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).
Issues with gear changing and oil pressure in a scavenger pump system.
| Identifier | WestWitteringFiles\N\July1925-September1925\ Scan272 | |
| Date | 7th September 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT -3- Expl. No. REF:- /AR/LGT.7.9.25. prevent rubbing. The fact that the engine is 3 H.P. down in power at 1800 r.p.m; supports this theory. (3) GEAR CHANGING. Difficulty was experienced from the first in changing from one gear to the other, the change taking place very slowly, especially from low to high gear. This may have been due to :- (a) The scavenger pump circuit is inherently incapable of holding up sufficient pressure to throw the toggle over. Calculation showed that the maximum pressure required to move the toggle is about 46 lbs/sq.in. (see curve 1.) The scavenger pump itself is capable of putting up a pressure of 300 lbs/sq.in. before the drive fractures. (b) The normal scavenger pump delivery at 400 r.p.m. is 6 pts/min. With the valve set for a change from low to high gear the return oil should be cut off while the toggle is being thrown over. Actually, it continued to flow at the rate of 5.5 pts/min. indicating a substantial leak either by the piston or by the control valves. Removal of the cylinder covers showed that with the valve set for a change from high to low gear there was no leak by the piston till the latter stood over port 'B' (see Figs. 1 and 2) in which position oil was seen to be escaping beneath the piston. Measurement of the ports 'B' and 'C' showed that their max. width exceeded that of the piston, and oil was passing beneath the piston as shown in Fig. 11. That the piston did not cover the whole of the port at once was due to the crescent shape of the latter, this peculiar shape being brought about by the use of straight cores placed on the slant when casting. To remedy this trouble the cyl. was bored out and steel sleeve shrunk in, having ports 'B' and 'C' cut parallel and 3/8" wide. With this alteration, no further difficulty was experienced in gear changing. (4) OIL PRESSURE IN SCAVENGER PUMP SYSTEM. Owing to the bursting of the scavenger pump wall on 2X-Eagle XV. it was thought desirable to investigate the max. oil pressure that could occur in the scavenger pump system under any conceivable circumstances. A pressure gauge contd :- | ||