Omni Wheels--FIRST Tech Challenge

I am part of a FIRST Tech Challenge robotics team working to better understand technology via robotic competitions that are based upon accomplishing certain tasks. For example, launching plastic balls into a hoop, capturing points on a field, and driving autonomously to locations on a field. Our mission is "For Inspiration and Recognition of Science and Technology" (FIRST) More info at https://www.firstinspires.org/

The team that I joined had just started this year. Because this can be a very expensive club, we had to create a number of parts for our robot based on what we had laying around. Parts we were unable to afford last season consisted of 4-inch "Omni wheels". Omni wheels are designed to make turning of a front/rear-drive robot easier. The nine rollers perpendicular to the main wheel allow this wheel to roll forward and backward, as well as left and right with no structural strain. 

Because I had some experience with 3-D modeling, I set out to learn a new SCAD program called "OpenSCAD", which I still use today for my other models. I coded these wheels from scratch using basic measurements of the 4-inch omni wheels I found on andymark.com. These wheels have been finished for a few months now. I figured it was time to add this to my small collection of models here on Pinshape. In the 2016-2017 FTC season, these wheels were LEGAL. So, I expect them to be legal next year as well. This design goes out to all the teams in the FTC community! I wish you the best of luck in the 2017-2018 season! 

Specs: 

Wheel Diameter: ~4in

Inner Bore: ~8mm

Screw holes: ~4mm

Rollers: See pictures

Instructions: 

YOU WILL NEED: 

Wire coat hanger (2.2mm diameter)

Hot glue gun or plastic cement

Clamps

Step 1: Print both halves (Omni side 1 and Omni side 2) of the omni wheels as well as NINE of the miniature rollers (per wheel). Make sure to print both files of the omni wheel halves. If you print two copies of the same half, THEY WILL NOT LINE UP.

Step 2: Cut the wire coat hanger into nine straight pieces, 23mm long per wheel. 

Step 3: Put the coat hanger axles through each of the rollers and place them into their fitting slots on the edge of one side of the omni wheel. 

Step 4: Apply glue to one side of the omni wheel and sandwich the two halves together with the rollers in the middle. There are tabs on each half of the omni wheel that make alignment easier.  DO NOT GLUE THE AXLES OR ROLLERS TO THE WHEEL HALVES! THEY WILL NOT TURN!

Step 5: Use a clamp to hold the two halves together until glue dries. 

Print settings: 

Material: PLA

Temperature: 190*C

Speed: 50mm/s

Infill: 30% or higher for durable wheels.