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).
Test results and modifications for the engine, gearbox, and exhaust system.
| Identifier | ExFiles\Box 4\1\ 01-page184 | |
| Date | 12th December 1934 | |
| -2- (4) Engine Unit. We have now concluded our slow running tests which were made on the 20/25, and have come to the conclusion that the existing system is about the best we shall do for slow running with the present carburetter arrangement. Whether this will be good enough with the short duration camshaft remains to be seen. We shall hope to have the car on the road again in about a fortnight with the best that we at present know of in this respect. The top power of the engine is good, we have obtained 200 H.P. open exhaust. We are proceeding with work on pistons, we have not yet obtained anything which is free from knocks and gives good power. By increasing the clearance in the Cadillac type tappet plungers we have been able to run up to 2500 r.p.m. and the tappets are still silent at low speeds. The next trial will tell us whether the hydraulic tappets riding were the cause of the wear on the camshaft follower, or whether a design modification is required at this point. A crankshaft period has developed in the unit of the car. Presumably the damper load has fallen. (5) Gearbox. We have been running this on the Vulture. The second speed still works out and we understand that Hardy is making a design modification. We cannot pass an opinion on the silence of the box until we have ground gears. (6) Exhaust System. We have improved the silencing of the exhaust system but it still absorbs too much power. We are carrying out investigations to reduce power loss. Now that we have a silent exhaust system we note that the intake roar is open to criticism, we are therefore dealing with this. | ||