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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Description of the motor starting system, including its electrical operation and gear reduction ratios.

Identifier  ExFiles\Box 34\3\  Scan026
Date  26th May 1919
  
extract from L.T.C 4/1 26.5.19.

AUXILIARY APPARATUS. X.3034. X.2641.

The starting current for the motor is switched on by means of an electrically operated main switch. This is operated by a relay current which is caused to flow upon the driver depressin a push button switch fitted on the dash. At the same time this relay current passes through magnet coils of an actuator box. The relay current in the coils of the main switch cause the heavy current motor circuit to be closed through contacts of ample area. In passing through the other magnet coils it causes, by means of a sui able mechanism, the motor to be put into gear with the engine through the gear box. There is a reduction gear built on to the motor as part of it, of 6 to 1. The motor then drives through a chain to the gear box with reduction of 14 to 13, then the power passes through an epicyclic gear of the gear box which gives a further reduction of 6 to 1, finally the power is transferred to the engine through a pair of gears in the box giving a speed increase of 5 to 3. The total reduction from the motor to the engine is 23.3, so that when the motor speed is 1,000 the engine speed is 43 R.P.M. The starting current drawn by the motor from the battery is in the neighbourhood of 100 amperes.

LND/D X.13
  
  


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