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 the cause of Bentley oil pump rattle and the results of three corrective tests.
| Identifier | ExFiles\Box 149\2\ scan0158 | |
| Date | 8th June 1937 | |
| 1265 Rm.{William Robotham - Chief Engineer} from Rm{William Robotham - Chief Engineer}/WB.{Mr Brazier/Mr Bell} 8.6.37. BENTLEY OIL PUMP. We have been investigating the cause of the rattle from the oil pump when the engine is revved starting from cold. It is only audible for a few minutes while the pressure is high and before the oil becomes sufficiently fluid. We formed the theory that the high pressure obtained with the cold oil and an insufficient feed on the suction side was responsible for a reaction being set up on the idler gear causing it to rattle. Working on the above we carried out the following tests:- (1) A .125" dia. hole drilled from the auxiliary feed back to the suction side of the gears with a non-return valve in the pipe to engine gears. This was successful in curing the rattle, but reduced the pressure to engine gears when the oil was hot. (2) A .750 feed pipe taken direct from a can of oil. This test was a cure, but the needle of the 80 lbs oil gauge was hard on the stop from cold. (3) A return feed from the main pressure line to suction side controlled by a ball valve set at, approx. 45 lbs square inch. This was successful, and from figures obtained there was no loss of pressure over the standard pump. The car is now running fitted as No.3. Rm{William Robotham - Chief Engineer}/W. Brazier. | ||