Chapter I: Part 1

Transcriber’s Notes:

Underscores “_” before and after a word or phrase indicate _italics_
in the original text.
Equal signs “=” before and after a word or phrase indicate =bold=
in the original text.
Small capitals have been converted to SOLID capitals.
Illustrations have been moved so they do not break up paragraphs.
Typographical and punctuation errors have been silently corrected.

Hoisting Appliances

By
I.C.S. STAFF

HOISTING
Parts 3-4

447
Published by
INTERNATIONAL TEXTBOOK COMPANY
SCRANTON, PA.

Hoisting, Parts 3 and 4:

Copyright, 1906,
by INTERNATIONAL TEXTBOOK COMPANY.

Entered at Stationers’ Hall, London

All rights reserved

Printed in U. S. A.

INTERNATIONAL TEXTBOOK PRESS
Scranton, Pa.

CONTENTS

NOTE.--This book is made up of separate parts,
or sections, as indicated by their titles, and the page
numbers of each usually begin with 1. In this list of
contents the titles of the parts are given in the order in
which they appear in the book, and under each title is a
full synopsis of the subjects treated.

HOISTING, PART 3
_Pages_
Hoisting Appliances 1-43

Hoist Indicators 1-5
Column indicators; Dial indicators; Special indicators.

Drums and Reels 6-20

Cylindrical Drums 7-8

Conical Drums 9-16
Hoisting with cylindrical drums; Hoisting with conical
drums; Comparison of cylindrical and conical drums.

Flat Rope Reels 17-20

Rope Wheels 21-26
Koepe system; Whiting system; Modified Whiting system.

Rope Fastenings 27

Clutches 28-31
Jaw clutch; Band friction clutches; Beekman friction
clutch.

Brakes 32-43
Block brake; Post brake; Strap brake; Differential
brake; Power for brakes; Differential lever;
Power brakes; Crank brake.

HOISTING, PART 4

Hoisting Appliances 1-51

Sheaves 1-5
Cast-iron sheave; Wood-lined sheaves; Diameter
of sheave; Rollers and carrying sheaves.

Cages for Vertical Shafts 6-11
Construction of cage; Safety catches;
Multiple-deck cages.

Automatic Dumping Cages 12-16
Definition; Slope, or inclined shaft hoisting;
Slope carriage.

Skips, or Gunboats 17-22
Definition; Method of loading skips; Method of
dumping skips; Skip cage.

Buckets 23

Car Locks 23-24

Cage Guides 25

Landing Fans, or Keeps 26-28
Common forms of fans; Hydrostatic fans;
Pneumatic fans; Cage chairs.

Head-Frames 29-45
Head-frames in general; Types of head-frames;
Examples of various types; Head-frame
specification.

Detaching Hooks 46-47

Signaling 48-51
Hammer-and-plate signal; Electric bells;
Speaking tubes; Pneumatic gong signal;
Telephones.

HOISTING

Serial 851C (PART 3) Edition 1

HOISTING APPLIANCES

HOIST INDICATORS

=1. 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 hoisting. The use of such indicators is sometimes required by law, but there is a great diversity of opinion as to the advisability of using them. The objections to them are that they are liable to get out of order, 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 commended. A hoisting engineer, however, depends for his stopping point mainly on a mark made on the rope, or on the drum, or on both, and uses an indicator mostly as a guide for the position of the cage during the hoist.

TYPES OF INDICATORS

=2. Column Indicators.=--A very simple indicator, and one that was formerly very commonly used, 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 cord, which corresponds to the hoisting rope as the pin corresponds to the drum. This chain or cord is led over a pulley placed at the top of a pair of guides, representing the shaft, and carries at its end a weight, pointer, or gong, representing the cage or car, as shown in Fig. 1.

The different landings in the shaft are marked on the guide; and as the pointer or gong rises and falls it indicates the position of the cage in the shaft. If a gong is used, 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 attention. Indicators of this kind, though cheap and easily constructed, are not reliable, for the cord and chain may stretch or they may overlap in winding on the pin, or may bind in the pulley and thus indicate a wrong position of the cage.

=3.= An indicator should have a positive motion and be driven by gearing or by link belts. Fig. 2 shows a =column indicator= that consists of a screw _a_ working inside of a slotted pipe _b_, which may be of any length necessary. This screw is revolved by means of the gears _c_, which are rotated by the sprocket wheel _d_. 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 shaft. The pipe standard _b_ is usually painted a dead black and the different levels may be marked on it with chalk or white paint. Chalk marks are not safe, as they may be tampered with and the engineer thus misled.

The pointer _a_, Fig. 3, is moved by the rotation of the screw shaft _b_, which is revolved by the bevel gears _c_ and _d_. This indicator also registers the number of hoists by means of the dials _e_, 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 dial.

=4. Dial Indicators.=--Fig. 4 shows a positive-motion indicator that is operated as follows: 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 _e_. The pointer _f_ is rigidly attached to the shaft _d_ and revolves in front of the properly marked dial _g_.

