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).
Steering geometry issues and proposed solutions for B.III and B.50 chassis.
| Identifier | ExFiles\Box 112\3\ scan0013 | |
| Date | 24th May 1938 | |
| 850 also To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} c. Da.{Bernard Day - Chassis Design} c. Da{Bernard Day - Chassis Design}/DB.{Donald Bastow - Suspensions} c. HPS.{Horace Percy Smith - Experimental Factory Mgr} Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer}6/MH.{M. Huckerby}24.5.38. B.III & B.50 STEERING. We are very concerned about the steering geometry of B.III. As originally built, chassis 7.B.V. wandered very badly. We fitted to the centre steering lever ball pins which made the inner ends of the cross steering tubes 0.500 lower than the designed position. This improved the steering considerably but wandering still occurs at high speeds on undulating roads. We attach a print showing these geometry errors. They were obtained by fixing the centre steering lever and measuring the angular movement of the road wheel while raising it from full rebound to full bump. The effect of altering the height of the centre of the cross steering is to move the error curve vertically. The position of the dotted curve No.(3) is estimated but we consider that this estimate is quite reliable as the measured curves agree with calculated curves. The conditions we have tried on the road are Nos.(1) and (3). No.(3) was very bad and No.(1) still not satisfactory. We anticipate that No.(4) will be worse than No.(3) and that No.(2) which we intend to try will be no better than No.(1). The B.50 chassis should be identical so far as steering geometry is concerned to the original condition of 7.B.V. The difference must be due to manufacturing errors. Even if we were able to make the steering reasonably satisfactory by precise positioning of the error curve it would be sensitive to manufacturing errors and the normal height of the front of the car. We consider that in addition to finding the best height of the cross steering tube ends it will be necessary to reduce the amount of the geometry error. This can be done by increasing the length of the side steering lever attached to the road wheel with the result that the same linear error at the cross steering tube would cause less angular error at the wheel. The geometry of B.III is at present worse than either Ph.III, Wraith or Packard owing to the shortness of this lever. As the lengthening of the side steering lever would involve the torque arm, cross steering tubes, and centre steering lever we regard the matter as urgent and we suggest that Da{Bernard Day - Chassis Design}/DB{Donald Bastow - Suspensions} should determine the best compromise that can be achieved on paper. We will then mock this up on 7.B.V. for road test. Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} | ||