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).
Comparing steering geometry errors between the B.III and Packard suspension systems.
| Identifier | ExFiles\Box 127\1\ scan0352 | |
| Date | 21th March 1938 | |
| To Da.{Bernard Day - Chassis Design}, from Da{Bernard Day - Chassis Design}/DB.{Donald Bastow - Suspensions} c. to By.{R.W. Bailey - Chief Engineer} c. to Rm.{William Robotham - Chief Engineer} c. to Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} c. to Ev.{Ivan Evernden - coachwork} 1086. also 450 Da{Bernard Day - Chassis Design}/DB.{Donald Bastow - Suspensions}7/N.21.3.38. F.J.H PLEASE DISCUSS Rm{William Robotham - Chief Engineer} Steering Geometry Errors, B.III and Packard. It was pointed out during the early stages of its design that the cross steering geometry of B.III with Packard type suspension would be worse than that of the Wraith ( see E/EV{Ivan Evernden - coachwork}/DB.{Donald Bastow - Suspensions}1/M.8.5.37). Now that we have had drawings of the Packard suspension itself from By/Ald{F. Allwood - Experimental Design}, we have/found that the cross steering geometry of B.III is worse than that of the Packard, the chief difference being in the length of the cross steering lever on the wheel, which is approximately 7.5" on the/Packard and 5.5" on the B.III. The shorter lever/of B.III is due to the lower car, for a given sideways position of the steering joint it must follow round the rim as it drops downwards. A 7.5" lever on B.III would bring the steering joint almost opposite the widest part of the tyre. Investigation of the Packard for a bump of approximately 2.75", that of B.III, shows a geometry error of only approximately 0º6', whereas that of the B.III is then 0º40'. On the full rebound of the Packard, approximately 2.6", the geometry error is 0º33', and at the same rebound figure the B.III has 0º18'. It is obvious, therefore, that the Packard geometry has been made to favour the bump condition more than the B.III, and to achieve a similar condition on B.III it is necessary to drop the ball joints on the centre steering lever. A position for these 0.250" below the present position reduces the bump error to 0º18' and increases the rebound error to 0º52'. Bump error becomes so small as to be immeasurable if the centre ball joints are dropped 0.500", the error at 2.5" rebound being then 1º17'. Da{Bernard Day - Chassis Design}/DB.{Donald Bastow - Suspensions} DB{Donald Bastow - Suspensions} | ||