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).
Calculation of crankshaft torsional stiffness and deflection for main bearings, comparing calculated figures with tested stiffness.
| Identifier | ExFiles\Box 25\3\ Scan313 | |
| Date | 7th February 1928 guessed | |
| contd :- -3- ∴ θ = .1648 radians. Main bearings. Only a length 2 b is included in the formula for one crank, so that when added together there is found to be a length of 4.5" of main bearings not included with the six cranks. For this, θ = (12 T l) / (C J) as before. T = 45,000 lbs.ft. l = 4.5" C = 11.8 X 10^6 J = π/32 (2.625^4 - 1.500^4) ∴ θ = .0494 radians. The remainder of the crankshaft consists of the six simple cranks. This has deflected through an angle. = 1.000 - (.1648 + .0494) = .7858 radians. Under the applied torque of 45,000 lbs.ft. so that its torsional stiffness is :- 45,000 lbs.ft. per .7858 radian or 57,300 lbs.ft/rad. Each individual crank will have twisted through 1/6 radians, there- fore its stiffness must be 6 X 57,300 lbs.ft/radian. = 4.13 X 10^6 lbs.ins/radian. We can now compare this with the calculated figures of 4.25 X 10^6. Then the ratio calculated stiffness / tested stiffness = 4.25 / 4.13 = 1.03. or within 3%. | ||