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.
› PTFE Sealed Ball Bearing Kit—FF060, $23
Crawford Performance Engineering/crawfordperformanceengineering.com
› Clod Buster Vertical Servo Mount—CPE-VERTSTR, $15
› Bounty Hunter 4X4 Body—discontinued
› Destroyer 2.6-inch tires—10114-02, $38
› Brawler Clod Buster 2.6-inch gray wheels, +17.5mm wider offset—2760-03, $35
› Preassembled Pro-Spec Shocks—6308-31, $73
› Pro-Spec short-course rear-spring assortment—6308-22, $22
› S6280 Ultra Torque HV digital servo—SPMSS6280, $130
› DX6R 6CH smart radio w/ Wi-Fi/Bluetooth—$520
› Super Clod Buster—58518, $300
› Vortex R8 ProX Extreme ESC—ORI65129, $270
› VST 2 PRO 540 2P lightweight modified 5.5T—ORI28307, $100
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 custom-made 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 Pro-Line 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.
TEAM ORION POWER
If you build a mod Clod, you have to give it a lot of power to get it through anything that it might come across. Since modified brushed motors are pretty much a thing of the past, I looked into getting two brushless systems to get the job done: one for the front gearbox and one for the rear. I went with the 220-amp Team Orion Vortex R8 ProX Extreme for speed controls. They are a bit of overkill, but with speed controls this heavy-duty, I know I won’t have any problems. They feature brushless fans to keep them cool, push-button switches, and lots of tuning options. I mounted them on the lower plate in my chassis. They have some serious heft to them, which is good because, in my opinion, a Clod Buster chassis generally doesn’t have enough weight. More weight in the chassis allows the chassis to move more and the suspension to work a little better. Connected to the speed controls are Team Orion 5.5-turn Vortex VST 2 PRO lightweight modified motors. When setting up the speed controls, I bumped up the timing in the front motor slightly to help pull the truck through the turns and kicked up the braking in the rear motor slightly to lock up the rear end more and allow the truck to pivot better in the turns.
I needed some new rubber for my truck, and when looking for that, I decided that I wanted something to go along with the great scale look of the Bounty Hunter body that I was using. Pro-Line Destroyer tires became the tire of choice for this project; they come molded in Pro-Line’s M3 compound and include foam inserts. I mounted them on Pro-Line’s Brawler wheels, but before I did, I took the time to paint the faux bead-locks and drilled four extra holes using a 5/32-inch drill bit. These holes allow more air to flow out of the rim when the tire takes a hit and, therefore, makes them feel softer, which lets them soak up bumps and jumps better.
With less than two weeks until I had to pack up my truck and head to the World Finals, I plugged in the battery, crossed my fingers, and made a few passes on my backyard track. I knew that my initial setup would be pretty good, but I was surprised when I saw the truck drive for the first time; it was better than I was expecting. The tires dug in well, the rear of the chassis sunk down, and the truck took off with authority. In the turns, the tires and dirt meshed well, and the truck made it around as good as some of my best mod Clods from the past. Jumping was also good but not as good as I had wanted: Off the ramp, the nose was slightly high, but it quickly came down, and the landing was a little bouncier than I was looking for. The good news was that I had a just enough time to print up a new set of cantilevers, so I made them slightly longer and added an extra mounting hole for the link to soften the suspension a bit. Back out on the track, the truck still landed nose first but soaked up the landing much better than before. After roughly a minute of running my Clod, I had to call it a day and put it in a shipping container. I arrived at the RC Monster Jam World Finals a day late and didn’t get the laps on the track that the others had. The track had a simple J-shaped layout, but you only get one lap and the surface was much different from what I was used to running on. Day 1 consisted of me trying to get the track figured out, and on day 2, I figured out that my setup wasn’t that great. The truck worked great at home, but the hard-packed and bumpy dirt was much different from the fluffy Georgia clay that I had set up at my house. These issues ended up hurting me, and I wasn’t able to get the truck out of the first round of bracket racing. On the morning of the last day, I made some changes, which were easy to do thanks to the design of the truck. I stiffened the front and rear swaybar, moved the battery back slightly, and stiffened the suspension by moving the cantilever link back one hole. This time around, the truck felt much better and more at home on the dirt, and I had a much better day.
I’m very happy with my truck and how it did at its first event. Sure, I ran into some issues, but that was really about not having enough wheel time and having the setup down before the racing began. I needed to get in the groove when it came to that style of racing, and I didn’t have much time to figure out a setup. The good news is that my truck was more than fast enough to get the job done, and changing the setup on my truck couldn’t have been any easier. With the ease of use of this truck, I have no problem making quick changes that make a real difference in performance. Unlike at this event, I’ll have a lot more time to get my truck dialed in and the bugs worked out before heading to the next RC Monster Jam World Finals.
by Kevin Hetmanski Photos by Kevin Hetmanski & Leigh Guarnieri