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).
Specifications and investigations for the 'Goshawk II' Dynamo.
| Identifier | ExFiles\Box 51\1\ Scan016 | |
| Date | 6th July 1921 | |
| r4383 6.7.21. X.4383 - "GOSHAWK II" DYNAMO. (SINGLE FIELD WINDING THIRD BRUSH CONTROLLED MACHINE). Hot cutting in speed to be 10 miles per hour. Drive ratio from engine to dynamo is 1.5 to 1. 10. m.p.h. of car corresponds to 427 R.P.M. of engine on top gear (with 4 : 1 back axle ratio), i.e. to 640 R.P.M. of dynamo. Dynamo must put up 13.6 volts on open circuit at this speed when hot. Investigations on the Rotax AT.12 and U.S.A. Bosch machines have shown that their cutting in speeds as controlled machines are only slightly greater than as shunt machines with their single field coils connected across the main brushes, the auxiliary brush being out of action. This is to be expected, as until the armature becomes appreciably loaded, causing distortion of the main flux, the span of the field winding on the commutator embraces the major portion of that flux. Hence, as the electrical and magnetic quantities of the dynamo are largely fixed up on the question of cutting in speed, it will be sufficient in the first instance to proceed as for a plain shunt machine, taking the cutting in speed to be 40 R.P.M. less, namely, 600 r.p.m. Contd. | ||