Dinotrux shadow wheels

I've added small (really small) wheels at the bottom of the tracks. They could be bigger, maybe in some other revision.

Tracks needs supports (not for wheels) but for other overhangs.
For printing wheels I suggest to use brim.

What do we have here:

- tracsks.stl - modified left/right tracks to fit in small wheels
- wheels.stl - four wheels with four rods
- joint.stl - this part was missing in the original design. I used this to join tracks to body.

Assembly:
Put wheels on rods and put them to tracks. There is zero tolerance to secure the rod in place. I was able with little bit of force to insert all four wheels without any problem.

Tracks are painted with acrylic.