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 and assumptions for seven and four-bearing Spectre engine crankshafts.
| Identifier | ExFiles\Box 93\5\ scan0091 | |
| Date | 29th June 1933 | |
| X Group. 317 To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}1/KT.29.6.33. SPECTRECodename for Phantom III CRANKSHAFTS. We send you herewith some calculations on the seven and four bearing crankshafts for the SpectreCodename for Phantom III engine. We have made the following assumptions :- (1) Big end weight per throw 3.75 lbs. (2) Reciprocating mass per cylinder 1.5 lbs. (3) Inertia of balance weights on both shafts 80 lbs.in2 This seems a reasonable assumption since the four bearing shaft will require a weight each end to steady the flywheel, one of two units in the middle and two more to provide static balance. (4) Inertia on nose of crankshaft 20 lbs.in2 The results are therefore :- Seven Bearing. Four Bearing. Stiffness lbs.ft/radian. 85,500 118,000 Inertia of shaft lbs.in2. 257 259 " of big ends. 113 113 " of pistons. 45 45 " of balance weights. 80 80 Total effective inertia 20+ 495/3 20+ 497/3 = 185 = 186 Critical frequency ~/sec 230 272 R.P.M. of 3 per rev. period 4600 5450. Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} | ||