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).
Initial test results and issues with the Wraith oil relief valve and filter system.
| Identifier | ExFiles\Box 10\3\ 03-page003 | |
| Date | 28th January 1937 | |
| SECRET LOG 654 To E.{Mr Elliott - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}10/AP.28.1.37. WRAITH OIL RELIEF VALVE AND FILTER. Our initial tests on the Wraith oil relief valve layout LeC.5179, shows that there is appreciable restriction in the valve box and as a new layout this is an undesirable feature. The following are a few results obtained on the unit during the short time we were able to retain it on the bed, before it had to be released for the chassis With relief valve and springs as designed for a main pressure of 30 lbs/sq.in., and a rocker feed pressure of 4 lbs/sq.in., the actual pressures obtained when running at 3750 R.P.M. to 4000 R.P.M. with an inlet oil temperature of 90°C. were 65 lbs/sq.in. main and 20 lbs/sq.in. rocker. By substituting the main pressure spring of 19 SWG. (.040") by a similar spring, but in 23 SWG. (.024"), then under the aforementioned conditions a pressure of 30 lbs/sq.in. was obtained. In conjunction with this spring a 26.SWG. spring was fitted in the rocker pressure valve, this bringing the pressure down to 8 lbs/sq.in. If there were no restrictions in the layout then from the rating of these special springs the valve opening pressures should come out at 4 lbs/sq.in. for the main and approximately 1 lb/sq.in. for the rocker pressure. If the rocker pressure ball valve be completely removed and the pipe which feeds the gears dis-connected at the relief valve box end, then the rocker pressure is still 6 lbs/sq.in. It will be seen from the above figures that the relief valve passages are much too restricted to be satisfactory, and that a big increase in their dimensions would be necessary, in order to control the pressures by the valve springs and not by the restrictions as at present. This fault appears to be a common one throughout the range of our chassis units, unless the precaution of providing a suction restriction is made. Considering the layout LeC.5179 and the external filter LeC.4692 combined with the rocker relief valve as housed on the wheelcase LeC.4412, the latter appears to possess points which are worth considering before re-designing LeC.5179, to cut out the restrictions, these being as follows:- continued | ||