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).
Technical analysis of crankshaft stiffness, dimensions, and the effect of counterweights on balance and inertia.
| Identifier | ExFiles\Box 137\4\ scan0017 | |
| Date | 1st June 1929 guessed | |
| contd :- -7- We think it could well be stiffer. The displaced volume of the engine is about 250 cu.ins., and comparison with published dimensions of other American cars over the range of 200 - 300 cu.ins. shows that the Chrysler shaft is almost the smallest. Of 29 other cars having 6 cyl. engines between 200 cu.ins. and 300 cu.ins., only 3 have smaller pins and journals, namely 1 7/8" and 2 1/8", and they are only 215 cu.ins. engines. Of the remaining 26 cars, 22 have larger pins and 20 have larger journals. COUNTERWEIGHTS. We intend to do a test on the road to determine whether these make any difference to the smoothness. One full sized C/wt. plus bolts weighs 1 lb. 14 ozs., and taking 2.250" as the radius of the C.G., the total amount balanced per crank is 8.44 lbs.ins. We estimate the out-of-balance of the other rotating parts as : 2 webs approx. 6.00 lbs.ins. Pin. 3.05 " " Big end 4.85 " " TOTAL : 14.90 " " So that only about 60% of this is balanced. The inertia of the crankshaft plus balance weights is .0712 slugs ft², and of the bare shaft .0489. The total equivalent inertia less balance weights is .02788, so that they only make 27% difference in inertia. The calculated period of 3600 r.p.m. with balance weights would be raised to 4050 RPM. without. They are fixed at a small radius, and their contd : | ||