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).
The effect of a Humber type damper on the critical speed of a B.60 crankshaft.
| Identifier | ExFiles\Box 132\2\ scan0211 | |
| Date | 8th May 1941 | |
| To Rm.{William Robotham - Chief Engineer} from Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden} c. to Jnr.{Charles L. Jenner} c. to Rm{William Robotham - Chief Engineer}/GHS. 1116 Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden}3/SW.8.5.41. Effect of Humber type damper on Crankshaft critical speed of B.60. With reference to your memo ref., Rm.{William Robotham - Chief Engineer}2/ML.20.4.41 to Jnr.{Charles L. Jenner} here is the answer to Item 5, which was the effect of the inertia of the Humber damper hub on the critical speed. State of the Crankshaft Natural frequency of the crankshaft system 3rd. order Major Critical speed No Damper Fitted 15,600 Vib/min. 5200 RPM R.R. type damper and spring drive 15,225 " 5075 " Humber type damper and single fan pulley (to PL.90) 14,430 " { 4810 " Thus the Humber type damper brings the critical speed down by 390 RPM, or 265 RPM more than the orthodox R.R. type damper. Appended is a list of the moments of inertia of the parts in front of No.1 cylinder centre line in each case. The journals, webs and crankpins were converted by Carter's formula to a common solid shaft of 2.75" dia. On this basis the inertia of the Humber damper parts was calculated to act 12.3" in front of No.1 cylinder centre line. This distance was 10.8" in the case of the R.R. Damper. (continued) | ||