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).
Analysis of the 'Myth' model's front roll rod, its stiffness, and impact on vehicle handling characteristics.
| Identifier | ExFiles\Box 110\3\ scan0055 | |
| Date | 17th April 1941 | |
| To Rm.{William Robotham - Chief Engineer} from Ev{Ivan Evernden - coachwork}/DB.{Donald Bastow - Suspensions} Copy to Rm{William Robotham - Chief Engineer}/HH. Ev.{Ivan Evernden - coachwork} Rm{William Robotham - Chief Engineer}/GB. Ev{Ivan Evernden - coachwork}/DB.{Donald Bastow - Suspensions}3/ST.17.4.41. MYTH FRONT ROLL ROD. ------------------- PL.545, the original of which is attached to Rm{William Robotham - Chief Engineer}/HH's copy, shows the front roll rod and front bumper brackets for Myth. The selected size .594" diameter gives a rating at the wheel of 31.2 lb/in., assuming that the rubber connections and bushes have their usual effect. This is in the neighbourhood of half the spring rating of 102 lb/in. at the wheel and is therefore the maximum that should be employed. With this roll rod, the front springs supplied by the Tempered Spring Co. Ltd. and the rear springs of Rm{William Robotham - Chief Engineer}/GB.8/ST.13.1.41, and assuming that the stiffening of the rear springs on roll due to torsion is 20%, the overall roll stiffness of the car (including the tyres) is 431 lbs.ft./deg. This, on the fully laden weight of the car, corresponds to 312 lbs.ft/deg./2001bs.{A J. Barnes - Assistant Manager} rolling weight. For the production B.V with .750" diameter front roll rod, the front spring rate in roll is 193 lb/in., the rear spring rate is 136 lb/in. and, taking the stiffening of this due to spring torsion as 50% (the extra amount over Myth being due to less rubber at the spring centre between spring and axle, and metal spring eye bushes instead of Harris rubber bushes), the overall roll stiffness is 654 lb.ft./deg., again including the effect of the tyres. For an all up weight of 41 cwt. laden (35 cwt. car + 6 cwt. passengers and luggage), this corresponds to a figure of 313 lb.ft./deg./2000 lbs. rolling weight. The ratio of front to rear roll stiffness of the B.V is 1.43, the corresponding ratio for Myth is 1.2. This will probably still give an understeering car, but at the moment, I have not sufficient information to calculate the handling characteristics. I may be able to get this information and if so will do the calculation and circulate the results. The maximum stress on this roll rod is higher than that of the B.V. and, for this reason, it may be found that the material to British Standard Specification 576 is not good enough. It should be worth trying in this, however. Ev{Ivan Evernden - coachwork}/DB.{Donald Bastow - Suspensions} Original to Rm{William Robotham - Chief Engineer}/HH. Prints to Rm{William Robotham - Chief Engineer}/HH, Ev{Ivan Evernden - coachwork} and Ashby. | ||