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).
Experiments to develop a 20/25 tank engine dynamo capable of delivering 20 amperes.
| Identifier | ExFiles\Box 163\2\ img080 | |
| Date | 11th December 1933 | |
| 86008 By.{R.W. Bailey - Chief Engineer} From Ha/Wst. c. to Sg.{Arthur F. Sidgreaves - MD} c. to Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} c. to Mx.{John H Maddocks - Chief Proving Officer} c. to F.{Mr Friese} Ha/Wst.1/MA.11.12.33. 20/25 TANK ENGINE DYNAMO. As a result of a request from the W.O. Armament Dept. that we should endeavour to provide a dynamo on the 20/25 tank engine capable of delivering 20 amperes we have carried out a few preliminary experiments both with the 20/25 size and the 40/50 size dynamo. We had previously informed the W.O. representatives that it was impossible to provide this output without :- (a) Providing a dynamo with external voltage control. (b) Raising the "cutting in" speed considerably. We were informed that the voltage controlled dynamo was permissible, also that we could raise the "cutting in" speed if necessary to approx. 1500 R.P.M. (dynamo). Experiments were first made with an R.R. Sch.344 shunt dynamo of the 20/25HP. size but we found that the iron losses in the armature and the brush losses were proportionately much larger than the windings losses and as it was felt that a considerable amount of experimental work would be necessary to get the required results from this dynamo it was decided to carry on with the 40/50 size dynamo in order to save time. By a simple alteration to the armature winding on this dynamo and by using different grade brushes we have produced 20 amperes output at 13 volts for a 55°C. temperature rise the "cutting in" speed being approx. 1350 R.P.M. | ||