=5.= Fig. 5 shows a =dial indicator= attached to drum hoists where the speed of rope is constant for each revolution. The wheel _a_ of this indicator may be a worm-wheel working in a worm on the drum shaft, as described in connection with the indicator shown in Fig. 4, or it may be a sprocket wheel driven by a link belt from a sprocket wheel on a drum, or it may be a gear-wheel driven directly from another gear-wheel on the drum. 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 spindle. The different levels from which hoisting is to be done may be painted on the dial, or better, they may be placed on movable targets that are clamped to the dial and can thus be moved as occasion requires.

EXAMPLE.--An indicator is desired for a shaft 800
feet deep at which the drum of the hoisting engine to be
used is 10 feet in diameter; what ratio of gearing must be
used so that the pointer will make one revolution during
the hoist?

SOLUTION.--The circumference of the drum is 31.42
ft. (π_D_ = 10 × 3.1416 = 31.416 ft.); hence, the
revolutions per hoist are 800 ÷ 31.42 = 25.46 revolutions.
Then, if the pointer is to make one revolution per hoist,
the ratio of the gearing will be 25.46 to 1. Ans.

=6. Special Indicators.=--One fault of nearly all indicators is that they give a regular movement throughout the winding, and the space over which the pointer travels is too small to enable the engineer to land the cage accurately. Indicators have been made with a differential motion to the pointer, the motion being greater at the time of landing and less during the middle of the hoist. They are also made with two pointers, one operating like the dial indicator above described and the other remaining stationary during all the hoist but the last few feet, when it moves around its circle.

FIG. 6]

=7.= Where flat ropes are used or where round ropes wind on a conical drum, the length of rope wound or unwound is different for each turn of the drum. With all the indicators thus far described, while the speed with which the indicator moves is proportional to the speed at which the drum and the drum shaft revolve, it is not proportional to the speed of the rope when winding and unwinding on a conical drum or on a flat rope reel. Fig. 6 (_a_) and (_b_) shows two views of a compensating dial indicator. By means of the spiral form of sheave _c_, the hand _d_ is made to move equal distances around the disk _e_ for equal distances of cage movement in the shaft. The rope _f_ passes about the spiral sheave and one end is attached at the small end _g_ of the spiral, while the other end is fastened to the periphery of the sheave _h_, which takes its motion from the drum shaft or crank-shaft of the hoisting engine by means of the bevel gear _i_. Consequently, while the sheave _h_ has a regular motion dependent directly on the revolution of the hoisting drum, the pointer _d_ moves irregularly, depending on the position of the spiral sheave _c_; that is, whether a small or large diameter of the spiral is presented to the rope. The rope _j_ carrying the counterweight _k_ is attached to a small circular drum _l_ that is on the same shaft as the spiral sheave. 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 _h_.

=8.= 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 bottom, and so that the engineer may be able to distinguish between the top and the bottom positions of the cage by the pointer, the ratio of the gearing is usually increased by allowing one or two extra teeth on the worm-wheel. In the example in Art. =5=, assume a ratio of 27: 1; that is, if a worm-gear is used, the worm-wheel will have 27 teeth.

If the pitch of the teeth is ¾ inch, the circumference of the pitch circle will be ¾ × 27 = 20.25 inches and the diameter 6.44 inches.

The pitch of the worm will, of course, be the same as that of the wheel, and its diameter will be whatever is necessary to give sufficient strength outside of the shaft, since it bears no relation to the ratio of the gearing.

DRUMS AND REELS

=9.= The =drum=, or =reel=, of a hoisting engine is the part on which the rope winds. It is either keyed fast to the engine shaft or is connected to the shaft by means of a clutch, the shaft being made extra heavy to carry the strain due to the weight of the drum and the pull of the rope.

CYLINDRICAL DRUMS

=10.= The outer part, or =shell=, of a drum _a_, Fig. 7, is supported on rims _b_, and these rims are connected by arms or spiders _c_ with the hubs _d_. The brake rings _e_ are for the band brakes, of which there may be one or two. The part _a_ may be lagged with strips of wood bolted to the rims _b_, the heads of the bolts being countersunk. Fig. 8 shows the detailed dimensions of a drum 8 feet in diameter having a 4-foot face designed to carry heavy loads and a large amount of rope. The shell is of boiler plate and the spiders of cast-steel.

=11.= The shell may be cast in one piece for small drums or built up in sections for large drums, as in Figs. 7 and 8. The shell may have a smooth surface, Fig. 8, or it may have grooves, Fig. 7, for the rope to lie in as it is wound on the drum. On an iron drum without grooves, the rope will chafe sidewise; and furthermore if the rope winds on a hard flat surface it bears here and there on a single wire and tends to flatten, causing internal wear between the wires; while, in the case of a rope winding in a groove, it is supported on about one-quarter of its circumference, bringing many more wires to bear on the drum and dividing the pressure between them. A wooden-lagged drum causes less wear on a rope than an ungrooved iron-shell drum, as grooves are gradually worn in the lagging, but is not so good as a grooved iron drum. It is not good practice to allow a rope to wind on itself, and the drum should be long enough to take the full length of the rope required for the hoist. At least two turns of the rope should be on the drum when the load is at the bottom, 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 drum. Allowance for two or three additional turns of the rope should also be made so that the cage may be hoisted above the landing.

