First job was to get the wheels finished. When I built the 'idler' wheels, I made a mould using latex. Smashing stuff, but for one obstacle – it takes ages to set and to get a good mould, you need to apply it in layers. The bottom line is it takes about a week to make a decent mould. I didn't fancy splashing out on RTV rubber, so used something that all you dentists should be familiar with - Alginate. This is a blue powder that when mixed with water forms a smooth paste. It's used by dentists to take moulds of your teeth! The good thing (or bad thing if you aren't quick about it) is that it sets in around 3 minutes! I built a master of the drive wheel, again using panel pins fitted through drilled holes for the rivets. A plastic card wall was built up around the wheel and the alginate was mixed up and poured in: