The Chassis

 Now that I had a working motor setup, I needed a way to hold it all together. For this I built a test bed body. I plan to 3D print a final body when I have a better idea what goes into the robot, so that I will have room and a better placement design. As the chassis is pretty simple, this is a post you can probably skip. If not, read on.
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The base for the chassis is an old sign I snagged from work. It is some kind of fiber board, with a bit of plastic in it, I think. It is light and really flexible. I folded it nearly in half and couldn't snap it. This will be great for my robot, though I hope it won't get folded in half. However, if you don't have access to crazy materials, MDF Hardboard will work great. Heavier thicker boards would work, but weight down on the motors. Acrylic sheets would also work, and have a fairly cool finished look.

As I mentioned before, I used the Tamiya double gearbox and track & wheel sets. As such, some of my design was already decided. Width was set at 3", because that would be the space between the hubs of my wheels, using the supplied axles. I made it 8" long, as I had figured out that with the configuration I wanted, that was about as long as I wanted it, so that I had minimal over hang in front and back of the wheels. I found this by cutting the sheet I had into a 3" wide board. I then laid out the tracks to roughly gauge where everything would go, and how long I would want it.

I then cut strips to make grooves for the axles on the wheels. As the wheels are free moving, that meant my axles didn't need to be super free to spin. If you are using wheels that lock to the axles, you will need to make sure the axles can spin, and I recommend using some way of lubricating and possibly even bearings. For this early setup, the plastic wheels around a metal axle is fine for my purposes.

For the front axle, which was going to have bigger wheels and I wanted to be higher, I built a slightly different setup. The axle will run a a full width channel, giving it greater strength, and creating a small mounting platform for my future distance sensor. You can see better in this image than in the last, where I cut larger space for the wheels hubs to fit. The wheel kit I have has hubs that stick out on the inside. If I didn't want to give up more space for the wheels, I had to accommodate.

Here is the base chassis with the wheels attached. It is hard to see here, but the front wheel is slightly up from the others. It is really only visible when it goes over anything. You can also see that the front wheel sticks out from the base. This is to allow it to do some climbing, which it is surprisingly good at. Had I not done so, the base would hit the object and stop it dead. As you will see later, the back does not stick out, and so it can get caught. Especially with some screws added later.

No it was time to add all of the movement components. The bottom "level" will house the motor, motor controller, and battery pack for the motors. A more adept robotics engineer would hook all of the power to one source, but that isn't me. Also, I want to be able to run the Raspberry Pi without turning on the robot.

Next time I will go into the upper level, putting it all together, and making it "mobile." Until then, keep building!