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 of aluminium pistons for the 40/50 Chassis X.3400 regarding engine knock issues.
| Identifier | ExFiles\Box 35\2\ scan 059 | |
| Date | 25th March 1919 | |
| To R.{Sir Henry Royce} from EH. c. to CJ. c. to E.{Mr Elliott - Chief Engineer} c. to BY.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} EHL/LG25.3.19. X 3429 ALUMINIUM PISTONS FOR 40/50 CHASSIS X.3400. We have carried out a number of tests with the aluminium pistons (the latest type) made for use with the standard length connecting rod. We have tried them with various clearances and find that with the minimum clearance, which will not seize, there are distinct knocks when the engine is cool. This is when we are using the maximum quantity of oil without causing over-oiling trouble. We get distinct piston knocks with these pistons even when we have a band on the skirt of the piston which has only .03" clearance. The engine we are running with the short connecting rods has so far shewn no signs of piston knocks. This is running with pistons which are slacker than the pistons which are knocking with the standard length of rod, the minimum clearance being .006". We are not in a position at present to recommend the short rods because we do not know how they will behave in other respects also we wish to confirm our tests on another engine before we can be definite as regards the improvement in piston knocks. EH. | ||