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).
Car vibration testing results and possible explanations related to the engine and chassis.
| Identifier | ExFiles\Box 137\4\ scan0026 | |
| Date | 1st July 1929 | |
| (3) Hs{Lord Ernest Hives - Chair}/TSN1/MS22.7.29 (7) Contd. The car still has a lot of distinct periods which we could separate as follows (in 2nd.gear) 21 m.p.h., 28 m.p.h., 36 m.p.h., 41 m.p.h., 45 & 48 m.p.h. (R.P.M.'s were : 1600, 2100, 2600, 3100, 3400, 3600). We still noticed that the chassis & body vibration appeared out of all proportion to or connection with the engine vibration, which again appeared very nearly uniform, with a slight peak at 2100 R.P.M. (8) Road Test. We discovered that the lower two of the three periods mentioned in test 3, can be picked out on the road. In 2nd. gear engine vibration is first distinguishable as a dull rumbling at about 22 m.p.h. followed by a smooth patch, and then the 28 m.p.h. period. Above 35 m.p.h. there was enough vibration to drown the 38 m.p.h. period. The 22 m.p.h. period in second was distinguishable at approx. 40 m.p.h. in top gear. Possible explanations. We are starting from the premise that it should certainly be possible to rotate a bare "SS{S. Smith}" crankshaft smoothly up to 4000 r.p.m. in its case, and until we can do this we cannot hope to cure engine roughness completely with rubber mountings. We think that most "engine periods" detectable are vibrations of parts of the chassis & body, but we believe in tackling the engine as the original source which feeds these vibrations. Our tests so far have shewn up the probability of vibration inside the crankcase, even with a bare shaft, and we think this probable explanation a serious one because with pistons and rods fitted, this type of vibration would be rendered very much worse and more apparent. Possible explanations to us are as follows. Broadly, perceptible vibration may either be: (a) In the engine, & transmitted through to the passengers, or more likely ( considering the rubber engine mounting) (b) In the chassis & body & induced by vibration in the engine. Engine vibrations that could exist are: (1) Shaft out of balance. Contd. | ||