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).
Comparison of piston ring details and oil consumption between Chevrolet and Bentley engines.
| Identifier | ExFiles\Box 144\3\ scan0058 | |
| Date | 23th June 1936 | |
| 4220 FILES. 23rd June, 1936. Comparison of Piston Ring Details and Oil Consumption. The rings compared in this report are those used on the Chevrolet and Bentley engines and although there is a wide difference in practically every detail it should be realised that conditions in the engines also vary considerably. The Chevrolet for instance has dip feed to the connecting rod bearings and consequently far more oil may be thrown into the cylinders; in fact Chevrolet's make a point of throwing plenty of oil into the bores, they also use a cast iron piston which of course has a close clearance all round, whereas with our aluminium piston we have a very large clearance on the relieved portions of the skirt. Chevrolet piston and rings have also to deal with low viscosity oils such as mobiloil "Artic". From the detailed comparison below it will be noticed that the present standard rings have a much lower cylinder wall pressure than the rings used by Chevrolet. Bentley Rings. Scraper Ring (E.60821). Tangential load = 3.219 lbs. dia. of ring. = 3.500 Width (total) = .177 Radial thickness = .130 Width of lands = .0885 Width of slots. = .0625 Cylinder wall pressure = 20.8 lbs/sq.in. Ratio Cylinder dia./Radial thickness = 26.9 : 1 | ||