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 memorandum discussing the causes and potential solutions for radiator shimmy.
| Identifier | ExFiles\Box 28\5\ Scan006 | |
| Date | 10th February 1930 | |
| Y457 TO HS{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} FROM EV.{Ivan Evernden - coachwork} EV{Ivan Evernden - coachwork}3/10.2.30. Y457. x7250 x7008 x7380. COPY TO EY. DA.{Bernard Day - Chassis Design} SG.{Arthur F. Sidgreaves - MD} RADIATOR SHIMMY. With reference to your Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}2/MJ.6.2.30. suggesting that we should change to harder rubber bushes for the scuttle isolation on P.2., we do not think we should do anything of this sort without tests having been made and a report circulated. We say this because Da.{Bernard Day - Chassis Design} has reported to us that if the body be mounted on a single central point of suspension at the front in the place of the present two rubber feet all traces of radiator shimmy disappear. It would appear, that by adding the stiffness of the body ( torsional stiffness) to the chassis the conditions which produce radiator shimmy are produced. Therefore, if we so attach the scuttle and dash so that there cannot be any appreciable movement between the two, we must be doing something to increase the tendancy to shimmy. As instructed by DA.{Bernard Day - Chassis Design} we are setting out a design for a single point of suspension of the body on the crossmember of the chassis just aft of the gearbox. This is a very bad point as far as the coachbuilder is concerned as the long cantilever of thebody over the forward support will make De Ville fronted cars impossible to make. We have had the forward supports back in this position and have had to move them forward for this very reason. Moreover, the movement at the dash will be twice what it is now. We found this to be the case when the supports were in the moved back position. If, with this new suspension, the scuttle and dash are tied together so as to bring this movement back to reasonable limits, the body will be stiffening the chassis torsionally and the object of the suspension will be lost. We would suggest that the following experiments be tried, if you have not already done so. (1) Remove the forward subframe suspension bolts and the scuttle isolation bolts. If removing the torsional stiffness of the body from the chassis cures radiator shimmy, this should do so. (2) Mr Royce has suggested the following suspension many times:- The front of the body is carried on a central pivot on the back of the pot in the dash, not far below the bonnet hinge. Plates to stiffen the body at the scuttle are bolted to the subframe, and at their top take the ends of the cross-beam. Rubber blocks are placed between the base of the scuttle/pillars and the dash flanges to act as dampers. We prefer this scheme to the one suggested by DA{Bernard Day - Chassis Design}, for the following reasons- (1) It is easier to fit into an existing chassis. (2) The support is in a better place for the coach-work. (3) A large amount of torsional movement can be permitted between the scuttle and the dash without it being seen by the driver, the pivot point being close to the top bonnet hinge. | ||