Motion picture projection : an elementary text book (1928)

670 MOTION PICTURE PROJECTION We find in the mounting of ball bearings it is universal practice to tightly hold the inner race of the bearing on its seat on the shaft and permit the outer race to have a free fit in its housing, yet without lateral shake, so that this outer race has enough freedom to adjust itself lengthwise of the shaft in order to avoid any binding action or end thrust between itself and the inner race. To accomplish this, each of the annular ball bearings used in Transverter is mounted so that the inner race is firmly bound to the shaft. It is pointed out, however, that as live or six ten-thousandths of an inch variation in bore is the commercial standard limit of accuracy set by the engineering societies and manufacturers of such bearings, and since the fit on the shaft must necessarily be tight, but not too tight, the limits of five to six ten-thousandths precludes the possibility of making a fit in this manner interchangeable, the best practice, therefore, is to clamp the inner race between a shoulder on the shaft on one side and a lock nut on the other. This construction has been adopted throughout in the Transverter. The cut, Fig. 280, shows the machine in cross section. The lower part is an induction motor of the required frequency phase and voltage, the rotor of which is supported on both ends of its shaft by annular ball bearings. The lower bearings are located in the housing of the base of the machine, the annular bearing taking side load, while all of the weight of the rotating elements is supported by the thrust bearing K. It will be noted that the bearing J rests against a shoulder of the shaft above and against a thrust