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).
Engine knocking issues with aluminium pistons on standard cars.
| Identifier | ExFiles\Box 180\M3\M3.7\ img015 | |
| Date | 18th August 1919 | |
| To R.{Sir Henry Royce} from EH. c. to CJ. c. to BN.{W.O. Bentley / Mr Barrington} c. to E.{Mr Elliott - Chief Engineer} c. to D.{John DeLooze - Company Secretary} c. to EF. ORIGINAL ALUMINIUM PISTONS ON STANDARD CARS. X.2748 We find from the average of a number of Production Chassis that the tendency for knocks when the engine is cold is more than we had expected from results on running similar pistons on experimental cars. Individual cars vary of course, considerably. It is possible to have one car which the pistons have more clearance than another car yet the one with tighter clearances is the worst for knocks. Mr. Northey was up at the Works last week and we took the opportunity of taking him out on several production chassis' to demonstrate the extent of these piston knocks. The conclusions Mr. Northey came to were, that he thought we could ignore all piston knocks which were not manifest when the temperature of the water at the top of the radiator was 50°C. Any knocks which were apparent when the water had reached that temperature should be cured. With this concession we think that the majority of cars will go through without piston trouble but we shall get a percentage of pistons which will knock at 50°C. These we have agreed to change. We are in the meantime carrying out experiments to try and find out the reason why some pistons knock and yet others, with identically the same clearance and as far as we can see the same amount of lubrication, do not. EH. | ||