Large Bot

Good for: line following, maze solving, general experimentation. This chassis gives you lots of room for electronics with two upper decks.

This chassis would be a good project for the new builder. It is simple to build, and uses the readily available Tamiya Twin Motor gearbox. This chassis does not use spacers, but instead uses a “slot together” building method. Be sure everything fits together nicely before you add any glue. You may be happy with a simple friction fit, and not use any glue at all.

Material needed:

-any flat material such as wood, plastic, MDF, etc. The platform was designed around common brown hardboard. The cutouts for the slots are .14″. You can adjust the width of the slots to match whatever material you end up using.
-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!)  🙂
-2ea. Harbor Freight 5/8″ Roller Ball Bearing. Available here.
-glue (optional)

DXF and JPEG files: LargeBot

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 between inside edge of the tires and the gearbox) 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.

Large Bot pieces

This design uses 2ea. of the Harbor Freight 5/8″ ball bearings. Mount the ball bearings either from above or from below, depending on wheels you end up attaching to the gear box. You want the bot to sit level, with just a tiny bit of gap between the bottom of the ball bearings and the floor. It is OK if the bot rocks back and forth a little.

Have fun building the Large Bot!

Tamiya Twin Motor Gearbox


Harbor Freight 5/8″ ball bearing