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 vibration, distortion balance, and potential solutions like using counter-weights.
| Identifier | WestWitteringFiles\T\November1928\ Scan119 | |
| Date | 13th November 1928 guessed | |
| contd :- -4- It is possible for this force, acting on the engine parts, to alternate between plus and minus nearly 2 tons. None of our materials of construction, being elastic, are capable of providing a reaction to a force without elastic yield, which is accentuated if the force is dynamic or alternating in nature; also there are 6 points of application of this force in a 6-cyl. engine, each one alternating say 50 times a second. Consequently, we should expect vibration and noise as the first indication of 'jellying' of the engine parts at high speeds. The ordinary crankshaft is constitutionally unsuited for high speeds of rotation, owing to the unbalanced distribution of mass, and to the poor stiffness due to the cranks in it. It is therefore poor in 'distortion balance', which is a recognised term to describe anything that distorts itself out of balance at high r.p.m., though initially in static and dynamic balance at low r.p.m. POSSIBLE CURES. The steps that can be taken to reduce these dynamic effects are: (1) Reduction of the inertia forces by means of counter weights (local balance) (2) Reduction of vibration purely by stiffening crankshaft and crankcase, e.g., by making the latter in cast-iron, or by adopting a stiffer crankcase construction. COUNTER-WEIGHTS. With the aid of these any degree of balance can be obtained. The maximum ever used is in motorcycle engines, where the whole rotating weight together with half the reciprocating weight (transferred to the crankpin) is balanced. Thus can they contd :- | ||