It seems to me that there are some valid points of contention in this.
Firstly, I don’t think there is only ONE reason tricycle tractors have disappeared. Stability of “stance” against tipping is certainly improved, due to weight transfer.
And..... Weight transfer is different for each wheel in-motion as compared to each wheel when static.
However, This weight transfer affects steering capability also.... a wider footprint is better in soggy terrain because a 4-wheel tractor simply has more traction than a trike. (True trikes were modified to V-trikes to improve steering control in soft soils....and spreading the front stance created additional steering effectiveness.).
Weight transfer is adversely affected by short wheelbase during braking.... and adversely affected by narrow track-width when cornering. Sleddog is likely thinking about cornering weight-transfer when he endorses wide front wheels. The reduction in weight transfer to the outside wheel is improved as the stance widens. (Think of a pendulum beneath the center.... How close will the pendulum weight approach a wheel during cornering. A wider stance means the pendulum weight remains closer to the center rather than closer to the outside wheel.)
BUT the problem arises when uneven terrain is encountered. When that happens with two stiff axles then at least one and sometimes two wheels can be unloaded in the extreme. THEN you have a serious “tipping” problem. (Imagine a tractor on a sharp ridge running diagonally. If the left front wheel and the right rear wheel are in the air because the RF and LR are the only ones on the ground.)
Not only would that create a stability issue, it also results in loss of traction, and loss of steering.
It would be extremely complicated/expensive to design a tractor with independent wheel suspension.... and it would likely result in a loss of overall strength unless a very extensive and heavy framework were created.
Pivoting the center of the tractor would address the issue. If the front axle and rear axles could rotate laterally with regard to each other...then all 4 wheels would remain on the ground...and stability and steering and traction would be less affected. But pivoting a tractor in it’s center.....which relies upon it’s engine/transmission castings for basic construction would really be troublesome.
Simple solution: Pivot only one axle.
Since a traction is mainly directed to the larger rear wheels it is simpler to pivot only one axle... the front axle. Simple is usually better because it can be stronger with fewer components.
