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).
Technical analysis of wheel wobble, its causes, and potential solutions including engine mounting.
| Identifier | ExFiles\Box 170\3\ img063 | |
| Date | 15th July 1935 guessed | |
| -7- kingpin line from front to rear, inertia moments are set up around the kingpin which promote wheel fight. The curvature of the path of the wheel centre is important because inertia forces produced by the curvature have a high frequency which will not cause wheel fight. (4) It follows from (c) that reduced overhang from wheel centre to kingpin is important in reducing wheel fight. Reduced offset on the ground obtained by increasing the kingpin angle, has little or no effect on these forces. (5) Changing wheel camber as the wheel moves up and down. Such an up is produced in "pivoting axles" or more moderately in the "bent axle". Lacking this however, gyroscopic action is one of the connecting links between the wobble motion and the tramp motion which causes the cycle to build up and continue. It is acknowledged however that this sort of wheel motion is highly desirable for bouncing cars. We are not sure whether the wheel motion may be used in flexible suspensions without trouble from shimmy, but it appears that on subonnet suspensions, in which the tendency is rather towards low speed wobble than shimmy, the wheel motion may be used in moderation without any consequent wheel fight. (6) From (e) above it follows that the puller type subonnet has an advantage in requiring less caster offset for a given "road feel" because of the centrifugal forces on the boxes. In the pusher type it is necessary to incline the kingpin back or the wheel centre so as to bring it more or less in line with the centre of the swinging masses. (7) Engine mount Pure low speed wobble can be cured almost completely by so mounting the engine on its rubber support that its rocking in long. is the material frequency of the low speed wobble. When the engine is mounted in this way a violent wobble may be built up with the engine blocked, which instantly stopped when the engine is released. (The... | ||