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 crankshaft balancing, counterweights, and flywheel modifications for smoother operation.
| Identifier | ExFiles\Box 14\2\ Scan093 | |
| Date | 9th January 1931 guessed | |
| (2) I should keep down the angular dimensions of the weight even if it asked for a slightly larger radius. Although it is better for the master period to keep the radius small I should favour a compromise for the sake of keeping the total weight down even if we cannot so completely balance the couples. It will be remembered that we shall always have with us the weight, and only at high speed any advantage from it. I do not like to cut into the oval of the crank so suggest we forge on the crank a facing, and use a simple flat surface and nearly all the fixing beyond the oval. Finally it will be seen that our usual compromises are the best and safest. A shaft of very large dia, is heavy and clumsy and increases the bearing trouble and probably the oil spray more than one benefit derived, and is a positive disadvantage unless it is counterweighted, which fortunately it permits, but even then has some disadvantages if it is overdone. We have therefore done wisely in approaching the maximum by steps. When we are stopped from a complete balance as we still expect to be we must at once try what can be done by stiffness to the crankchamber. There seems a definite demand and possibility for this at once, and it may prove to require very little alteration and weight added to the lower flange of the crankcase to produce a definite improvement. I suggest we make a trial of this at once, and in addition we fit four counterweights at once, but only of the size that will not trouble us with the master period. These two moves, with the flywheel modification already on test should be three things all contributing towards a smoother engine at high speed. Our low speed (torque reaction) and over-run is being improved by the trunnion support and soft rubber mounting. Probably a 6 cyl. so treated will be better than both types of 8 cyl. Suggested speed of master period with balance weights and lighter flywheel 3300 for 45HP., 4000 for 25HP. If it falls less than this we must reduce balance weights. R.{Sir Henry Royce} | ||