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).
Investigation into petrol spray from the Phantom III float chamber vent pipe under braking and full bore flooding conditions.
| Identifier | ExFiles\Box 93\2\ scan0170 | |
| Date | 23th June 1936 | |
| To Rm.{William Robotham - Chief Engineer} x308 Hs{Lord Ernest Hives - Chair}/FD.{Frank Dodd - Bodies}11/KW.23.6.36. Phantom III Float Chamber Vent Pipe. GWH{George W. Hancock - Head Chateauroux}/HFH{Hoppy F. Hamilton} has reported that petrol spray has been observed coming from the float chamber vent pipe when the car is braked severely; he also reports that the trouble is cured by moving the vent to the centre of the float chamber. We have tried to reproduce this on both 33-EX and 36-EX, but have not been successful. We have tried braking from high speeds, medium speeds and in descending hills. We cannot even force the petrol down the drain pipe and the vent outlet stands 3" higher than the drain. A test has been made with a glass bowl fixed level with the float chamber and having the same liquid level. The braking effect was observed, the level increasing at the front end by .75"; actually in the float chamber this would not be so great, as the float would steady the petrol. From our tests we cannot therefore understand how it has been possible on 32-EX to obtain their results. Three things may have misled them - (1) Not a standard vent pipe. (2) Incorrect petrol level. (3) Very effective front brakes. All our tests were carried out with the vent in the old standard position. Full Bore Flooding. We have also tested the vent under full bore flooding conditions and find that with water temperatures up to 80°C. the present arrangement is satisfactory. With water temperatures in excess of 80°C., the petrol and vapour will not immediately take to the drain, and we get a spray of petrol from the vent. We have made a new vent which is satisfactory up to 93°C. water temperature. This extra margin will be required as the engine temperature rises after standing. | ||