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 starting tests for a Bentley engine, discussing issues and proposed improvements.
| Identifier | ExFiles\Box 62\1\ scan0216 | |
| Date | 25th November 1933 | |
| -2- Hs{Lord Ernest Hives - Chair}/Wst.6/MA.25.11.33. The engine static torque at this temperature was found to be 220 lb/inches, the current taken by the motor was 298 amperes, the battery volts being 8.1 and the motor volts 6.25. We have shown by previous tests that as the temp. drops still further below zero the viscosity of the oil increases, thus increasing the turning torque of the engine. It will be seen, therefore, that the starting performance of the Bentley under extreme cold conditions - i.e., below -5°C - would be very poor. The modifications proposed to improve the starting are the fitting of a larger diameter motor, possibly changing the engine oil to a grade of oil which has a better viscosity at low temperatures, reducing the voltage drop between the battery and the armature with the use of larger conductors where possible, tapping the feed wire for the ignition to the battery itself, and the fitting of an eleven plate battery instead of the nine plate. Some very interesting figures were obtained from Messrs Lucas giving the relative viscosities of various grades of oil at low temperatures, and these will be extremely helpful in deciding the best oil for use on the Bentley from the point of view of cold starting. It is proposed to utilise this freezing chamber of Messrs Lucas, which they have kindly placed at our disposal whenever we require to use it, for further tests in connection with the Bentley and Rolls-Royce chassis. The next move is to change the oil to Prices Motorine 'C' and repeat the test, as it is believed that Motorine 'C' is much better at low temperatures than Mobiloil 'D'. Messrs Lucas were surprised that we were able to effect a start at all with the Bentley, with the engine turning over at only 40 R.P.M. The usual figure they get with cars in their freezing chamber is almost double this. Although it is true to state that they have little or no experience with large cars of a capacity similar to the Bentley. Hs{Lord Ernest Hives - Chair}/Wst. | ||