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).
Technical memo answering questions on lowering crankshaft critical speed by analysing connecting rod weights and damper types.
| Identifier | ExFiles\Box 132\2\ scan0214 | |
| Date | 12th June 1941 | |
| 111b 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}/OTS. Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden}1/SW.12.6.41. Crankshaft Dampers. Herewith the answers to questions on the lowering of crankshaft critical speed contained in Rm.{William Robotham - Chief Engineer}3/SW.24.5.41. 1. Effect of Connecting Rod Weights. Comparing RE.297/8 used on B.60, and having Vandervell big end bearings. with :- EB.2815/6 - B.11 AC.9 big end (solid) The increase in weight at the big end, with bearing fitted, on the B.60 rod is 3 1/4 ozs. (little end weights remain approximately the same). This is equivalent to an increase in I of .0026 lb.in/sec2 and lowers the critical speed by 55 RPM. 2. Reduction of Weight on the Humber type Damper. More than half the reduction in critical speed with the Humber type damper, as against the R.R. damper, is due to the fan pulley. Critical Speed with the Humber type damper, is 265 RPM lower than with the R.R. damper. 165 RPM are accounted for by the pulley. I for the pulley is equal to .026 lb.in/sec2. I for the flange plates is .023 lb.in/sec2. Crankshaft pinion, crankshaft nose etc., are of no importance. It does not appear practicable to reduce by very much the inertia of the flange plates without redesigning the slipper flywheel section. (continued) | ||