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).
Complaints and proposing solutions for the Phantom suspension system.
| Identifier | WestWitteringFiles\O\April1926-June1926\ Scan28 | |
| Date | 17th April 1926 | |
| TO R.{Sir Henry Royce} FROM DA.{Bernard Day - Chassis Design} C. to - HS.{Lord Ernest Hives - Chair} ORIGINAL DA{Bernard Day - Chassis Design}2/M17.4.26. PHANTOM SUSPENSION. X8420 44048 X8430 (1) With reference to the complaints about the suspension at moderate speeds over smooth roads it was suggested in Derby that the immediate way to overcome this is to return to the original flexibility of the springs, that is 3 1/2" initial deflection instead of 3.1 and reduce the braking by a corresponding amount. If the braking on the front is now 33 1/3% of the total braking the necessary reduction would be 12 1/2% of this, that is, the loss of about 4.2% of the total braking. The object of this is to reduce the danger of the front axle turning over under the braking, and the steering taking charge. (2) In order to retain the present amount of braking and yet use more flexible springs without getting anymore turn over from the axle we suggest that it might be possible to lengthen the springs still further backwards, for which there appears to be room. We have calculated the springs and shall shortly be sending you a drawing giving an outline of the suggestion. We believe that we could arrange springs like this without the natural tilting of the axle which results from the eccentric loading when the spring is bouncing being anything very much. (3) We are also investigating the possibility of applying a parallel control of the type originally suggested by you, that is, with the spring as one of the torque members, but with the rod above the axle instead of underneath it, and propose to send you a preliminary scheme of this. (4) We also wonder whether the scheme on the Lancia Lambda would not be worth a preliminary investigation. The coil springs are very much lighter than the plate springs for an equivalent stress, (we calculate that the coil spring would weigh 15 lbs. against 62 lbs. for the plate spring) and the shock damper is combined with the pivot. The pistons and guides are of course additional weight which would tend to offset the weight saved on the springs, but the bulk of this is sprung weight including the axle itself. It appears as though the arrangement could be carried out by bolting something equivalent to the present axle forging across the frame side members and constructing the pistons and guides out at the ends in a manner similar to the present pivot joints, but of course larger. This arrangement one thinks will also allow of a much deeper radiator, which might be an additional advantage. We are also preparing some data from the information we have at our disposal as to the position of the centre of gravity on the different cars, the relative spring stiffness with the probable resulting effect on the rear seats of blows from the front delivered by springs with some internal friction and shock dampers, on the theory that the front is a forced oscillation of the sprung mass of the car about its centre of gravity by the road irregularities acting on the front axle. (1) | ||