Hi Rom,
I considered a few different turntable designs, but finally settled on that shown in this thread
http://www.iceinspace.com.au/forum/s...ad.php?t=36222 where I've just added some more info on the turntable. Also refer to post#1 for a pic of the obs frame with top ring and wheels fitted.
The choice of wheels is important to help reduce rolling resistance, since you don't want the wheels to skid. Therefore, they either need to be of conical section or at least have a curved (rather than square) profile. I found hard plastic wheels, approx. 75 mm dia. with a curved profile, for $6 each at a local bearing / industrial hardware place in the local regional town. You need to consider the load capacity of the wheels, and allow for some of them not carrying load (ie. over-design the arrangement). If I recall correctly, the $6 wheels have a rating of at least 80 kg each. I used eight, and the combined static load is around 240 kg.
Hope this helps,
Chris