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).
Explaining the attached blueprint curves for the 20/25 dynamo, detailing the methodology for temperature rise settings.
| Identifier | WestWitteringFiles\V\December1930-February1931\ Scan163 | |
| Date | 26th January 1931 | |
| To R.{Sir Henry Royce} from EFC. c. Sg.{Arthur F. Sidgreaves - MD} c. E.{Mr Elliott - Chief Engineer} Ev.{Ivan Evernden - coachwork} c. Wor.{Arthur Wormald - General Works Manager} PN.{Mr Northey} EP.{G. Eric Platford - Chief Quality Engineer} EFC4/AD26.1.31. X.5661 X.5663 20/25 56 AND 48 COIL DYNAMOSOF VARIOUS OUTPUTS. X.6005. We now attach a blue print set of curves for 20/25 dynamo labelled 1. As in the case of 40/50 dynamo output curves recently issued under cover of our EFC3/AD9.1.31, these output curves are (and all future curves will be unless otherwise specifically stated) for a constant operating terminal voltage of 14.0 at the same time as for a dynamo carcase temperature of 80°C. as indicated in the usual way. Thus the only variable from curve to curve is the allowed temperature rise setting in C° which setting is, on the present set of curves and will be on all future sets of curves, stated as a number followed by C°. (NB. C° is used to indicate a range of temperature and to distinguish it from °C. which indicatesthe temperature). The reason the curves will not now always be compared on an identical temperature rise setting is that different temperature rise settings are appropriate to different circumstances of use of the machine, for instance, if the machine is to be used in conjunction with a battery with no form of control either automatic or hand switching, then the setting must be such that the allowed temperature rise is a minimum in view of the fact that the machine may be run in hot weather with sustained high battery P.D. for which a good margin of safety against overheating must be allowed. Taking the other extreme case, where the rise of terminal P.D. is arrested by automatic control, then the setting may be such that the allowed temperature rise is very considerably greater. The preliminary remarks on the first page of our EFC3/AD9.1.30 again, of course, apply in the present instance. The curves for the 20/25 on the present sheet 1. similarly represent progressive stages from early cutting in with low output to late cutting in with high output. | ||