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).
Causes and potential solutions for engine gear rattles.
| Identifier | ExFiles\Box 136\1\ scan0037 | |
| Date | 30th May 1933 | |
| X-11 To WOR.{Arthur Wormald - General Works Manager} from E.{Mr Elliott - Chief Engineer} c. Hs.{Lord Ernest Hives - Chair} By.{R.W. Bailey - Chief Engineer} Sft.{Mr Swift} RHC.{R. H. Coverley - Production Engineer} re Engine Gear Rattles. We are going over this job generally from the design end, with a view to improving the situation as regards production of this section. There is no doubt that these rattles arise from the camshaft, and as maximum engine speeds have been pushed up more and more on our engines, this has necessitated the valve springs being made heavier and heavier, with the result that the anti-torque of the camshaft has become more pronounced until it reaches its present maximum on the 3½ litre Bentley. Since the camshaft is the offender, having the gears at the rear end of the engine is of no advantage in respect of these rattles over the gears at the front, and only makes it more important to obtain some improvement as the gears at the rear end are naturally more inaccessible. There are various measures which can be taken to deal with the difficulties, and these can be enumerated as follows: No.1. Fitting a 6 lobe balancing cam on camshaft, or alternatively 2/3 lobe cams with two tappets. We are trying out the balancing cam scheme at the moment on the drawing board. No.2. The use of Fabroil Gears. This material used for the camshaft wheel itself might substantially reduce the noise arising from the gearing, both in respect to (a) rattles due to slack (b) sing, due to close fitting gears. We think some experiments with Fabroil would be well worth while, particularly as this material is much favoured on certain American cars which run very quietly. No.3. Silent chain drive. We believe it is possible by using silent chains to fairly easily achieve a high standard of silence but not so high as a first class job with gears. The chain drive in itself appears | ||