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).
Test bench summary on the experimental overhead camshaft conversion for the 4¼-Litre Bentley, focusing on chain drive oscillation.
| Identifier | ExFiles\Box 113\5\ scan0182 | |
| Date | 28th January 1937 | |
| To E.{Mr Elliott - Chief Engineer} from Rm.{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation} c. to Sg.{Arthur F. Sidgreaves - MD} c. to Hs.{Lord Ernest Hives - Chair} c. to By.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} Rm{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation}11/R.28.1.37. 4¼-Litre Bentley - Experimental Development. Overhead Camshaft Conversion. We give herewith a summary of the test bench work carried out on the above conversion scheme in conjunction with the two previous reports:- Rm{William Robotham - Chief Engineer}/CTS{C. Trot Salt - Carburation}1/MJ.27.10.36. Rm{William Robotham - Chief Engineer}/CTS{C. Trot Salt - Carburation}4/R.5.12.36. The Chain Drive. As has already been seen from the previous reports issued, we have had considerable difficulty in getting all the oscillation out of the chain. In the last report we were left with a low speed rattle at 1000 R.P.M. so a cam balancer (as fitted to the standard 4¼-litre Bentley) was rigged up (externally) on the overhead camshaft. This was so arranged that the actual timing of the balancing cam, in relation to the camshaft itself, could be altered while the engine is running. The result of this experiment is as follows:- The rattle at 1000 R.P.M. is completely 'tuned out' when the max. lift of the balancing cams is equally spaced between inlet opening and exhaust closing. But only when run in conjunction with the two tensioners is this rattle completely cured. This means, therefore, that to damp out all the periods of oscillation in the speed range, we are having to use two tensioners, a cam balancer and a flywheel on the end of the camshaft. Having reached this stage, the following combinations were tried in an effort to reduce the damping medium on the chain, to the absolute minimum required. | ||