I've been thinking a bit on suspension designs recently, and thought I might see what people's thoughts & experience is with suspension system modifications - things like raising, lowering, (blocks, shackles, longer or shorter springs), wheel-base changes (re-locating axle placement pins, etc),
suspension re-design (solid axle swap, incorporating removing of torsion-arm suspension & replacing with alternative (usually longitudinal leaf springs), and consideration of other types (someone could, for example, try a transverse leaf-spring set-up, or coil-spring & locating bar linkage)

So, just throwing this topic out there...

 

Now, for a bit of my experience, and some things that I had to consider..

My set-up goal was a Tandem-Axle, Dual-Drive rear-wheel-drive, for increased wheel-base & load-hauling capacity.

I wanted to maintain an even load on the axles to prevent breakage, thus a balancing system was required - I settled for an equalized leaf-spring solution, commonly used on trailers & heavy trucks.

I also wanted to use stock-width (~2 3/8") springs, which would fit the stock u-bolts and clamping plate. Shorter springs are needed with multiple axles, and they were not available, in that combination.

But -
Leaf springs DO NOT HAVE TO HAVE EYES at either (or both) ends of the spring to function. Designing for a Double Slipper-type spring mount (as is used on some heavy trucks), requires a system to locate the axle (as does a coil-spring set-up). The Front Eye usualy secures the axle to the frame, allowing the axle limited travel forwards & backward, as the spring arch changes. Not a detail usually thought about...

This travel is related to the vertical travel of the axle & chassis, with either an anchored leaf spring, or placement torque rods, or arms... (and, this also requires the driveline to be able to travel forward & backwards, to follow the differential...

So, I wound up with a Tandem Axle, 4 Double-Slipper Springs, side-ways placement by the springs & the spring brackets, and longitudinal placement by 4 'dog-bone' torque rods or placement bars, angled to keep longitudinal shifting of the axle to a minimum (the axles will shift rearwards under light load, then forwards as the load gets heavier - this is related to the angle of the placement bars).

All in all, the design seems to work well enough, other than the fact that I don't have a lot of weight to the drive axle, and it gets stuck easily off pavement...