Some photos of the mechanical and electrical build.
I have cut a piece of the plastic for the robot body. 98 mm wide and 85 mm long. Two pieces of aluminum are connected to the body. The front piece will be the base for the thing that will hold the pencils. The second piece is used to fix and align the motor on. Tie-wraps are used to keep the motors in place.
As a third 'wheel' I use a Tamiya 70144 Ball Caster Kit.
I use a piece of prototyping PCB to solder the components. Because I'm only going to make one robot, there is no need to design and etch a PCB. The two black vertical strips will hold the STM32F4 Discovery board. The red board is the motor driver.
The result up till now, complete with the STM32F4 Discovery board in place.