About this 3D model
This is an idler with teeth to increase the ability to hold the tracks in place. If attached to a power source somehow they'd be able to drive the treads but that was not my intention (I'll be making one of those soon based on this design). This is for: http://www.thingiverse.com/thing:35668 The length between points was found to be different than expected through trial and error. Sorry - Had to update... it helps to double-check that the hub doesn't interfere with the gear part of it. Now fixed. And one more fix - I should really test before releasing my items. hehehe. Adjusted outside diameter of teeth down quite a ways. Adjusted width of teeth up a bit and made angle a little better for printing.