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).
Worked example of a calculation for the torsional stiffness of one crank for the standard Phantom shaft using Carter's Formula.
| Identifier | ExFiles\Box 25\3\ Scan312 | |
| Date | 7th February 1928 guessed | |
| contd :- -2- The following is a worked example of a calculation of the torsional stiffness of one crank for the standard Phantom shaft (E.{Mr Elliott - Chief Engineer} 75216) using Carter's Formula) :- l = 2b + .8 h + 3/4 a (d₁⁴ - δ₁⁴)/(d₂⁴ - δ₂⁴) + 3/2 + (d₁⁴ - δ₁⁴)/(h w³) = 1.500 + .850 + 3/4 X 1.850 (2.625⁴ - 1.5⁴)/(2.125⁴ - 1.125⁴) + 3/2 X 2.750 X (2.625⁴ - 1.5⁴)/(1.065 X 3.0³) = 1.500 + .850 + 3.125 + 6.08 = 11.56" This is the equivalent length of one crank. The stiffness of one crank is :- Stiffness = G J / l where G = 11.8 X 10⁶ J = π / 32 (d₁⁴ - δ₁⁴ ) so that stiffness = (11.8 X 10⁶ X π X 42.39) / (11.56 X 32) = 4.250 X 10⁶ lbs.ins/rad. From this, we may calculate the stiffness of the whole shaft if required as previously stated. Here however we will take the measured stiffness of the whole shaft and reduce it to compare with the above value. The measured stiffness of the whole shaft in the crankcase is 45,000 lbs.ft/radian, This value is corrected as follows :- Under the applied torque T lbs.ft., the nose will deflect through an angle θ = (12 T l) / (C J) radians. T = 45,000 lbs.ft. l = length = 3.200" C = 11.8 X 10⁶ J = π / 32 (1.750⁴ - .750⁴) contd :- | ||