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 conclusions regarding engine 2 node vibrations, stress, and torque.
| Identifier | ExFiles\Box 132\2\ scan0200 | |
| Date | 17th February 1941 guessed | |
| - 3 - 2 Node Vibrations . (Engine P). The 10th order is zero because of the 90° bank angle, and lower orders than this will occur at 3000 r.p.m. and more, and so will be above the running range. Orders above the 12th should be examined as a measure of precaution when the proposal is taken in hand seriously and the calculations made afresh, based on more certain data. 11th order (at 2450 r.p.m.) Resultant equivalent exciting torque expressed at Crk.1 = T₁₁ Σaᵣ = 1147 lbs.ins. Amplitude at Crk.1 = θ°₁₁ = 0.1075 (Shannon) or 0.1326 (Carter). Crankpin stress at centre of crankshaft = ± 2.365 tons/sq.in. (Shannon) or ± 2.915 tons/sq.in. (Carter). 12th order (at 2250 r.p.m.) Resultant equivalent exciting torque expressed at Crk.1 = T₁₂ Σaᵣ = 508 lbs.ins. Amplitude at Crk.1 = θ°₁₂ = 0.0476 (Shannon method). Crankpin stress at centre of crankshaft = ± 1.047 tons/sq.in. --------- Combined effect at 2340 r.p.m. of 5th order 1 node and 11th order 2 node (off resonance) vibrations. The higher (Carter) figure for 2 node vibrations is taken. Total stress in crankpin next to flywheel = ± 7.47 tons/sq.in. when no damper. or = ± 1.71 tons/sq.in. with damper for 1 node vibrations only. --------- CONCLUSIONS. It seems extremely probable that, if a suitably tuned and damped, spring controlled vibration absorber is fitted to take care of the single node vibrations, the engine (P) will be very satisfactory as regards torsional vibrations. The calculations should be repeated, including higher orders of 2 node vibrations, when the design is commenced and exact numerical data is available. P.T.O. | ||