Sean can you outline the principle of what you built?
Here you go Mike.
Basic construction is a barn door mount; the basic principal of construction is this :
https://blarg.co.uk/astronomy/barn-door-tracker, and this site has a handy calculator on it to work out the correct length of distance between hinge centre and drive bolt centre (and one of the few that seem to take in to account sidereal time instead of how many hours on a watch) :
https://blarg.co.uk/astronomy/barn-door-tracker-calculator
Wood on mine is 2 pieces of 50x20x300mm pine, as it what was kicking about on the floor of the local carpenters when I went past. It's a bit soft for this purpose I think, but it does the job.
Hinge wise, a lot of folk have said piano hinges, or butt hinges, however after trying a couple of different ones found in the basement with varying degrees of slop and internal binding (jumps), I used a 4" flush mount with bearings on them like this :
For holding the bolt, one of these inset furniture studs (though this is for a 10mm bolt, as it's easier to photograph with the mobile than the 6mm ones!), and the bolt goes through that with a dome nut on the top and on the underside of the top arm I've put a piece of stainless steel (an old paint scraper on this) on top of which is a bit of smooth plastic for a bearing. I put that on not for an actual bearing but to distribute the pressure as a dome nut would soon punch holes in to pine.
Basically that's it, the mounts for the unit and the camera, those are just arca-swiss rails that I had kicking about in the office, saves on trying to source a few 3/8" bolts and captive nuts around these parts.
That contraption with the wires, a stepper motor connected to a microcontroller, as whilst one of these is good for about 5 minutes normally rotating a drive at 1rpm, it'll start throwing errors at differing times (depends on focal length); so what I'm working on with this is to calculate each rotation based on the last. That's where the magic is going to be but still not finished yet; when I've got it all worked out I'll put a proper thing on my blog about it with things like circuit diagrams and the drive code.
The elastic bands are there just for holding tension (it wouldn't be a prototype without elastic bands or bodge tape!) or vibration dampening; when it comes to being built properly, I'll be using spring tensioners and a damper mount on the motor as whilst elastic bands and straps are cheap, they fail usually at the most inappropriate times.
And to fasten it on the tripod, it's a monopod head (that's the Sirui L10 on there, really should write a review on it sometime as that's the best 100€ I've spent in the last couple of years) and the rotator plate for doing pano stuff with. The L10 is controlling latitude adjustment, and the rotator is for north/south alignment.
When it's built fully, instead of just a few bits of wood with scribbles on them, it's going to be more like
this as there's more room around the frame to move the camera around.
