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).
Two-cycle engines and methods for improving Merlin valve springs, including shot-blasting and a new clamping design.
| Identifier | ExFiles\Box 158\3\ scan0024 | |
| Date | 26th November 1939 guessed | |
| To Rm.{William Robotham - Chief Engineer} - 3 - Other developments are G.M's two cycle passenger car engines. This is logical because it allows the engine to be tucked away in inaccessible places and reduces volume and weight of power plant for a given output. Therefore is a logical development for cars and trucks. Balancing troubles on two cycle engines become unimportant as the science of engine-mounting on rubber becomes understood. Since B.M.E.P.'s are high it is true that four cylinders will do the work of eight. I should guess that the war will develop two cycle aircraft engines, and peace will see two cycle vehicle engines as a natural result. Another note on coil springs and torsion rods. I think you could greatly improve the life of Merlin valve springs by learning the use of a wheelabrator for shot-blasting them. It has been general experience that really reliable valve springs cannot be made except with shot-blasting. What is needed is some methodical fatigue torsion testing on straight lengths of wire with a means for automatically adjusting the fixed end to compensate for permanent set. Such tests would aim to settle once and for all the questions - (a) Best method of shot blasting. (b) Best method of presettling. (c) Material and heat treat. Once this was done good valve springs would be cheap and easy. Instead of machining the ends of the wire I would form them into semi-circular loops and clamp them thus:- [DIAGRAM OF A SEMI-CIRCULAR LOOP CLAMP] In response to a note from Pearson to Lessells about valve spring material, Lessells and I are shortly going to spend some time with Zimmerle of Barnes, Gibson, Raymond on the subject of material and manufacturing practice. | ||