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).
Tests and modifications to address engine and torque reaction vibrations, specifically 'booms'.
| Identifier | ExFiles\Box 137\4\ scan0200 | |
| Date | 9th February 1931 | |
| -2- Hs.{Lord Ernest Hives - Chair}S/141.9.2.31.Contd. the test with the Diabolo feet because on a previous test we thought we had gained a definite advantage. We have recently tried the effect of making the rear half of the flywheel and the pressure plate of the clutch in Aluminium. The result of this on the road was that there was no appreciable improvement. We have tried the effect of balance weights on and off and these give very little improvement for the fault which is being complained of. The alteration which gives us the greatest improvement is obtained by the 'Diamond' mounting. This proved successful on the 25 HP. car 18-G4, the last car which was run in France, and also 24-EX. We still, of course, want to try it out on other cars before we could be satisfied that it is going to give us consistent results. We have been astonished lately by some tests which show how slight changes in engine fixing can cause or prevent a car booming. On the 25 HP. which has torque reaction dampers at the front it has been demonstrated on a number of cars that with these dampers set at six pounds there is a very bad boom, reduce the load to three pounds and the boom disappears. Reduce it further, and torque reaction vibrations appear. On the 'Diamond' mounting, if we have the Diabolo rubbers which take the torque at all tight, the boom comes up immediately. In considering booms one cannot overlook the effect of bodies. Our troubles are enormously increased by having all kinds of bodies, which even if they look the same we have no means of knowing whether they are identical. Although I am all out for the 12 cylinder engine I do not believe this is going to be an immediate cure for all our troubles. I have not yet tried a 12 cylinder car which does not suffer from booms. Torque Reaction Vibrations. This has always been with us and is going to be very difficult to eliminate. The sample car 24-EX. which was submitted to Sales and which they were pleased with as regards improvements in torque reaction brought about by (1) tightened up rubbers between scuttle and dash (2) fitting torque reaction dampers at the front. Of these two adjustments the tightening of the dash to the scuttle is the most effective. Evidence goes to show however that if we have a | ||