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).
Advantages and disadvantages of the Dubonnet suspension system.
| Identifier | ExFiles\Box 154\1\ scan0117 | |
| Date | 27th February 1934 | |
| X3873 To E.{Mr Elliott - Chief Engineer} from Da.{Bernard Day - Chassis Design} c.c. Sg.{Arthur F. Sidgreaves - MD} Hor. Hs.{Lord Ernest Hives - Chair} By.{R.W. Bailey - Chief Engineer} Hdy.{William Hardy} Da.{Bernard Day - Chassis Design}1/HP.27.2.34. Dubonnet Suspension The Dubonnet suspension as fitted to the Pontiac which we tried yesterday has the advantage of being simpler than our scheme. It has five essential bearings instead of seven. It can have perfect steering geometry with a conventional steering linkage. Also the question of side scrubbing of the tyres does not arise. The drawbacks are that even to get such a high transverse pivot angle as 7º the brake drum must be pushed right inside the inner wheel hub, limiting the drum diameter, with 17" rims, to about 14", preventing the use of ribs as well as enclosing the drums. It would cause us to use either a wheel with spokes all on one side such as Austin use or very short spokes, as the Pontiac had. As tried, the Pontiac had extremely strong self-centring in spite of the very low steering ratio which had been adopted to overcome it and which made the car difficult to control at speed. In addition to the natural increase of self-centring due to the independent wheels, the Pontiac had its spring boxes pointing forward instead of rearward, which would add 15% to 20% to the self-centring due to castoring, the angle of which was the same as the 20-HP. The other cause of increase was the 7º angle of transverse pivot lean. So that taking into account the probability of running into brake trouble with the enclosed and rib-less drums, and the greater difficulties presented by the self-centreing in the Dubonnet arrangement, we think we should still go on with our own scheme for SpectreCodename for Phantom III. Da.{Bernard Day - Chassis Design} | ||