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).
Car springing, weight distribution, and comparing specifications between Springfield and Derby plants.
| Identifier | ExFiles\Box 43\2\ Scan095 | |
| Date | 8th February 1926 | |
| Oy3-E-2826 -4- February 8, 1926 Springing complete cars. It is difficult to compare your formulae with ours because:- (a) We work back from the complete car weights (and are now making the custom coachbuilder give us these accurately front and rear, as well as our own coachworks). (b) We make no allowance for torque and driver and spring both sides of the car alike. (The torque is negligible for 95% of the time and the driver's weight, if it needs any consideration, opposes the effect of road camber. When cars are sprung unequally the weak side tends to settle in use and the car gradually gets a noticeable tilt towards the weak side, leading the complaint.) (c) Our springs are flat at rated load. Fronts have 3-1/2" deflection and rears 3" deflection. Your springs have 1/2" negative camber at rated load. Fronts have 3.100" deflection, rears 3" deflection. The attached standard springing list of October 20, 1925 will serve to give you all necessary information on what we are doing. Attached list of weights in detail of June 26, 1925 will show how the weights are made up. To judge by 12-MC your long wheelbase cars are 300 lbs. heavier in front than ours, made up approximately thus:- Springfield Derby Difference Unsprung weight Wheels, axle and 2/3 front springs 350 510 160 (460 + 50) Sprung weight (Sedan empty) 2100 2240 140 (In my letter to By.{R.W. Bailey - Chief Engineer} I did not know that your allowance of 460 lbs. did not include 2/3 of the spring weight which is the standard allowance for front springs - 1/6 for cantilevers.) On this assumption we have drawn up a preliminary springing schedule thus: Road. Phae. Tour. Sal. E.D.Cab. Full Cab. Sedan Limousine Front 1150 1150 1150 1150 1200 1200 1200 1200 Rear 1800 1800 2000 1900 1900 2000 2000 2000 | ||