The shell usually has a flange at each end, as shown in Figs. 7 and 8, but it may have a flange at one end only, or may be without flanges entirely. If, however, the flanges are not used, the drum must be extra long to prevent the rope running off the end. If the drum is very long, a third spider is added midway between the other two to stiffen it against collapse.

EXAMPLE.--Find the length of a drum 6 feet 3 inches in
diameter necessary to hold 1,000 feet of 1¼-inch wire-rope.

SOLUTION.--The diameter from center to center of the rope
when wound on the drum is 6 ft. 3 in. plus 1¼ in., or 6
ft. 4¼ in., which is equal to 19.96 ft. (approximately
20 ft.) of circumference. Then, to wind 1,000 ft. will
require ¹,⁰⁰⁰/₂₀ = 50 turns on the drum. Allowing two
turns of the rope to protect the fastening and three
turns in case of overwinding, gives fifty-five turns to
be allowed for on the drum. If the drum is of iron with
grooves turned in it, ¼ in. must be left between adjacent
parts of the rope, or 1½ in. from the center of one turn
to the center of the next. Then, 55 × 1½ = 82½ in. plus ¾
in. at each end = 84 in., or 7 ft. for the length of the
drum between the flanges. Ans.

If the drum has wooden lagging, clearance need not be
allowed between two adjacent coils of rope, as in this
case the rope winds against itself and so takes up only 1¼
in. It will then be 55 × 1¼ in. = 68¾ in., or 5 ft. 8¾ in.
long (say 5 ft. 9 in.). Ans.

CONICAL DRUMS

=12.= In hoisting in balance from deep shafts with cylindrical drums, if no tail-rope is used, or in hoisting from a single shaft with an unbalanced cage, the hoisting engine is not loaded equally at different points of the hoist owing to the gradually changing weight of the unbalanced rope. The following illustrations will further explain this.

=13. Hoisting With a Cylindrical Drum.=--Suppose that, from a single-compartment vertical shaft 1,000 feet deep, it is required to hoist each trip a load, including friction, of 11,000 pounds made up as follows:

POUNDS
Weight of material 4,000
Weight of car 3,000
Weight of cage 3,000
Friction, 10 per cent. 1,000
------
Total 11,000

If a 1⅜-inch cast-steel rope weighing 3 pounds per foot is used, winding about a drum 7 feet in diameter, the weight of rope is then 3 × 1,000 = 3,000 pounds and the load on the rope, when the cage is at the bottom, is 11,000 + 3,000 = 14,000 pounds, while at the top the load on the rope is only 11,000 pounds. The moment of the load at the bottom is then the load 14,000 multiplied by the radius 3½, or 14,000 × 3½ = 49,000 foot-pounds; and at the top, 11,000 × 3½ = 38,500 foot-pounds. This shows that the load against the engine is much greater at the beginning than at the end of the hoist.

=14.= Take now a double-compartment vertical shaft of the same depth as in Art. _13_ and assume the same amount of material hoisted at a trip, in the same mine car and on the same cage; but that an empty car and cage are lowered in one compartment while the loaded car and cage are hoisted in the other. The two cars and the two cages will balance each other, and the loads will be as follows: At the beginning of the hoist, when the loaded car and cage are at the bottom, the gross load is 14,000 pounds, made up as follows:

POUNDS
Weight of material 4,000
Weight of mine car 3,000
Weight of cage 3,000
Friction, 10 per cent. of above 1,000
Weight of rope 3,000
------
Total 14,000

Multiplying this by the radius of the drum, the gross turning moment is 14,000 pounds × 3½ feet = 49,000 foot-pounds, as before, but there is a counterbalancing load of 6,000 pounds, made up as follows:

POUNDS
Weight of mine car 3,000
Weight of cage 3,000
-----
Total 6,000
Less friction, 10 per cent. 600
-----
5,400

This means a counterbalancing load moment of 5,400 pounds × 3½ feet = 18,900 foot-pounds. The net load moment to be overcome by the engine at the beginning of the hoist is, therefore, 49,000-18,900 = 30,100 foot-pounds.

At the end of the hoist there is a gross load on the loaded side of 11,000 pounds, made up as follows:

POUNDS
Weight of material 4,000
Weight of mine car 3,000
Weight of cage 3,000
Friction, 10 per cent. 1,000
------
Total 11,000

This is equal to a gross load moment of 11,000 pounds × 3½ feet = 38,500 foot-pounds, but there is a counterbalancing load of 8,100 pounds, made up as follows:

POUNDS
Weight of mine car 3,000
Weight of cage 3,000
Weight of rope 3,000
-----
Total 9,000
Less friction, 10 per cent. of 6,000 600
-----
8,400

This is equal to a counterbalancing load moment of 8,400 pounds × 3½ feet = 29,400 foot-pounds, and leaves a net load moment against the engine of 38,500-29,400 = 9,100 foot-pounds. In other words, the load moment that the engine has to overcome varies from 30,100 foot-pounds at the beginning of the hoist to 9,100 foot-pounds at the end of the hoist.

