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).
25/30 HP engine water temperature tests, identifying poor circulation and proposing corrections.
| Identifier | ExFiles\Box 103\4\ scan0166 | |
| Date | 23th April 1936 | |
| x519 To E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} c. to Mx.{John H Maddocks - Chief Proving Officer} Hs{Lord Ernest Hives - Chair}/Std.16/KW.23.4.36. 25/30 HP. Water Temperature. We send you herewith a copy of some results of radiator tests carried out by G.W.H. on 22-G-V at Brooklands. From these figures it will be seen that the water temperature at the rear of the cylinder head, as measured by the standard thermometer, runs from 5°C. to 10°C. hotter than the water in the top tank. Previous Brooklands tests on Bentley indicate a similar temperature difference, which is not so great, however - 3°C. to 6°C. approximately. Further, on both 22-G-V and 21-G-IV, if the car was braked sharply after a full throttle run, the dashboard thermometer immediately shot up to over 100°C., indicating that the water was leaving the rear of the cylinder head and allowing a steam pocket to form. This temperature difference is due to poor water circulation at the back of the block, caused by short-circuiting owing to the water inlet and outlet both being at the front of the engine. To prove this the temperatures at the spots already mentioned were measured on 22-G-V and 21-G-IV with the water passages between the block and the head on the front three cylinders blanked off. The result of this was to reduce the temperature difference to a negligible amount - actually Hancock quoted that on 22-G-V as 2°C., while on 21-G-IV the difference was 1°C. in the opposite sense; i.e., hotter at top tank than rear of cylinder head. Further, braking on the cars had no effect on the water temperature under these test conditions. In view of this, we think that this short circuiting of the circulation should be corrected at the earliest possible moment. The correction should reduce hot spots and consequently tendency to detonation and would enable us to run with a higher general water temperature (this is desirable from a carburation point of view) without registering abnormally high temperatures on the dashboard thermometer. | ||