. Transactions. ^ fordrilling. Straight contracting was finally adopted, based on the squarefoot of vein area broken; the contractors are obliged to keep the wallsfree from ore and maintain the stopes within limits designated by theforemen. The company furnishes the powder and the men do the shoot-ing. The usual price in such contracts is from 12 to 15 c. per square foot,at which rate the men make from 25 to 75 per cent, more than dayspay. J. V. N. DORK AND L. D. DOUGAN 83 Loading and TrammingThe chutes on each level are spaced about 27 ft. (8 m.) apart, and areequipped with the gate shown in
. Transactions. ^ fordrilling. Straight contracting was finally adopted, based on the squarefoot of vein area broken; the contractors are obliged to keep the wallsfree from ore and maintain the stopes within limits designated by theforemen. The company furnishes the powder and the men do the shoot-ing. The usual price in such contracts is from 12 to 15 c. per square foot,at which rate the men make from 25 to 75 per cent, more than dayspay. J. V. N. DORK AND L. D. DOUGAN 83 Loading and TrammingThe chutes on each level are spaced about 27 ft. (8 m.) apart, and areequipped with the gate shown in Fig. 3. By having the gate boards ex-tend across the end of the chute, they can be knocked open at either side,without Fig. 3.—Ax ore chute. The mine cars are 30-cu. ft. ( cu. m.), Truax side-dump carsweighing 1100 lb. One man and a horse readily handle 60 tons a daywith an average haul of 1100ft. (), using a five-car train from the300-ft. drift to the mill bins. Hand tramming is done on the lower levels,two men handling the full tonnage. Hoisting The selection of hoisting equipment was determined hx the followingconsiderations: 1. The shaft followed the changing dip of the vein, making rapidhoisting dangerous. 2. It was expected that, with the size of engine available for the powerplant, this would be fully loaded, making a high load factor im-perative. 3. With the small tonnage, the saving of a single man meant a largecut in the cost per ton. A Denver Engineering Works double-drum electric hoist, with coun-terweight, was selected. It is driven by a 10-hp., 550-volt, motor,and has a hoisting speed of 150 ft. per minute. The complete cycle takes5 min. from the 600-ft. to the 300-ft
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
