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).
Analysis of engine vibration, harmonic orders, and damper settings for different engine configurations.
| Identifier | ExFiles\Box 132\2\ scan0186 | |
| Date | 26th October 1940 guessed | |
| 3. When fitting a damper the optimum torque setting = 1.11 ΣαART_N for a constant friction damper. Where A = the piston area and R = the crank radius for the 6/rev. vibration the optimum setting = 323 lb/in. for B.60 and 542 lb/in. for the flat 12. Thus although the amplitudes are the same on both engines, the flat 12 vibration is 68% more severe to damp, owing to a much higher component of tangential effort. ------------------- 2. The range over which the 6/rev. vibration on the flat 12 might be expected to extend. This is comparatively small and should be of the same order as that for the 6/rev. vibration on B.60. ------------------- 3. Whether any of the other harmonics can be expected to be of sufficient amplitude to cause trouble. The 4½ and 3½ order amplitudes are of the same order on the flat 12 as on B.60. They are both more severe, however, from the point of view of optimum damper setting. 4½ order - Flat 12 optimum setting = 425 lb/in.) B.60 " " = 284 lb/in.) 50% more severe. 3½ order - Flat 12 optimum setting = 232 lb/in.) B.60 " " = 187 lb/in.) 25% more severe. The flank of the high 2nd order vibration causes ± ½° amplitude at 4000 R.P.M. ------------------- 4. Whether a flat 12 cylinder 2 stroke engine would be worse with regard to the 6/rev. vibration. The 6/rev. vibration on the 2 stroke is the same as on the 4 stroke engine. There are of course no ½ order vibrations. | ||