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).
Specifications for a set of test pistons for Phantom and Bentley engines to investigate mechanical efficiency at high speed.
| Identifier | ExFiles\Box 148\3\ scan0078 | |
| Date | 17th June 1933 | |
| X2748 To RHC.{R. H. Coverley - Production Engineer} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}1/KT.17.6.33. the effect of. Higher speeds at present being utilised on the Phantom and Bentley engines has brought up the question of mechanical efficiency. There is no doubt that engines become tight when they have had a burst of speed at full power. To satisfy ourselves once and for all what is the maximum advantage we are likely to get by fitting slack pistons we want to make up a set for the Phantom and the Bentley as follows. (1) Pistons to be made from castings normally used for pistons for these engines. (2) Pistons to have no sawcut in skirt. (3) Pistons to be ground concentrically to diameters shown on attached sketch. (4) Dimensions not shown on sketch to be as shown on (a) Phantom. - Drgs. E.83783. E.83790. (b) Bensport. Drgs. E.57122. E.55350. (5) Sides of pistons to be relieved as shown on sketch - max. depth of relief not to exceed .025". (6) Phantom pistons to be fitted with two top rings and scraper rings. With regard to the relief, we leave this to you so that you can utilise the simplest machining operation. We appreciate that these pistons will probably slap, this is immaterial for test purposes. We should be glad if you would let us have the pistons as soon as possible. Hs.{Lord Ernest Hives - Chair}1044. attached Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer} | ||