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).
Tests conducted to resolve piston knock issues using different oil pressure schemes.
| Identifier | ExFiles\Box 180\M2\M2.4\ img020 | |
| Date | 17th October 1919 | |
| To [Redacted] c. to Co. c. to [Redacted] c. to [Redacted] ORIGINAL. 17th.Oct. 1919. X.2448 X.3651. PISTON KNOCKS. We have carried out a number of tests with pistons fitted with plunger operated by oil pressure. So far we have made use of our temporary scheme but this we have fixed up in the same way as the scheme got out by Mr. Day. We found if we ran with pistons which had .001" more clearance than the standard, that the 1.00" ram operated by 15 lbs. oil pressure, was not sufficient to cure a bad knock, it would subdue a knock at very light throttle loads but the knock would be very distinct with picking up loads. We tried with a spring as well as the oil pressure; this improved it slightly. The best arrangement we have so far, however, is to make the relief valve in the oil pump choc-a-bloc and instead of having a valve, to drill a number of very small holes through the valve. With this, when the engine is cold and the knocks are bad, we get the maximum oil pressure - 70 to 80 lbs at 500 R.P.M. of the engine. This is quite effective in stopping the knock, as the engine warms up and the knocks become less, the oil pressure drops to nearly normal. We think this scheme promises to work very well. The fact of having the big oil pressure when the engine is cold is all gain, apart from making the plunger more effective, it would give us more oil at a time when the engine badly needs it. quite apart from piston knocks we had come to the Contd. | ||