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).
Experiments to reduce engine vibration and booms by removing or lightening the flywheel.
| Identifier | ExFiles\Box 182\M19\ img023 | |
| Date | 17th February 1931 | |
| ORIGINAL To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} c. to By.{R.W. Bailey - Chief Engineer} FLYWHEELS. Our experiments to reduce engine vibration and booms caused by the flywheel have consisted of three main types - (1) Removal of the flywheel. (2) Use of lighter flywheels. (3) Use of extra flywheel bearings. The tests we have carried out have been on the road with the engine under its own power and also with the car being towed; and on the test bed using optical means for magnification of vibrations. This latter has the disadvantage in the 25 HP. in that the constraining influence of the gearbox is absent and speeds of vibration on the test bed are lower than those obtained on the road. On Phantom 11 this is not the case and we get good agreement between road and test bed experiments. (1) No Flywheel. We first tried this on the 25 HP. the car being towed with only a bare crankshaft present. Vibrations were greatly reduced in amplitude but did still exist at the main speed of 3100 r.p.m. On the test bed we got a small disturbance at 1900 r.p.m. and then a smooth engine up to 3850 r.p.m. the engine in this case being under its own power. On 25-EX. (Phantom 11) we have tried removing all the flywheel overhang retaining only the plate fixed to the crankshaft and utilising a solid drive to the Hardy joint in front of the gearbox. This very greatly reduced the booms but made the engine rougher. It does seem that the flywheel is responsible for roughness in the 25 HP. and booms in Phantom 11. (2) Light Flywheels. We have tried two of these on the 25 HP. one consisted of a standard flywheel machined where possible to reduce the inertia by 33%. This also reduced the stiffness of the flywheel and centre of gravity moved further from the engine. The effect of this flywheel was to make no difference to the amplitude or speed of the 3100 r.p.m. period, except slightly to broaden the range of roughness on either side of it. | ||