Tamiya Clod Buster Project

Page 2: Upgrades!

Let's get something out of the way right from the start. The Clod Buster is not a high performance truck. Adding high performance parts to it pretty much just makes it worse. This is an old design truck made for bouncing around the lawn, and it does that job just fine. The upgrades I made were mostly just for fun, and in most cases I had to make additional mods just to restore the original performance.

The friction dampers are adequate for this truck, but it still bothers me to have "shocks" which are so low-tech. I happened to have 8 extra oil shocks from my TXT-2 because I upgraded that truck to aluminum shocks. They are not quite the same length, but if you put the longer rod ends on the oil shocks they are pretty close. I can't claim to have actually noticed any performance difference after installing these shocks, but they do make me feel better somehow.

RC4WD offers aluminum beadlock wheels for the Clod Buster, and I thought they were so cool that I ordered them before even building the model. You also need an adapter to fit the hex size of your particular model, in this case that's 12mm. In the pictures you can see the stock plastic wheel compared to the aluminum wheel, front and back. In the first photo you can also see the white mold release agent that was present on the tires out of the box. It took me a lot of scrubbing with my official Tamiya brush to get them to look smooth and clean on the right.

As cool as these new wheels are, they are a big problem. First of all, the Clod Buster steering system is terrible right out of the box. All of the servo force is lost in the servo saver, and the steering geometry is all wrong. The Ackerman angle is backwards and so is the caster. The result is that the front wheels basically don't steer at all and the back wheels steer a lot so it drives like a forklift. The aluminum wheels do not have the same offset as the stock wheels which results in the track width increasing by almost two inches. While this might be good for stability, it makes the steering completely unusable and it doesn't look right either. To solve the problem, I decided to modify the wheels to decrease the offset. The pictures above show the CAD model I made of the wheels. On the left is the aluminum wheel as it comes from RC4WD. Once the adapter is on, the mounting face is essentially flush with the edge of the wheel. I wanted to the mount to be deep inside the wheel, so I decided to remove 23mm of aluminum which I accomplished on a friend's mill. This is a pretty major modification and I screwed up some of the dimensions despite all my preparations which required that I build a spacer to install the final wheels, but in the end it worked. The difference is incredible. It drives so much better now. Note that I also replaced the servo horn with a much longer version to give the steering rods more travel and tightened the servo savers almost to the stops. There are aftermarket companies which offer conversions to move the steering servo to the axles, but I didn't want to do this since it ruins the scale appearance.

For reference, I did try swapping the wheels and tires with the TXT-2. This worked OK for the Clod Buster, but the TXT-2 couldn't handle the heavy aluminum wheels either so I switched back.

Phase 2:

Those aluminum wheels and oil shocks were nice, but I was always unhappy with the performance of the Clod. Part of it was all the extra weight I added, but in particular the steering was just terrible. I resisted any kind of servo-on-axle steering because I wanted it to stay a Clod, but I finally found some parts at CPE (Crawford Performance Engineering) that I thought kept it close enough to stock while addressing some of the more serious issues. The picture above just looks like a pile of links, but there is a lot more going on here.

This step took me several hours. I tore off the original plastic suspension links and replaced them with a real 4-link suspension. I also replaced the steering tie rod and servo link with much stronger versions. But most importantly I replaced the mushy servo saver with an aluminum version. This system has no springs. Rather it is a solid connection, but it is only kept solid with friction so it can slip if enough pressure is applied. It needs to be quite tight to steer these heavy wheels. You can also see the new shock mounts which are quite a bit higher than the old versions which were connected to the lower link. This give some welcome extra clearance to the servo links.

Here we can see the new system installed on the front with the old system on the back. The difference is substantial. The original suspension is not a true 4-link because the lower links are not independent. Instead they attach to the middle of the upper links and provide lateral support. The new system is a real 4-link which allows more motion. The right hand image shows all the replaced parts.

Next up is a 3D printed supercharged V-8. I bought this a while ago off of eBay because it was so cool and I had been trying to find a home for it. The Clod Buster already has a fake blower sticking out of the hood and plenty of room in the front of the chassis so it seemed like a good home. I can't believe how much cool stuff comes in this kit. Dozens of 3D printed parts, a bag of hardware, and 2 servos. Everything you need to built a (fake) working V8.

