[DampRobot]

Ok, a few things to suggest.

First, go hex. It's 2014, no one should ever have to use keys again (except maybe in CIMs).

I challenge that you'll be able to build a lot of this stuff better than COTs. The COTs wheel trucks (WCP and VersaBlocks) are already really well thought out, and even if you have the resources to make them for less than you can buy them for, I'm not sure you can really make them "better." For gearboxes, (again, depending on resources) you can probably make them cheaper and maybe lighter than COTs options, but no way will they be easier to machine or faster to make, and they probably will be less efficient as well. Well, except if you're 1717.

It sounds like you basically want to copy the poofs machine. That's cool, you'll definitely learn something from it, and the kids definitely will too. But there are other ways of throwing t-shirts that might be worth investigating. Could you catapult them, or maybe slingshot them?

But, other than that, it sounds like you know what you want. Good luck with your project, and have fun.