #cd ,springs are sometimes placed under the journals of the head-sheaves to lessen the strain on the rope while starting the load2 the #ae-;foot head-sheaves of the ,robinson deep mine at ,johannesburg have locomotive springs under the journal boxes1 the actual load on each spring due to the weight of the sheave1 rope1 skip1 and rock being equal to about #bj1jjj pounds2 it was estimated that the sheave would thus be lowered by the load on it1 about #c inches1 which would be equal to an action of a spring giving motion of #f inches at the cage4 ,springs can often be used both on the rope and under the sheave in the same plant to advantage4 ,illustration3 ,,fig4 #cf #cf4 ,square ,type ,with ,inclined ,brace4--,fig4 #cf shows a very substantial frame with square tower and inclined brace4 ,illustration3 ,,fig4 #cg ,its principal dimensions are as follows3 height to sheave center #ei feet #f inches2 base of tower #ae feet #h inches by #ad feet2 distance of bottom of inclined leg from vertical post #dh feet4 ,each end post a is composed of two channels1 double-latticed4 ,the horizontal members b are ,i beams and each inclined member c is made up of two angles4 ,the inclined leg d is trussed as shown and built of channel and angle beams1 the main member being made of two channels1 the incline and base members of the truss being made up of two angles1 and the short vertical member of two channels4 ,the center post of the tower is similar to the end posts1 except that the uprights are ,i beams instead of channels4 ,the frame is designed for a static weight of #af1jjj pounds and for a maximum strain on the cable of #cb1jjj pounds4 ,fig4 #cg shows a frame of similar form1 but in which the landing platform is placed at a height above the surface1 so that the cars hoisted can be run off on a trestle and thus be delivered at the top of a car1 breaker1 tipple1 or ore house4 ,its principal dimensions are as follows3 height to sheave center #ge feet2 base #dj feet #aa inches by #ba feet #h inches4 ,the leg a is made of two angles4 ,the bracing leg b is built of two angles4 ,the diagonal braces c are single angles4 ,the horizontal braces are angles or channels of various sizes depending on the stresses4 #cg4 ,the head-sheave is supported directly on top of the main frame1 as shown in ,figs4 #cb1 #cd1 #cf1 and #cg1 or a small superstructure a is built on top of the main frame1 as shown in ,fig4 #ch1 so that the base of the sheave journals is perpendicular to the resultant pull on the frame1 that is1 to the theoretical direction of the inclined leg of the frame if one is used4 #ch4 ,timber frames are usually built by the mining company from its own designs4 ,steel frames are generally built by the structural steel companies from detailed plans and designs furnished by the mining company1 or from a skeleton diagram furnished by the mining company1 giving the loads on the rope and the general conditions about the shaft to which the frame must conform1 the frame being then designed and erected in detail by the steel company4 #ci4 ,enclosing ,head-,frames4--,head-frames are sometimes wholly or partially enclosed to protect them and the men from the weather4 ,a covering of boards is warmest4 ,all woodwork should be painted with fireproof paint and ample means for extinguishing fire should be provided4 ,a covering of corrugated sheet iron well painted on both sides to prevent rusting is often used instead of wood and lessens the danger of fire1 but is not as warm a covering as wood4 ,illustration3 ,,fig4 #ch #dj4 ,in many states1 it is required by law that the top of the shaft be protected by a fence or by gates to prevent persons falling down the shaft4 ,this protection is secured at the sides of head-frames by extra timbers or beams forming part of the frame1 or by means of a fence placed near the sides of the frame4 ,the ends of the shaft are protected by a bar placed across uprights1 by gates that swing like an ordinary door1 or more generally by vertical sliding gates that are raised by the cage when it comes to the surface and drop into place when the cage descends4 ,similar gates1 doors1 or bars should be used at all landings below the surface4 ,,head-,,frame ,,specifications #da4 ,the following is a sample set of specifications for a steel head-frame to be built from detailed plans furnished by the mining company4 ,this head-frame to be made from drawings to be furnished by the---- ,coal ,company1 and placed on foundations furnished by said company4 ,material4--,structure to be built throughout of soft structural steel1 net strength #ee1jjj to #fb1jjj pounds per square inch2 elastic limit not less than #cj1jjj pounds per square inch2 elongation1 #be per cent42 bending test1 bend flat on itself without fracture4 ,builder agrees to guarantee structure to withstand strains specified on drawings with factor of safety of #aj1 to provide for possible overwinding or sticking in shaft4 ,no steel shall be used less than inch thick except for lining or filling vacant places4 ,workmanship4--,the tower to be built in a neat and workman-like manner4 ,the pitch of the rivets 7distance between centers7 shall not exceed #f inches or sixteen times the thinnest plate1 nor be less than three diameters