t78 VARIABLE SPEED CCO ilROL. INov. 21, ate systems of speed control for individual motors may be justified. If each operator has a constant incentive to keep the output of his machine up to its full rated capacity for a given grade of work-and it is possible to vary this output by changing the speed of the machine by easy steps through a wide rangethen the results obtained by the most efficient operation of the tool at all times may make insignificant the question of the extra investment

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... ed to install the control system. On the other hand, there are situations in which an easy method of controlling the speed may be a disadvantage. For a large printing establishment, it was found necessary to design a device to lock the speed controllers so that if the press was run at all it was operated at a given speed, which speed was determined by the foreman for each job. In this way, it was made impossible for the feeder to soldier on his work behind the bosses' back. This incident is intended to emphasize the idea that if full advantage is to be taken of refined methods of electrical control, the operators in charge should also be worked up to their highest efficien'cy. The practice at the present seems to be to put all tools requirir-g 5 h.p. and over on the individual motor basis and group all the smaller tools. There is certainly a tendency toward equipping even smaller machines wit-h separate motors, down perhaps to 3 h.p. and also a corresponding tendency to reduce the size of the shafting motors driving groups, with the idea of having, as far as possible, one standard size for shafting motors all through the plant.