I was just in the process of doing the same thing............except I'm using a fan, that way when not spinning carts it can still be used as a fan. I started collecting my parts a few weeks ago when my elbow started to hurt from spinning too hard by hand.
Congrats 2pack, nice job man! our minds must work similar........especially since we did it at the same time! LOL At least you saved me from having to post pics
I'm using PVC for tubes, with plugs, to hold the cart.