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).
Methods to reduce engine vibration by using heavy crankshafts, balance-weights, and providing more support to main bearings.
| Identifier | ExFiles\Box 25\3\ Scan379 | |
| Date | 9th January 1929 guessed | |
| contd :- -3- torque variations of the engine, resisted on the spot by the flywheel, do not reach the back wheels. It is on the above reasoning that I advocate heavy crankshafts, since it helps both methods (a) and (b) but takes particular advantage of method (a). The inertia-resistance to being vibrated of a heavy body increases as the square of the frequency of the vibrating load (resonant condition neglected). Small racing engines now-adays have cyls. about half the size of our 20 HP. and crankshafts about five times as heavy, and run safely up to 10,000 r.p.m. or so. Another conclusion from the above reasoning is to use balance-weights, since they reduce some of the loads on the shaft, and also increase its mass, i.e., they provide distributed flywheel effect along the crankshaft. They would help to resist the inertia torque for instance. Disc webs also help this way, which may explain their popularity, particularly on the Continent. Probably the heaviest of all are those in the 14-45 Talbot. We know the effect of the flywheel in steadying the crankshaft as a whole, and can thus visualise the possib-ility of steadying it locally by the same means. A third line of action to attain smoothness is the provision of more support to the main bearings and thus help the crankshaft to resist distortional loads. The Americans go so far as to make the crankcase in C.I. for the stated purpose of reducing vibration. contd :- | ||