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).
Describing the construction and operation of a Grav-Vac vacuum petrol feed tank, comparing it to the Autovac.
| Identifier | ExFiles\Box 40\3\ Scan078 | |
| Date | 26th June 1928 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/AJL. c. to BJ. WoR.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} c. to BY.{R.W. Bailey - Chief Engineer} X3575 Hs{Lord Ernest Hives - Chair}/AJL/LG26.6.28 Maxxxk GRAV-VAC VACUUM FEED TANK. The attached sketch shows the construction of the latest Grav-vac petrol feed tank. Instead of using a float (as in the Autovac) a partially open ended bell is employed, the air being vacated from this by the induction pipe suction, and the petrol takes its place. As the bell fills with petrol it gradually falls until it closes the suction valve and opens the air valve. The outer petrol is then used by the engine until the level in the outer tank uncovers the bottom of the bell, thus breaking the liquid seal, the bell rises again, opens the suction valve and closes the air valve, and petrol is again drawn in. The valve action is not as good as in the Autovac because it is gradual and not helped by spring toggling; the effects of this, which have been demonstrated during tests on the Grav-vac, are (a) Engine filled up with petrol due to suction valve being open and air valve closed after the inner bell is full of petrol. (b) Failure to work under vibration due to valves not definitely closing. Apart from these faults, non-existent in the Autovac, the tank has the usual ill-effects upon the slow running of the engine (N.B. there is no restriction in the suction line to help overcome this effect). The curves shewing comparative petrol deliveries shew that the Grav-vac is superior in this respect to the Autovac. contd :- | ||