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).
Use and effects of crankshaft balance weights on both aero and car engines.
| Identifier | ExFiles\Box 14\2\ Scan108 | |
| Date | 2nd April 1931 | |
| K7010 R.{Sir Henry Royce} C. Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} C. Hs.{Lord Ernest Hives - Chair} E.{Mr Elliott - Chief Engineer} By.{R.W. Bailey - Chief Engineer} Rg{Mr Rowledge}/Tsnl/DM.{D. Munro}2.4.31. K7010 Y5010 Crankshaft Balance Weights. ------------------------- Our previous note with regard to the above referred to aero engines. We thought this was understood. We regard the scheme which you sent us by telegram as particularly applicable for aero use, for the following reasons : (1) Easier to attach the balance weights to the shaft, since they are all at 180° or opposite to the webs on which they fix. (2) For a given total weight of balance weight it gives more balance on the centre main bearing, which gets twice the inertia loading of any of the others. We have adopted this arrangement for development on aero engines, and are making the first few shafts with the balance weights forged integral. Car Engines. With balance weights on the cars, tests have not shown any improvement in engine vibration which is appreciable to the driver. May be this because other vibrations, in the chassis in particular, are of greater importance. It would appear that reduction in bearing wear is the sole justification at present for balance weights. The Phantom car, which has its top torsional period at about 95 m.p.h. with the standard crankshaft and at about 100 m.p.h. with the big pin shaft, will not stand balance weights owing to the risk of running on to the torsional period, particularly on the gears. It would require a new crankshaft. The standard 20 H.P. would appear to be capable of carrying quite a lot of balance weights. 18-G-IV is now fitted with a crankshaft which has 12 balance weights to the original W.W. Scheme, balancing the crank only. These are slightly too heavy, & it is possible to get up to the torsional period on the gears. Contd. | ||