How to build a beam bot twin motor robot base

This robot is BEAM bot inspired. First we build up the Motor Drive, an excellent and cheap Robot Bot-Base. We start with the Tamiya kit, get it going, then strap on a battery and a drag wheel, center the drag wheel. Tape it all in place with bright yellow tape and make a BEAM Bot with batteries. Plans for this BEAM framework are to add smarts.

The Tamiya Twin Motor Gearbox has two motors, so with a small H-Bridge I can control forward, reverse, make it turn...