Application of Electric Power to Mining Work in the Witwatersrand Area, South Africa

Discussion of the paper of J. NORMAN BULKLEY, presented at the New York meeting, February, 1916, and printed in Bulletin No. 110, February, 1916, pp. 355 to 373. GRAHAM BRIGHT, E.. Pittsburgh, Pa.-On p. 265 mention is made of a change from steam hoist to electric hoist. The arrangement mentioned, of using a geared motor, and having the gearing and counter-shaft in a separate, self-contained unit, and then connecting that to the hoist by means of a flexible coupling, is very good. Sometimes, however, it is necessary to change a geared hoist over to an electric hoist. 'In that case the motor could be either direct-connected to the countershaft or geared to the countershaft, making a double-reduction gearing. Trouble has been experienced with this method on account of the hoist not being designed for electric drive. It may be of a rather light construction which will not stand the forces obtained by steam operation, the maximum being determined by the steam pressure which can be obtained in the cylinder. With motors of hoisting types, torques, can be obtained, which are so far in excess of anything that the steam engine could give, that this sometimes results in disaster when a motor is applied to a hoist of that type. If the operator gets a little careless, he may overstrain the hoist, And cause damage, so that this question should be looked into when changing from a steam hoist to an electric hoist. The hoist should be rugged enough to stand the torques which may be attained by careless operation, in which case, instead of using a three-bearing motor, with a pinion between two of the bearings, it is much better to arrange for a two-bearing motor, arranging for a coupling through a flexible coupler. In another place trouble is mentioned as due to the vibration of a geared hoisting motor. That can be overcome by supplying a flexible coupling between the motor and the hoist proper. You will find, if a flexible coupling is furnished, that the motor troubles will largely disappear. K. A. PAULY (communication to the Secretary*), Schenectady, N. Y. -This paper is deserving of careful consideration by all interested in general electrical mining problems and the recommendations made should be given weight because of the author's long experience in dealing with various problems encountered from the beginning of mine electrification.