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).
Summary of critical speeds for various crankshaft configurations on the Bentley Engine.
| Identifier | ExFiles\Box 82\4\ scan0085 | |
| Date | 19th January 1935 | |
| -3- Summarising the critical speeds of various shafts for the Bentley Engine we get - Crankshaft Critical Speed r.p.m. Observed Calculated (1) Standard 7 bearing 5000 (2) Narrow pin 7 bearing, strip lead bronze rods 5320 (3) (1) with disc flywheel 5150 (4) Exp. 4 bearing shaft, narrow strip l.b. rods, disc flywheel 5400 (5) As (4) but standard flywheel 5250 (6) Best possible 4 bearing shaft with redesigned cyl. centres and standard flywheel 5700 NOTE. Number (2) has standard balance weights and hence a greater degree of balance owing to shorter crankpins and lighter connecting rods. With the standard 62% balance the critical speed of this shaft would rise about 150 r.p.m. to 5470 r.p.m. The maximum calculated gain possible by adopting a 4 bearing engine using the same journal and pin size and amount of balance is therefore about 230 r.p.m. Ha/Gry.{Shadwell Grylls} | ||