Evening Republican, Volume 18, Number 85, Rensselaer, Jasper County, 9 April 1914 — SHRAPNEL A FLYING CANNON [ARTICLE]

SHRAPNEL A FLYING CANNON

It Must Withstand a Pressure of 35,000 Pounds to the Square Inch. a New York. —The shrapnel Is really a flying cannon which shoots its charge while in flight or explodes on Impact, says the American Machinist. Its design involves many interesting features, as the case must be strong enough to withstand the bursting pressure and the stresses developed in firing. The smaller cases are now made from bar stock on automatic turret machines at less than the cost of the forgings previously used. The design and making of a shrapnel case has more behind it than appears on the surface for, in addition to being a piece of steel turned and bored to the right dimensions, it must have special mechanical properties. It must be able to withstand a pressure of from thirty to thirty-five thousand pounds per square inch from the powder which drives it out of the gun, though It is tested to 40,000 pounds. In addition to this it must resist the charge of explosive in the base of the case; this base charge drives the head and balls out of the case, when a time or distance fuse is used, or explodes it on impact with the earth or any other resisting substance. _ * This expelling or bursting charge exerts a pressure varying from twenty Ip twenty-five thousand pounds per square inch. Further than this, the tenslonal stress when the case is started whirling through the rifling of the gun by the force behind it must be counted. This rotation starts the Instant the shell begins its movement from the breech of the gun, and when we consider that by the time it leaves the muzzle it must have attained a ‘velocity of 1,700 feet per second we can begin to see how an acceleration of 500,000 feet per-second is attained. These pressures explain why it is necessary to make the cases of such high quality material, a tensile strength of 135,000 pounds to the square inch, an elastic limit of 110,000 pounds per square inch, an elongation in two inches of 11 per cent., and the contraction of area 25 per cent -