History and necessity of the camshaft balancer for the Wraith model, referencing issues with the 20/25 HP engine.
| Identifier | ExFiles\Box 7\8\ X 607 Camshaft-page22 | |
| Date | 27th April 1938 | |
| To (MR.) From MR. H.I.C. C. to Sg. {Arthur F. Sidgreaves - MD} Hs. {Lord Ernest Hives - Chair} By. {R.W. Bailey - Chief Engineer} C. to Da. {Bernard Day - Chassis Design} MX. {John H Maddocks - Chief Proving Officer} La. {L. A. Archer} 607 RHU.1/MJ.27.4.38. WRAITH CAMSHAFT BALANCER. With reference to Rm. {William Robotham - Chief Engineer} S/13.4.38 our impression is that the Camshaft Balancer was originally rendered necessary shortly after the introduction of the 20/25 HP. Chassis owing to the trouble we had with an engine gear rattle at idling speeds. The 20/25 HP. engine was formerly fitted with a spring drive the damper of which was separate from the crankshaft damper and with this type it was possible to adjust the spring drive damper to overcome the engine gear rattle on the pick up at speeds of approx. 1000 r.p.m. without affecting the crankshaft damper loading. After the introduction of the Low Inertia type of damper, engine gear rattle troubles in general were magnified and could not be dealt with as formerly by adjustment of the spring drive damping, and it thus became necessary to maintain a very high standard of gear manufacture, particularly with regard to backlash. These factors were somewhat eased by the introduction of the cam balancer, but this was not entirely effective in that it only improved the low speed rattle and had no effect on the pick up one. In consequence, whilst conditions on Wraith and 20/25 HP. are different because the former has three engine gears and the latter five, it can still be anticipated that rattles will occur and therefore it is suggested that the type of slipper drive prior to the low inertia type be introduced on Wraith so that adjustments could be made to the spring drive to suit the engine gear condition. Having in mind the influence of previously mentioned design differences between Wraith and 25/30 HP. it may be found that the adjustment possible with the separate spring drive and slipper type of crank shaft damper is such as to entirely eliminate the need for the camshaft balancer, whilst from a production point of view the fact that many existing P.III slipper drive parts could be utilized and made common on also the B.3 and Wraith would offer advantages both in manufacture and tooling. | ||
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).