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 regarding a solenoid for operating the starter motor on a Phantom II tank engine.
| Identifier | ExFiles\Box 62\1\ scan0254 | |
| Date | 5th June 1934 | |
| 86079 5.6.34. SOLE-NOID FOR OPERATING STARTER MOTOR ON PHANTOM II TANK ENGINE. Force required in the out position = 22 lbs. Ampere turns necessary to produce this force in the out position of existing design of solenoid D 74401 - 4800 i.e. 11.2 amperes x 428 turns. Resistance required = 9 volts / 11.2 amperes = .803 ohms. Present resistance = .495 ohms. Ratio of resistance = .803 / .495 = 1.62 If we rewind the solenoid with 428 turns of 17 S.W.G. wire assuming the same length of mean turn the resistance will be .812 ohms. As the length of the mean turn will be slightly less due to the reduced wire dia. the resistance should be almost exactly correct. With the current reduced corresponding to the most extreme condition of low battery voltage of 6 on the motor terminals the solenoid will still exert a force easily capable of holding the pinion in mesh. --------- | ||