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).
Calculations on the Peregrine crankshaft using Carter's formula to determine critical speed.
| Identifier | ExFiles\Box 2\3\ B002_X 116 117 119 120-page13 | |
| Date | 30th December 1931 | |
| To E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} HS{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}9/KT.30.12.31. PEREGRINE CRANKSHAFT. We have done some calculations by Carter's formula on this crankshaft to see up to what speed we shall be able to run. We have obtained the following results :- Stiffness 35200 lbs.ft. per radian. Inertia of crankshaft 68.54 lbs in² " Big ends & Pistons 35.80 " " Blnce Wts. 33.20 " Total. 137.54 lbs in² Effective inertia is 1/3rd of this = 45.85 lbs in² = .0100 slugs ft² If A.{Mr Adams} is the inertia on the nose of the crankshaft then the critical frequency N. N = 1/2π * √(35200 / (.0100 + A)) If A.{Mr Adams} = 0, then N. = 300 cycles/sec. or 6000 R.P.M. If we desire a critical speed of 5000 R.P.M. then A must not exceed 19.7lbs in². An estimate of the inertia of the fixed part of the drum type J.3. damper is 38 lb in⁴ in addition to which is the fan pulley, and on B.2. the supercharger drive. Our present China unit in France has reached its master period of 4200 R.P.M. on top gear, and our J.1. unit runs up to 4500 R.P.M. On B.2. with a higher B.M.E.P. the crankshaft will be the limiting factor of the speed of the engine, which is not a satisfactory state of affairs. Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} | ||