=15. Hoisting With Conical Drums.--Conical drums= are designed to make the work of the engine as nearly uniform as possible throughout the hoist. To accomplish this, when the cage is at the bottom of the shaft, and the load is therefore heaviest, the rope winds on that part of the drum having the smallest diameter. As hoisting continues, the rope winds on a gradually increasing diameter of drum, and when the cage is at the top of the hoist, and the load therefore least, the rope is winding on that part of the drum having the greatest diameter; in this way, the moment of the load at every point of the hoist is approximately the same. 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 drum; hence, the less the weight of the rope in proportion to the total load on the engine, the more nearly uniform is the load on the engine.

=16.= Fig. 9 (_a_) shows the condition at the beginning of the hoist when conical drums are used. Cage _a_ is at the bottom and carries a loaded car; cage _b_ is at the top and carries an empty car. The net moment that the engine must overcome is the sum of the weight of the material to be hoisted, weight of the cage and car at _a_, and the weight of the rope attached to _a_, multiplied by the small radius _r_ of the drum, minus the weight of the car and cage at _b_, multiplied by the large radius _R_ of the drum.

Fig. 9 (_b_) shows the condition of things at the end of the hoist, when the cage _a_ is at the top and cage _b_ at the bottom. The loaded car and cage _a_, whose rope in Fig. 9 (_a_) was winding on the smallest diameter of the drum, is now at the top and the rope is winding on the largest diameter of the drum. The cage _b_ with the empty car is now at the bottom and the rope is unwinding from the smallest diameter of the drum. The net moment that the engine must overcome in this position is equal to the sum of the weight of the material hoisted, the weight of the cage _a_ and the car, multiplied by the larger radius _R_ of the drum, minus the sum of the weights of the cage _b_, the car, and the rope, multiplied by the small radius _r_ of the drum.

=17.= If the moment of the load against the engine at the beginning of the hoist is to equal that at the end of the hoist, it is possible to determine what relative diameters of drum will produce such an effect, as follows:

Let _Wₘ_ = weight of material hoisted;
_Wₖ_ = weight of cage and car;
_Wᵣ_ = weight of rope;
_R_ = large radius of drum;
_r_ = small radius of drum.

The load moment may be calculated by including friction as ⅒ of the total weight hoisted, except the weight of the rope, as shown in Art. =14=; or the friction may be disregarded without serious error. Then, under the conditions shown in Fig. 9 (_a_), and disregarding friction,

Load moment = (_Wₘ_+_Wₖ_+_Wᵣ_)_r_ - _Wₖ__R_ (=1=)

and under the conditions shown in Fig. 9(_b_),

Load moment = (_Wₘ_ + _Wₖ_)_R_ - (_Wₖ_ + _Wᵣ_)_r_ (=2=)

Placing formula =1= = formula =2=,

(_Wₘ_+_Wₖ_)_R_ - (_Wₖ_+_Wᵣ_)_r_ = (_Wₘ_+_Wₖ_+_Wᵣ_)_r_ - _Wₖ__R_,

and
(_Wₘ_+ 2_Wₖ_+ 2_Wᵣ_)
_R_ = _r_ ------------------- (=3=)
(_Wₘ_ + _2Wₖ_)

Since the diameter of a drum is generally given instead of the radius, it follows that if _D_ = larger diameter, _d_ = smaller diameter, and then, since _D_ = 2_R_ and _d_ = 2_r_, formula =3= may be written

(_Wₘ_ + 2_Wₖ_ + 2_Wᵣ_)
_D_ = _d_ ---------------------- (=4=)
(_Wₘ_ + 2_Wₖ_)

Formula =4= gives only approximate results, which are, however, sufficiently accurate for the mine superintendent’s use, and for this reason friction has been omitted, as it would make the formula much more complex. It may be expressed as a rule as follows:

=Rule.=--_To find the large diameter of a conical drum, multiply the small diameter by the sum of the weight of the material to be hoisted, twice the weight of the cage and car, and twice the weight of the rope; divide this product by the sum of the weight of the material, and twice the weight of the cage and car._

Applying this rule to the problem given in Art. =14= and omitting friction,

7(4,000 + 12,000 + 6,000)
_D_ = ------------------------- = 9.6 feet
(4,000 + 12,000)

The drum would then be 7 feet in diameter at the small end and 9 feet 7¼ inches at the larger end.

=18=. Fig. 10 shows a special form of combined conical and cylindrical drum designed for hoisting a total balanced load of 25 tons through a vertical height of 550 feet.

Fig. 11 shows a combined conical and cylindrical drum; an unusual feature is the rope reel shown at each end of the drum, which permits of properly storing a few hundred feet of extra rope, allowing the rope to be lengthened, when needed, without splicing.

=19. Comparison of Cylindrical and Conical Drums.= The disadvantages of the cylindrical drum lie entirely in the fact that the load on the engines is variable, but it is possible to overcome this disadvantage by adding a tail-rope to the cages to balance the weight of the rope. This system gives its best results where hoisting is done from one level only, but in deep hoisting it is impracticable because of the extra weight added and because of possible excessive swaying of the rope.

The conical drum has two strong points in its favor: first, the load on the engine may be nearly equalized during the entire hoisting period; and, second, the starting of the engines with the load requires less power.

