V0.2-Mechanical and Actuation Update

A project log for Project Scrappy

Open Source Modular Robot

daniel-resioDaniel Resio 10/12/2021 at 23:570 Comments

Since the last update, I started looking at sourcing and standardizing some of the components, and looked at the price of doing so. Although it looked cool, the previous design required 2 beveled gears to power the wheel, and 2 bearings to support the wheel itself. A quick search on McMasterCarr found each component costs ~$5 USD. So for a robot with 4 wheels it  would be ~$80 USD just for mounting hardware. Not including I was planning on implementing a servo so the wheels can control better. This prompted me to redesign the main structure for stepper motors. 

Core Platform:
I split it up instead of 4 modular segments to 8 segments. This way the wheels and cover for protection can be separated allowing the assembly to be more modular. For rigidity there is now a second one stacked underneath it.  

Wheel base: 
The wheels now connect directly in line with the stepper motors to not only remove the need for the beveled gears, but one of the bearings. The second bearing is used somewhere else, however removing the beveled gears should save ~$40 USD and reduce failure points. 

Servo Actuation:
Servos have been added on each leg so the drive train can be rotated. This allows the wheels to not have to fight friction as they were before. Another solution would be to create some omni-wheels or make it a mechanum drive. Those however, may be different modules I develop in the future. For now I feel I can learn more developing controls on an over-actuated platform. 

Before I was doing line renders for the system as I enjoyed the style it was in, but also because I was pretty lazy with appearance properties. I had some fun with that this time around when I went a little overkill with modeling a servo... I went back and added some textures on the battery too and made a full render of the system so far (3D printed materials in white).

This time it felt like I was just deleting so much of the old progress I had made, but such is part of the design process. You cannot improve a design if you don't remove the parts that are inefficient or don't make sense. Even now, this will probably change significantly 1 or 2 more times before the "final" design gets created. And even after that once 3D printing, assembly, and testing begin a lot will be completely redesigned once again as it attempts to become reality. This project is just getting started!