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).
Springs in the universal gearbox, comparing Buick and Vauxhall synchromesh systems.
| Identifier | ExFiles\Box 136\4\ scan0174 | |
| Date | 2nd September 1937 | |
| To Da.{Bernard Day - Chassis Design} from Da{Bernard Day - Chassis Design}/Hdy.{William Hardy} c. By.{R.W. Bailey - Chief Engineer} [crossed out] c. Rm.{William Robotham - Chief Engineer} [Handwritten: GRY{Shadwell Grylls}] [Handwritten: 115 3] Da{Bernard Day - Chassis Design}/Hdy{William Hardy}6/N.2.9.37. Re: Universal Gearbox. With reference to the Buick type synchromesh, it occurs to us that should a spring break, there is nothing to stop the pieces from coming out into the box. Even if they can be prevented from working out radially, we do not yet see how they can be stopped from working out endwise and then working back and out into the box. This cannot happen with the Vauxhall type synchromesh. The springs recommended in our Da{Bernard Day - Chassis Design}/HB.{C. E. Harcombe}21/N. 27.8.37 were stressed to 120,000 lbs sq.inch, which is Messrs.Salter's recommendation as a maximum permissible stress. Whether these will be free from breakage partly depends upon whether the cam surfaces produce serious wear of the springs. The evidence we had from our Buick with Vauxhall type synchromesh is that there was serious wear. There is also the fact the springs on the Vauxhall have now thickened ends, presumably on account of wear of the ends. However, the springs on our 25 HP. Vauxhall do not show any appreciable wear, mileage is small of course. In the case of the latest Buick springs wear reduces the thickness at the place of greatest stress, whereas on the Vauxhall the wear is at the place of least stress, and yet the thickened ends are used. We calculate that the Buick springs are stressed to 94,000 lbs sq.inch, but the spring shewn on N.Sch.5193 at 106,000 lbs sq.inch does not give what we consider to be a sufficiently low rating. Hence our recommendation as in Da{Bernard Day - Chassis Design}/HB.{C. E. Harcombe}21/N.27.8.37. Retaining the same stress as in the recommended low rating spring ( 120,000 lbs.sq.inch) we can remedy the effect of wear by making the centre solid or thicker. We are quoted by Messrs.Salter 46/- per gross for solid springs against 8/- per gross for plain springs. The solid centre stiffens the spring appreciably but we think there is something in hand in this case. Cont'd.{John DeLooze - Company Secretary} | ||