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 autovac float failures caused by petrol vapour condensation after heating.
| Identifier | ExFiles\Box 40\4\ Scan339 | |
| Date | 22th May 1930 guessed | |
| -3- and had the engine been allowed to run, petrol would have been drawn into the crankcase. With the autovac in this condition and the float "dead", it was taken to the Test Dept. and fitted up on a Phantom II chassis. The results were the same as on 1-WJ. The reason why the float failed under these conditions was because when the petrol was heated the float was filled with petrol vapour and as it cooled down, so the vapour condensed and caused a partial vacuum; the petrol was then drawn into the float, thus causing it to drop and become dead and in so doing, prevented the suction valve from closing. The experiments prove that, providing the petrol is cold and there is a leak at the bottom, the self draining device will always operate, but as soon as the petrol is heated to a fairly high temperature, as it would be on a car, and allowed to cool, the float will fail. Of course, if the leak was at the top the float would fail irrespective of temperature. F.C.T. Evershed. | ||