Tank tracks are both simple and complex. They are built of repeating linked parts attached in a loop that's simple. The complex part is ensuring the links freely bend along the length of the track while maintaining enough purchase and integrity to stay on the wheels.
You can build tracks for tank models up to about 1/4 scale. Any larger and you start to need factory equipment. Follow these instructions to make working tracks out of hardware. The size of hardware to use depends on the scale and design of the tank. These instructions are for 2.5-inch-wide tracks.
Lay one hinge on your work surface so that the round side of the hinge is against the surface and the flatter side faces you.
The flat side of this and all hinges will comprise the interior surface of the track. The rounded-hinge sides will contact the ground as the track rotates.
Place a second hinge on top of the first so that its left leaf overlaps the right leaf of the one below. Align the three pairs of holes in the overlapping leaves.
Insert a screw in each pair of aligned holes so that the head of the screw is on the outside of the track and the barrel of the screw extends into the inside.
Secure each screw with a lock nut.
Repeat the previous three steps until you have sufficient track for your project. Remember to build two tracks of equal length.
Measure the distance between the screws and use that to space the gears of your sprocket wheels, which will transfer the engine power to your tracks. The sprocket wheel can engage the barrels of all three screws on each two-leaf pad.
Place your vehicle's wheel on the tracks so that the trailing edge of each track hinge points toward the back, for better grip.
The track's middle set of screws serve as guide horns to keep it from slipping off. Your road or bogey wheels should have a central groove to accommodate the guide-horn screws.
Wrap the track over the sprocket wheel on one end and over the tensioned idler at the other end. Pull the track together and connect the track's two loose ends with screws and lock nuts.
Repeat for the track on other side.
There are many varieties of homemade caterpillar track. You can use bicycle chain, old treadmills, and even make track links out of wood.
This style of track works best with rear-wheel drive.