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).
Implications of wheel and tyre dimensions on the steering geometry for models B.111 and B.50.
| Identifier | ExFiles\Box 100\2\ scan0049 | |
| Date | 28th April 1938 | |
| Rm.{William Robotham - Chief Engineer} c. Da{Bernard Day - Chassis Design}/ c. BY c. De/Ev.{Ivan Evernden - coachwork} c. Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} c. Rm{William Robotham - Chief Engineer}/APH. CROSS STEERING LEVER. B.111 & B.50. 1300 Replying to Rm.{William Robotham - Chief Engineer}12/R.23.3.38. the use of a 17.000" diameter rim for B.50 of width not greater than 4.500", means that the closest clearance between steering ball joint and tyre, accepting the limitation of a common steering lever for B.111 and B.50 will occur on B.111, with rims 16.00" diameter and 4.500" wide. Taking full advantage of this, for the lock angle of inside wheel of 41°, the lock angle of the outside wheel can be increased to 29°, as compared with the 28° possible when a 16.00" rim, 5.00" wide has to be catered for, and the effect of this is to give a turning circle diameter of 40.45 ft. as against 41.12 ft. with the 5.00" rim. (These figures are for B.111). To obtain this result, the dimension 0.050" of PD.134 is increased to 0.250". B.50 would then have a turning circle of 42.45 ft. diameter, the difference being due to the longer wheelbase. Since the final wheel and tyre size for B.50 cannot be decided at this stage, see Da{Bernard Day - Chassis Design}/EV.{Ivan Evernden - coachwork}15/N.21.4.38, it seems best for 1.B.50 to have the lever of PD.134. Any improvement in turning circle is obviously welcome, and from that point of view the use of 6.500" section tyres on both B.111 and B.50 would be an improvement. To obtain benefit from the increased rim diameter for B.50 it would seem logical to use a 4.500" wide rim, as on the 16.00 diameter rim of B.111. Da{Bernard Day - Chassis Design}/DB.{Donald Bastow - Suspensions} | ||