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).
Technical memorandum on the development and improvement of Spectre carburetters.
| Identifier | ExFiles\Box 93\2\ scan0031 | |
| Date | 13th February 1938 | |
| To E.{Mr Elliott - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Swd1.10/KW.13.2.38. SpectreCodename for Phantom III Carburetters. Little or no development work has been carried out on the SpectreCodename for Phantom III carburetters in view of the fact that experiments were being carried out on the 25 HP. carburetter and being a single carburetter shews up any faults more obviously than multiple carburetters. With regard to the general running of the carburetters both for power, slow running, and acceleration, they are fairly good in their present condition, and it is only by the work carried out on the 25 HP. that we can improve them. Quoting the 25 HP., improved metering has been obtained by the use of the reversed throttle, which lowers the changeover speed and confines the throttle edge feed to slow running only. We have experienced on SpectreCodename for Phantom III that adjustment of the slow running choke, other than affecting the idling mixture, also affects the mixture at much higher speeds. This means that the choke is more or less fixed by the mixture at speeds above idling, as the main taper needle is a fixture without adjustment. The use of reverse throttles should overcome this effect, but think that there should be a fine adjustment for the main jet and needle to cover small differences between assembly of carburetters and that the needle be pushed up to a definite stop in the piston. Another improvement carried out on the 25 HP. is the separation of the float chamber balance passage from the slow running air passage. As a temporary measure to be up to date, we have instructed an external floatchamber balance similar to the 25 HP. scheme Lec.4292. | ||