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).
Evaluation of a submitted cut-out model, detailing its performance under cold and hot conditions against specification.
| Identifier | WestWitteringFiles\F\April1921\ Scan69 | |
| Date | 19th April 1921 | |
| Contd. -3- EPC/S/19.4.21. The size of the model submitted to us is not large enough to satisfactorily overcome the variations of cutting in point due to temperature rise, and does not, for this reason, satisfy our specification of operation in the hot condition. The cut-out is, however, very definite in operation and as received by us is in accordance with the following figures :- Instrument cold 20°C Shunt coil operates cut-out when dynamo has raised voltage to 12.4 on shunt coil terminals (D+ to D-). Shunt current .110 (The cutting-in point as adjusted is according to our specification. The cut-out is deoperated at 7.1 volts .060 amperes on shunt coil only, battery disconnected. N.B. The relatively great difference between these two voltages is an indication of large reverse current required to de-operate, when the battery is connected. De-operation with battery connected occurred at 12.1 volts 2.5 reverse series amperes. (Our limit for an ordinary cut-out is 2.0 amperes and for special cut-outs such as Bleriot, which is designed to avoid reverse amperes, 1.0 amps). Instrument hot - after running for two hours with not less than 10 amperes through series coil. Operation on volt coil occurred at 15.0 volts .113 ampere. De-operation on volt coil only at 8.5 volts .060 amp. When connected to a battery it required 2.5 reverse series amperes to de-operate. This cut-out is provided with gold-silver contacts, one of which exerts a rubbing motion on the other in coming into operation. The cut-out is of a size which renders it capable of being put in the Lucas switchbox in place of the present Lucas cut-out, but as already stated, on account of its small size, suffers from the effect of too much change of operating point with temperature. This cut-out is now being sent to Mr. Royce for his examination. EPC. | ||