I dragged Forkhead into the Hackspace today with a plan to cut one of the ring gears from a 22mm motor in half to make a 22mm brushed motor with 3 reduction stages (64:1 reduction) instead of the 4 stage (256:1) reduction thought I had from cobbling two of the ring gears together and stuffing extra reduction stages in.
Taking apart the modified gearbox I almost immediately realised I’d actually stuffed 4 intermediate stages plus the output stage in for a whopping 5 stages, giving 1024:1 reduction. Suddenly the glacially slow lifter action at North Down Havok made perfect sense!
After I’d gotten over this surprise I was left me a choice between cutting one of the 10mm ring gears in half and making two 3mm sections (for two 3 stage gearboxes), or milling two of them down to 6mm (for two 4 stage gearboxes). If the version I went for worked then great, otherwise I’d wasted at least 1 ring gear either way.
After staring at the parts for a few minutes and wondering how make the workholding for the ring gear happen I realised that the output stage had at least 3mm of thickness in front of the sun gears. This meant I could just make a 3mm spacer with no teeth on it, with no need to sacrifice any motor parts to try out the 3 stage gearbox. Conveniently while clearing out my storage box at the Hackspace I happened to find some 22mm aluminium bar which was perfect for the job.
After a little bit of cursing at random lathe issues (stalling when the drill broke through and blowing a fuse…twice, and the annoying size gap between my largest drill and the clearance needed for my smallest boring bar) I had a couple of 22mm OD, 13.8mm ID, 3mm thick spacers with some holes in roughly the right places and I took them home to try out.
After installing two of these in Forkhead these had enough grunt that I couldn’t backdrive them by hand and decent speed. Annoyingly but unsurprisingly the HTD5 belts were the weakspot again, slipping just on the verge of lifting the chassis of Forkhead v1 (about 1kg with the guts removed).
Time to make some larger pulleys, see if I can get them to fit the belts better, and then maybe add some tensioners.