https://youtu.be/Ud2lKCYvATc Reminiscent of the battery and windup powered "no fall" toys of my childhood, I designed this "No Fall Toy Mechanism" to illustrate how the battery and windup powered "no fall" toys I was gifted over fifty years ago avoided falling off the edge of a tabletop, countertop, or other elevated surface, without the use of micro controllers, servos and / or electronic sensors. While designing my version of this mechanism using the computational features of Autodesk Fusion 360 for balance (e.g. "Center of Mass") and a scientific calculator for geometry, I was truly amazed by the skills and talents of the mechanical engineers who designed mechanisms such as this using drafting machines and slide rules over half a century ago. In the demonstration video, I let the mechanism loose on an 8 1/2" by 11" (the size of "standard" notebook paper) by 1/2" thick piece of untreated MDF. As can be seen in the video, using only electro mechanical techniques, when the mechanism approaches the edge of the MDF the conical front wheels allow the front yoke to pivot thus lowering the chassis front to the point where the rotation gear contacts the MDF surface. When this occurs, the mechanism rotates clockwise (as viewed from the top), steers away from the MDF edge, then continues on a new path to the next edge. As usual, I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to ask as I do make plenty of mistakes. One final note, I receive no compensation in any form whatsoever for the design, equipment, parts and/or materials used in this mechanism. Designed using Autodesk Fusion 360, sliced using Cura 4.4.0, and printed in PLA on an Ultimaker 3 Extended and an Ultimaker S5.