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).
Cold start tests conducted on the Wraith car to identify and resolve issues compared to the Bentley model.
| Identifier | ExFiles\Box 151\3\ scan0361 | |
| Date | 4th February 1938 | |
| To By. {R.W. Bailey - Chief Engineer} from Rm {William Robotham - Chief Engineer} /wym. {G. Harold Whyman - Experimental Manager} c. HS. {Lord Ernest Hives - Chair} c. RHC. {R. H. Coverley - Production Engineer} c. Da. {Bernard Day - Chassis Design} c. Fx. RC {R. Childs} also 1290 Rm {William Robotham - Chief Engineer} /wym. {G. Harold Whyman - Experimental Manager} 1/MH. {M. Huckerby} 4.2.38. COLD START TESTS ON WRAITH CAR. We have just completed a series of cold starting tests on the Wraith car to find out why it does not start so well as the Bentley under extreme conditions. As the attached report shows, the present type Wraith battery is inferior to the Bentley battery, and the Wraith engine requires more effort to move it, thus causing a bigger voltage drop at the battery owing to the self starter operation. These things combined result in a low starting R.P.M. and a low voltage at the coil. We have been able to overcome these deficiencies by fitting either a 25/30 H.P. standard battery or a P.III battery and a Delco coil which fires the engine at a lower voltage than the R.R. coil. For even better starting from cold we shall have to devise some means of reducing the friction in the Wraith engine, and also modifying the self starter to take less current out of the battery. We intend to try a Lucas starter motor on a Wraith car as soon as convenient, and comparative tests will be taken in the cold chamber. For comparative purposes the tests on both engines were carried out firstly with .020" plug gap and secondly with .030" plug gap. The latest Delco coil has proved better than the R.R. 20,000 turn coil for starting tests, and we are running 2 of them on endurance tests. Summarized, the position is that we require the 25/30 H.P. standard battery and the Delco coil to obtain a good cold start with a .030" plug gap. | ||