› Project: Mod Clod
A unique take on Tamiya’s signature monster
I had a blast when I competed in the first Monster Jam World Finals RC race in Las Vegas. I also learned a lot about the two trucks that I brought to the race. When Bari Musawwir gave me a call and invited me back to the World Finals, I decided I wanted to step up my game in the modified Clod Buster department. Now, there are plenty of great offerings out there for chassis and suspension kits, but I was looking for something that didn’t yet exist, so I took matters into my own hands and decided to design and build the ultimate chassis and suspension kit for the Tamiya
Clod Buster. That way I could show up to the race with something that would be fast and tunable in just the way I wanted. After working on it intermittently for months (in between other projects), I finally had a truck that I could plug a battery into and pull the trigger. Here’s how I made it happen.
When the time came to design the chassis, I decided to go with something that looked a little more realistic. This meant that I had to use a
4-link suspension that had the upper and lower links closer together. After figuring out what
I was going to do with the 4-links, I was able to move on to my chassis design. I didn’t have time to draw the Clod Buster gearboxes so that I could use them while designing parts, so I took a bunch of measurements and hoped for the best. I designed it to be wide enough for motor clearance and long enough for gearbox clearance. I had the carbon plates cut, but made the bottom plate and all the cross members myself.
You can’t really have a mod Clod without a 4-link suspension, so that’s what I designed for my truck. A 4-link suspension allows the gearboxes to move up and down freely and articulate smoothly. I laid out the links on the computer and used that information to make upper and lower links out of aluminum rod with Traxxas rod ends. The mounting points are in line with each other, and the links are parallel to keep the gearboxes from twisting when moving up and down. The gearbox side of the links are mounted in custommade C-channel aluminum mounts, which are secured to some square stock that runs from the gearbox out to the hub carrier. This allowed me to move the links in more for improved tire clearance, and the square stock strengthened the hub carriers a bit. On the chassis side of the links, there are three mounts for the upper links, which allow me to alter anti-squat, while the lower links are secured to the lower plate with hingepins that I made. A 4mm hex-head screw on each side secures the plate to the chassis and keeps the pins in place.
Since I didn’t have traditional axle tube stiffeners in my truck, I had to figure out a new way to mount my steering servo since I couldn’t use the stock stiffeners as a mount. I ended up running out of time, so instead of designing my own servo mount, I went with a gearbox-mounted one from Crawford Performance Engineering. It uses a plate, two spacers, screws, and Traxxas servo mounts to secure the servo to the gearbox. Before mounting my Spektrum S6280 servo, I drilled new mounting holes in the plate so that I could mount my servo farther back and out of harm’s way. I made steering links out of aluminum rod and Traxxas rod ends, and bent the upper link so that I would clear the servo and its mount.
When you run in different conditions, you may want to alter the feel of the swaybar, and on my truck, I wanted something that was easy to change and tune. I came up with this basic design a few years ago and tried it out on two other trucks before refining it to what you see here. The main part of the swaybar is an aluminum rod that pivots on ball bearings, and those bearings are housed in mounts that I made on my Zeus 3D printer. In each end of the rod is a hole that is used to hold a steel rod by way of a setscrew. On the other end of the steel rod is a mount for the link that connects it to the gearbox, and a single setscrew secures it. When the time comes to change the rod, you simply loosen the setscrew in the aluminum rod and the one in the link mount. You can then remove the rod and replace it with the size of your choice, and it only takes about 10 seconds to change each steel rod. If you only need a slight change in swaybar tension, you loosen the setscrew in the aluminum rod and move the steel rod toward the center of the chassis to tighten the feel or move it out toward the outside of the chassis to loosen it.
Multiple Shock Positions
Even when it came to the shocks, I wanted a lot of tuning options. A truck like this can see a high-traction and smooth carpet track or a low-traction and rough dirt track, so the suspension can be easily tuned for any condition that the truck might see. I can mount the shocks from the gearboxes to the chassis for a stiff setup, or I can mount the shocks on the chassis and use a cantilever to soften up the setup. When mounted directly, the bottom of the shocks is secured to the link mount and the top uses one of three mounting holes in the chassis. The three holes allow the shock angle to be changed to fine-tune how they feel. When using the cantilever setup, I connect the gearbox to the cant through a short link, then the bottom of the shock is mounted to the other side, while the top of the shock is secured to the chassis. The cantilever has four mounting holes for the links; the farther you move them out, the softer the suspension feels and the more travel you have. With this setup, you can have a stiff or loose setup without having to change anything on the shocks. My shock of choice for this truck is the Pro-line Pro-spec and the softest spring available from Pro-line; inside the shocks is 10wt oil.
After being invited to the RC Monster Jam World Finals, I was assigned a body for this truck to replicate one of the full-size trucks that were invited to the World Finals. I was given Bounty Hunter, and my plan was to use the beat-up body from before, but a surprise package arrived from Bari Musawwir. Inside was a new Bounty Hunter body, with the updated trim scheme. Bari used an old HPI Bounty Hunter body, made a wrap for it, and applied it for me. Before mounting it on my Proline adjustable body mounts, I took the time to detail the front windshield with black around the edges and silver dots to represent the bolts that the full-size truckers use to hold them in.
Here I am, standing next to the Bounty Hunter monster truck at the Monster Jam World Finals in Las Vegas, Nevada. It almost looks as good as my Clod!
I designed my chassis plates to have a scale look, and once the design was done, I had them cut out of 2.5mm carbon-fiber plate.
A Crawford Performance vertical servo mount secures my Spektrum servo to the gearbox. Before attaching the servo and mount, I took the time to drill new holes and move the servo back a bit for more clearance.
Square stock between the gearbox and hub carrier allowed me to attach a C-channel aluminum suspension mount closer to the gearbox, which provides more clearance for the front tires when steering.
An old HPI Racing Bounty Hunter body was wrapped by Bari Musawwir, and it features the newer version of the Bounty Hunter trim scheme.
My swaybar design may look a little unusual, but it’s functional, easy to use, and very tunable.
The Pro-line Pro-spec shocks can be mounted directly to the chassis or on 3D-printed cantilevers. The cantilevers have multiple mounting holes available to adjust the softness of the shocks.