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).
Decision to delete the designed pressure oil filter on the Wraith in favour of a bye-pass filter.
| Identifier | ExFiles\Box 135\3\ scan0144 | |
| Date | 21th May 1937 | |
| SECRET To H.{Arthur M. Hanbury - Head Complaints} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} c. to Da.{Bernard Day - Chassis Design} c. to By.{R.W. Bailey - Chief Engineer} 1139 Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}7/AP.21.5.37 WRAITH OIL FILTER. In view of the decision not to adopt the external oil pressure filter on Bentley and 25/30, it is assumed that its merit does not warrant the additional cost. On this basis therefore and with regard to the intended economy on Wraith, the designed pressure filter should be deleted. The position of the designed pressure filter has by necessity been housed on the opposite side of the engine to the oil pump, and consequently a cross passage has to be taken through the crankcase to the filter which makes its inclusion more expensive than the filter as rejected on Bentley. Following Rm.{William Robotham - Chief Engineer}'s return from America, his recommendations are that we use a bye-pass filter of which type we have received several from America, these being produced by the General Filters Inc., Detroit, Michigan, U.S.A. The advantages of this particular type of filter are as follows:- (a) Retains the oil in its original new condition and takes out the carbon content and other foreign matter. (b) Both light and cheap, is easily detachable and the filtering cartridge removed without even getting oil on ones hands. (c) Can be tapped and operated from low pressure oil 2 lbs/sq.in. such that when choked does not interfere with the main pressure, in any way. This type of filter does not of course cope for a new engine where particles of metal have to be dealt with and prevented from getting into the bearings. The idea, however, is that during the complete testing of the unit in the Works a temporary pressure filter be used to prevent all particles of metal etc. getting to the bearings. On the test run before delivery, the test tackle pressure filter is removed and the bye-pass filter connected up. In this way we know that all the injurious particles will have been removed and the only work the bye-pass filter has to do is to keep the oil in a clean condition. The filters we have received from America are available for your inspection with a view to incorporating this type on Wraith and future engines. In order to confirm the promising reports received, both the next Bentley and Phantom III. going out for 15,000 miles French test are to be equipped with these filters. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} | ||