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).
Investigation into the function and issues of 20% stiffer rear springs for continentally sprung cars.
| Identifier | ExFiles\Box 67a\1\ scan0281 | |
| Date | 2nd February 1927 | |
| X8440 Please return To BY, from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to Wor.{Arthur Wormald - General Works Manager} Hs{Lord Ernest Hives - Chair}/Rml/LG28. 2.2.27. REAR SPRINGS - CONTINENTALLY SPRUNG CARS. X8440 X2628 Some time ago we took up the question of buffer clearance on the rear springs of cars sprung for the Continent with F.{Mr Friese} Dept. Since then Sales have been complaining about the springing of cars in Spain etc. We have therefore been investigating the position of the 20% stiffer spring which appears to be the main cause of the trouble. As we see it, the function of the 20% stiffer spring is to provide a means of - (a) Keeping the axle off the buffers on the worst Continental roads where with normal springs the frame might suffer. (b) In addition to providing a greater spring load before the axle hits the buffer, to ensure that the rear spring shall be stressed no higher than at present. These two requirements could obviously be fulfilled by fitting a stronger spring. However a 20% stronger spring makes the car look as if it was perched up on stilts and raises the centre of gravity which is undesirable. Therefore what we require is a 20% stronger spring with 20% less initial camber, to give the car the benefits specified in (a) and (b) with a normal low riding position. Therefore, from this reasoning, unless we have mistaken the function of a 20% stiffer spring, we should expect a 2000 lbs. 20% stiffer spring to be a 2400 lbs. standard spring with 20% less initial camber. Actually however, we find that a 2400 lbs. standard spring has 11 plates which is the number contained by a 2000 lbs. standard spring. This gives us the impression that we are getting absolutely nothing from the 20% stiffer springs except more uncomfortable riding, because in an attempt to put up the load with these springs before the axle hits the buffer they will be over-stressed - (that is, always assuming that the standard spring is correctly designed and is only just strong enough for its load.) The buffer clearance which is assigned to these springs rather confirms this impression. Until quite recently, we understand that all 20% stiffer rear springs were sent out with 2.400 ins. buffer clearance. Why such a buffer clearance was selected is somewhat obscure. If we are correctly informed however, it means that whereas a car when contd :- | ||