Fantastic, thanks so much for the help everyone! I've redesigned around it, I've got a 20mm rod for the shaft on the way, and I'm looking into some much thicker bulkheads now, going to see if I can get something working with a bit of steel (a bit like how Last Rites' looks, with the frame) but again, it's just seeing if I can get the parts that'd work with that!

Just a matter of engineering this bar a bit better now, It's still mild steel for now (I've got plenty of it to hand for ridiculously cheap prices, somehow...) but I'm definitely going to upgrade it to something better when I get the chance! Been having a look at a few bearings, and I should be able to get things all done under budget (going for less than £200 overall, currently on track to spent about £180) if everything goes to plan, so that's all a good sign!

Also, those bevel gears from the picture of Buzzbar's spinner - are there any like that available to buy anywhere, or have they been machined specifically? I was having a look at a few bevel gears for the system, instead of a chain drive (more reliability than a bike chain!) but they're all either really small or not quite suitable for the application...

Thanks again, it's a huge help!