I created for a project I was working on (Wall-E Made From Scratch). Being that it was too rigid and wobbly, I was unable to use it (plus I was short on time). However if proper support is given on both sides (an L-shaped piece on both sides) or a bracket / box in between, the tracks should run smoothly.
Suggestion: If you don't like the design, you can take out the L-Shaped piece and the inner frame and use the same type of chain and only the big gears to drive. This would make it look much more like a tank.
p.s. if you like it, please vote for me for the competitions rptech
Step 1: Designing
The first thing I did was plan everything.
You can use anything you want to design. I used an open source 3d animation program called blender to generate animations and images of the intended project. To make the blueprints, I rendered 3d meshes as 2d images.
The next thing I did was use a program called gear generator to print life size images of the gears. I then attached the images to wood and cut it out with an electric coping saw. I used such dies to cut out the gears.
Step 2: Chain
In order to follow the measurements accurately, I created a jig for the links. Such jig was also helpful when drilling holes for the wooden dowel. I sanded down the corners of the inside so they wouldn't hit each other when driven. For a smoother movement of the gears' teeth, I placed a 1/2 inch wide pvc pipe in the center of the wooden dowel.
Step 3: The Support
An aluminum bar was used to allow smooth spinning of the small gear.
Rubber rollers (from a printer) were used on the top bar for a smoother movement of the chain.
Motor used is a windshield wiper motor attached to a motor cycle well cell battery (also works with a drill battery)
Step 4: Programming and Control
It is pretty simple as it is done the same way it is shown on the images below.
All wires are attached to the switch which is connected to an aluminum bar that is connected to a servo.
When you move the servo, the switch drives one of the tracks forward or back
for programming, I used a controller called the E-Z Robot Bluetooth controller but you can use any rc controller
I assigned ports to the controller and programmed (it's free software) in a way that when you press a button, the servo moves to a certain degree (in this case, a 90* turn) and returns to it's stable position in the middle.