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Tandem-axle trucks scream old-school minitruck in a way that I don't think any other mod really can. Most of the other popular mods were simple in comparison.
Body kits bolted on-of course many were molded in, but that's relatively easy. High-offset wheels are obviously simple, and wild "heartbeat" paintjobs aren't necessarily easy but were still just paint. If you screwed up the paint, you still had a completely driveable vehicle. Tandem-axles on the other hand required not only major frame work but extensive body mods as well. So how would we go about building a tandem-axle truck today? Looking at the history of minis over the last 20 years has shown a major increase in quality and time invested. What used to be a fairly simple show scene to compete in has been filled with trucks reaching hot-rod quality and beyond. Aaron Iha built a tandem-axle dualie a couple of years ago, and it was definitely all you would expect from a builder of his caliber. Both axles were drive axles, and the suspension was far from simple or thrown together. It was a perfect demonstration of thought and fabrication built into an old idea. But what about a minitruck? Space is more limited, airbags are a necessity these days, and good ride quality has become expected.
Being the geek that I am, I have thought about this conundrum long before Mike ever told me that he's doing a tandem special issue. So how would a self-proclaimed suspension designer build a tandem-axle suspension these days? I have two different scenarios: one that has two driven axles and one that has only one driven with the other just along for the ride.
In this design, both axles are driven so I have to concern myself with making sure that the drive forces are properly transferred to the chassis. I don't use any computer programs to help me figure out what works best, so I can only rely on my gut. The front axle has a link system with a favorable instant center, and the rear axle is attached to the front axle through links that also follow a similar instant center. The 'bags and shocks would need to be half as stiff as typical because there are four of them.
Here we have a more simple system because the rear axle isn't driven. What that does is remove any concern of proper geometry because it doesn't create any forces that we need to contend with. The front axle would have the same link system as the front axle in the first design, but the rear axle can have a reverse four-link (yes I said reverse four-link). The 'bags and shocks would still need to be extra soft to keep the ride tolerable.