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).
Comparison of various schemes of balance weights for the Wraith III engine crankshaft.
| Identifier | ExFiles\Box 115\2\ scan0395 | |
| Date | 29th December 1938 | |
| COPY. BY.{R.W. Bailey - Chief Engineer} DA.{Bernard Day - Chassis Design} Rm.{William Robotham - Chief Engineer} Rm{William Robotham - Chief Engineer}/Spooner WRAITH III. COMPARISON OF VARIOUS SCHEMES OF BALANCE WEIGHTS. In the schedule below of existing and proposed schemes the balance masses are designated 1A, 1B, 2A, 2B, 2C.... etc. the number being that of the crank directly opposite to which the mass is attached in all cases, and the letter denoting the web of that crank which is the nearer to the bearing to which the letter relates; e.g. balance masses 1B and 5E in the diagrams above. In each of the schemes considered the total balance mass is the same, and is, in the calculations, taken to be equal to that used at present on Wraith III. The relative figures for masses in the schedule are given on the basis of unity representing the balance mass opposite Crank 1. (At 3500 R.P.M. of Wraith, the balance force corresponding to 'unit' balance mass as above = 1166 lbs.) Relative balance mass on extension of crank web. System 1A 1B 2B 2C 3C 3D R.R. 1 0 .5 .5 0 1 Scheme (a) 0 1 .5 .5 .5 .5 Scheme (b) 0 1 0 1 0 1 Scheme (c) 0 1 .25 .75 .25 .75 The figures in the table below correspond, at 3500 r.p.m. to a centrifugal force, due to crank and big end, of 2625 lbs. at the centre of each crank, and a variable reciprocating force, due to each piston and small end, having a value at T.D.C. of 2028 lbs, also acting at the centre of each crank. The sum of all the balance forces is, in each scheme investigated = 6 x 1166 = 6996 lbs. | ||