Iron yoke

Equipment. At the time of publication of Ref 1 (1931), there were two Bichel Closed Bombs at BurMines, each of them made of strong cast steel. The No 1 apparatus had an interior capacity of 15 liters,. while the No 2 was of 20 liters. Their walls were 12.5cm thick. The heads of their cylinders were provided with lead gaskets, which were secured in pLace by 12 heavy stud bolts and aa iron yoke. For exhausting the air there was a tube inserted in a hole bored in an upper segment of each cylinder (See Fig on p C332-L of Vol 3 of Encycl), near one end. Exhaust tuhe of each cylinder was connected with a rotary, vacuum-air pump, driven by a 2-HP motor and provided with a valve which excluded the outside air after the desired vacuum was reached (usually 50li5ram of Hg). 

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