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).
Report comparing the oil consumption, power output, and weight of various piston designs.
| Identifier | ExFiles\Box 94\5\ scan0102 | |
| Date | 21th October 1935 | |
| -2- Hs{Lord Ernest Hives - Chair}/Mths.{Reg Matthews}S/KW.21.10.35. The oil consumption over the run was 1.14 pints/hr. which compares fairly well with Bentley using Aerolite pistons, but is better than Bentley when using EB.1299 pistons. This is no doubt due to the better ring arrangement which follows the Aerolite arrangement very closely except that the scraper ring instead of being slotted as in Aerolite design is drilled with series of holes. The rings of course are approximately the same width as the Aerolite rings and have approximately the same radial pressure. The power output with the test bed exhaust system was rather higher than the Bentley unit using EB.1299 pistons and this we have still to investigate, as there were several departures from standard on the unit used for the test. For instance, apart from the pistons there were (1) Longer connecting rods. (2) Hall's metal bearings. (3) Larger balance weights than standard. The weight of the pistons we had for test, Ex.19713, was 17¾ ozs., whereas the Bentley EB.1299 piston is only 16½ ozs., so that the weight could be reduced somewhat as we have proved that EB.1299, the standard Bentley pistons, are quite satisfactory in service. The weight of the full split piston to E.87347 is much too high, being 19 to 19¼ ozs., this may be due to the fact that they have been produced from sand castings in which case we may expect the weight to be a little lower when die-cast. In any case it would appear that a weight of 16½ ozs. should be aimed at as anything above this weight is unnecessary. Hs{Lord Ernest Hives - Chair}/R.Matthews. | ||