teynon:
Obviously, this is not the end design goal. This is a stepping platform to ensure that I am able to make stuff connect and function (ie program it to do stuff).
I kinda figured that.
teynon:
The point of cardboard is that I can move stuff around. Right now I can just reposition stuff as needed.
I think cardboard is a fine material to prototype with; heck, you can even build the final with it, if you wanted to (for extra stiffness, fiberglass over it). Still, you might want to try playing with foam-core board; it tends to be lighter weight (for the same thickness), and has greater bend resistance.
teynon:
Also, duck tape can hit up to 80 lbs per wrap. Just because it's not pretty and poorly done in the picture, doesn't mean it wouldn't work. Never underestimate the power of duck tape.
Nothing wrong with duct tape, when used properly; I wasn't actually harping on the construction, just that it seemed you expected the motors, with some wheels attached, to move the platform (with the weight of the Arduino, motor shield, batteries, etc). It was that part I was more concerned about, because we have had a ton of newbies in the past trying to build essentially the same kind of platform, and wondering why they can't get it to move.
teynon:
I bought a robot kit that came in the mail today and it has some elbow shaped motors that have the edges on the drives trimmed down to be non-circular. Some people at work suggested filing them as well.
I'm not sure what you mean here, unless you are meaning a "D" or crescent shaft profile? Typically those are used when the part you are attaching has a similar hole profile, and/or also has a setscrew which can be tightened against the "flat" of the shaft. You may or may not find it easy to flatten the shaft of your small motors; it can be difficult to do unless you can remove the armature from the motor, and clamp it in a vice. Those small motors are meant to be taken apart in that fashion. Plus, while this could be used to keep the shaft from "spinning" inside the wheel (or gear), it's not ideal for such a small motor.
Most of the time, such gears or wheels are fixed to small diameter shafts with a friction fit. Sometimes, the shaft end will be knurled (and the part to go on the end will be plastic with a slightly undersized hole; the knurling grips the plastic, and bites in - kinda a cheap spline fit). Otherwise, a drop of superglue, loctite blue, or some epoxy is a better solution to affixing a wheel or a gear to a small shaft. If it's a metal gear, you could do an interference fit by freezing the rotor (and shaft), and heating the gear (that has a slightly smaller bore) - to expand it; fit it over quickly, and when everything comes to room temp, just about nothing will budge the gear off the shaft.