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).
The torsional stiffness testing of a large pin crankshaft compared to standard models.
| Identifier | ExFiles\Box 14\2\ Scan048 | |
| Date | 29th August 1929 | |
| X7010 To R.{Sir Henry Royce} from Ha/Tsn. c. to SE. Wor.{Arthur Wormald - General Works Manager} c. to c. to Ry. Ha/Tsn.1/WJ.29.8.29. X7010 X8010 X1418 S.S. CRANKSHAFT WITH LARGE PINS. We have twisted this shaft in its case, and find it to be 17% stiffer torsionally than the standard S.S. shaft, and 40% stiffer than the original standard Phantom shaft. Figures are :- Original Std. Phantom E.75216 - 45,000 lbs.ft/rad. Std. S.S. (unchamfered) - 52,700 " : Large Pin S.S. E.79331 - 62,000 " : The latter shaft incorporates the following features:- Pin dia. increased from 2.125 to 2.375". Pin bore reduced from 1.125 to 1.000". Journal bore reduced from 1.500 to 1.000". Web width 4.000" as before. The webs are unchamfered, as this feature has now been adopted on production. The reasons were that it gives a slight increase in stiffness, and very considerably simplifies the production. The weights of the above shafts are :- Original Std. Phantom 75lbs. 12ozs. Std. S.S. (unchamfered) 79lbs. 8ozs. Large Pin S.S. 90lbs. 14ozs. We cannot get big-end weights yet for the new shaft. The stiffness of a single crank comes out at 6.2 x 10^6lbs.ins/radian, as against a calculated figure using Carter's formula of 7.03 x 10^6lbs.ins/radian. The formula is thus 13% too high. Ha/Tsn. | ||