If I wanted to make it into a 4th axis driven by a spare Nema 34 Could anyone suggest the toothed belt ratios to use please. It seems 50:1 or 100:1 are popular?
With a single belt, you'll have trouble getting more than a 4:1 ratio, due to the size difference between pulleys. To get to 50:1, you'd need a worm gear, or harmonc or planetary gearbox.