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Unread 28-02-2011, 14:45
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JVN JVN is offline
@JohnVNeun
AKA: John Vielkind-Neun
FRC #0148 (Robowranglers)
Team Role: Engineer
 
Join Date: May 2001
Rookie Year: 2000
Location: Greenville, Tx
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Re: pic: Team 148 - 2011 - Raptor

Quote:
Originally Posted by Joe G. View Post
I can imagine that the all-omni wheel drivetrain would create a nice "drift" effect when turning around during high-speed motion, a maneuver that can be seen at about 1:44 in their video. I can imagine that this will come in handy, due to the "back and forth" nature of driving in this game, and that this may have actually been hampered by the kicker wheel.

CAD drawings that flash by all feature a kicker wheel, as well as many practice bot pictures. But all footage of the final robot seems to place the battery in the center of the robot, in place of the mass of sheet metal that (presumably) supported the sideways wheel.

Also, John mentions a major change to subsystem 1 (the drivetrain) here. Coincidence? Or iterative design?
You got it.
The original drivetrain was a full Nonadrive system, but we ended up removing the sideways wheels around Day 31 (see the blog post linked above). After a week of practice we decided it wasn't necessary. In my mind, all our work and testing since that point has confirmed we made the right decision.

When we removed the middle wheel our original plan was to swap out the 4 primary omni wheels with 6" traction wheels, however... well... we were impressed with what our driver Connor can do with it.

We call this configuration "Butterfly Drive." Which is a joke in reference to how this robot can be pushed sideways while on all omni wheels (obviously when we drop the traction wheels she stops floating like a butterfly and stings like a... you know.)

I don't think all of it's virtues are readily apparent. I assure you there are more reasons to do an articulating drive than moving sideways. Though I realize most other teams may not value the same things we do, and as such may not make the same tradeoffs we did.

We love "traction mode" and it's virtues in autonomous and driver control. We love the simplicity and modularity of this module design. We love how the drivetrain performs on all omni-wheels (super efficient geartrain + 4 omni wheels = smooth like butter). We're very happy with what we ended up with...

-John
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In the interest of full disclosure: I work for VEX Robotics a subsidiary of Innovation First International (IFI) Crown Supplier & Proud Supporter of FIRST
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