Underland: The Un-Overland

Background:

Back in early February 2002, the sum of my R/C work was documented in my fledgling little site known as UltimateTraxxas.com. The site's EZBoard-hosted forums had right around 500 registered users and just topped 5,000 total posts. However, something very small had just happened that would lead to very large changes in the progression of my experience in the hobby. I had purchased my first non-Traxxas R/C's, two Kyosho Mini-Z's (click for a pic); one for me, one for my girlfriend. My own, the red Porsche, was destined from the start to undergo a massive transformation that would surely turn the rapidly exploding Mini-Z world on its lid. I gave a few nebulous hints on the forums about what I planned to do, without giving it away. While most Mini-Z enthusiasts were going crazy with stiff-handling suspension mods and doubled-up "turbo" units for speed, I was moving in the exact opposite direction. Secretly, I was working on the first total Mini-Z offroad conversion.

Most of the modifications were done within about 6 weeks, but unfortunately for me, I never got around to calling the project "done" and revealing it to the public. Too many other things just kept creeping up, higher on my list of priorities. A year went by and before I knew it, Kyosho had unveiled the Overland. So much for my chance at great Mini-Z fame!

I had originally planned to reveal the project on UltimateRC.com (then only a concept in my head), but I had trouble convincing myself to give it a go. In Fall '03, with the release of MiniOffRoaders.com, I ran out of excuses, and so here it is, Underland, the Mini-Z offroad conversion that came a year before the Overland, but that I was too stupid to unveil to the public.

Modifications:

There were three stages in turning the diminutive, low-slung Mini-Z, a vehicle that would practically high-center on a quarter, into a somewhat respectable scale offroader. First, the suspension would need to be softened up dramatically, giving the vehicle some uncharacteristic articulation.

Up front, I first completely removed the front tiebar which tended to act as an anti-roll device. On the stock 'Z, the front springs are mounted on this bar, so I needed a new place to put them. By trimming both the tops & bottoms of the axle carriers, I was able to mount the springs on the kingpins in 1/12th-scale style, while giving the vehicle more static ride height and lowering the tension on the springs. For even more downtravel, I trimmed down the steering arm that protrudes from the servo to allow the knuckles (and thus the entire axle carriers, spindles and front wheels) to slip another millimeter or so farther down. Finally, I picked up an aftermarket spring set and installed the softest ones in the kit.

At the rear, I started out by dramatically Dremelling down the stock "H-bar," the sole mechanical attachment between the rear motor/axle pod and the main chassis, and the only way the rear half of the stock Mini-Z had any "suspension" action. By removing material from this bar, the stiffness of the joint was rapidly reduced, adding quite a bit to the car's articulation. Not only did this give rear section the ability to twist in a rolling motion, though, but it also allowed the whole assembly to bend & turn as viewed from the top. By the time I was done softening up the H-bar, it was a wet noodle and I needed to add another source of stability to keep the rear axle reasonably located.

A 3-shock setup with graphite mounts would do the trick nicely. I assembled the rear lower mount below the h-bar instead of above as had been recommended in the instructions, to reduce the amount of preloading on the side springs and soften them up. I also again installed the softest springs all around that I could find.

While getting used to the layout & engineering of the car, I went ahead & added a bearing kit, Delrin servo gears, and some black gloss-coated alloy rims. A little bit of speed & efficiency, a little bit of durability, and a little bit of "bling" factor. Can't complain!

The final two steps of the transformation would be the fitting of an appropriate body and some off-road tires. On the body, I got extremely lucky. A trip to a hobby shop local to my job at the time yielded a 1/35th scale military plastic model kit by Italieri. It was kit #273, the "Commando HUM-V." Hummer it was! The body had absolutely perfect dimensions and was entirely original. It took a good deal of Dremelling and selective building to get the innerbody to fit around the Mini-Z chassis, but it worked out well in the end. To mount the shell, I simply transplanted the original side body mounts from the Porsche body to the Hummer, gluing them on & painting them. The entire shell was finished in a Tamiya gunmetal gray.

For tires, I found some good-fitting treads in the toy aisles at Target. A customizable quad/ATV toy set yielded some very wide, thick tires which, though harder in compound than I wanted, slipped right onto the stock Mini-Z wheels. I just had to trim some material away from the front of the battery trays to allow a full range of steering (take a look at this pic again to see what I mean).

When the time came to finally put this article together, I decided to take advantage of more recent developments in the Mini-Z field and put on some better-fitting Overland tires for a neater final appearance. These are also taller, so they give the truck still more ground clearance, while the softer compound greatly increases traction.

Conclusion:

Better late than never, right? Under power, the Underland project truck actually drives quite nicely. It has very little hesitation driving over medium-pile carpet and miscellaneous small obstacles on makeshift courses. Of course, the Mini-Z is not made to be driven outdoors, as its parts & joints are too small and could get badly clogged by dirt. I don't want to ruin the thing after putting this work into it, so I've kept it in its true element, inside. All in all, it's a fun little truck and looks pretty decent, especially with the new rims & tires. It's definitely a far better rainy day stress reliever than the stock Mini-Z, as it can be driven numerous places without having to worry about it getting stuck everywhere.

Bonus!

Check out still more photos of the Underland in the photo gallery, including more articulation poses.