Find number abc
If a3554 - c58c3 = 4bb4c find number abc. Multiple solutions may exist.Correct answers: 2
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Steam percussion rock drillIn 1849, Joseph J. Couch received the first U.S. patent for a steam-powered percussion rock drill (No. 6,237) as “improved machinery for drilling rocks”. It was driven by steam power and acted without need of gravity supplying any part of the motion. A sliding drill support frame enabled it to be operated in any desirable position or direction. Power was supplied by the piston of a steam cylinder connected to a suitable steam generator. The machine would be held stationary as the rotating drill was thrown against the rock. The drill rod would disengaged at each stroke, and travel with its own momentum, so that upon striking the rock, the shock was not transmitted back to the rest of the machine, preventing it from damage. After each blow, the tool was seized by means of friction-grips to retract and repeat.« |