Modular Marble Machine for 8mm Ball Bearings

This is a modular marble machine I built a little bit ago that is meant to be easily printable on even a small printer (4in by 4in). As such it is standardized so that a 1U block will be 12mm by 12 mm by 12mm. It is easy to create your own parts and make endless tracks. This can also easily be scaled up for larger marbles as you see fit.

Holes:
The holes are .125" in diameter and are .1" deep. The pegs that go into the holes are roughly .125" and .9" deep. Their is a hole in the centre of ev