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).
Comparison between an R.R. motor and a Lucas motor, focusing on horse power, efficiency, and safety.
| Identifier | ExFiles\Box 34\3\ Scan164 | |
| Date | 17th April 1918 guessed | |
| Contd. -2- R 3/G17417. each motor so that the maximum horse power and maximum efficiency is at approximately the same speed in each machine. For instance, supposing the R.R. motor shewed its maximum efficiency at 1500 revs. whereas the maximum efficiency of the Lucas was at 2000 revs. the voltage should then be increased from 12 to about 16 for the R.R. motor, so that the armatures will both be running approximately at the same speed. If then the horse power and efficiency were the same, there will be little to chose between them. In a series wound machine so much depends upon the field winding what is going to be the maximum horse power, but in a starter motor (since you use no resistance to start with) it is advisable for this field winding to be arranged so as to prevent a great rush of current when first closing the switch. This rush of current apparently is not damaging to the battery, but as I pointed out before my views are that the switch contact or commutator brushes are likely to be damaged. You will see that from this point of view the R.R. motor was very safely arranged, having a large brush area with the commutator, and small current for a good torque, and also a small rush of current. It was also considered that if the motor had to obtain a high rate of revolution before giving a good back electromotice force, it would be dangerous for the motor circuit. In this respect the higher speed motor is worse and also one which has a large moment of inertia. So you will see, in comparing motors of this description Contd. | ||