Anyone help design me a...

[sloth]

Not a bad idea matelot, cheers. I'd still be very interested in your idea Alec, I've gone back and re-read it and just can't picture it.

I've just cobbled this together from my kids old scooter as a prototype of sorts, as the bearings in it feel full of sand (they may well be!), and I still have 4 wheels in total to sort. This (apart from having already grumbling bearings) seems to work OK secured to the plywood cage side; and there's another wheel I can pinch off the scooter which is completely seized at the moment. So if it works well I can buy some replacement bearings and a cheapo ten quid scooter, and all 4 wheels will hopefully be whisper quiet!