of the rivets4 ,the rivets used shall generally be inch1 inch1 and inch in diameter4 ,the distance between edges of any piece and the center of rivet hole shall not be less than #a inches1 except for bars less than #b inches wide2 when practicable it shall be at least two diameters of the rivet4 ,all rivet holes shall be spaced and punched1 so that when the several parts are assembled together a rivet of _/ inch less diameter than the hole can be entered hot into any hole1 without reaming or drifting4 ,the rivets when driven should fill the holes4 ,the heads must be rounded2 they must be full and neatly made1 and be concentric to the rivet hole1 and thoroughly pinch the connecting pieces together4 ,field riveting must be reduced to a minimum4 ,all joints and connections shall be neatly made1 the several parts to be brought together without twists1 bends1 or open joints4 ,inspection4--,all facilities for inspecting the material and workmanship shall be given by the builders during the erection of the head-frame4 ,the company reserves the right to reject any or all parts not built in accordance with the plans or these specifications4 ,final inspection of work #a month after being in actual service4 ,painting4--,all work1 before leaving the shops1 shall be thoroughly cleaned from all loose rust and scale1 and be given one good coat of paint well worked into all joints and open spaces4 ,in riveted ironwork1 the surfaces coming in contact shall each be painted before being riveted together4 ,bottoms of bearing plates and any parts that are not accessible for painting after erection shall have two coats of paint4 ,after the structure is erected in place1 it shall be given one coat of paint4 ,all recesses that will retain water1 or through which water can enter1 must be filled with thick paint or some waterproof cement before receiving the final painting4 ,the paint shall be a lampblack paint1 mixed with pure linseed oil1 or of red lead mixed with raw linseed oil containing ,japan dryer4 ,general ,clauses4--,the specifications and drawings are intended to cooperate and to indicate the principal dimensions and requirements necessary to the complete structure4 ,it being understood that while some work may be shown in the plans and not described in the specifications1 or vice versa1 and some minor details and fastenings are omitted from both plans and specifications1 the work is to be executed without extra charge therefor1 the same as if the minutest details were set forth in full in both drawings and specifications4 ,the contractor is to make good any defects of material or workmanship developing within #a year after final acceptance4 ,the contractor shall furnish a location plan and also two copies of the detail shop drawings for convenience in making future alterations and repairs4 ,erection4--,the head-frame is to be erected complete1 secured to foundations provided by the---- ,company4 ,contractor shall furnish all foundation bolts and washers4 ,iron stairway with hand rails beside main back bracers and platform with wooden floor under sheaves1 also iron stairs from platform under sheaves to back sheave pedestal for oiling4 ,wood furnished by the---- ,company4 ,price includes all material for completion of work delivered1 erected1 and riveted in place and painted4 ,the---- ,company will furnish and place in position the sheaves1 with the shafts and boxes belonging to the same1 also the wooden guides4 ,delivery4--,the head-frame to be erected1 complete1 and secured to foundations in---- weeks from date of order4 ,,detaching ,,hooks ,illustration3 ,,fig4 #ci #db4 ,in hoisting1 there is more or less danger of overwinding or lifting the cage too far1 and dashing it against the top of the head-frame1 or if the top is open the cage may be pulled entirely over the top4 ,detaching hooks are intended to prevent this4 ,several varieties of such hooks are made1 which differ from each other only in their smaller details4 ,in all of them1 detachment is effected by passing the rope through a circular hole in an iron plate or through an iron cylinder1 the diameter of which is sufficient to allow the upper portion of the hooks to pass through when passing upwards1 but the lower portion is made larger and so arranged that when this larger part strikes the plate the upper portion is forced open and the hoisting rope released4 ,after the upper part has been thus opened1 it is too large to pass back through the opening and the plate and the cage is therefore held suspended4 ,fig4 #ci shows such a hook4 ,it consists of two outside fixed plates slightly narrower at the top than the diameter of the hole in the disengaging plate h4 ,between the frame plates a are two inner plates b that move about a strong pin c passing through both plates a and b1 but near the bottoms there are two projections d to prevent the hook from passing entirely through the hole4 ,the winding rope is attached to the top shackle e and the cage to the lower shackle f4 ,when the two movable plates b are closed as tightly as possible at the top about the pin of the shackle e1 they are secured by a copper pin g4 ,in case of overwinding1 when the hook passes into the hole of the disengaging plate h1 the two projections