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).
Technical analysis of the out-of-balance forces and couples in a connecting rod system.
| Identifier | WestWitteringFiles\M\2October1924-December1924\ Scan8 | |
| Date | 20th October 1924 guessed | |
| -9- Contd. showing that when complete linear balance has been effected, the transverse out-of-balance con. rod couple is not Mk²Ø̈ as might perhaps be thought, but M (a b - k²) Ø̈ and is, if ab is greater than k², as is usually the case, opposite in direction to Mk² Ø̈ N.B.1. Ø̈ represents the angular acceleration of the con. rod. N.B.2. The expression for the out-of-balance couple may, of course, be obtained in other ways, viz, (a) Taking the algebraic sum of the moments of the two component con. rod linear accelerating forces at its centre of mass, about the crankshaft axis of the engine, as referred to on p.3 (bottom), subtracting this, viz. M a b, which is larger than Mk², from Mk², and changing the sign to accommodate the reversal. or (b) Taking the algebraic sum of the moments of the Mg balancing force along XO and PO about the centre of mass G of the con. rod, which is really the same thing, as we have done. The above method of arriving at the result is thought, however, to be less difficult to appreciate. The case may be stated thus :- (i) With no linear balancing of the con. rod there is an out-of-balance linear force acting at G, of known magnitude and direction, and an out-of-balance couple of magnitude Mk² Ø̈. (ii) By effecting linear balance of the con. rod to the extent of the balancing Mₓ and Mₚ, we annihilate the out-of-balance couple but leave unbalanced a linear force acting at G of direction similar to that of (i), but of magnitude reduced in the proportion of M₉ to M.{Mr Moon / Mr Moore} Contd. | ||