Step 1: Materials
2 ball bearings
Bike inner tube
4 Chinese take out containers
Spare blocks of wood
Various PVC pipe fittings
1/2 in. conduit pipe
Multi purpose caulk
Heat Shrink Tubing
A lot of my materials were improvised based on what was happening. For instance, I already had pipe, and when I got the bearings, they were different sizes, hence the PVC fittings.
Step 2: PVC Box
Drill a hole the size of your conduit in the middle of 2 rectangles as close to the bottom as you can, allowing space for the bearings. i.e. put the bearing at the bottom of the plexi, and trace the inside of it to know where to drill.
If you don't have the right sized drill bit, go one size up, and make a bushing out of the inner tube.
Be warned that when using any power tools on the plexi, it will start to melt as you go, so you will have to stop frequently.
Use the caulk to glue all but one of the squares together. (so it's a rectangular prism without a top) Book ends are helpful for keeping the pieces in position while they're drying.