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).
Investigation into oil pump troubles and the solution of fitting a reservoir on the suction side to cure noise and inefficiency.
| Identifier | ExFiles\Box 149\2\ scan0035 | |
| Date | 14th January 1931 | |
| X3449 To Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer} & GWH.{George W. Hancock - Head Chateauroux} ) C. Wor{Arthur Wormald - General Works Manager} & Hy.{Tom Haldenby - Plant Engineer} ) from RHC.{R. H. Coverley - Production Engineer} C. AEM. ) RHC{R. H. Coverley - Production Engineer}2/BE14.1.31. RE: OIL PUMPS We have been investigating the cause of oil pump troubles, and after careful investigation and numerous tests, it has been definitely established that gears are not the sole cause of the trouble. At a pump speed of 425/450 r.p.m.(equal to an engine speed of 850/900 r.p.m) with oil temperature of 80°C. the pump strikes a period at which the velocity of oil on the suction side of pump drops and passes through in waves, consequently with oil supply being of an intermittent nature, gears commence to rattle. If this speed is maintained, the period is such that the pump becomes extremely noisy. When this condition arises, the efficiency of the pump is affected, as indicated by the drop in oil pressure on the gauge. After careful experiment, it was discovered that by the application of a reservoir having a capacity of one cubic inch(= 16.4 c.c's) on the suction side of pump, this condition can be overcome and a constant oil supply is maintained. The effect of the reservoir is that it eliminates the period referred to. Reservoir takes the place of the present suction pipe union connection, and is a proved solution for faulty pumps, as by it's adaptation to pumps in the Test Dept. which have been rejected, such pumps have proved to be perfectly satisfactory. This scheme was demonstrated to E.{Mr Elliott - Chief Engineer} and a very noisy pump was run, reservoir when fitted, immediately eliminated the trouble. He considered the correct explanation was, the reservoir increased the turbulence of the oil at the critical speed and damped out the period. It was considered that camshaft and other periods influenced pump troubles, but we have proved that the trouble applies to pump only, as the condition can be re-produced on test rig at the same r.p.m. and oil temperature and the reservoir under these conditions cures the trouble. The present gears have saw cuts at the bottom of the teeth, and casings have oil ducts. These were introduced some time ago, apparently with the view of overcoming pump troubles, and investigation proved them to be unnecessary. In addition, these features lower the efficiency of the pump. -continued- | ||