The disadvantages of the conical drum are as follows: To maintain a certain average speed of hoisting, 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 place, so that more care must be exercised when making the landing. To prevent the rope from being drawn out of the grooves, the latter must be made deep and with a large pitch, thereby increasing the width of the face or length of the drum. In making a landing, when the rope is on the conical face, the rope must be kept taut, as any slackness will permit the rope to leave the groove, with the result that all the rope will pile up in the bottom grooves of the drum allowing the cage to drop into the mine, unless it is resting on the chairs. If there are several levels to be hoisted from, the equalizing of the load on the engines can only be realized for one level; for all other levels this advantage will be lost. For large depths, conical drums become very long and require correspondingly long leads from head-frame to drum. To hold the same amount of rope, conical drums are heavier than cylindrical ones, and as a result, the power required in starting the load is somewhat increased owing to the greater inertia of the rotating parts.

Some of these disadvantages have been overcome by making a combination of cone and cylindrical drums. The drums are so designed that the landing takes place only when the rope is on the cylindrical portion of the drum. For deep hoisting, the greater diameter of the drum and its length must be inconveniently large if the load is equalized. 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 drum. In all cases, however, these modifications are made at the expense of the equalization of the load on the engines, and it is not possible to obtain the latter without including some serious disadvantage.

There are certain objections to both cylindrical and conical drums: their great size and weight, for large hoists, make them very expensive; their width necessitates placing the engines far apart, which adds to the cost of the engines, foundations, and buildings; the great weight of the drums is also objectionable, because it forms a large part of the mass to be put in motion and brought to rest at each hoist.

FLAT ROPE REELS

=20=. To overcome the objections to conical and cylindrical drums, several other systems of hoisting have been tried, among them being one that uses a reel, Fig. 12, and a flat rope. The hub _a_ is increased in diameter, above what is necessary for strength, to such a size as is suitable to wind the rope on. It is then cored out from the inside, so as not to contain too great a mass of metal.

The arms _b_ of the reel extend radially from the hub to confine the rope laterally when it is all wound on the drum. These arms are connected at their outer ends by a continuous flange _c_, which flange is flared out, as shown at _d_, so as to take in the rope easily, if it is deflected at all sidewise.

In the larger-sized reels, the arms are bolted to the hub, and often the outer rim connecting the arms is omitted. Hardwood lining was formerly used on the arms under the impression that the wear on the rope would be less than with bare iron arms, but sand and grit become embedded in the wood and grind the rope. Polished iron arms with rounded corners and lubricated with oil or tar are best. The end of the rope is fastened in a pocket _e_ provided for it in the hub.

The rope winds on itself, so that the diameter of the reel increases as the hoist is made and as the load due to the weight of the rope decreases. This serves to equalize the load due to the rope in the same manner as the conical drum. Two reels are generally put on the same shaft, and while one is hoisting from one compartment of the shaft the other is lowering into another compartment. The periphery of the hub where the rope winds should not be round but of gradually increasing radius, 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 revolution. 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 wrap, so that it will wind on itself without jar at the point of attachment, as well as on succeeding wraps.

=21.= In America, it is customary to wind on reels of small diameter, that is, starting at 3 or 5 feet and increasing to 8 or 12 feet; but several large plants have been built with reels starting at 8 feet and increasing to 19 feet. In England, reels have been made starting at 16 feet and increasing to 20 or 22 feet. Such large reels are easier on the rope but require large engines, as hoisting in balance is used to only a slight extent. The large reel is easy on the rope, both from the fact that it bends the rope but little and also gives less pressure on the bottom wraps, as each wrap adds to the pressure. These reels are driven by means of plain jaw or friction clutches.

The wear of a flat rope is excessive and the rope itself costs more than a round rope of the same strength, does not last as long, and requires more care and attention.

=22. Calculating Size of Flat Rope and Reel.=--The calculation of the size of a flat rope for given work is not so simple as that of a round rope, as there is a variable factor in the width and thickness of the rope that must be taken into account. To illustrate the method of calculation, suppose that it is required to hoist 5,000 pounds of material in a 3,000-pound skip from a vertical two-compartment shaft 2,000 feet deep under conditions requiring a factor of safety of about 9 for the rope.

The determination of the size of the rope and the small and large diameters of the reels must proceed together. The latter calculations are performed in much the same manner as for conical drums.

Referring to Table relating to flat wire ropes in _Hoisting_, Part 2, it is found that a flat steel rope 6 inches by ½ inch in size and with a breaking strength of 150,000 pounds weighs 5.1 pounds per foot; hence, 2,000 feet of it weighs 2,000 × 5.1 = 10,200 pounds. The total load on the rope will then be 19,000 pounds, made up as follows:

POUNDS
Weight of material 5,000
Weight of skip 3,000
Friction, 10 per cent. 800
Weight of rope 10,200
------
Total 19,000

This rope gives a factor of safety of 150,000/19,000 = 7.8, which is not quite enough when figured from the dead load without that due to acceleration.

