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).
Carburettor and intake pipe design, including S.U. horizontal and downdraught carburettors, and petrol pumps.
| Identifier | ExFiles\Box 121\3\ scan0090 | |
| Date | 14th November 1940 | |
| Rm{William Robotham - Chief Engineer}/OTS.6/ST.14.11.40. - 2 - the predominating factor was a wave effect, the nodes of which could be adjusted to give varying effects on the intake, by adjusting the length of intake pipe. We are acquainted with this problem ourselves, inasmuch as we know that the causes and effects just mentioned can be considerably reduced, by using a sufficiently large capacity intake, with carefully developed bends. The former may be considered as being a desirable necessity, but the latter has to be considered as an absolute essential. Referring to the pressure variations on the atmospheric side of the air valve, it may be remembered that, when we tried a forward intake under certain conditions it was possible, by raising this pressure above the effective suction tending to raise the piston, that we actually blew the petrol back down the jet, into the float chamber. The S.U. horizontal carburettor, by virtue of its length, has left the small car manufacturer with a very limited space, into which an intake bend may be fitted. In the majority of cases, there just is not sufficient space to provide a bend which will give the carburettor a straight column of air free from pulsations out of phase with the suction impulses on the air-valve. Returning, however to the requirement of the moment, which is a twelve-cylinder engine, we would suggest that there should be a separate intake and oil bath at each end of the engine, which will at least allow uniform conditions to exist for each carburettor. Regarding the induction pipe proper, we would rather make suggestions for what they are worth, when one starts a layout, than propound a list of theories around the many ways of getting the mixture from carburettor to cylinder, under these unusual conditions. It may be, however, that we shall not have the opportunity of using our usual means of tailoring the pipes to suit, owing to limited man hours, during which we shall be allowed to use an aero test bed. We would suggest, therefore, that our preliminary layout should cater for the maximum amount of adjustment, by being able to pull pieces off and put other pieces back. The material should be brass, to enable brazing or soldering to be done. 2. Petrol pumps for use with l. - This arrangement was suggested to be in the form of 2 Phantom III type high pressure pumps mounted on a common casting, to deliver 250 pints/Hr., at a pressure of 1 lb./sq. inch at the float chamber. S.U. will submit pumps built up accordingly. 3. Downdraught carburetter (Expanding Choke). - They have not progressed with this project during the past few months. Their main difficult is manufacturing small pieces, as it is with us. We were to have been supplied with a specimen carburettor with a | ||