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).
Proposal to add a fifth ring to pistons on post-war cars to improve slow running and gas tightness.
| Identifier | ExFiles\Box 148\3\ scan0014 | |
| Date | 18th July 1921 | |
| R.R. 235a (10 T) (S.J 194.9.6-21). X2748 To R.R. from Hm.{Capt. W. Hallam - Head Repairs} " SH. " " Sor. " " Hs.{Lord Ernest Hives - Chair} " Hm{Capt. W. Hallam - Head Repairs}12/W18.7.21. [STAMP: RECEIVED] On post-war cars fitted with four ring pistons, we have difficulty in getting good slow running, especially after cleaning the carbon deposit away. We think the chief reason for this is the difficulty of getting the rings gas tight. Probably sufficient air is sucked into the cylinder on the suction stroke to upset the carburation. Hs.{Lord Ernest Hives - Chair} has suggested on this type of piston a fifth groove is turned, and an extra ring fitted. Would you please let us know if you agree to this? [Handwritten Initials: Wl] [Handwritten: Hm.{Capt. W. Hallam - Head Repairs} 6/212/35.30, 16, 32] | ||