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).
Analysis of seven-bearing crankshafts, comparing component inertia and stiffness for different balance configurations.
| Identifier | ExFiles\Box 85\5\ scan0092 | |
| Date | 29th January 1935 | |
| To H.{Arthur M. Hanbury - Head Complaints} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} c. to Rg.{Mr Rowledge} 427 Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}21/KW.29.1.35. Seven Bearing Crankshafts. We have been looking into whether it is possible to raise the critical speed of the narrow pin Bentley crankshaft by halving the thickness of the webs and increasing the length of the 2.700 dia. collars on either side of the journals. We find by comparing the features of the crankshafts on Peregrine, Bentley and Phantom that the inertia of the components is made up approximately as follows - 60% Balance 100% Balance Crankpins 1 Unit 1 Webs 4 " 4 Balance weights 2½ " 4 (2½ of which balances webs only) Big ends 2 " 2 Pistons 1 " 1 ____ ____ 10½ 12 The equivalent length in Carter's formula which is inversely proportional to the stiffness is made up of - Journals 2 units proportional to length Crankpins 2 " " " Webs 5 " " reciprocal of thickness. | ||