Hey, all - my first experience with electronics, soldering irons, and wires ever turned out as a success, thanks to the great $50 robot tutorial and the very helpful responses to my questions on the forum so thanks all of you. I took some pictures to share and posted them HERE
The wheel I picked up at Home Depot (I just happened to spot them because they were next to the screws - you get 4 of them for like 2 bucks, so I figured it was worth the 2 bucks to make it look a tiny bit more fancy than the plastic bottle method. The front of the robot is so light that it doesn't even really roll, though
- it just slides around.
The HiTec 311 servos did not come with mounts included, but these brackets
are cheap and fit great if you have a dremel tool to shave down one of the sides. #8 or M4 screws fit perfectly.
I had some 1/8" HDPE sitting around from a ski boot repair I had done a few years ago and that was plenty strong enough, plus thin enough that the screws that came with those aluminum hex standoffs (holding up the circuit board) were long enough to go through a washer and the plastic and still engage with the standoffs.
Finally, for the cardboard wheels I didn't need to use any sticky tape or anything else. The Hitec servos come with a bunch of servohorns, or whatever you call those connectors, one of which is just a small square with raised edges (I think it's supposed to be used in conjunction with the sliding bar piece - the square piece I'm talking about is the far upper left of this image
and it engages the longer piece underneath). If you smash the raised edges into your cardboard wheels they will effectively key into it and prevent it from spinning. You can kind of see what I did on the screen right wheel of this image
of my robot. The big circular servo piece on the outside is unrelated - it's just there to eat up screw length and also to act as a big fat washer.
Anyways, thanks for everybody's help! Time for robot #2 next