Making a motorised "race track"

Ok, let's go into this softly, softly. It's been a while. And some of us have slept since the last incarnation of the Nerd Club blog and we've forgotten an awful lot. But something that immediately springs to mind for a game that involves bringing two horse-mounted characters into the centre of a battle arena is stepper motors and timing belts. But unlike make "bed slinging" 3d printers or other CNC-based machinery, we're going to need a "closed loop" timing belt. 

 What if we had a complete loop of toothed belt under our jousting arena? And attached to it were to magnets at opposite sides of the loop? And placed above it, two horse-mounted characters with magnets in the based, pulled along as the belt rotates under the jousting arena? 

 That sounds like a pretty cool starting point for an animated diorama, let alone a tabletop game with built-in automation!

Many years ago we successfully used some cheap 28BYJ stepper motors and some ULN2803A darlington arrays without the need for rather more expensive Nema-type steppers and associated driver boards. So before we take this project any further, we're going to see if we can get a closed loop timing belt spinning around some fixed points.

We may yet replace the two steppers with a single drive point and make use of some miniature bearings like these from Amazon:

But before we get too carried away with laser-cutting terrain and making complicated enclosures, let's ease ourselves back into this nice and gently - by making a stepper motor spin, with a home-made pulley that can make a length of T2.5 timing belt rotate between two fixed points....