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).
Cause of knocks in lower gears and potential solutions involving couplings, propeller shafts, and torque tubes.
| Identifier | ExFiles\Box 183\M22\ img190 | |
| Date | 30th August 1920 | |
| To HS.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} -3- H1/030/8/20 Contd. they have been for many years. It will, however, be slightly worse in these lower geared cars because the change of speed in the transmission shaft is proportionate to the gear ratio. In this case the lower gear will give about 10% more angular variation but I think the chief change is more likely to be due to the change in the tyres and road conditions. You will remember that this fault shews itself more manifest, as suggested by OY. when the car is fitted with cord tyres, so that in 6 EX. we have all the conditions favourable to obtaining a knock, and we regret that a new car should have sufficient torsional slack to enable the knocks to be so manifest.* *X1228 The phenomena, as you know, is absent with the parallel control, and will, we hope, be less apparent with the long propeller shaft, and the gear box on the propeller shaft, as in our new models. In the meantime, it only seems possible to fit up the couplings with a minimum slack. We do not think for a minute it is possible to fit fabric discs, although we might try a set of Fellows cut serrated couplings, which would naturally have less backlash. We hope, however, for road improvements, in which this shortcoming of practically all makes of cars will be less manifest. You will remember that I have always favoured the longest practical torque tubes, whereas many of our competitors are using torque tubes much shorter than they need, even in their new post-War chassis. See other memos about this X1228 R.{Sir Henry Royce} last mentioned phenomena | ||