Where there’s a wheel, there’s a way… 2011-05-21

Today we got a bit further with the new robot wheels. We’ve been using Singapore School of Robotics omni-wheels so far: Lego-compatible omni-wheels These are Lego Mindstorms compatible, and gave us a big advantage over the other UK teams last year. However, compared with the wheels of some of our opponents in Singapore last year, these weren’t quite what we needed, and so Andrew and Eric have come up with an omni-wheel design which uses a split ring (like a large keyring), 32 washers, a custom-machined piece of aluminium and a handful of cable ties.

First off, we ordered 10 split rings (from ebay, where else?) and a load of washers. Then, disaster struck – the internal diameter of the washers was just very slightly too small to fit on to the split ring. Andrew and I spent a while in ScrewFix in Cambridge where, after we’d explained what we needed and why we needed it, the patient staff pulled out box after box of washers and let us try them on the split ring, but their washers were either no better than the ones we had already, or else they were much worse. So we went to Mackays on East Road in Cambridge, and had a look at their washer collection too. The same, sadly – either no better or else worse. But we were told that they did have a workshop, and that the workshop might well be able to do something to our split rings to make them fit. So we trotted off to the workshop and the helpful chap in there took a look at the rings and reckoned that he might well be able to do something with a grinding disc. He disappeared with one of the rings and brought it back a couple of minutes later – and the washers now fitted on to it and moved freely.

Now we just need to get a bunch of these laser-cut from 4mm aluminium: Wheel aluminium blank The blue bit is the aluminium, the white ring around the outside is the split ring with the washers (32 – count ‘em) threaded on it, and the outer ring of 8 black circles on the blue is the holes for the cable ties – an important component. The inner ring of 4 black circles is the mountings for the bit that goes on to the axle. I’m a bit concerned that they might do a rather-too-thorough job of mincing up the pitch, but we’ll practise at home shredding our own carpet first.