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 crankshaft balancing schemes, including 4-weight and 8-weight options for a 6-cylinder engine.
| Identifier | ExFiles\Box 14\2\ Scan109 | |
| Date | 2nd April 1931 guessed | |
| -2- We have investigated the Japan III. crankshaft and this would appear to be capable of being fully balanced. We think it should be definitely impossible to get on to the torsional period with balance weights, as the stresses in the bolts are then incalculable, and must be very large. Schemes Available. The attached sketch shews all the schemes applicable to a 7 bearing 6 cylinder. On the assumption that we propose to balance the rotating loads only and not the pistons, we give on a table also attached an analysis of the main bearing loads with the various schemes shown on the sketch. On the Chrysler the crank only was balanced. From the point of view of bearing wear there is not much advantage in balancing more than the crank and big end, as we do not need to make the main bearings last much longer than the big ends. Also, there will be the loads on them in any case which we cannot reduce. The five schemes are considered individually below: A.{Mr Adams} 4-Weight Scheme. This scheme was intended to balance the two 3-cylinder couples only, but if this is done then the bearing loads are actually not reduced at all, but merely reversed in direction. Each balance weight is twice the size it need be to balance the load on that web, and therefore substitutes an equal and opposite load. It would not be expected to reduce bearing wear therefore unless we only balance half the couple. We are trying this scheme on 27-EX. B. 8-Weight Scheme. This is an advance on scheme A.{Mr Adams} in that if used to balance the couple it does reduce the bearing loads, but only by 50% of the constant rotating load. contd. | ||