The advantage of holonomic drivetrains

[irishninja]

Adding to what Ian said this happened with my team this year. We originally were using a tread drive sytem but our tread snapped. By the time we were on our 5th drivetrain and it was Thursday at the NYC regional we swapped for omni wheels in the front, knowing full well we wouldn't be able to get up the ramp.

Consequences of the omni wheels
We were able to turn which let us realign ourselves for shooting very quickly
We were able to be pushed very quickly while shooting
Instead of turning in very small degrees we made huge arcs, although our drivers got that under control
Our omni wheels actually broke
We were able to wreak havoc during the last 20 seconds of the game on the other side stopping from robots getting up the ramp knowing that we couldn't
We usually played backbot

In my opinion the good outweighed the bad, (we came in second), so it was a good tradeoff. If we had been primarily defensive and not played backbot, I'm not so sure the omni wheels would have been a good idea.

[newton418]

Team 231 chose us as alliance partners in the finals. I'm not sure, but I believe they had omni wheels that were all at 45 degree angles.
Yes, they did get pushed around; however, their driver did manage to "roll" around defending robots and pop a couple in the goal. Another advantage they had was, their infeed rollers were mounted on the long side of their robot, and their shooter was too. This provided room for the shooter and a large margin of error for the driver when they needed to pick up balls.
Here's the second match in the Lone Star Regional finals, if you really watch it you can see that nifty roll move used a couple of times.
http://video.google.com/videoplay?do...gional&pl=true

[ClayScales]

Originally Posted by newton418

Team 231 chose us as alliance partners in the finals. I'm not sure, but I believe they had omni wheels that were all at 45 degree angles.
Yes, they did get pushed around; however, their driver did manage to "roll" around defending robots and pop a couple in the goal. Another advantage they had was, their infeed rollers were mounted on the long side of their robot, and their shooter was too. This provided room for the shooter and a large margin of error for the driver when they needed to pick up balls.
Here's the second match in the Lone Star Regional finals, if you really watch it you can see that nifty roll move used a couple of times.
http://video.google.com/videoplay?do...gional&pl=true

Team 231's robot uses only two omni wheels in front of two pneumatic traction wheels (conventionally aligned). These afford extreme maneuverability at the cost of some lateral traction... surprisingly though, the omni wheels have pretty good traction fore and aft. Also, since our machine is oriented such that our wheel base is shorter than the track (wide and short), it maximizes the leverage of the traction wheels and we're still able to 'point' fairly well. Omni's do carry liabilities, but the trade off seems to have been worth it. NOT holonomic though.

Clay