This article first appeared in Practical Engineering 1940 Vol1 No22. The information within the piece pertains to information as of 1940. This article describes developments within Industry and Engineering at the time.
Electrically-Driven Clay Gun
In a recent issue of the Journal of the Institution of Electrical Engineers Mr. H. G. Weaver reviews the progress made in the applications of electricity in iron and steel works during the past four years. Among recent applications is an electrically-driven clay gun. Its purpose is to provide a satisfactory method of stopping up the iron tapping hole when required, without the necessity of shutting off the blast.
The gun is suspended from a boom, which swings it into position and holds it against the hole while plugging takes place. A 20 h.p. motor drives the gun, and a 10 h.p. motor drives the boom. They are switched direct on to the line without any overload or other type of protection, but limit switches are provided on both motions to prevent mechanical damage due to mal-operation of the controllers.
The stalling torque of the 20 h.p. motor is 1.6 times full load torque and, in the case of the 10 h.p. motor 1.35 times full load torque. In each case when taking 2.5 times full load current at full line voltage. The boom motor is stalled when holding the gun against the hole. The motors have to be capable of withstanding stalling for half a minute without excessive heating.
The shafts are of 3 per cent, nickel-steel, running in ball and roller bearings, and are of welded steel construction throughout. The rotor windings consist of bronze bars secured in semi-enclosed slots, which are lined with anodized aluminium.