Tanks use to have very complicated tracks. In this Thing, we use an endless 130XL timing belt, inside out. This thing uses a belt with a length of 33 cm. Just look for XL130 on the internet. The small geared motor comes from AliExpress.
It gives excellent grip on most floor types, because the material is rubber.
Two small pulleys deliver the traction and the wheels guide the timing belt.
The shafts are M4.
A basic frame is added just to demonstrate in a video how it works.
If you want to program it, use an ATtiny85 combined with an L293D.
Track too large? The SCAD-file for the frame is included.