Friction Gear.

Friction gear is seldom employed on winding plants at large collieries, but the use of the cone and other friction gears for operating dirt-planes, is very common.

At the Cross Creek colliery No. 2, at which coal is raised simultaneously through a double slope from different levels, the winding is effected by the friction gear introduced by Mr. Coxe, which has recently been adopted at other works, and with some modifications, is being applied to winding machinery for ore mining.

*

The drums both run free on the main driving shaft, and the power is transmitted by a series of friction blocks which bear against the inside of a rim forming part of the drum frame. The friction blocks form a complete circle almost as large as the inside diameter of the drum. They are held in shoes somewhat resembling a brake block holder, toggle jointed to a rod which is attached in like manner to a movable sleeve on the driving shaft; this sleeve runs with the driving shaft. The whole device resembles a dished wheel in which the sleeve is the hub, the rods, the spokes, the friction blocks forming the circumference.

When the sleeve is forced in towards the drum, the wheel becomes less dished than before, its diameter is increased, the friction blocks take hold, and the drum revolves with the shaft.

The descent of the car can be controlled either by a brake or by making the drum work against the friction blocks. I expected to obtain an accurate description of this device from Mr. Coxe, but have not received it as this goes to press. The above imperfect description is compiled from memory

Drums.

Conical drums are rapidly coming into general favor for shaft collieries, but as yet only a few have been built, and cylindrical drums are still in general use for winding throughout the anthracite region, both at shaft and slope collieries.

*A similar winding plant was built for Mr. Edwin Mickley, mining superintendent of the Thomas Iron company at the company's shops in 1882.

Cylinder drums of moderate size are commonly constructed of heavy cast-iron spiders with six or eight arms, surrounded by a lagging of timber six or eight inches thick. When very large the spiders are cast in two or more pieces and bolted together. Very heavy spiders are always necessary, and their number depends not so much upon the size of the drum as upon the number of coils the rope makes upon it.

Drums driven by geared engines often have the spur wheel placed in the center, as shown by Fig. 46. This has been considered to be one of the best plans for geared engines, as it reduces and localizes the tortional strain to which the drum shaft is subjected.

When the center of the drum is not occupied by this pinion, this location is frequently chosen for the brake. This latter arrangement is probably better than the former, and the center of the drum seems to be an especially favorable position for the brake; and it seems doubtful whether it is not better to gear the driving-pinion to a cog-wheel placed at the side of the drum, or on the drum shaft entirely independent of the drum, and to make the drum shaft strong enough to bear any tortional strain to which it may be subjected.

Some very large cylindrical drums are in use, even larger than circumstances seem to require. Those at the Kohinoor colliery (two on one shaft) are twenty feet in diameter by little over two feet in breadth.

Probably more than three fourths of the total number of drums in use at shaft collieries are between eight and sixteen feet in diameter. There are very few large shaft collieries at which the drums are less than ten feet, and the majority of such workings are furnished with drums twelve feet and upwards in diameter. Drums at slope collieries usually range from eight to twelve feet in diameter.

Atlas sheet No. VI shows in detail the drum at the Laurel Hill colliery. Four heavy cast-iron centers, strengthened by twelve ribs, are keyed to the drum shaft, and to each of these centers twelve heavy wrought-iron arms are bolted, which carry the angle plates (made in segments) to which

the lagging is bolted. This is probably one of the best methods of constructing large cylinder drums for very heavy work.

Conical drums are as yet principally confined to shaft collieries in the Wyoming district. While the engineers throughout the region, with few exceptions, believe that conical drums should be adopted at all large collieries at which the coal is raised from a considerable depth, the comparatively small cost of cylindrical drums as compared with that of conical drums, the impossibility of determining the proper shape of the cone before the exact depth of the shaft is known, and the time then consumed in the manufacture of the conical drum, have induced many engineers, while admitting the superiority of the conical form, to adhere to the old style cylinder drum.

Brakes.

Wrought-iron brake bands mounted as shown by Altas Plates Nos. III and VI, are used to the almost entire exclusion of other forms. The levers for transmitting the power from the hand-lever or treadle to the brake band, are variously arranged. In some cases the force is multiplied by several short levers, in others one long lever is used.

The treadle is rapidly being replaced by the hand-lever, and is now seldom seen except at old collieries.

A single brake band entirely surrounding the drum is sometimes used, but the necessity of providing springs or counterweights to prevent it from resting on the drum, and its tendency to oscillate, are serious objections; for very small drums it makes a perfectly satisfactory brake.

Brakes operated by a small winch and chain-the chain being attached to a long lever or series of levers-are common enough at old collieries, and have been adopted at some recently opened works. They have been most largely used on self-acting planes, to the requirements of which they seem admirably adapted.

Brake blocks are rarely used. While better results can doubtless be obtained with brake blocks (when properly made to give the highest coefficient of friction) than with

iron bands, the latter are probably safer and less likely to get out of order and work badly. This subject is ably discussed in Percy's recent work on the "Mechanical Engineering of Collieries."

CHAPTER XV.

Winding Machinery and Appliances.

We may distinguish three separate classes into which all the various forms of head-frames now seen at anthracite collieries may be divided.

The majority of head-frames in the Wyoming basin, where shaft collieries are most common, are of the square upright pattern, [See Atlas Plates IV and XX for illustrations of the Exeter and Oakwood shaft head-frames,] with or without inclined braces.

An example of an upright frame with inclined braces is shown by Atlas Sheet No. XVI. This form may be considered a compromise between the two elementary forms shown by Figs. 44 and 45.

The triangular form is in use principally in the English coal fields,—in the last few years has been adopted by the Philadelphia and Reading Coal and Iron company at a number of collieries.

In the illustration D is the drum, C the sheaves, on one of which the force aD acts, on the other the force a'D, being the pull towards the drum,-the two vertical forces

D.

SHAFT

Fig.44.

(245 AC.)