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).
Two approaches to solving high oil consumption on the 25/30 model.
| Identifier | ExFiles\Box 144\3\ scan0098 | |
| Date | 8th August 1935 | |
| X1220 To Sg.{Arthur F. Sidgreaves - MD} & Mor. From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to C. c. to R.{Sir Henry Royce} c. to Hy.{Tom Haldenby - Plant Engineer} c. to Mx.{John H Maddocks - Chief Proving Officer} d.{John DeLooze - Company Secretary} to Da.{Bernard Day - Chassis Design} c. to He. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}1/MJ.8.8.35. HIGH OIL CONSUMPTION ON THE 25/30. This problem has been attacked in two ways - (1) A four ring stop piston has been designed which, with the exception of the increased diameter, resembles as nearly as possible the 20/25 which has proved satisfactory. (2) In view of the fact that 200 cars have been delivered with the present piston rings and that inevitably some delay must occur in bringing in the four ring stop piston even if this was satisfactory on test, experiments were undertaken to determine the minimum modification required to the parts at present in production to overcome the existing complaints. -------------------------------- (1) The position of (1) is self explanatory. We consider however that this piston will require quite a lot of testing before we can go into production with it. The fact that it is a scaled up edition of something which has given satisfaction in the past does not mean that it is going to be free from trouble when used with the new cylinder head, bearings, carburetter, and induction pipe arrangement. In particular, in view of the increased blow-by which we have observed takes place with stopped rings, we may find that the crankcase breathing arrangement has to be modified otherwise oil will be consumed through the carburetter. (2) Our objective in this case was to discover a modification which - (a) Had previously been used on R.R. cars and given satisfaction. (b) Involve the minimum amount of scrap and dislocation of production. (c) Would improve the oil consumption to a reasonable degree without making it so good that there will be danger of piston seizure. In 1929 we had severe trouble with overoiling on the Phantom 1. we found that we could get over the trouble by fitting 'L' | ||