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).
Tests conducted on the Diamond Engine Mounting for a 25 HP car.
| Identifier | Morton\M13.2\ img052 | |
| Date | 11th May 1931 | |
| To R.{Sir Henry Royce} From Hm{Capt. W. Hallam - Head Repairs}/Rm.{William Robotham - Chief Engineer} c. to IG. Wor.{Arthur Wormald - General Works Manager} c. to I. Da.{Bernard Day - Chassis Design} c. to BY.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}5/KT.11.5.31 Y8005. DIAMOND ENGINE MOUNTING. 25 HP. We have conducted a test to see whether we can produce a car fitted with the Japan engine, which would be sufficiently smooth to go into production. On the whole the Japan units we have so far made have not been so smooth as our China units. The car we used for the test was 18.G.IV. which has a typical body for emphasising engine booms. We first of all fitted up the Japan engine with the standard mounting. The car boomed at 40 M.P.H. on the overrun, and had several minor engine periods. We then fitted the diamond engine mounting, inserting the rear engine foot rubbers so that they were under no appreciable compression. The result was encouraging, the booms being reduced, they were still sufficient to make the car unpleasant on the overrun even with the front torque reaction dampers set with 2 3/4 lbs. load, which is the minimum to eliminate "pick-up" vibrations. We therefore removed the rear engine foot rubbers entirely leaving only the steel plates attaching the engine foot to the frame. The result was then remarkably good, the car being entirely free from booms, and smoother than the standard production car over its whole range. The one objectionable feature was the movement of the brake lever when picking up, this was particularly violent at 8 M.P.H, while at 18 M.P.H. the gear lever knob rattled. The existing brake lever seems to be highly susceptible to any low frequency transverse vibration such as torque reaction, whilst the knobs on the brake levers are always prone to set up irritating noises. Apart from the visual and oral evidence of the side lever movement, no pick up vibration or boom was transmitted to the body which could be said to be completely free from torque reaction. REMARK. We removed the spring plates from the rear feet and thought that we could detect an improvement in smoothness, but only to a small extent. The test with the rear engine foot rubbers indicates how highly sensitive the diamond engine mounting is to the torque being taken through this point. SUMMARY. The conclusion we draw from these results is that we can get a better result from the Japan unit and the diamond engine mounting than we can from the China | ||