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).
The comparison of dynamo output curves under various engine temperature and test conditions.
| Identifier | ExFiles\Box 51\1\ Scan348 | |
| Date | 3rd March 1924 | |
| Contd. -3- EFC {E. Fowler Clarke - Electrical Engineer} 2/T3.3.24. (this temp. being obtained temporarily by partially heat insulating the machine) We generally take for comparison an output curve of the dynamo at 85°C - this we call 'the engine hot curve'; and this is intended to be representative of the actual output curve with the dynamo in position on the engine and in the fully hot condition. But it may happen, as in the case of the GoshawkAero EngineCodename for 20HP Car / Aero Engine after KestrelAero Engine dynamo, that the engine hot curve, with the brush setting to suit the general specification, will be higher than that agreed upon between ourselves and the battery makers, in which case the control brush will be (lower output) rather more advanced for this output curve than it would be for compliance with the general specification. At the same time we may also gain improved commutation. There are then two engine hot curves, one corresponding to 'general specification setting', and a lower one corresponding to 'production test setting'. Referring to the comparative curves for the Lucas E.575 and the RR. 20 HP. machines recently sent to E. {Mr Elliott - Chief Engineer} under cover of our EFC {E. Fowler Clarke - Electrical Engineer} 1/LG19.2.24, the curve for the Lucas machine, which is the average of a number of curves for the hot condition taken on this machine before the present basis was exactly fixed, probably represents a temperature condition of about 80°C, i.e. mid-way between general specification and engine hot condition. The curve for the RR. 20 HP. represents the engine hot output curve (at about 83°C) for the machine as set in present-day production. This, as explained, Contd. [Handwritten in right margin]: initial 'plumped' down in the usual way | ||