If any of it doesn't seem finished, it's because I ran out of time. This wheel was mostly a full-scale experiment that my brother will (hopefully) use with his Bengals. I used my parents help (and their house...oh, the horrors that happened to that living room) for a good week and a half constructing this monstrosity, and while I know they would be willing to let me stay longer, I have to report back to school on Monday (plus I ran out of the cat food I brought).
I did buy a rubber runner (I dislike the idea of using carpet on any cat toy) for a running surface, but there's enough traction on the unfinished wood for them to get the wheel to move already. I don't think the weight of the wheel matters much; a prior project with my dad involved welding together a cat wheel (which failed for several reasons), and that 48" steel wheel was around 25 lbs as well. I'm actually quite pleased that this wheel was only 28 lbs. I wouldn't be at all surprised if the other hubless wheel linked earlier weighs 40+ lbs.
The groove the skate wheels fit in (1/2" deep; I don't think the wheel will ever come out) could use a little more sanding so that the skate wheels can roll a little more smoothly, but it is functional. Also, there are a total of 8 skate wheels spread around, which should minimize the chance it could come off the tracks (and will also help it retain its form better than only two wheels on each side).
The wheel is 3/4" thick and consumed around 2.5 sheets of 1/8" 5'x5' Baltic Birch. It *is* hollow, but it is quite sturdy. We did a lot of lamination to put it together, and consumed three sheets of 3/4" 4'x8' particle board just for molds. The main mold we constructed the wheel around was 84 lbs (it essentially was a hubless wheel).
The base isn't quite what I planned, but it works. Only 1/8" of clearance exists between the base and the wheel; any more and there would be a multitude of issues with the base.
More pics to come soon. If my dad works on it any more, I'll be sure to share additional pictures.