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 properties, manufacturing methods, and performance.
| Identifier | ExFiles\Box 144\3\ scan0061 | |
| Date | 23th June 1936 guessed | |
| -4- rings vary as much as 15% but even allowing for the fact that we may have a set of the strong rings and assuming their variation to be similar to our own they would still have a considerably higher pressure than we are using. We have calculated the En value of the Plain Compression ring as used on Chevrolet and this was found to be 18,350,000 lbs/sq.in. whereas the ring we use which is produced by hammering has an En value of 15,000,000 lbs/sq.in. as calculated from the load required to close the gap, the effect of hammering is to reduce the En value by about 1,500,000 lbs/sq.in. so that the true value for the iron used is approximately 16,500,000 lbs/sq.in. The Rockwell Hardness number for the Chevrolet rings is 98 - 106 (B scale), the rings we use have hardness number of 98 (B scale). All the Chevrolet rings have a turned finish on the periphery, the feed used being .0065 per turn, the rings are individually cast whereas our rings are centrifugally cast. We are having made two sets of rings to similar proportions to the Chevrolet rings all rings having a cylinder dia./radial thickness ratio of 23.3 : 1 one set produced by centrifugally casting and one set individually cast by Messrs. Hepworth & Grandage, and all rings having a turned finish for rapid bedding. The rings are to be used with low viscosity oils and a main oil pressure of about 40 lbs/sq.in. We have, since starting the investigation into high oil consumption, obtained some figures with oils of various viscosity and these are given below in Pints/hr. the readings being taken at 4000 r.p.m. with an oil inlet temperature of 90°C. and outlet of 115°C - 120°C. and pressure of 25 lbs/sq.in. | ||