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 crankshaft stiffness comparing Peregrine and Bensport designs.
| Identifier | ExFiles\Box 2\3\ B002_X 116 117 119 120-page14 | |
| Date | 27th April 1932 | |
| BENSPORT CRANKSHAFT. X 119. 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 10.38-6(.175)=9.330 " Webs .587 .654 " Pins 1.225 1.225 Inertia of Journals d^4-d'^4 (Handwritten: 2^4-1.8^4) 14.4 2 1/4^4 - 1 3/4^4=22.0 " Pins d^4-d'^4 7.7 1 3/4^4 - 1^4=8.3 EQUIVALENT LENGTH Journals 10.38 9.33 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/radian 34500 43000 The bensport crankshaft with 2 1/4" journals has a calculated stiffness of 43000. We can correct the calculated stiffness with 2 1/4" journals from J.{Mr Johnson W.M.} S. 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 (20.9 lbs in^2) fixed to the nose this figure would fall to 5400 R.P.M. | ||