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 findings on the 20 HP, G.1. type spring drive and its effect on engine harmonics.
| Identifier | ExFiles\Box 25\3\ Scan279 | |
| Date | 1st November 1927 | |
| Hs{Lord Ernest Hives - Chair}/RmL/LGL.11.27. 20 HP. SPRING DRIVE. The main points which stand out from our tests on the G.1. type spring drive are :- (1) The G.1. type of spring drive arranged as indicated in the blue print attached is capable of completely eliminating all harmonics beyond the 6th. if properly made. (2) Any slack in the splines of the damper plates is likely to make it quite ineffective in dealing with the harmonics of the crankshaft vibrations. Though therefore the splines on the latest damper for the 40/50 and 20 HP. are very much less likely to give trouble than those which we have been using, we should much prefer their total elimination as on the initial designs. (3) We still have to face the large range of engine roughness in the vicinity of the master period. With the 20 HP. engine fitted with a Stromberg and heavy valve springs it is quite easy to run into this master period on 3rd. speed. We believe that the stiffer crankshaft is most necessary. (4) <s>The master period with the new type spring slipper drive is still intolerable.</s> With larger flywheel and more damping we can reduce the risk of crankshaft failure, but the period of roughness on each side of the master period is slightly extended. (5) So far for proportions we have found the best compromise to be 1-C-1 flywheel and driving springs with 9 lbs.ft. damping. We are trying other combinations. (6) Actually 1-C-1 spring drive on G.11. has given us :- (a) A 200 r.p.m. speed range before hitting the master period. (b) A slightly less violent master period. (c) An elimination of harmonics below the 6th. -------------------- Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||