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).
Experiments to reduce engine over-oiling, focusing on piston types and oil flow through bearings.
| Identifier | ExFiles\Box 178\1\ img144 | |
| Date | 19th May 1926 | |
| - 11 - Hs{Lord Ernest Hives - Chair}/ACL/T19.5.26. some of our experiments have shewn, but with any of the types tested we have been unable to effect a cure on a badly overoiling engine. Probably the most effective type tested was of the std. pattern but ground in such a way that the bottom of the skirt just fitted the cylinder bore when cold and relied upon the flexibility of the split skirt to absorb expansion when hot. The principle upon which it operated was similar to the "L" section ring and although a slight reduction in consumption resulted from these particular pistons it was found to be at the expense of mechanical efficiency - the engine becoming tight when hot. Various other types have been tested in which the pistons were either liberally drilled, grooved or rifled in an attempt to reduce the hydraulic pressure, or the "rolling up" of oil against the rings, but in no case, even where there happened to be a reduction of consumption, has it been of a sufficient degree to warrant the employment of such a type. The above cited experiments are only a few of the more prominent ones we have carried out in this direction. OIL FLOW THROUGH BEARINGS AND CONSUMPTION. Variation of the aggregate rate of oil flow through the bearings produces a definite variation of the oil consumption as the appended curve shews, and which curve is an average for several cars fitted with plain concentric piston rings. contd. | ||