Ralph - I did cheat, I didn't actually make them myself, all I did was draw it... Once I'd got CamBam to do the hard work, all I had to do was find an easy way of centreing each disk; fortunately, I have a pointy tool, I have no idea what it's for in reality, but it fits nicely in a collet, and the point sits nicely in the hole made by an ordinary centre drill; so; stick it in the lathe, centre drill a hole, use pointy tool to align & press piece onto parallels, clamp in vice. Job done

winklmj - Hmm, drifting.... I'd need to somehow lock the wheels to the axles for that, for that locked-diff feeling... So, first person who can suggest a way of welding aluminium to steel? Go!

Andy - Drifting, as you have been corrected; actually, we DO have a coffee machine in the office now, I got bored of rowing the chair all the way to the kitchen and back... now I only need to do it once a week when the machine runs out of water...
