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).
Balance issues and proposed modifications for a Bensport crankshaft.
| Identifier | ExFiles\Box 85\5\ scan0028 | |
| Date | 29th April 1933 | |
| To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} X217 Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}8/KT.29.4.33. BENSPORT CRANKSHAFT. As we understand that you are instructing a light-ened crankshaft for this unit, we are sending you the information below showing that an additional weight of 3.5 lbs. in balance weight is required to obtain the amount of balance we are accustomed to on 20/25 engines. | | China. | Bensport J.1 | |---|---|---| | Out of balance per crank including big end. | 8.68 lbs.ins. | 9.08 lbs.ins. | | Balance weight. | 3.50 | 2.82 | | % Balance. | 80 | 62. | This has arisen partly due to the small weights of EB.39 being too small, the large weights having been reduced considerably below the drawing size to obtain static balance, and secondly because of the increased width of the webs. We suggest increasing the widths of all the balance weights from .700 to .870 keeping the small weights the same plan form, and arranging the outside radius of the large weights to give correct static balance. Aprox. 3.2" will be correct. The weights will then overhang the webs by .170 but clear the connecting rod by more than .150". By this method least inertia will be added to the crankshaft. Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} | ||