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 regarding crankshaft stiffness, specifically the impact of increasing pin diameter and altering inertia.
| Identifier | ExFiles\Box 25\3\ Scan298 | |
| Date | 6th December 1927 | |
| CRANKSHAFT STIFFNESS - V634 - File X5010 With reference to R1/723/11/27 In an endeavour to obtain a value for increasing the dia. of the 20 H.P. pins on the shaft-period, we made the following approximation. Total effective inertia concentrated at shaft end is. Spring drive hub. .00582 Big ends total. .00266 Half pistons .00187 Crankshaft .00561 ------- .01596 Of this the big end contribution is .00266 or 16.8%, the pins .0013 or 8.4%. Now if we increase the pin dia from 1.5" to 2" and increase the hole in the pins from .75" to 1.00", from the tests given in Hs{Lord Ernest Hives - Chair}|Rm{William Robotham - Chief Engineer}|Lg 6/12/27 we expect to increase the shaft stiffness by 40%. And this alteration, by reference to all the big ends dimensions we already have, will alter the inertia as follows. Weight - 1.5" Dia Pins 2.0" Dia Pins Big End 1.187 1.900 Shaft Pins .56 1.02 ------ ------ 1.747 2.92 or 70% total increase on pins & big end | ||