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).
Cases of piston rattles, tests conducted to resolve the issue, and subsequent recommendations.
| Identifier | ExFiles\Box 35\2\ scan 200 | |
| Date | 13th February 1920 | |
| R.R. 235A (100 T) (S.F. 846, 6-8-19) (?) 2460 X.2748 13 2 20 X.2748 FACTS WITH REFERENCE TO PISTON RATTLES X 1434. 1. The first case of piston rattles was on 7-CA Car, it was being used by Mr. Royce. The pistons Zephyr type fitted with 4 narrow rings low down pistons had a clearance of .020" on the top but was not until the car had run several thousand that the trouble became apparent. The car was run on Prices' oil. The top bands of the pistons embedded by carbon deposit proving that carbon from Prices oil will score the aluminium. 2. The next case of piston rattles was on the 100 hour bench test with the first split aluminium 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 oil. 3. The next case of piston rattles was on 2.EX 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 6000 miles. 4. A further case of piston rattles has been manifest on 49-GB Car. The pistons were standard as regards rings and clearances 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 1700 miles. The car was run on Castrol oil. TESTS TAKEN TO OVERCOME RATTLES. 1. 49-GB Car has run 2800 miles fitted with pistons with rings high. Examination after that run showed the rings and pistons to be in excellent condition. The previous pistons on 49-GB were some which developed rattles after 1700 miles - these were standard as regards number of springs and clearances. 2. Set of pistons run on bench test - 53 hours on test bench - examined after that run and found to be in excellent condition. RECOMMENDATIONS. Upon consideration of the above facts the Expl: Dept: recommend that the present pistons should have the extra rings fitted as soon as every possible. Our reasons for recommending this are as follows:- Contd. | ||