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).
Calculations and specifications for the Goshawk II starter motor.
| Identifier | ExFiles\Box 35\4\ scan 034 | |
| Date | 1st July 1921 | |
| X4384 1.7.21. X.4384 - GOSHAWK II STARTER MOTOR. Torque required to turn Goshawk engine = 500 lb-inches. Speed reduction ratio = 8.4 Take 90% gearing efficiency, then effective torque ratio .90 x 8.4 = 7.56 Motor torque when rolling engine is therefore required to be 66.1 lb-inches. It is considered that the motor windings should be such that the motor, when rolling the engine, should be working approximately at its maximum power, the volt-ampere characteristic of the supply to the motor being according to our standard. It is estimated that the maximum B.H.P. should be about .85, which makes the motor speed when rolling the engine to be 810 and the engine speed 96.5 Assuming 50% efficiency we get Elec. H.P. = 1.7 Amperes - 137 Volts - 9.26 The running torque at this current is to be 66.1 lb-inches. The static torque must be about 10% greater to Contd | ||