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 of different dynamo models for small and large cars, detailing specifications and prices.
| Identifier | ExFiles\Box 36\4\ scan 207 | |
| Date | 21th April 1921 | |
| Contd. -7- EFC4/T21.4.21. Dynamo for Small Car. There is a smaller Rotax dynamo than the A.T.12 listed, namely, A.T.4, or called A.T.8 if with flange fixing. The lowest balancing speed of this machine in the cold condition is 480 r.p.m. Weight 17 lbs. Carcase dia. 5" It is thought that this machine would be very suitable for the small car, and we have accordingly asked for a sample to be ordered. The cutting in speed, as in the case of the A.T.12, is perhaps unnecessarily low, and it might be better in the case of the A.T.12 if the armature were wound with fewer turns so as to give a higher cutting in speed and more amperes. This machine would then more nearly correspond to our specification. We are visiting the Rotax Company next week for the purpose of taking up these points. Smith Dynamo type 3D. This dynamo is similar to the type 2D machine, but of smaller dimensions. Weight - 25 lbs. Earliest cutting in speed (cold) 550 r.p.m. Outside dia. 5¼" Quantity price with all minor improvements required by R.R. £15.5.0. The output is perhaps rather small for the large car; on the other hand, the carcase diameter 5¼" would be too large for the small car. Smith 4D Dynamo. This is a smaller machine with a carcase diameter of 5". Weight 19 lbs. Earliest cutting in point (cold) 750 r.p.m. (Note:- this cutting in point would be rather late). Quantity price with all minor improvements required by R.R. £11.10.0. Contd. | ||