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).
Description of the action and design of a self-draining float for an Autovac petrol feed system.
| Identifier | ExFiles\Box 40\4\ Scan190 | |
| Date | 22th December 1926 | |
| AUTOVAC PETROL FEED. SELF DRAINING FLOAT. The action of the self draining float fitted to the Autovac tank is as follows :- Fitted to the float is a hollow stem in which are drilled two small holes, one at the bottom of the stem inside the float and the second at the top of the stem outside the float. If petrol should leak into the float it will automatically be evacuated from the float during the suction period of the apparatus and during the periods of atmospheric pressure air will flow into the float to take the place of the evacuated petrol thereby enabling the float to function as when air-tight. We have made a leak in a self-draining float by drilling a hole .075" dia. in the bottom of the float. Even with this large puncture the mechanism works quite normally, the self draining action being sufficiently efficient to drain out the petrol leaking into the float. We produced one condition in which the float would not drain itself. The float was approximately 75% filled with petrol and assembled in this position. The suction was not sufficient however to drain the float before the float chamber was filled with petrol from the rear tank and consequently the float could not rise and cut off the suction. Pure petrol was then sucked into the induction pipe. This condition can never occur in service as the petrol level in the float chamber is never high enough to allow the float to be filled contd :- | ||