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).
Oil consumption and cylinder wear with conclusions on piston rings, clearance, and oil viscosity.
| Identifier | ExFiles\Box 132\4\ scan0093 | |
| Date | 19th October 1937 | |
| Rm{William Robotham - Chief Engineer}/Mths.{Reg Matthews}8/KH.19.10.37. OIL CONSUMPTION & CYLINDER WEAR REPORT. This report covers the work done in attempting to improve oil consumption and in investigating the factors contributing to cylinder bore wear. The majority of the work carried out has been done on Bentley engines, since we have had so many reports of poor oil consumption and excessive bore wear on this chassis. All recommendations, however, are adaptable to 25/30 HP. or Wraith chassis. Conclusions. Oil Consumption. (1) Piston rings having a high cylinder wall pressure do not have a great effect on oil consumption under full throttle conditions. Under 'over run' conditions, however, they have a marked effect and show improved consumption. (2) Ring flutter appears to be the reason why occasional engines on 4 1/4 litre Bentley and 25/30 HP. chassis give poor oil consumption. 'Over run' conditions appear to have a disastrous effect on oil consumption with rings having a flutter speed in the region of 4000 r.p.m. (3) Piston clearance also has an effect on oil consumption, hence the need for true bores. (4) Compression rings are as much, if not more important than scraper rings in controlling oil consumption. (5) With rings thoroughly 'run-in' chamfering of the edges makes no difference to oil consumption. (6) Oil viscosity is not a reliable indication of the probable oil consumption. (7) The extra oil hole in connecting-rod can be retained with correctly designed rings. (8) 'L' section ring has proved to be good for controlling oil consumption on 25/30 HP. chassis, although its flutter speed is below 4000 r.p.m., the probable reason | ||