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).
Engine smoothness and the effects of various balance weight schemes on the flywheel and crankshaft.
| Identifier | ExFiles\Box 14\2\ Scan118 | |
| Date | 8th May 1931 | |
| X7010 Hs.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} c. Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. Rg.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} R5/M8.5.31. ENGINE SMOOTHNESS X.634 X.5010 X.7010. It is understood that you are satisfied with the smoothness of our engine without in any reducing the possibilities of torsional periods at the harmonics. It will be understood that whatever we did with the single bearing between the crankcase and the flywheel we could not permanently hold the flywheel steady, but I have pointed out for many months that the balance weights should reduce the disturbing tendency. We do not look upon the flywheel vibration as an ordinary whirl, but a periodic vibration set up by the reciprocating piston. If the balance weights did reduce the forces on this No.7 bearing then it would keep the flywheel steadier. The system of balance weights I suggested, known as the 8 weight scheme is the best for this purpose, because the balance weight on the 12th web is exactly opposite the big end and piston forces. We hope it will be heavy enough to balance the crank and big end and therefore only leave the piston and little end in the vertical plane. We quite disagree with the idea that the flexibility of the rear bearing can permanently help the smoothness of the engine. If the housing was stiffer as is natural in the cast iron crankcase chamber it might do some good for a short time until the bearings are bell-mouthed, which has been detected on many engines, including aero. We shall be intensely interested to learn the effect of the balance weights in the "R" engine, which is such a splendid test. We must not expect too much however as they are only a moderate percentage of the total centrifugal forces. We believe that Tsn. is helping to direct the experiments with the car engine balance weights and we must look to him as a specialist in this line, and perhaps Gry.{Shadwell Grylls} will be able to tell us whether the flywheel is steadier with the system of balance weights suggested. The 4 balance weight scheme which you have fitted to 27-EX does not have the same pacifying effect on the crank and flywheel as the system where the balance weight is exactly opposite the 12th web. R.{Sir Henry Royce} | ||