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 report detailing investigations into engine vibration, chain oscillation, and the effects of tensioners, camshafts, and flywheels.
| Identifier | ExFiles\Box 113\5\ scan0212 | |
| Date | 13th February 1939 guessed | |
| -4- (1) The removal of the fabroil block and chain tensioner made the amplitude of vibration so great that the engine could not be run over 2000 RPM for fear of breaking the chain. (2) Replacing the tensioner only and locking the spring drive, increased all the vibrations to the extent of overcoming the tensioner. They could however, be faded out by increasing the tensioner load from 10lbs to 35 lbs. (3) A flywheel fitted to the end of the cam-shaft made practically no difference if the spring drive was working, but some 50% reduction in amplitude was effected, if the drive was bolted up solid. 35lb tensioner load was still required to fade out all the vibrations. (4) Cutting out one of the inlet-valves effected a reduction in amplitude of some 50% and a further very slight improvement could be made by removing the inner spring on the remaining inlet valve. Fitting the flywheel however, made no difference, nor did returning the spring drive to normal operation. (5) The engine was now returned to standard, and a second tensioner fitted on the drive side, both having a 10lb load. Very slight shake could be observed at the peak speeds, but the only noisy period was 1000 RPM. It was found essential to use the cam-shaft flywheel for the above tests, as without this the 2000 RPM period did not appear to be improved. (6) The rattle at 1000 RPM was completely tuned out by fitting a standard 4¼ litre cam balancer, phased so that the maximum lift of the balancing cams came equally between the inlet opening and exhaust closing positions. It was found essential however, to have both tensioners and the flywheel as well as the cam balancers. General Conclusions. - These results show that with the existing camshaft, it is necessary to use both tensioners, with a cam-shaft flywheel and a cam-shaft balancer. We would undoubtedly get some help in the question of chain oscillation from lighter reciprocating loads, as affected by the valve spring load. As will be seen from the table above, lifts and seat loads are considerably in excess of standard, and a modified camshaft has been designed, but not tested, with the object of reducing these items. Exhaust Valve Expansions. The method adopted for measuring this item is as follows:- A micrometer is arranged to make an electrical contact with the top valve spring washer. The mike being clamped to the camshaft housing, the engine is then run at 4000 RPM full throttle with the mic- | ||