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 two engine balancing schemes and their effects on bearings and critical speed.
| Identifier | ExFiles\Box 115\2\ scan0397 | |
| Date | 29th December 1938 | |
| - 3 - Effects on bearings. Comparing it with the R.R. system, Scheme (b) requires only 6 identical pieces against 8 pieces, (of two sizes) with the RR. system. Scheme (b) gives rather lighter loading of the intermediate bearings, whilst, with the present bearing lengths, the pressure intensity when using Scheme (b) is equal on both intermediate and centre bearings. More striking results cannot be expected with the limited amount of balancing mass employed, which is rather swamped by the sum of the rotating and reciprocating masses. The top line of the table shows, though, that we cannot dispense altogether with balance weights, which have a very beneficial effect on the centre bearing D.{John DeLooze - Company Secretary} Effect on critical speed. Scheme (b) should give a rather higher critical speed than the RR. system, for the same total mass in each case. C. being the flywheel end, the good effect of moving the balance mass of crank 1 from the outer web 1A to the inner web 1B is greater than the bad effect of moving the balance mass of crank 6 from web 6 C to web 6 F.{Mr Friese} This is because crank 1 is the high amplitude end of the shaft. The same argument applies to the transference of the balance weights on webs 2 B and 5 F to 2 C and 5 E respectively. With a new design of engine it would be possible to gain a little by shortening the rear end journal, so as to subject it to the same pressure intensity as the other bearings. NOTE: The connecting rod assumed in the calculations was that used in the calculations of memo BY/B.6/C.5.12.38. and is rather lighter than the present production rod. That the present figures for bearing loads due to rotating and reciprocating masses using the R.R. system, do not quite agree with corresponding figures in the above memo is due to a mistake in the latter (affecting only the RR. system) which has been corrected in the present investigation, (for which I have used my crankshaft bearing load coefficient table). BY/B. | ||