2-3-4-5-Owl - Ridged Y Carriage for Mendel and Prusa

UPDATED belt holder (see below)

This is an ridged and precise y carriage for mendel and prusa printers.

This owl shape y carriage features some advantages over the original frog design:
- It utilizes all 5 mounting holes of the heatbed to achieve maximum stiffens for the heatbed.
- It utilizes 4 linear bearings to improve accuracy.
- It uses 3 point bed leveling (4 point leveling is over constraint. 4 Point leveling only seams to work if the construction is flimsy enough)
- 2 guiding r