First step is to attach the starter to the block. Yes, this thing is detailed enough to have a starter. Next step is the oil pump and filter. Note that the cylinder bores are purely ornamental; nothing will go into them. There are no pistons.

Now I attach the water pump to the front of the block followed by the alternator and its support bracket. There is no timing chain.

Next up is the heads and then the valve covers. This is certainly starting to look like an engine.

Now we'll start to put some electronics inside. At first I thought this was a supercharger impeller, but it is actually a little fan to cool the motor. The motor is extracted from a full size servo. The potentiometer is used to set the idle speed by telling the servo it is a little bit off center. The throttle can then be used to rev up to full speed. A very clever solution. The 4-sided control horn from the micro servo is re-used as a connector for the fan and then pushes onto the gear of the servo motor.

From the bottom you can see how the servo motor directly drives the lower pulley which would be the crankshaft connection. We then add some motor mounts and an oil pan which is slotted to allow cooling the motor. Servo motors are not really designed to run continually, and I don't know how this one is going to hold up.

Here's the air intake for the supercharger. The butterfly valves can pivot to open and close. A micro servo (here painted chrome) is installed on the bottom with a small servo horn protruding.

A tiny arm connects the servo horn to the butterfly valve which allows it to open and close. At idle it will be closed and it will flare open as a function of throttle position. The upper drive pulley has also been installed to the intake manifold.

Now the exhaust manifolds have been installed. There are several styles available. I chose these because I didn't want to cut so big a hole in the hood to allow vertical pipes. In the right hand image the intake is installed.

From the back of the engine you can see where the pot sits and how the PCB is tucked away. Once the bell housing is installed all of this is hidden but you can still access the pot to control the idle speed.

Now the fiddly bits: the spark plug wires. I actually found installing these kind of relaxing. The instructional video made it all quite clear, and I love how neat they look once the wire looms are installed. The image doesn't show the alternator belt or supercharger belt, but you can see them in the following image. To install in the Clod I had to do some thinking. I cut the cross brace between the shock supports and attached the engine using tall standoffs from below. I added another small support in the rear so it wouldn't wobble since this truck is quite bouncy.

Here's the truck before and after the update. The old blower just sat on top of the hood in a small recess. I had to cut a large irregular hole to make room for the new engine, but it looks great. So far I've found that the system draws a lot of power and keeps cutting out even after I added a BEC. I probably have too much friction somewhere so it deserves a close look.

Phase 3:

I really wanted a simple interior in this truck including a driver, and that meant swapping out the stock tinted plastic window with a clear polycarbonate version. Luckily I found just the thing at RC4WD.

The installation couldn't really be any easier. Unscrew the old one piece window and screw in the new one. Because the new version is flexible it doesn't fit quite as snugly, but it looks good. See before and after above.

Next up is the driver. I used a Tamiya 1/10 scale figure. He seems a little large for this model, but it was as close as I could get. I had to saw off his legs to get him to fit while still keeping room for the electronics beneath. I chose the head with the helmet since that seemed appropriate for a monster truck. Behind him I put a pair of bucket seat backs.

A couple of final shots of the driver.

The last thing to do is improve the lighting. I got these tail light lenses and housings 3D printed from AMPro Engineering and then painted the lenses as shown.

Here is the rear end before and after. The stock tail lights are just stickers. I used a drill, a Dremel, and a file to hollow out a spot for the lenses and then glued them in. There are red LEDs in back and halogen LEDs up front controlled by a Tamiya light box.

Phase 4:

Another summer arrived and I found that I wasn't really driving my Clod because the steering was so bad. I finally decided to cave in and go to dual axle mounted servos instead of the single standard chassis mounted servo. I started by ordering the nice BTA (Behind the Axle) servo mount and link set from CPE shown on the left , but it didn't work. The servo mount interferes with the shock mounts so it can't be used. Instead I found a set of aluminum front bumpers with an integrated servo mount on eBay.

Here are some pictures of the front axle before and after the upgrade. The changes are pretty obvious. The original blue plastic front bumper has been replaced with aluminum and now I have dual steering servos. It made all the difference in the world. The Clod now handles like it should and is actually fun to drive.

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