An 8" × ½" rope with a breaking strength of 200,000 pounds weighs 6.9 pounds per foot; hence, 2,000 feet of it weighs 2,000 × 6.9 = 13,800 pounds. The load on the rope will then be 22,600 pounds, made up as follows:

POUNDS
Weight of material 5,000
Weight of skip 3,000
Friction, 10 per cent. 800
Weight of rope 13,800
------
Total 22,600

200,000
This rope gives a factor of safety of -------- = 8.8.
22,600

Substituting the foregoing weights of material, skip, and rope in formula =4=, in Art. =17=, gives

(5,000 + 6,000 + 27,600)
_D_ = _d_ ------------------------ .
(5,000 + 6,000)

Hence, the equation of moments is _D_ = 3.5_d_. In other words, the large diameter, or that of the last coil of rope, should be 3.5 times the small diameter, or that of the reel hub.

=23.= Fig. 13 represents a coil of flat rope whose greater diameter _D_ and smaller diameter _d_ are to be determined. The area of the hub about which the rope is to coil is (¼)π_d_², while the area included by the outer coil of rope is (¼)π_D_² hence, the area of annular space occupied by the rope is

(¼)π_D_² - (¼)π_d_² = (¼)π(_D_² - _d_²).

Such values for _D_ and _d_ must be chosen that the equation of moments in Art. =22= is satisfied, while the area (¼)π(_D_²-_d_²) must correspond to the space occupied by the given rope when rolled.

ILLUSTRATION.--2,000 feet of rope ½ inch thick requires

2,000 × 12
---------- = 12,000
2

square inches in which to be coiled. To satisfy the equation of
moments, _D_ must equal 3.5 _d_; hence, to satisfy both
these conditions

(¼)π[(3.5_d_)² - _d_²] = 12,000;
_d_ = 37 inches, or 3 feet 1 inch;
_D_ = 37 × 3.5 = 129.5 inches, or 10 feet 9½ inches.

The dimensions of the reel will then be: diameter of
hub 3 feet 1 inch; width between flanges, 8½ inches,
allowing ¼ inch on each side of the rope for clearance;
diameter of the flanges where they flare, 10 feet 9½
inches.

ROPE WHEELS

=24. Koepe System.=--In its lightest form, a drum requires a large amount of power to set it in motion, which power is absorbed by the brake and lost when it is brought to rest again. Furthermore, with deep shafts requiring long drums, the fleet, or angle that the rope makes with the head-sheave due to its traveling from one end of the drum to the other, is not only a disadvantage and possible cause of accident, but it is a source of wear. To overcome these objections and also the great cost of large cylindrical or conical drums, the =Koepe system= of hoisting, shown in Fig. 14, was devised by Mr. Frederick Koepe. A single grooved driving sheave _a_ is used in place of a drum. The winding rope _b_ passes from one cage _A_ up over a head-sheave, thence around the sheave _a_ and back over another head-sheave, and down to a second cage _B_; it encircles a little over half the periphery of the driving sheave and is driven by the friction between the sheave and rope. 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 points. The driving sheave is stronger than an ordinary carrying sheave, as it has to do the driving and is usually lined with hardwood, which is grooved to receive the winding rope, the depth of the groove being generally equal to twice the diameter of the rope. Instead of being placed parallel, the head-sheaves are placed at an angle with each other, each pointing to the groove in the driving sheave, thus reducing the side friction of the rope on the sheaves.

The system has been in successful operation since 1877, and experiments made on it have determined that, with a rope passing only one-half turn around the drum sheave, the coefficient of adhesion with clean ropes is about .3. If the ropes are oiled, the adhesion becomes less, and sometimes slippage occurs, producing not only wear of the driving sheave lining but giving an incorrect reading of the hoist indicator and thus possibly producing overwinding, unless the position of the cage is indicated by marks on the rope, or unless the engineer can see the cage.

At the end of the hoist, if the upper cage is allowed to rest on the keep, its weight and the weight of the tail-rope are taken from the hoisting rope, and there is then not enough pull on the hoisting rope to produce sufficient friction with the drum sheave to start the next hoist. To prevent this trouble, the keeps are dispensed with, or the rope is made continuous and independent of the cage. To do this, crossheads are placed above and below each cage and connected by ropes or chains outside of the cages. The bridle chains are then hung from the top crosshead, and when the cage rests on the keeps, the weight of the winding and tail-ropes remains on the driving sheaves.

=25. Advantages and Disadvantages of the Koepe System.=--With this system, only one driving sheave is necessary for the operation of two compartments, and it is light, inexpensive to build, and very narrow, admitting of a short sheave shaft and small foundations. This system permits a perfect balance of rope and cage, so that the work to be done by the engine is uniform, except for the acceleration, and consists only in lifting the material and overcoming the friction. There is no fleeting of the rope between the driving sheaves and the head-sheaves.

The system has the following disadvantages, which prevent its being used to any considerable extent: Liability to slippage of the rope on the drum; if the rope breaks, both cages may fall to the bottom; hoisting from different levels cannot be well done, for, since the cages are at fixed distances from each other, the length of the rope is such that when one cage _A_ is at the top, the other cage _B_ is at the bottom. If hoisting is to be done from the bottom, this is satisfactory, but if hoisting is to be done from some upper level, cage _B_, which is at the bottom, must be hoisted to that level to be loaded before it can go to the top. Then, when cage _B_ goes to the top with its load, cage _A_ must go to the bottom, wait there while cage _B_ is being unloaded, and then be hoisted to the upper level to receive its load. For each trip, therefore, the time required for a cage to go from the bottom to the upper level and be loaded is lost; and two movements of the engines are necessary for a hoist instead of one.

