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).
Calculating the crankshaft torsional frequency for a 3-litre 6-cylinder engine.
| Identifier | ExFiles\Box 124\2\ scan0013 | |
| Date | 11th January 1940 | |
| To Ev.{Ivan Evernden - coachwork} c. to Jnr.{Charles L. Jenner} c. to Gry.{Shadwell Grylls} Rm{William Robotham - Chief Engineer}/JRS.7/JH.11.1.40. CRANKSHAFT TORSIONAL FREQUENCY 3 LITRE 6 CYL. ENGINE. With reference to your memo. Rm.{William Robotham - Chief Engineer}9/JH.30.12.39 I have calculated the 3 per rev. critical for this engine and find it to be at 5200 r.p.m. corresponding to a natural frequency of 260 per second. With this frequency the undamped amplitude at 4500 r.p.m. due to the third harmonic comes out at approximately .5 degrees, which should be handled safely by the damper. In view of the fact that the weights of piston, con-rod, etc. have had to be estimated I propose to perform a more detailed calculation of the critical speeds and also the vibration amplitudes when these weights are known. Rm{William Robotham - Chief Engineer}/JRS. | ||