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).
Proposal and trial of a third petrol pump scheme for the Phantom III.
| Identifier | ExFiles\Box 149\4\ scan0210 | |
| Date | 5th March 1937 | |
| 1263. THE THIRD PUMP SCHEME ON THE PHANTOM III. This additional unit was presumably suggested owing to the opinion that failure of one side of the double unit S.U. petrol pump caused complete failure of both sides. The reason for this idea we think, is that the trouble we were having was due to shrinkage of the diaphragm material G.l. which we were then using, at the same time the customers were unaware when one side of the pump failed and it was only on the failure of the remaining unit that the trouble was brought forcibly to their notice. Both diaphragms were subject to the same defect and conditions causing it and it is not surprising that both failed after approximately the same service, thus giving rise to the above opinion. A trial switch is now fitted and the customers can assure themselves that both sides of the pump are in order. One unit being sufficient to supply the engine up to 80 M.P.H. under normal conditions. With 3 pumps fitted it would be necessary to have a four-way switch slecting each pump separately and an all-on position, but this would seem to be too much to ask. As it is now fitted on 35-EX. running in France with three pumps the switch selects either the single or double pump and a failure in the double would be very difficult to detect and it would only be when both sides were out of action that it would show up by using the switch. The factor of safety as regards complete breakdown on the road would be the same as at present. The only advantage we can see is that theoretically each pump should do 1/3. less work that is if all the springs were absolutely equal. For vapour trouble in hot weather, we are unable to expect any benefit as it is impossible to lift petrol by suction at high temperatures. The reduced pressure merely lowering the looking point and causing more vapour to be given off. The main objection is one of cost, the single unit costing £l. 18. 0. exclusive of pipe work and mounting and we do not feel it is justified. We contend that the present system with switch is equivalent to having two separate supplies up to 80 M.P.H. under ordinary conditions. Rm{William Robotham - Chief Engineer}/J.B.Dixon. | ||