I have seen a video of a square or rectangular base that had omni wheels in the corners. I think it was a youtube video but I can’t find it. Does anyone know what the title of that video is? From what I remember the robot could go straight and diagonal pretty well. thanks in advance for any help.
Rusty
VEX Team 2118
[email protected]
What you believe you are looking for is a holonomic drive. Here are some videos:
Is this the type of drive you are referring to
http://botsnstuff.com/wiki/X_Drive
It’s called an X-Drive. Google that, and you can find plenty of videos and CAD models.
Wow
3 answers within a minute of each other
Thanks everyone, that is exactly what I was looking for.
Rusty
For any other FRC people on this forum; I feel I must suggest a nonagon drive as it is clearly superior in every way to an octagon.
If you didn’t get the joke, watch this video
Oh my god. That is so cool. That gearing is amazing. And that wiring. Everything looks so clean and polished.
You’re making me wish we had a decent FRC team around here for me to join…
You do. Hall Of Fame Team 842 is in your area.
Here’s a video of their 2013 robot: http://youtu.be/4nHd_bG5dZE
-Nick
It has nine sides but it only has three wheels.
Is that basically a three wheel drive on pivot streering? I hesitate to call it three wheel omni since it’s not exactly like three wheel holonomic you see in Vex because it is without roller wheels. You would get some wicked grip and steer exactly where you want to go over omnis. No getting pushed around either!
Are there advantages over a 4 wheel pivot drive? (Other than being much cooler looking?)
Yup, a three-wheeled swerve drive (although to be specific, it was more of a crab drive because all of the wheels pivot together). I think it was made this way because back in the year it was constructed, FRC teams were only allowed to use a maximum of 4 CIM motors (the big black cylinders). This meant they could use one per wheel and then the fourth to steer. The game this year relied on your robot driving laps of the field to score points (among a few other methods) so clearly the strategy for this team was to build a small, lightweight, maneuverable robot that could drive as many laps as possible. Really, there are no advantages over traditional 4-wheel swerves other than that it is the minimum amount of motors (a huge source of mass in FRC robots) required to do a “swerve” system (other than using castors, which is sketchy on a good day). That being said however, statistically nonagons are infinitely better than octagons or traditional swerve drives. 100% of nonagons have become world champions.
That’s what we call a Type II error. 
This is incorrect. Tumbleweed’s wheels were powered by 4CIMs and 2 Fisher Price motors (through AM planetaries to ‘make’ them into CIM motors,) and the modules were steered likely by a Globe motor, which was a motor we used to use in the KOP that had a gearbox attached to it.
Photos:
http://www.chiefdelphi.com/media/photos/31434
[http://www.chiefdelphi.com/media/photos/30599