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).
Investigating and solving 'chunking in the drive' by using a dashpot in the carburetter.
| Identifier | ExFiles\Box 94\1\ scan0250 | |
| Date | 6th December 1935 | |
| X328 To E.{Mr Elliott - Chief Engineer} from HB{C. E. Harcombe}/Rm.{William Robotham - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} c. to Sft.{Mr Swift} c. to RHC.{R. H. Coverley - Production Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}18/KW.6.12.35. Chunking in the Drive. We noticed that the Hudson people fit a dashpot on their carburetter to overcome chunking in the drive, and we therefore contacted with them through Railton, who uses a lot of their chassis over here, to find out what experience they had of chunking. The following is the information obtained - "This backlash noise was quite apparent on the introduction of the present rear axle, and was found to be all due to the clearance between the teeth of the pinion and the ring gear proper. Our practice at that time was to hold this clearance from about .003 to .008, the shop stating that this was the best tolerance they could maintain due to the warpage of the parts during the heat treat operations. However, it was distinctly shown that if these limits could be kept down to a maximum of .003, the backlash or clocking noise was no longer apparent, but with subsequent improvements in shop methods we have been able to maintain this backlash clearance between the teeth from the minimum of .001 to a maximum of .003, which has eliminated entirely this difficulty. At this same time working along a different method of attack, we developed the dashpot in the carburetter which would eliminate the noise by changing the speed of deceleration after lifting the foot from the accelerator pedal. With our present limits it would be possible to discontinue the use of the dashpot in the carburetter if it were for this particular feature only. However, with the adoption of the automatic clutch the dashpot in the carburetter improves greatly the smoothness of action of this device. So much so that we feel that it is advisable to keep this feature as a part of our carburetter". HB{C. E. Harcombe}/Rm.{William Robotham - Chief Engineer} | ||