Small Bot

Good for: line following, maze solving, general experimentation. This chassis is a bit too big for regulation Mini Sumo competitions, but for informal battles it would work fine.

This small chassis would be a good project for the new builder. It is simple to build, and uses the readily available Tamiya Twin Motor gearbox.

Material needed:

-any flat material such as wood, plastic, MDF, etc. The platform was designed around 1/4″ MDF.
-1ea. Tamiya Twin Motor gearbox. Available at most R/C hobby stores and also online. You can find them for $8.95 at Pololu. Available here. (Don’t forget to buy wheels!)  🙂
-1ea. Harbor Freight 5/8″ Roller Ball Bearing. Available here.
-4ea. spacers to hold the top deck. Can be 4 pieces of wooden dowel rod or whatever you have handy.

DXF and JPEG files: SmallBot

If you need a program to view and print the DXF files, try Inkscape. It is a fully featured graphics program that can view and print DXF drawings. Available here.

If you print out the DXF file using a Cad program or Cad viewer, the dimensions should be correct. If you print out the JPEG, make sure the distance between the centers of the gearbox mounting holes (the ones with two concentric circles) is as close to 1.95″ as you can get. This is so the Tamiya Twin Motor gearbox will mount properly. Print it out on paper and cut it out for a trial fit before you cut any wood.


The Harbor Freight ball bearing goes in the cutout at the top of the piece pictured on the left. Mount the ball bearing either from above or below the hole, depending on the exact tires you use with the Dual Gear box. You may have to shim the ball bearing to make the bot sit level.

Have fun building the Small Bot!

Tamiya Twin Motor Gearbox


Harbor Freight 5/8″ ball bearing