=26. The Whiting System.=--This is a system of hoisting with round ropes, in which two rope wheels placed tandem are used in place of cylindrical or conical drums. As shown in Fig. 15, for a two-compartment shaft the rope passes from one cage _a_ up over a head-sheave _c_, down under a guide sheave _d_, and is then wound three times about the rope wheels _e_ and _f_, to secure a good hold, then around a fleet sheave _g_, and back under another guide sheave _h_, up over another head-sheave _i_, and down to the other cage _b_. When the system is to be used for a single-compartment shaft, one end of the rope carries the cage and the other end carries a balance weight, which is run up and down in a corner of the shaft. A balance rope below the cages, as shown, is generally used, though it is not essential to the working of the system, as it is in the Koepe system. When sinking a shaft, a balance rope cannot be used as it interferes with the work at the bottom of the shaft.

The drums or wheels _e_, _f_ are light, inexpensive, and narrow, thus permitting short sheave shafts and small foundations. They are lined with hardwood blocks, each lining having three rope grooves turned in it. The main wheel _e_ is driven by a hoisting engine, which may be either first or second motion. The following wheel _f_ is coupled to the main wheel by a pair of parallel rods, one on each side, like the drivers of a locomotive. As the rope wraps about the wheels _e_, _f_ three times, there are six semi-circumferences of driving contact with the rope, as compared with the one semi-circumference in the Koepe system, and there is no slipping of the rope on the wheels. The following wheel _f_ is best tilted or inclined from the vertical an amount equal, in the diameter of the wheels, to the pitch of the rope on the wheel, 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 grooves.

The capacity of the wheels _e_, _f_ is unlimited, while grooved cylindrical drums, conical drums, and reels will hold only the fixed length of rope for which they are designed.

As shown by the dotted lines, the fleet sheave _g_ is arranged to travel backwards and forwards, in order to change the working length of the rope from time to time to provide for an increased depth of shaft, and for the changes in the length of rope due to stretching and when the ends are cut off to resocket the rope. The fleet sheave _g_ is moved a distance equal to half the change in the length of rope.

=27=. Hoisting from intermediate levels can be readily done with the Whiting system; for instance, if the cage _a_ is at the top and cage _b_ at the bottom, and hoisting is to be done from some upper level, it is only necessary to run the fleet sheave _g_ out, and thus shorten the working length of the rope until cage _b_ comes up to the upper level. It can then be loaded and go to the top. While cage _b_ goes to the top, cage _a_ descends to the same level, where it can be loaded while cage _b_ is being unloaded, and can then go directly to the top without any of the lost time, as is the case in the Koepe system.

The system permits a perfect balance of rope and cage, so that the work to be done by the engines is uniform, except for the acceleration, and consists only in lifting the material and overcoming the friction.

There is no fleeting of the rope, so the rope wheels can be placed as close to the shaft as may be desired.

=28.= This system was tried as early as 1862 in Eastern Pennsylvania, but it was not used extensively because hoisting from great depths was not necessary, since, for depths of less than 1,000 feet, cylindrical and conical drums are quite satisfactory. In the Lake Superior copper region, there are now three Whiting hoists, two of which are probably the largest hoisting plants in the world. Each plant consists of a pair of triple-expansion, vertical, inverted-beam engines, driving direct a pair of 19-foot drums. The high-pressure cylinders are 20 inches in diameter, the intermediate cylinders 32 inches, and the low-pressure cylinders 50 inches, and all six of them have a 72-inch stroke. The rope used is a 2¼-inch plow-steel rope and hoists 10 tons of material at a trip, in one case from a depth of 4,980 feet, the deepest shaft in the world. Several plants on the Whiting system have been built in England, and two or more are working in South Africa.

=29. Modified Whiting System.=--A modification of the Whiting system is sometimes used in which a large drum keyed to the crank-shaft replaces the small tandem drums, and even the slight probability of the rope slipping in the Whiting system is thus obviated. One rope is fastened to one end of the drum, 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 drum. One rope passes directly to the head-sheave while the other passes first around a fleet sheave, similar to that used for the Whiting system, but preferably placed horizontal, and thence to the head-sheave. This system possesses the same advantages as the Whiting system except that the depth of hoist is limited by the size of the drum, and that there is a fleet of the rope. Up to the limiting depth, as determined by the size of the drum, this system can be used with equal economy for any depth. This hoist, as well as the Whiting, is therefore especially suitable for a place where one mining company operates several mines, for it enables the company to select one size for all their permanent work, with all the advantages that come from duplicate machinery.

ROPE FASTENINGS

=30.= A common method of fastening a rope to a drum, Fig. 16 (_a_), is to pass the rope through a hole in the drum rim and then around the shaft, clamping the end to the rope between the shaft and shell, as shown. 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 necessary. When an iron drum is used, 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 purpose, as shown at Fig. 16 (_b_). 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 pocket.

