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 choker and primer schemes, and a proposal for a new air valve mechanism.
| Identifier | ExFiles\Box 50\3\ Scan029 | |
| Date | 19th February 1923 | |
| -2- continuously if the choker is left on, failing after a few seconds from over richness. We think this latter is an advantage as it ensures that the car will not be run with the choker on, a condition which has caused trouble with the present primer in the hands of careless drivers. The fact that the high vacuum with the choker scheme tends to suck oil up past the pistons, is in its favor, we think, because with the primer alone the tendency is to dry the cylinder by washing the oil down into the crankchamber. How this scheme (which is essentially the standard American scheme) would compare with the use of a pilot jet for starting and slow running, we do not know, not having tried the latter under American conditions. I would suggest, however, that the pilot jet, since it must be able to run the engine efficiently when warm, would probably not give a sufficiently rich mixture for starting with American gasoline in American winter temperatures, when I think it can be assumed that only the lighter fractions of the petrol are actually fired in the cylinder. The fault with the scheme on 41EX is that the air on the extra air valve cannot be prevented from leaking a little when closed, thus upsetting the carburation at low speeds. We therefore suggest that as an immediate experiment some means should be devised to mechanically hold down the extra air valve, while nearly closing the low speed air intake with a butterfly valve. We think this could be combined with the priming cock (if the latter were still found to be necessary) and the whole thing actuated from a handle on the instrument board, where it can be easily reached. Yours truly ROLLS ROYCE OF AMERICA, Inc. Per......... M.Olley. MO/G CC Mr. Belnap Mr. Deaver. Mr. Fadin Mr. Bagnall. Mr. Hulley Mr. Southern. | ||