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Ebook has 175 lines and 37451 words, and 4 pages

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.

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 Edition 1

HOISTING APPLIANCES

HOIST INDICATORS

TYPES OF INDICATORS

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.

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?

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

CYLINDRICAL DRUMS

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 1 1/4 -inch wire-rope.

CONICAL DRUMS

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

and under the conditions shown in Fig. 9,

The drum would then be 7 feet in diameter at the small end and 9 feet 7 1/4 inches at the larger end.

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.

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

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.

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.

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.

ILLUSTRATION.--2,000 feet of rope 1/2 inch thick requires

The dimensions of the reel will then be: diameter of hub 3 feet 1 inch; width between flanges, 8 1/2 inches, allowing 1/4 inch on each side of the rope for clearance; diameter of the flanges where they flare, 10 feet 9 1/2 inches.

ROPE WHEELS

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