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).
Comparison of Dubonnet and Cadillac wishbone suspension systems for the Spectre model.
| Identifier | ExFiles\Box 173\3\ img126 | |
| Date | 16th April 1934 | |
| - 3 - S.1/HP.16.4.34. The RR. scheme can have linkage of similar proportions to the Cadillac to raise the rolling base but the Dubonnet is definitely unalterable. So far however as we can see any great move with respect to this feature in connection with low rating free springing can only be made by retaining the present solid axle anchored to the chassis by suitable radius rods and links etc. but the necessity for this remains yet to be proved. No apology is offered for going into this question of rolling at some length as at the moment it can be said to represent the largest unknown factor in the situation. With regard to other points in connection with front suspension the Dubonnet has limitations as regards brake and wheel design not possessed by the Cadillac and RR. schemes whereby the brake drum has to be positioned within the road wheel with the result that the brake and tyre cooling facilities are reduced and the wheel hub has to be large enough to envelop the brake drum. Also our present types of detachable hubs would be unsuitable and the large pot bolted on design would probably be required. As the road wheels must be interchangeable all round this would affect the back axle as well. The brake operation too is practically compelled to be either cable or hydraulic. The Dubonnet principle is also open to constructional criticisms and although it is simple to lubricate we should agree in view of the sum of its limitations and objections that it is not to be preferred to the wishbone scheme. Comparing the Cadillac wishbone scheme and the one with which RR. have experimented hitherto, the former has the advantage that perfect steering geometry can be obtained with less complication and fewer pieces. There are other arguable pros and cons but from a design point of view this is the main advantage which stands out in front of everything else. We are therefore setting out a suspension scheme for the SpectreCodename for Phantom III on Cadillac lines but retaining the RR.character. | ||