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 to eliminate the carburetter floatchamber vent on the Wraith III model to reduce costs, due to design changes that mitigate petrol vapourisation.
| Identifier | ExFiles\Box 7\4\ X 608 Carburetter-page46 | |
| Date | 9th November 1938 | |
| 608 WRAITH 111. CARBURETTER FLOATCHAMBER VENT. With reference to the proposal in Rm{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation}6/R.4.10.38. re a simplified form of lamp post type breather for the carburetter floatchamber, we suggest that it might be possible to do away with this feature altogether in view of the altered conditions affecting vapourisation of petrol, which had a detrimental effect when starting with engine hot on the 25/30 engine. The change in conditions, since the introduction of the lamp post, are as follows :- (1). The petrol pumps and piping are now arranged in much cooler positions than before, a large amount of the vapour was originally formed in this part of the system. (2). The carburetter is now on the opposite side of the engine from the exhaust pipes, and is therefore in a cooler position. (3). The petrol drain pipe from the floatchamber lid{A. J. Lidsey} to cope with full bore flooding is a separate pipe with much freer flow, and should certainly be able to cope with the breathing of the floatchamber. To put the case briefly, the conditions for the Wraith 111 carburetter are now similar to those on the Bentley engine, which has only a .1875 o/d.{John DeLooze - Company Secretary} drain pipe, and which also serves as the floatchamber breather, against the .3125" o/d.{John DeLooze - Company Secretary} pipe fitted to the Wraith 111 carburetter floatchamber. It would therefore appear worth while making tests to prove whether the lamp post breather is now necessary, as it would obviously reduce costs if it could be deleted altogether. DA.{Bernard Day - Chassis Design} | ||