Tiny Trak wheelbase finder tools

Hi, welcome to my first published, er, thing!

I've been playing with 123D design remixing a few Tiny Trak type models, I will upload once they are done, while remixing I found it difficult to find the exact wheelbase to use for undocumented Lego tracks or even, random eBay rubber tank treads.

While I have not printed it yet, here is a tool I've just about finished (it's work in progress so things may change) to make finding the correct wheelbase easier.

1. First thing to do is print out