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).
Comparison report on bumper chassis endurance and wheel flutter tests between a Bentley III and a Packard.
| Identifier | ExFiles\Box 99\2\ scan0144 | |
| Date | 28th March 1938 | |
| File Rm{William Robotham - Chief Engineer}/Les.6/MH.{M. Huckerby}28.3.38. BENTLEY III BUMPER CHASSIS. FRAME TO FB.3303. The front end of the above chassis has run on drums with 3" cams for 32 hours 10 mins. It was bumped at the rate of 115 bumps/min. The run was terminated at this point owing to the collapse of the frame. Prior to any endurance running thefollowing data was obtained - Castor angle. Pivot lean. Packard 2° pos. 1½° B.III 1½° pos. 3½° The angle between the axis of the upper triangle pivot and the ⊄ of frame is - Packard 24° B.III 22½° This difference would result in a larger end thrust on the top end of the yoke on the Packard, all else being equal. But owing to the much lower spring rate on the Packard the end thrust on the upper yoke bearing will in effect, be very much smaller. The out of centre point distances are :- Packard 2.1" B.III 2.125" Wheel flutter was found to be a maximum at 115 Bumps/min. using the Wraith type springs in the side steering tube. This is the speed at which the constant speed motor runs. With a rigid drag link the frequency increased to 132 per min. However, wheel movement about the king pins was still present at this speed, but only due to the static effect of the bumps producing a couple about the king pins. The movement was further reduced by not lashing the steering wheel. Even less movement could be effected by removing the steering wheel altogether owing to the reduction of inertia. | ||