Routing a closed loop belt

 Ok, we're not sure yet how to even make a length of T2.5 timing belt into a closed loop yet. But when we do, we want the belt to run between a series of fixed bearings, to make a "track" for our miniature 3d printed horses to follow.

As with our previous designs, we're still working out how this is going to work - or even if it will at all! But we're going to need some uprights for the bearings to fit over. It's tempting to just drill some holes, pop an M4 bolt through and fix it in place with an appropriately sized nut.

But that will then add additional height to the bearings - they will effectively stand proud of the baseplate (and we're not sure if we want that just yet). So instead, we're going to cut the holes for them at 3.5mm then use a die tap to thread the holes out to M4 sized

This then allows the bolts to hold themselves locked into the baseplate without the need of fixing them in place with a nut on the other side

So now the bearings can just sit over the bolts and act as guides for the belt.
Once we've worked out how to make a closed loop from the timing belt, we'll be able to add in bearings at each corner (note the slotted holes for the corner bearings, to allow us to more them in an out slightly, to add (or remove) tension in the belt, once the loop is complete.

Once the bearings are added to the corners, you should be able to see the path that the horses will take. We'll start with a horse on the track in the bottom left corner of the baseplate, and one in the topright. The stepper motor will rotate anti-clockwise, pulling the two horses towards each other on the track.

As they approach the middle, each will appear to approach the "bar" (the separator running along the middle of a jousting arena). Then, they will run past each other, before moving away from the bar in order to complete their turnaround and prepare for the next pass.

It's all looking quite hopeful at the minute.
So long as we can reliably join the two ends of the belt, we should be ok. Then we get to wire everything up and see if it works!

As a fallback option, you can see the Nema17 type stepper motor waiting in the wings (complete with "proper" pulley for precise CNC operation) should it be necessary to use something a bit more "tried and tested". But let's hope it doesn't come to that.....