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).
Comparing different oil filter and pressure relief valve systems, recommending the use of the external filter LeC.4692.
| Identifier | ExFiles\Box 10\3\ 03-page005 | |
| Date | 28th January 1937 | |
| -2- (1) LeC.4692 filter only deals with the actual oil feed to the bearings, and will therefore have a longer life before silting up than LeC.5170, which deals with the whole of the oil pump delivery. (2) The main pressure relief valve as housed in the pump (std.) combined with the rockercontrol box on the wheelcase LeC.4412, does not involve any complicated passage ways. (3) That when starting with cold thick oil, the back pressure created by the filter element or bye-pass valve, if opening does in effect reduce the effective control pressure of the main pump relief valve spring and save the oil pressure gauge from excessively high pressures. (4) LeC.5179 does necessitate increased piping, not being so direct in its job. (5) By using the external filter LeC.4692, we should be encouraging the interchangeability which goes for cheapness, as a standardisation sheet has been issued for this external filter to be incorporated on Bentley. (6) Though we have no comparative costs available, we should, from the drawings, say that LeC.5179, if anything, would be a more costly job than the combined LeC.4692 and LeC.4412. In view of the fact that we have run so long on the 25/30 and Bentley without a rocker pressure control, LeC.4412 can, although doing some useful work, be regarded as a luxury. The inclusion of this, however, and the job it does, makes it comparable with the complete layout LeC.5179. The main disadvantage, if this can be regarded as such, with LeC.4692, is that if the filter and the bye pass valve be choked at the same time, then there will be no oil pressure. It is unlikely that this would occur in unison, however, and even if it did, then the oil pressure gauge would tell its tale before any damage was done. For the reasons mentioned in this memo, we would recommend therefore that the question of using the external filter only (LeC.4692) instead of the combined filter and relief valve box LeC.5179 with modifications be considered before the Wraith design is issued. continued | ||