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).
Summary of useful data for Phantom II and 25HP engines, detailing weights and performance characteristics of crankshafts and other components.
| Identifier | ExFiles\Box 14\2\ Scan124 | |
| Date | 1st May 1931 | |
| FILES. 87010. (handwritten) May 1931. X.634. X.7010. X.5010. USEFUL DATA. P.II. Torsional period at 100 m.p.h. or 3900 r.p.m. standard crankshaft. Torsional period of chamfered shaft, with 12 weights to LeC.2616 begins 80 m.p.h. (Handwritten notes: '24EX' above 'chamfered shaft', 'quiet' above 'begins') " " " 2 " " 6 weights begins 86 m.p.h. Out of balance per crank standard shaft = 14.6 lb ins. chamfered 24-EX. = 11.74 lb ins. Out of balance of big end (2.531 lbs) = 6.95 lb. ins. 24-EX. shaft with 12 wts. balances shaft + 41% of big ends. Weight of con rod 3.34 lbs. Weight of piston 1.84 lbs. Reciprocating mass 2.65 lbs per crank. 25 HP. 2" pin crankshaft E.55619 torsional period 5000 r.p.m. standard " E.55127 " 4700 r.p.m. Period of E.55619 with 12 wts. to Sch.1402 balancing shaft only = 4200 r.p.m. Out of balance per crank E.55619 = 6.20 lb ins. Wt. of big end for crankshaft E.55619 = 1.28 lbs. " " " " " E.55127 = 1.27 lbs. Out of balance for 2" pin big end = 2.88 lb ins. Wt. of little end .384 lbs. Wt. of piston 1 lb approx. Standard flywheel weighs 95 lbs. - polar moment of inertia .691 slugs ft Lightened " LeC.2830. 87 lbs. - " " " .555 " | ||