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 discussing the steering and suspension geometry implications of fitting 17-inch rims to a 20/25 HP chassis.
| Identifier | ExFiles\Box 101\4\ scan0015 | |
| Date | 28th March 1935 | |
| TO BY.{R.W. Bailey - Chief Engineer} Copy to HCF. HS.{Lord Ernest Hives - Chair} RMG. 17 Rims on 20/25 H.P. Chassis. On N.Sch.4429 we have shown the present side steering tube and axle control geometry. We also show how the geometry of both these is affected by raising the frame .950 with reference to the axle. The side steering tube geometry is scarcely affected, but if we maintain the present length of axle control triangle, the control geometry is made considerably worse. The alternatives are to increase the length of the triangle .950 keeping the shock damper in its present mounting on the frame, or to lower the shock damper and maintain the present length of triangle. This latter we have shown on N.Sch 4430 also herewith, and it will be seen that the only important alteration called for is a new flange-end-piece for the engine supporting cross-member. In the case of the longer triangle the geometry will be very slightly better than now, and in the case of the lowered shock damper it will also be better as the shock damper is lowered slightly more than .950 We have chosen the latter alternative as being the least alteration, but if the longer triangle is preferred for production reasons no further instructions would be necessary. Another alternative is to mount the present triangle on a base .950 thick, using longer eye bolts than standard. The objections to this are - appearance, weight and the fact that the side steering tube comes rather close to the cover for the lubricating coil on the triangle end, though it does not actually foul it. In all these cases, the intention is to put an aluminium packing plate .950 thick under the front springs to maintain them unaltered. N.Sch.4426 shows the clearance between the end of the cross steering tube and the 17 wheel rim. The proposed modifications to the rear suspension we are sending shortly. Da.{Bernard Day - Chassis Design} | ||