Some oscillograph tests on electric startors for motor-cars

The following paper describes an investigation of the operating current of the electric motors ordinarily used for starting motor-car engines. The standard type of Duddell oscillograph was used to record the startor current and the voltage at the terminals of the car battery respectively. The tests were made on three cars, one of which was fitted with a different type of startor from the other two. A large number of tests were carried out on the three cars, showing the effect of various conditions on the operating currents. A selection of typical oscillograms is reproduced in the paper, which also includes tabulated summaries of the results obtained on each of the three cars. These tables show the maximum currents recorded, the speed of the engine being driven by the startor motor, the time required to start up the engine, and the quantity of electricity discharged from the battery during the starting operation. In the discussion of the results a comparison is made between the results obtained on the two types of startor employed and of the effect of engine temperature upon the starting conditions. In the last section a description is given of a brief investigation carried out to locate the cause of the somewhat peculiar current peak which was observed in connection with one type of startor.