Nelson Traveling Sprinkler Parts

We have a [Nelson Traveling Sprinkler](http://amzn.com/B00002N6AN) that got hung up and stripped the final drive gear. We could've bought a full gear set from Nelson, but it costs $30!

So whats a person with calipers and a 3d printer to do?

Reverse engineer it, of course!

There are three versions of this gear uploaded. The "correct" gear is the .45 inch version. On my printer all the dimensions, except the center hole, were printing correctly so I made a .47 inch version since they were