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).
Letter from F.H. Royce discussing the causes and solutions for high-speed steering wobbles, known as 'sobbles'.
| Identifier | ExFiles\Box 28\4\ Scan312 | |
| Date | 21th August 1925 | |
| Copy to CJ. BJ. HS.{Lord Ernest Hives - Chair} PN.{Mr Northey} BY.{R.W. Bailey - Chief Engineer} EP.{G. Eric Platford - Chief Quality Engineer} 4457 "ELMSTEADHenry Royce's home in West Wittering" WEST WITTERINGHenry Royce's home town, CHICHESTER. Senor C. de Salamanca, MADRID. 21st. Aug. 1925. My dear Carlos, STEERING. X.457 X.8430 X.4565 Regarding the high speed sobbles this question has had our constant attention since they first appeared in conjunction with an attempt to use low pressure tyres. The problem of the phenomenon has now been almost certainly demonstrated to be governed by the tyre pressure, the weight of the axle, tyres, and wheels, and out of balance. It is pretty certain there is nothing physically wrong with the chassis or steering gear, though we are hoping to render the phenomenon less manifest to drivers, and also to those in the car. A certain way to avoid it is to have the front road wheels in proper balance, because each kilogram exerts a force of 100 kilos, at 60 m.p.h. The out of balance should not exceed one-tenth of a kilo. To keep the tyre pressure high both increases the speed at which it occurs, and which you probably will not touch, and keeps down its severity. The third point - but not yet reported to positively have marked influence - is to keep the front shock dampers in an effective state of tightness. The reason why our big chassis shews the phenomenon is because of its increased speed, and weight of the front axle, due to fitting front wheel brakes, and the practice we have recommended of using lower pressure in the tyres. If the phenomenon is not of frightful severity it can be passed through by running faster. Fortunately also if it appears at a very high speed it is much less severe. We may add that it is quite an epidemic affecting all makes of cars, especially big high speed ones with low pressure tyres. Yours very sincerely, Sgd.F.H.Royce. | ||