k on plates b are pressed inwards1 shearing off the copper pin g and allowing the plates b to turn about the central bolt c1 thus releasing the shackle e4 ,the plates b are then in such a position that the projections l on them cannot pass down through the hole4 ,the cage then hangs by the hooks from the disengaging plate1 and the rope passes on4 ,an objection raised against this hook is that1 being constructed of plates1 there is considerable surface in contact between the moving parts1 and unless they are regularly taken apart and oiled1 there is danger of their rusting firmly together4 ,in ,england1 detaching hooks are used quite commonly1 and also in certain parts of the ,central ,basin in the ,united ,states1 but they have not yet been generally adopted throughout the ,united ,states4 #dc4 ,it is claimed by many that such devices inspire the engineer with a misleading feeling of security2 that they are more or less complicated in construction and so need care1 and destroy the simplicity of the plant2 that they may be the direct cause of accident by introducing new elements of danger2 that they add to the cost2 and that they are not thoroughly reliable4 ,again1 it is held that the surest prevention of overwinding is obtained by the employment of a sober1 reliable1 and competent engineer1 who is held personally responsible for overwinding accidents2 by having a good brake and an engine thoroughly under the control of the engineer2 by a reliable method of indicating the position of the cage2 by sufficient height to head-sheaves to allow of considerable hoisting over and above that necessary for landing4 ,,signaling #dd4 ,some method must be provided for communicating between the bottom or any level of a shaft and the top landing or the engine room1 also between the top landing and the engine room1 so that the hoisting engineer may be notified when both the head-man and foot-man are ready for him to hoist4 ,a common method of signaling is by means of a gong1 bell1 or triangle placed in the engine room and connected by a wire or small wire-rope with the point from which it is desired to signal4 ,attempts have been made in different localities and by different associations to adopt a standard code of hoisting signals1 and while it would be advantageous if this could be done1 none of the attempts made have been entirely successful4 ,although there is no uniform system of signals1 one bell generally means stop1 two bells lower1 three bells hoist1 and four bells hoist men4 ,illustration3 ,,fig4 #dj #de4 ,hammer-and-,plate ,signal4--,fig4 #dj shows a hammer-and-plate signal1 the plate being a piece of boiler iron or steel4 ,the hammer is often located beneath the plate instead of above1 as shown4 ,another style of hammer-and-plate is shown in ,fig4 #da4 ,the hammer is made of #b-;inch square iron and heavy enough to balance the weight of wire hanging in the shaft and to take the sag out of the horizontal wire connecting the top of the shaft with the lever a4 ,a simple dial turned by a ratchet motion attached to the lever a is sometimes used to show the number of strokes1 and thus check the number counted by the engineer4 ,the dial is reset by the engineer as soon as he understands the signal4 ,illustration3 ,,fig4 #da ,illustration3 ,,fig4 #db #df4 ,electric ,bells4--,electric bells operated by push buttons are rapidly coming into use for mine signaling on account of the ease and completeness with which such a system can be installed4 ,electric flash lights are also extensively used for signaling purposes4 ,the principle of action and details of the wiring for electric signals and flash lights have been described in ,transmission1 ,signaling1 and ,lighting4 #dg4 ,speaking ,tubes4--,the laws of certain states require speaking tubes1 in addition to the ordinary means of signaling4 ,these speaking tubes are generally made of #b-;inch iron pipe and are from #cjj to #a1ejj feet long1 and are often provided with whistles at the end of the pipe and at each level of the mine1 by which the attention of persons at any level can be attracted or the whistle may be omitted and the attention of persons attracted merely by rapping on the pipe with a piece of iron4 ,illustration3 ,,fig4 #dc #dh4 ,pneumatic ,gong ,signal4--,fig4 #db shows an attachment that can be connected to a speaking tube and that is widely used for signaling4 ,it consists of a brass cylinder a fitted with a piston b containing valves c4 ,the gong d is attached to the cylinder e inside of which the clapper f fits loosely4 ,when the piston is pushed inwards1 as shown by the arrow1 by means of the handle1 the air in the cylinder and in the pipe h is compressed and forces the clapper f upwards against the gong d4 ,the arrangement of these gongs in the mine is shown in ,fig4 #dc4 ,a cylinder and whistle are usually placed at each landing and a gong and whistle in the engine room1 though1 if desired1 a cylinder1 whistle1 and gong may be placed at each landing and in the engine room4 #di4 ,telephones4--,telephones connecting the different levels with the top and the engine room are now frequently used in connection with other signal systems1 but they are not as well adapted as bells or gongs for rapid-hoisting signaling4