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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).
Analysis of engine vibration issues with proposed modifications to the crankshaft, flywheel, and bearings.

Identifier  ExFiles\Box 137\4\  scan0314
Date  12th April 1931 guessed
  
(2)

ment or the damper cannot damp but it is possible that the movement is excessive - i.e. it is letting the shaft vibrate torsionally over a great range. One would not expect much benefit from balance weights; they might make matters worse - i.e. like a weaker shaft. On the test plate the angle of oscillation should be watched and measured, and I think it will be found to agree with one of the troublesome speeds.

If not, then it must be the flywheel. Mr. Ricardo says that with several engines this has been a very persistent fault over a great range of speeds, and very difficult to alter. Apparently he introduced the double bearing after trying all other methods of supporting.

This brings us to altering our P. 2. pattern of crankchamber at once even if we have to bolt an extension on existing crankshafts. In the meantime we must do something to existing chassis, and after testing the lightest flywheel we can use without other troubles and the stiffest back plate and flange, we can test the value of the larger crankpins, and of balance weights to my 8 weight scheme (which is the lightest, most practical, and most efficient, especially for this particular trouble) and if we cannot move it out of range we must go to the gearbox for help, at least in the original way that was found to have helped the 20 HP. unintentionally. This would need cancelling the universal in the clutch and the fabric one could be fitted with steel discs that would permit a slight want in the alignment of the 3 bearings but we must not theorise, but try if any harm comes from the usual imperfections. This is rather a different way than has been tried; it may have some slight damping.

If we still cannot keep the wheel steady some design of second bearing should be schemed even if it means some modification to other parts.

These conclusions are arrived at by running up our engine on 18-EX. with the car standing, when definite periods can be picked out. The moderate speed one may be torsional, and the high speed one, which, even with no rear feet shivers one's spine when sitting in the driver's seat, is I think lateral.

I very much regret to hear that nothing was done for Mr. Iden whose car may have had a bad or difficult body, but evidently was unpassable as a complete car.
  
  


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