Chicago : Engineering and Contracting Pub. Co. · leaf 49
air 800 ft. is3 ins. and will cost at Cripple Creek $75 3The total cost of compressor, motor, and pipeis $2,689.14. 34 ENGINEERING & CONTRACTING Vol. XXXVI. No. 2. Shaft Sinking.—The area of a 12 X 7.5-ft.shaft is 90 sq. ft., and the arrangement andnumber of drills decided on is shown in Fig.3.… … Fig. 2—Shaft Timbering. of drilling 39 ft. in 8 hrs., or at the rate of 4%ft. per hour. If 2 drillers are put at work theycan put in the 72 ft. in 7.4 hours. In this way an advance of 3 ft. is made everyrojnd; blocking out 3 X 12 X7.5 = 270 cu. ft. 270 of solid material, which is equivalent to 12.4…
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