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).
Calculations for ride and roll rates on the 'Myth' project, using a Vauxhall 12 car as an example.
| Identifier | ExFiles\Box 110\3\ scan0003 | |
| Date | 31th July 1940 | |
| Ev.{Ivan Evernden - coachwork} from Rm{William Robotham - Chief Engineer}/GB. c. Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} Rm{William Robotham - Chief Engineer}/GB.1/ML.31.7.40. 746 ROLL BARS ON MYTH. In your note Ev.{Ivan Evernden - coachwork}7/ML.5.7.40. the following occurs :- "Rm{William Robotham - Chief Engineer}/GB said that we shall require a rear roll bar in any case -" It should be understood that this only applies if the usual suspension deflection of 7" is adhered to. In order to see the reasons for this statement, suppose we take a Vauxhall 12 car (which is probably of a similar size to the Myth and give it a 51" front track, a 52 1/2" rear and suspension deflections - front and rear - of 7". The ride and roll rate figures will then be something like this :- Unsprung weight per wheel - front - 50 lbs. " " " " - rear - 90 lbs. 4 pass: wt. sprung - front - 550 lbs. " " " - rear - 670 lbs. Front suspension rate = 550/7 = 78.5 lbs/ins. Overall front ride rate (tyre rate 1,000 lbs/ins) = 72.8 lbs/ins. Overall front roll rate (no stabiliser) = 138 lb. ft/deg. Rear suspension rate = 670/7 = 95.7 lbs/ins. Rear suspension roll rate allowing 30% stiffening due to spring torsion and assuming a spring separation of 41" which is about as much as can be obtained = 152 lb. ft/deg. | ||