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 front suspension spring rates for the B.V and B.50 models, investigating discrepancies.
| Identifier | ExFiles\Box 154a\4\ scan0109 | |
| Date | 30th March 1939 | |
| Da. {Bernard Day - Chassis Design} from Da {Bernard Day - Chassis Design} /DB. {Donald Bastow - Suspensions} (crossed out) c. BY Rm. {William Robotham - Chief Engineer} Rm {William Robotham - Chief Engineer} /AEM. (crossed out) c. Da {Bernard Day - Chassis Design} /SV. and Da {Bernard Day - Chassis Design} /JD. {J. Draper - Frames} (crossed out) 1306. Da {Bernard Day - Chassis Design} /DB. {Donald Bastow - Suspensions} 10/G.30.3.39. FRONT SUSPENSION SPRING RATE. B.V and B.50. Fairly wide differences have been noted between the actual measured front spring rates at the wheel for B.V. and B.50 cars, and the corresponding rates at the wheel obtained by taking the rating of the coil spring and dividing it by the square of the leverage ratio between wheel and spring in the mid position i.e. the square of the actual leverage ratio of the lower triangle lever. A search for possible reasons for these differences revealed three :- (1). Effect of rubber bushes in suspension. (2). What Olley calls the 'toggle' effect of the triangle levers. (3). The bending of the coil spring due to the angle of the lower triangle lever. (1). The effect of the rubber bushes was evaluated by a test on the suspension linkage without a spring in place, and this revealed that the rating of the rubber bushes alone is 23 lbs/in. (2). The toggle effect can be determined graphically and this has been done. PD.404 shews the construction used and the results. The reason for this effect can be understood by referring to the sketch in the lower left hand corner of PD.404 (Sheet 1) and to the triangles of forces, Figs. 1 and 2, in the lower left hand corner of sheet 2. Referring first to the sketch on Sheet 1, the three forces acting on the wheel yoke piece assembly, from the road and the two triangle levers, must meet in a point for equilibrium to exist; the road reaction B is vertical, the force A due to the upper triangle is along the line of that triangle, and therefore the direction of C, the force from the lower triangle, is also fixed. C can be resolved into components D and E respectively, perpendicular and parallel to the lower triangle, and the perpendicular one is known from the spring characteristics, and so C is known. B is then found by taking moments about the yoke piece upper bearing or by completing the triangle of forces. I presume Olley calls this the toggle effect because of the inward force on the | ||