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 damper application, crankshaft stiffness, and inertia management for high-speed engines.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 43 | |
| Date | 22th April 1927 guessed | |
| contd :- -10- With the former we have had sufficient experience to shew that it is perfectly satisfactory below the master period but the latter type, although used on several American cars, would probably require some investigation and development on our engines. The essential condition to fulfil for the satisfactory application of either of these dampers is that the master period must be outside the working range. With a high speed engine this necessitates :- (1) Maximum stiffness of the crankshaft. (2) Low polar inertia of the system forward of the flywheel and particularly avoid rigid masses adding inertia to the front end of the crankshaft as these have approx. three times the value of the other parts. Increasing the stiffness of the shaft by enlarging the journals and crankpins naturally increases the inertia but due to the fact that from 35% to 45% of the inertia is due to the big ends and pistons any increase of stiffness, even with increased inertia, is of direct benefit in raising the natural period of the shaft. Reduction in weight of the big ends and pistons is helpful but the big ends are the more important of the two in this respect because the equivalent inertia of the pistons is approx. equal to one half their total mass concentrated at the radius of the throw. Timing gear drive from the flywheel end has much to recommend it in keeping down the inertia of the front end and also in obtaining a smoother drive for the timing gears which should result in a reduction of noise and contd :- | ||