A 35-stamp mill, with concentrating apparatus, etc., requiring about 70 horse-power.
The total amount of power required being say 320 horse-power, for which seven Pelton hurdy-gurdy wheels are employed.
The power in all cases is transmitted by systems of Manila rope belting; the rope is 2 inches in diameter; the grooves in the sheaves or pulleys are slightly oval, so that the rope does not go quite to the bottom; the ropes are horizontal, and run very slack (no tighteners), with no appreciable slip; the splices are made very long, to obtain uniformity in diameter.
This method of transmitting power appears to work most perfectly and has given excellent satisfaction. It is thought, at the Idaho, to be greatly preferable to the gearing formerly in use when the works were driven by steam (for such work as pumping or hoisting, leather or rubber belting is never used), besides being much cheaper in first cost.
The wheel driving the air-compressor is 6 feet in diameter, running 300 turns[5] per minute, with 1-15/18-inch nozzle; three ropes are used from the wheel shaft to the counter-shaft, and six ropes from the latter to the fly-wheel shaft.
[Footnote 5: The revolutions per minute, of these wheels, as here given, are only approximate, as the design was to have the bucket speed=½ 2(gh)^{ ½}.]
For driving the pumps, there are two water-wheels, set on the same shaft, one 5 feet and the other 7 feet in diameter, either of which can be used at will, thus permitting different rates of speed; two nozzles are placed on each wheel, so that if necessary the power can at any time be doubled. The smaller wheel has a 1-1/4 inch nozzle, and runs 360 turns a minute; the larger has 1-1/8-inch nozzle, and makes 270 turns a minute. There are two ropes from the wheel-shaft to a counter-shaft, and four ropes to the fly-wheel shaft, on which is the pinion driving the spur-wheel attached to the pitman of the pump-bob. Hoisting is done by two wheels placed side by side on the same shaft, the buckets and nozzle of each wheel being placed in opposite directions. Both wheels are 8 feet in diameter, with 15/16-inch nozzles, and make at full speed about 225 turns a minute. Reversing the movement of the shaft is done by shutting off water from one wheel, and turning water on the other wheel; the two water-gates for these nozzles are quickly opened or closed by hydrostatic pressure, afforded from the water main. In addition to the usual brakes on the winding-reels, a brake is placed on the wheel-shaft, so that it can be stopped in a very short period of time.