Every year, the WRAM (Westchester Radio AeroModelers) hobby show in White Plains, NY is a big deal for RC fans in the Northeast. In addition to the usual displays, the show also hosts an indoor monster truck race on a tight concrete course. I figured it was time I showed up with a new rig to show those boys how it's done. I could have reworked on of the Clod Busters in my collection, but that would have been too easy. I had been working on a few designs of my own, and I figured that this would be a good opportunity to see if all the designs I had been playing with would actually work. I started out with a pair of Tamiya TXT-1 axles and a dream. After a lot of thinking, some CAD time and bunch of machining, I had the truck you see here: a completely original tube-frame truck with hybrid suspension, a custom transmission and full tunability.

Chassis
I wanted my truck to closely resemble the real deal, so I bought a die-cast model of the full-size Bigfoot monster truck to use as my reference for the chassis. After I picked out a body—a Pro-Line F-350—and chose the wheelbase I wanted the truck to have, I began to design the chassis in AutoCad. Once I was happy with the design, I printed out a full-size drawing to use as a template. Most of the chassis is constructed out of 1/4-inch brass tube assembled with silver solder. When I was happy with the design of the chassis, and everything fit the way it was supposed to, I built the roll cage out of brass tube and fit it to the body. The chassis is pretty well balanced: the motors are in the center, the battery is in the back and the steering servo, receiver and speed control are in front.

Suspension
The four-link suspension is also my own design. The suspension-arm mounts on the axles are machined out of 1/4-inch aluminum and held in place by screws that come out of the axle housing. I machined the suspension links out of 1/4-inch aluminum round stock and installed DuBro ball ends to connect them to the chassis and axles. Carbon-fiber plates cut from Art's Hobbies 3mm-graphite blanks provide a mounting location for the side links, and the lower links are bolted to a 1/4-inch aluminum square stock. You'll notice that the truck has cantilevered rear shocks and standard mounting in front for greater rear travel. Trucks typically land off jumps on their rear tires first, and I wanted more travel to absorb that impact. Each cantilever is supported by two ball bearings, and two mounting positions for each shock allow you to adjust the suspension travel. Like the chassis' side plates, the shock tower and cantis are cut out of Art's Hobbies graphite blanks. The cantilever pivots are actually Traxxas aluminum pivots for the Revo. With my lathe, I shortened them and removed their threaded sections. I drilled them out and sent a 4-40 tap through them so I could mount them on the chassis. Because I run cantilevers in the rear, I had to install a swaybar to prevent the chassis from swaying from side to side. Thunder Tech Racing's Ripper swaybar works well, looks great and was one less thing I had to make. Kyosho /8-scale buggy shocks provide the damping all around; I stripped off the anodizing and polished them to match the finish of the chassis. Kyosho yellow springs support the rear of the truck, and gray Losi truck springs hold up the front.

Steering
I used a set of aluminum Juggernaut 2 bumpers from New Era as my servo mount. They're much more rigid than the stock plastic parts and much lighter than the aluminum units offered for the TXT-1. The bash plate is also a modified Juggernaut piece, and Tamiya aluminum mounts hold the servo. Thunder Tech Racing axle wideners improve the steering of the TXT-1 axles.

 I built the chassis to be realistic and functional. It’s constructed out of brass tube and silver solder.

 The battery mount is made out of carbon-fiber. Strapping tape ensures that the battery is secure at all times.

 Except for the shocks and the swaybar, all of the suspension components are custom-made.

Drivetrain
The transmission is fully boxed to shield it from prying eyes until the patent for my custom design comes through. [Editor's note: I told Kev he was being ridiculous, but he insisted on keeping this thing a secret. Even I don't know what it looks like!—Pete] I can say that Traxxas T-Maxx driveshafts connect the transmission to the Tamiya TXT-1 axles, but that's all I'm giving up.

Body, wheels and tires
I shipped the Pro-Line F-350 body off to Bill Zegers to have it painted. After I got it back, I cut out the side and rear windows so it would look a little more realistic. I made a tonneau cover out of a sheet of Parma Lexan. When I was happy with the shape, I covered it with thin black cloth and attached it to the body using clear silicone. While I had the Lexan out, I made a wing for the back end.

When it comes to choosing tires for WRAM-style racing, weight is more important than looks. Stock TXT-1 tires look more like the ones used on a full-size monster truck, but they're a little too heavy. A set of Imex puller tires were the ticket! They don't weigh much and provide plenty of traction. They are mounted on a set of Tamiya TXT-1 wheels.

Electronics
I installed two Trinity 12-turn cobalt motors and wired them in parallel for maximum power (it's equivalent to running a single, 6-turn motor). A 6-cell Trinity GP3300 matched pack provides the juice, and an LRP Quantum speed control receives commands from a Novak XXtra receiver. For steering power, I chose an Airtronics 94359Z servo, and my trusty Airtronics M8 radio connects me to the truck.

 New Era’s Jug bumpers and a modified a Jug bash plate fit my narrow setup.

 Rear toe is fully adjustable. Two Lunsford titanium turnbuckles and DuBro ball ends hold the settings.

 

The shocks are Kyosho units. I stripped off the anodizing and polished them to match the chassis and rest of the parts that I machined.

Performance

Well, the race was on, and I had very little time to run the truck, so I was very curious to see how it would do and whether the tranny would hold up. The course was very simple: slick concrete oval with jumps on the left and right sides. At the WRAM show, just like full-size monster truck racing, two trucks run at a time in a ladder-type elimination. I got nervous as I watched the guys practice; they clearly spent much more time running and tuning their trucks. I only had a few laps around my basement. My confidence grew after I defeated my opponent in the first race. The truck accelerated very well and with very little wheel spin. It tracked straight with every stab of the throttle, thanks to my transmission design. It jumped with a slightly nose-up attitude, and the rear shocks absorbed the impact perfectly. There wasn’t any sign of body roll in the corners, the chassis stayed flat every time I turned the wheel. Steering was responsive—almost too responsive, as I cut the corner too tightly a few times. After the dust settled and the racing was over, I went home with a second place finish to local racer Artie Fie, who wins all the time. I was in first place going into the last round of racing, but that all went away when I screwed up and jumped the gun on the first race of the round. Not a bad showing for my first time out with a truck that I designed and built!