Seg...stick.

Step 6 It's starting to look like a...something.

Unfortunately, you can't just stick the wheels on a shaft, put it in the drill, strap it to a stick, and go. (I wish...that was my original intention.) The drill chuck can't handle that much bending load. So, external bearings to support the rider weight are very necessary. Segstick uses mounted 1/2" ball bearings (McMaster PN: 5913K61). These are great because they can tolerate quite a bit of misalignment.

The process: Cut a piece of 3/4" plywood to the dimensions for the deck (where you put your feet), which will also hold the drills, bearings, and eventually the electronics. Then, mark out some holes for the bearings and for extra-extra-large zip ties to hold the drill in place. Hose clamps might work too. Then, drilled all those holes.

Pro Tip: If you leave one drill unmodified until the very end, you can use it to make everything else. ;)

The bearings are attached with 1/4-20 bolts. In this case, they require 1/2" spacers to match the height of the drill. While fastening everything down, it's useful to put the drive shaft into the bearing and drill chuck, and possibly even to have the drill motor running. This ensures good alignment as things are zip-tied/screwed/bolted/what have you. 

When everything is ready to go, the wheels go on with locking collars on either side to constrain them axially. Don't forget the key! And don't forget to tighten the chuck...a lot!