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).
Proposing a modification to the New Phantom vacuum feed tank, with a diagram, to resolve sooted spark plugs by introducing an air-only autovac mechanism.
| Identifier | WestWitteringFiles\N\2July1925-September1925\ Scan41 | |
| Date | 1st August 1925 | |
| R.R. 235A (100 T) (S.H. 159. 11-8-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2800 TO HS.{Lord Ernest Hives - Chair} FROM E.{Mr Elliott - Chief Engineer} Copy to - CJ. (handwritten, struck through) re. NEW PHANTOMCodename for PHANTOM I VACUUM FEED TANK. Referring to report HS{Lord Ernest Hives - Chair}/AJL/LG13825., we should suggest that the piston in the special modified suction elbow should not be allowed to close the passageway entirely between the induction pipe and the autovac, but that a permanent restricted passageway should always be left open. This could be arranged by milling a groove in the stem of the piston. When running 9-PK. during the holidays the mixture was weakened until the engine would only just fire evenly under all conditions, also the shutters were manipulated so that the temperature indicated on the thermometer was 85º. Under these conditions the sparking plugs on both ignitions became badly sooted up. It is possible that this effect was due to the autovac, as the car was running mostly at low speed under these conditions, never exceeding 30 MPH.* It has occurred to me that we could fairly easily make an autovac mechanism which drew only pure air into the induction system, if we could obtain a sufficiently flexible bellows. The sketch below shews how this would be arranged. The petrol pump portion of this apparatus is so designed that it will not hold air; the delivery valve is at the top and all air is expelled through this valve. The interior of the petrol pump could easily be filled with petrol to give the apparatus an initial start if necessary, but itlooks as if it would start itself after a certain time which would be required for expelling the air. E.{Mr Elliott - Chief Engineer} OE (signature) * When the temperature was dropped 20º the plugs appeared to remain clean (handwritten note) [Diagram Labels] PETROL TANK TIME VALVE VALVE SPRING AIR TO CARBURRETER USUAL VACUUM FEED TOGGLE VALVE SWITCH AIR INDUCTION PIPE | ||