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).
Letter to a supplier requesting scraper rings and discussing ongoing tests on other piston and ring designs for Bentley engines.
| Identifier | ExFiles\Box 87\2\ scan0178 | |
| Date | 28th April 1936 | |
| Exptl. Dept. 28th April, 1936. Hs{Lord Ernest Hives - Chair}/Wths.19/KW. The Light Production Co.Ltd., 60/66, Rochester Row, Westminster, LONDON, S.W.1. For the attention of Mr. C.H.Brooks. Dear Sirs, Will you please supply us as soon as possible with 36. Scraper Rings suitable for 3 1/4" bores having a unit pressure of 25 lbs/sq.in. and interchangeable with the standard ring as fitted to the 3 1/2 litre Bentley, that is, to our drawing EB.2378. With regard to the rings you have supplied for the 4 1/4 litre Bentley, we have not tested these yet but we are hoping to test the turned finish rings in the course of the next day or so. We shall then follow up with the rings having the ground surface and with varying unit pressures. This will take us some time to do but we shall let you know which ring we finally decide upon. With regard to the pistons having the heat break sawcut in the ring groove, as you know we have found them to be much better than the existing piston in their freedom from cracking but we have not yet decided whether the taper skirt is any better for power, and this we want to do at the earliest possible moment. We know that we could put the sawcut in the existing piston and retain the present clearances, but there is also another point and that is, what effect has the sawcut on the scraper ring. On the existing standard piston we can say that the scraper ring groove part of the crown and the scraper ring movement is controlled by the movement of the piston crown, but in the case of the piston having the sawcut in the ring groove, we can almost say that half the groove is controlled by the crown and half by the skirt. | ||