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).
Tests and conclusions regarding various proprietary windscreen demisting and defrosting heater units.
| Identifier | ExFiles\Box 137\3\ scan0025 | |
| Date | 23th January 1939 | |
| -7- SM/Std.C/ER.23.1.39. to overcome resistance in ducts etc. and maintain a good air flow - the idea of taking demisting air from the main heater fan was found to be useless on S.D.V. car in France recently. Actually on this car it was found that opening the Fisher ventilators on the door side windows cleared mist effectively from the screen, the cooling effect being counteracted by keeping heater full on, while opening the screen slightly had a similar effect. As regards defrosting of the outside of the screen, we have never had an opportunity of making tests on this subject under running conditions - the only time the writer has had experience of a car windscreen actually icing up on the exterior was on a car which was not fitted with a heater. We think, however, that defrosting of the outside of the screen, and even demisting of the interior, would be better done by supplying hot air to the outside of the screen from under the bonnet, and are rigging up such a scheme on 1.B.30 - alternatively a scheme, whereby fresh air (cold) was made to pass from vents across the inner surface of the screen, seems a promising one. Our chief criticism of the demisting arrangements which we have tried, is that with the units available, only small portions of the screen are cleared, whereas it is desirable to clear the whole screen. The following are the conclusions from tests on the three most promising proprietary heaters which we have tried. (1) A.C. Sphinx heater:- This unit has sufficient heat output to warm any of our cars by method (B) or (C) above, is noisy as standard unit supplied, but fairly quiet with separate motor operation - the unit, however, is useless as a defrosting unit, giving an entirely inadequate air supply to the screen. Weight is approx. 6 1/2 lbs., cost approx. 30/- to 35/-d.{John DeLooze - Company Secretary} (2) A.A. design (SSD.221 modified) combined heater and de-froster:- This unit has sufficient heat for warming any of our cars by methods (B) or (C) above, is quiet as designed (separate motor operation), defroster and demisting blower is reasonably effective as regards demisting, but no opportunity has occurred as yet to test it for defrosting. Weight is approx. 6 lbs., cost approx. £2.10.0d. (Tool cost approx. £150). | ||