For fear of stating the obvious, as swing shackles are an essential component part of any leaf sprung suspension system, and on a traditionally chassis Morgan we have rear mounted swing shackles, when the rear suspensions is under compression a Morgan axle not only rises, as the leaf spring flattens and so lengthens it also must also be allowed to roll backwards with the shackles.
If you fit a rigid bar tying the axle directly to the chassis, the axle can no longer roll back, the anti-tramp bar used by Morgan is just this, it is also therefore no different to removing the rear spring shackle and replacing it with a fixed pivot point on the chassis. Swing shackles exist for a reason, removing them or fitting a rigid bar tying the axle to the chassis (essentially the same thing) is to completely ignore the natural flattening and disregard the consequent lengthening of the leaf springs under compression.
In such a setup the poor leaf spring ceases to function as a spring, compression loads are now effectively moved along the spring length end to end, it will therefore largely function as a solid bar itself. Of course the Morgan ant-tramp bar is not strictly speaking fully rigid, while it does have pivots at both ends these should be ignored as they will have no effect on the compression and expansion loads placed on the bar as the axle attempts to roll back and forth, so the only reason the Morgan ant-tramp bar is not fully rigid is because it's been fitted with a big rubber bush.
Goodness. That's an excellent desription of what's happening in engineering terms, thanks. I had drawn the same conclusion regarding the seemingly illogical and pointless ATB (especially just one), but having re-fitted it at least I'm not now tripping over it on the bathroom floor where I had stored it. I may de-mount it again next spring when I've covered some more miles, but next time I will get a ratchet ring-spanner as getting to that bolt from above (I don' t have a ramp) is a pain.
