JackMcCornack wrote:
The torque that the axle housing experiences from power is the torque necessary to keep the diff housing from walking up the ring, and a one sided 3-link would (at worst) have that half of the housing experience double the torque of a well balanced 4-link (which would share the torque equally between R and L sides of the axle housing).
Don't forget the rotational torque along the longitudinal axis of the car, which is what load the rear tires unequally under acceleration. This is what having the 3rd link offset to the right side of the car can balance out. But more importantly, don't forget about braking. Acceleration may be limited by the engine, but braking is (or at least, should be) only limited by the tires. And you're now leveraging that braking from the left side of the car through the entire length of the axle. As with any torsion spring, the longer it is without increasing its diameter, the softer its rate becomes and the more total deflection you'll have. So, stiffening the axle with gussets might still be best done on both sides.
JackMcCornack wrote:
Maybe stick with the 4-link, but change one rod end on each side to a bushing?
Why switch to a bushing on both sides? The 4th link is the only one over-constraining the system. Give it some compliance and the rest
should work as intended, while still providing some extra support to the axle when needed...And if not, then stick a bushing in the link on the opposite side too.
a.moore wrote:
With the Locost 4-link the housing sees minimal torsional loading (well until you have binding).
Under acceleration, the same amount of torque is being transmitted through the housing, regardless of 3-link or 4-link. The main difference is that each side of the housing is loaded with half the torque in a 4-link, and just one side is loaded with all of the torque in the offset 3-link. So it's not minimal, it's simply half. Therefore, the housing must basically be strong enough to support 2x the load in the heavily offset 3-link vs a 4-link. Braking is another story, but a 4th link that is compliant under acceleration but rigid under braking, would help resolve that.
Warren Nethercote wrote:
To quote Des (p. 64.) "Unfortunately, such suspension arrangement is not good for circuit work and , more specifically under hard braking (axle tramp), but for drag racing it's ideal."
I don't think Des is giving credit where credit is due. The Jaguar C-Type used a substantially offset third link that fully balanced the torque inputs, to provide equal loading of the tires under acceleration, and was not only successful...But is still considered by many to arguably be one of the best live axle designs. For 'circuit' use the possibility of 'axle tramp' at the onset of tire-lockup provided fewer drawbacks than advantages on acceleration. It was actually for
street use, where panic braking was a larger concern, that they stuck with the 4-link. Again, the compliant/locking 4th link would be great....But more realistically, as noted above, I think that simply adding some resistive compliance to the 4th link via a bushing could be an easy compromise to start with.