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).
Resolving piston rattles by adjusting piston ring position, referencing pre-war designs and lubrication.
| Identifier | ExFiles\Box 35\2\ scan 201 | |
| Date | 1st June 1919 | |
| Contd. -2- 1. In placing a ring high up on the piston we are only reverting to a practice which was used successfully on all our pre-war cast iron pistons. All R-R Cars on the road (previous to the war) had rings high up. 2. On the present production cars which are being run on Prices oil, although there are no cases of piston rattles, there are distinct signs of carbon marking the top band of the piston. 3. The cause of the piston rattles is quite clear. There is only one possible means of preventing the cause of it i.e., to fit a ring to the top band of the piston. We think it will be disastrous to R-R if, when we have seen a fault on a car, can see a clear cause for the fault and have a straight forward means of overcoming that fault, we do not take immediate steps to overcome it. 4. The only excuse we have for saying that the present cars will not have piston rattles the same as 2.EX Car is the fact that 2.EX Car was run on Castrol oil, yet, at the same time we have got to admit that Castrol oil is the best lubricant we know of and if one of our cars was going to take part in an arduous endurance test there is not much doubt that Castrol oil would be used. We believe a part of the niceness of 2.EX Car after running 10,000 miles is due to the fact that it has been lubricated with castrol oil throughout. 5. Apart from overcoming piston rattles we need the extra rings to improve gas tightness of the pistons. Ha. (Text at the bottom of the page, upside down) R.R. 233 A.{Mr Adams} (100) Y. 252 (S) (P. 246. 6-S-19) (L) 2160 | ||