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).
List of specifications and actions for the development of dynamos and motors for large and small cars.
| Identifier | ExFiles\Box 37\1\ scan 100 | |
| Date | 1st March 1921 | |
| To EFC. from E.{Mr Elliott - Chief Engineer} -2- E1/G31/3/21 Contd. (g) Modify all the experimental dynamos being dealt with into third brush machines if possible. (h) We want the following models of dynamos for our large and small cars :- At ordinary working temperatures. { 6" carcase 12 volts 10 amperes (12 amps max) (8 amps min) cut-in 500 (10 miles per hour) full output 750 (15 miles per hour) for 40/50 H.P. { 5¼" carcase 12 volts 7 amperes (8½ amps max) (5½ amps min) cut-in 600 for 15 & 20 H.P. It is permissible for the dynamo to have a falling characteristic, provided its first rise is sharp enough. What can we buy to fit these specifications? (i) The 40/50 H.P. dynamo made from starter motor parts should be finished as 3rd brush machine, as Mr. Royce thinks we may learn something from it. (j) If we fix our standards as 6" and 5¼" for our two dynamos, we can easily put in other makers' smaller machine for test. (k) Mr. Clark to find out what are the proportions of other people's armature and carcase diameters. The R.R. table of dynamos and motors is as follows:- [Diagrams with handwritten labels 'ARMATURE' and 'DIA OF CARCASE'] [Diagram 1: Armature 3.5, Carcase 6] [Diagram 2: Armature 3.325, Carcase 5.25] [Diagram 3: Armature 2.75, Carcase 4.75] (l) Mr. Clark to get out the winding with even number of teeth and dummy coil, and a moderate number of teeth, so as to use punched plates and avoid milling. This should give us a silent machine and good insulation to earth by grouping coils. (m) The radial air space for R.R. machines should be as follows:- 6" dynamo .015 5¼" dynamo .012 5¼" motor .015 4¾" motor .012 (n) Also dynamo should have spiral teeth and gentle approach of poles for silence, spirally castellated or knurled shaft with identical armature punchings located on tops of teeth. (o) Mr. Clark to take the Bosch ignition coil back with him and find out why the Bosch ignition set can be sold at a price of £3.15.0 while R.R. coil costs £4.10.0. | ||