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).
Requesting details for an experiment to increase the size of crankshaft balance weights on the Wraith III engine.
| Identifier | ExFiles\Box 8\5\ 05-page09 | |
| Date | 1st November 1937 | |
| c. Rm.{William Robotham - Chief Engineer} 617 DA.{Bernard Day - Chassis Design}16/G.S.11.37. WRAITH 111. CRANKSHAFT BALANCE WEIGHTS. Will you please issue details for increased size of balance weights to be tried on the Wraith 111 engine as follows :- Width of both large and small weights to be increased from .700" to .825", the increased width to be all on the crankpin side of weights, making them offset relative to the holding studs and dowels. This will increase the percentage of balance for the Wraith 111 crankshaft from 68% to 80% which is the same percentage balance as the standard 25/30 HP. crankshaft. The reason for the amount of balance being only 68% on the existing Wraith 111 crankshaft was, that it was hoped to keep the crankshaft unit completely similar for Wraith 111 and Bentley 111 engine, and the present crankshaft with 68% balance has already 6% greater balance than the standard Bentley 11 engine, which has 62%. The object of the experiment for increased weights for Wraith 111 is to make the engine smoother, although the critical speed of the crankshaft will be slightly lowered. DA.{Bernard Day - Chassis Design} | ||