Unique-ish gear

I’m looking for a single model (or maybe a few sizes of a single model) to be made. I need an “inverted” gear. In other words, I need a ring model with gear teeth on the inside. Hopefully sized and collisioned to match either the PHX gears or that one guy’s new gear pack (which is really helpful by the way). If people really need a concept picture, I’ll post one.

Thanks!

How would a gear with teeth on the inside even work? I would very much like to see this concept picture.

http://img401.imageshack.us/img401/903/gearconcept.png

The gear inside is powered; it turns the outside gear, which would be attached to something behind it.

Honest question: How hard can it possibly be?

It honestly isn’t that hard. The hard part it making it not look like absolute shit, which can be very time consuming.

For the use I’m planning (i.e. testing a theory) it doesn’t have to look good.

BUUUURP

'Scuse me.

I think there’s a reason why this was never mass produced in real life.

Actually, these gears are found in practically every single handheld power drill in existence. In fact, that’s where I got the idea.