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).
Crankshaft vibration periods, comparing their design to Bentley's and noting weaknesses in the latter's approach.
| Identifier | ExFiles\Box 21\2\ Scan112 | |
| Date | 21th January 1932 | |
| To R.{Sir Henry Royce} From Hs.{Lord Ernest Hives - Chair} c. to Sg.{Arthur F. Sidgreaves - MD} c. to Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} c. to Rg.{Mr Rowledge} X3805 Hs.{Lord Ernest Hives - Chair}9/MAJ.21. 1. 32. CRANKSHAFT PERIODS. X.634. X.3918. X.3805. We ought to have mentioned in our report Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}3/MA. 12.1.32 that although the period on the Bentley shaft is not as bad as on our car, actually they are in a very much worse position because their period comes within the speed range of the car, whereas our master period we keep outside the speed range. When we had the failure of the crankshaft, it was when we were running on Brooklands with heavy balance weights. Our interest in the Bentley was that we knew they had got a weak crankshaft and we were interested to know how they dealt with the master period. The schemes they use for reducing the period are not very permanent. The dynamo driven off the front end of the crankshaft by means of fabric joints, gives a certain amount of trouble, and after the engine is run through the period several times the joints are destroyed. Also the damper loses its efficiency due to slack developing in the serrations. Proof that they are not happy about their crankshafts size is shown by the fact that on the 8 litre the journal is 2.1/8" dia. and on their latest 4 litre car the journal dia is 3". We think it must be more than a coincidence, the fact that on more than four Bentley cars we have tried the petrol feed is restricted by the size of the needle valve seating in the carburetter so that the engine could not get enough petrol to go through the period at top gear. We are continuing our tests with the centrifugally loaded damper. HS.{Lord Ernest Hives - Chair} | ||