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).
Comparative analysis of the stiffness of Peregrine and Bensport crankshafts.
| Identifier | ExFiles\Box 85\5\ scan0007 | |
| Date | 27th April 1932 | |
| X217 27. 4. 32. XGOP BENSPORT CRANKSHAFT. Effect on the stiffness of the Peregrine crankshaft of lengthening the webs by decreasing the length of the journals and of using a journal size of 2 1/4" dia. PEREGRINE. | BENSPORT. Length of Journals 1.3 + 1.1 + 7(1.140)=10.380 | 10.380-6(.175)=9.330 " " Webs .567 | .654 " " Pins 1.225 | 1.225 Inertia of Journals d^4-S.4 2 1/4^4 - 1 1/8^4 = 14.4 | 2 1/4^4 - 1 1/4 = 22.0 " " Pins d^4-S.4 1 3/4^4 - 1 1/8^4 = 7.7 | 1 3/4^4 - 1 = 8.3 ------------------------------------------------------------- EQUIVALENT | Journals 10.38 | 9.33 LENGTH. | Pins 10.30 | 14.60 | Webs 2.72 | 3.14 | " 17.50 | 23.20 |--------------------|-------- | Total 40.90 | 50.27 | 1.41 | 2.16 ------------------------------------------------------------- Stiffness lbs ft/radium 34500 | 43000 The bensport crankshaft with 2 1/4" journals has a calculated stiffness of 48000. We can correct the calculated stiffness with 2 1/4" journals from J.{Mr Johnson W.M.} 3. results and get :- 32000 ---- X 43000 = 40000 34500 This raises the critical speed with no inertia on the nose from the Peregrine figure of 5750 to 6400 R.P.M. With the supercharger (20.8 lbs in^2) fixed to the nose this figure would fall to 5400 R.P.M. | ||