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).
Facts and tests related to piston rattles in various car models.
| Identifier | ExFiles\Box 171\3\ img036 | |
| Date | 13th February 1920 | |
| FACTS WITH REFERENCE TO PISTON RATTLES. 1. The first case of piston rattles was on 7CA. Car when it was first being used by Mr. Royce. The pistons were the Zephyr type fitted with four narrow rings low down. The pistons had a clearance of .020" on the top band. It was not until the car had run several thousand miles that the trouble became apparent. The car was running on Price's oil. The top band of the pistons were deeply embedded by carbon deposit, proving that carbon formed by Price's oil will score the aluminium. The next case of piston rattles was on the 100 hour bench test with the first split,pistons. On there we had two cases of piston seizure and signs of others commencing to seize, caused undoubtedly by the carbon binding on the piston. The engine was run on Castrol. The next case of piston rattles was on 2EX. Car when run in France. These pistons have the extra clearance on the top band, and were the same as regards clearance as the present standard pistons we are now fitting to the cars. The car was run on Castrol Oil. The rattles started after 6,000 miles. A further case of piston rattles has been manifest on 49GB. Car. The pistons were standard as regards rings and clearance on the top band and had the extra clearance on the top band, but the skirt of the piston was fitted with the spring loaded plunger. The rattles on there became apparent after the car had only run 1,700 miles The car was run on Castrol oil. TESTS TAKEN TO OVERCOME RATTLES. 49GB. Car has run 2,800 miles fitted with pistons with rings high. Examination after that run showed the rings and pistons to be in excellent condition. The previous pistons run on 49GB. were some which developed rattles after 1,700 miles - these were standard as regards number of rings and clearances. Set of pistons run on bench test - 53 hours on bench test - examined after that run and found to be in excellent condition. (Contd). | ||