CLUTCHES

=31.= It is often desired to have the drum of a hoisting engine run loosely on the engine shaft, so that it may run independently of the engine. With such loose-running drums, the engine generally runs only in the direction required to hoist the load, while the cage is lowered entirely by means of the brake. In this way, 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 time. Such a loose-running drum is connected to the engine shaft when a load is to be hoisted by means of a clutch, of which there are two forms commonly used for hoisting machinery: _jaw_ or _piston clutches_ and _friction clutches_.

=32. Jaw Clutch.=--Fig. 17 shows a =jaw clutch=, one-half _a_ of which is shown ready to be bolted to a drum or flat rope reel, which is loose on the shaft _b_. 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 _a_. The half _c_ slides freely on a feather key _f_, which is driven tightly into a deep key seat in the shaft _b_; a collar _g_, fitting loosely in a groove in the hub of _c_, is provided with trunnions _h_ on each side; levers _i_ connect these trunnions with the lever _j_ attached to a suitable handle, 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 clutch. There are generally four or six jaws _d_ that engage the same number of jaws _e_ on the drum, 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 shock. The clutch is about 2 feet in diameter, and the jaws are 3 or 4 inches deep for the average 20" × 48" first-motion hoisting engine. Instead of the clutch being fastened to the shaft by feather keys, the shaft may be hexagonal where the clutch slides on it and the clutch is machined to match. Jaw clutches are made of either cast-iron or cast-steel, and should be in halves, for convenience of repair, and securely bolted together.

=33. Band Friction Clutches.=--Fig. 18 shows a =band friction clutch= that is attached to and revolves with the shaft _a_. The winding drum runs loosely on the same shaft and has a driving-band ring or seat _b_ on one end; when the ring _c_ of the clutch is tightened by means of the mechanism shown, the clutch and driving band become practically one piece and the drum revolves with the clutch. The clutch is constructed as follows: The driving disk _d_ keyed to the driving shaft _a_ is connected to one end of the ring _c_ by a fixed arm _e_, which is bolted firmly to the disk _d_ and revolves with it; a movable arm _f_ that connects with the other end of the band _c_ turns on the pin _g_. When the band _c_ is loose, it can revolve about the seat _b_ without touching it, but the band can be tightened and made to clamp _b_ either when revolving or standing still, as follows: The sliding sleeve _h_ may be caused to slide about 6 inches along the hub of the disk _d_ by levers (not shown) that take hold of trunnions _i_ on a ring on the sliding sleeve; this sleeve is connected to the movable arm _f_ by a link _j_, and when the sleeve is on the end of the hub the link stands at an angle of about 60° with the shaft; by sliding the sleeve toward the disk _d_, the link is made to move the arm _f_ about 1½ inches at its outer end and to thus tighten the driving-band _c_, so that it grips the ring _b_. The adjusting nuts _k_ take up the wear of the wooden blocks with which the ring _c_ is lined. Band lifters _l_ hold the band clear of the ring when it is loose. The clutch shown is built to run in the direction indicated by the arrow, but such clutches may be built to run in either direction; they should always be run in the direction for which they are designed, so that the load may always come on the fixed arm. If the band be tightened slowly, there will be no sudden start or jerk on the rope, as the slip of the band will prevent the entire force of the grip taking effect at once; and after the drum reaches full speed, there is little or no slipping of the driving-band. It is best to keep the band only just tight enough to do the work, for should the car get off the track, or be overwound, or should a cage stick in the shaft for any reason, the band will slip and thus become a safety appliance, and not strain or break the rope, shaft timbering, or machinery, as would be the case if a positive clutch, Fig. 17, were used.

=34. The Beekman Friction Clutch.=--A simple friction clutch is shown in Fig. 19, in which _a_ is a section of the drum shell. 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 drum. The steel spring _e_ between the two steel washers _f_, _f_ disengages the clutch, as soon as the pressure is relieved, by reversing the motion of the lever _g_ and screw _h_ from the opposite end of the drum. When the lever _g_ is turned, the screw _h_ is forced against the end of the pin _i_, which, in turn, presses the cross-key _j_ against the collar _k_, forcing the drum against the blocks _b_ and frictionally engaging the gear-wheel _c_. This drum shaft is prevented from moving endwise by means of the collar _l_ and the grooves _m_ in the babbitted pillow-block. The wide bearings of the drum on its shaft are lubricated by means of the pipes _n_.

A clutch is often used to change the length of the hoisting rope when hoisting from two or more lifts or levels. In this case the shaft carries two drums, one of which is fixed to the shaft, while the other is provided with a friction clutch. When it is desired to change the length of the rope, the cage attached to the loose drum is brought to, say, the upper landing. The cages both resting on the wings, the clutch is loosened and the other cage attached to the fixed drum is now brought to the desired level, when the clutch is again tightened and hoisting proceeds. The change is made in 2 or 3 minutes.

BRAKES

=35=. A =brake= is a device by means of which the motion of a hoisting drum may be retarded or stopped. This is accomplished by friction of the brake against the circumference of the brake wheel. There are three types of brakes, known as _block brakes_, _post brakes_, and _strap brakes_.