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).
High under-bonnet temperatures and a proposal for a new cooling system design separating engine temperature control from radiator shutter operation.
| Identifier | ExFiles\Box 92\6\ scan0274 | |
| Date | 29th October 1936 | |
| 305 hlet Rly/STD Sg.{Arthur F. Sidgreaves - MD} and Hs.{Lord Ernest Hives - Chair} from E.{Mr Elliott - Chief Engineer} C. Hy.{Tom Haldenby - Plant Engineer} Rm.{William Robotham - Chief Engineer} Ea. /Unr. D/Tsn. E.3/HP.29.10.36. Under Bonnet Temperature. There is very little doubt that we are operating at a serious disadvantage compared with the majority of other cars by reason of our high under bonnet temperatures. Some little time ago we made efforts to produce a grille, with the object of dispensing with radiator shutter control, without spoiling the appearance. The effect however was not liked, and a decision was made both in the case of the Bentley and Phantom III, to retain the polished shutters. The advantages of the grille in reducing the average under bonnet temperature were demonstrated in a test on the Bentley driven at fast touring speed. With the shutter control fitted, the air intake temperature was 48°, and with the grille only 32°, showing a reduction of 16°. We ought to make strenuous efforts to get away from our present position, and it has occurred to me that one means of doing this would be to divorce the control of the shutters from the unit controlling the engine temperature. It will be appreciated that with our present system the shutter control maintains the engine at its operational temperature by restricting the air flow through the bonnet. If, therefore, we equip the engine with a bypass thermostat and use a distant control thermostat for operating the radiator shutters, the engine can be maintained at its correct working temperature, and we can then make the shutters pass the maximum stream of cooling air through the bonnet the whole of the time the engine is above any selected temperature. It would not be necessary to make this control open the shutters wide and leave them so, but an intermediate position could be selected, say 3/4 open at 85° engine jacket temperature. They could then open from 3/4 to full if the engine temperature arose above 85°. | ||