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).
Series of tests to diagnose engine and chassis vibrations by systematically removing or modifying components.
| Identifier | ExFiles\Box 137\4\ scan0025 | |
| Date | 22th July 1929 | |
| (2) (3) Contd. vibrations was really bad and shook the car. We verified by tests in bottom gear and in neutral that these periods came from the engine and not from the transmission. (4) Cylinder blocks & head removed. From inside the car, the 38 m.p.h. period appeared to vanish, but the 28 m.p.h. & 22 m.p.h. periods appeared rather worse. Vibration was worse above 40 m.p.h. (in 2nd. gear) (5) Slipper wheels removed. No Notable difference. (6) 4 Intermediate Bearings removed. Bearings left in were 1, 4, & 7. Booming periods appeared to have dropped to 29-31, 25, & 21 m.p.h. all fairly sharp with the 21 m.p.h. the clearest of the three. From 35 m.p.h. onwards the vibration was bad, getting steadily worse up to 50 m.p.h.(3800 r.p.m. approx) when it appeared almost as bad as a master period. Crankcase vibration was much worse with only 3 bearings. Very rapid lateral vibrations could be felt at the centre of the two side panels of the crankcase, in line with the centre bearing. There was no vibration of the rear feet, and very little at the front feet or on top of the crankcase. (7) Big ends(sawn off) clamped on pins 1 & 7. We thought that if the vibrations hitherto discovered were due to out-of-balance in the shaft, we would make them worse by increasing the out-of-balance. The two big ends weighed 2 lbs.2 ozs each. and were really too heavy. Vibration throughout the car was excessive and the whole car shook. Periods appeared at almost every point in the speed range: the front underguards vibrated at 4 critical speeds; the running boards at 3 or 4; the steering column brake lever & gear lever all had periods, and so on. We eliminated a whole lot of these by removing the offending items. However, by feeling the crankcase, and keeping ones eyes shut, it was difficult to pick out any engine period at all, as the vibration here ( of the whole case) appeared continuous and uniform, with possible peaks at 2100 R.P.M. and 1760 R.P.M. barely detectable as periods. We considered this an unfair test, and reduced the amount of out-of-balance to 1 lb. on the no.1. pin only. Contd. | ||