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Re: 2017 Drive Train
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Re: 2017 Drive Train
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Re: 2017 Drive Train
So just so some newer teams don't read this thread and think that mecanum wheels are completely useless at holding their own in a game like this, check out this video from 2014. https://www.thebluealliance.com/match/2014arc_qm29
The bright red and yellow robot (us) were running the new vexpro mecanums (before the metal casters oh how we wish they had the metal insert like they do now) and we easily could hold our own in a pushing contest. The key with mecanums is that the center of gravity needs to be as low and as perfectly centered as possible. So, do a lot of mecanum drives get pushed around, yes. BUT, if they are optimized, can they hold their own against the most pushy of robots, absolutely! Just something to think about before teams blindly throw it out because they are under the assumption they can be pushed around with minimal effort. |
Re: 2017 Drive Train
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Re: 2017 Drive Train
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Re: 2017 Drive Train
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Re: 2017 Drive Train
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Just Sayin. |
Re: 2017 Drive Train
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Re: 2017 Drive Train
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Re: 2017 Drive Train
In my view, if you haven't built a swerve drive or H drive or mecanuum drive and had your coders code it and your drivers drive it, you really need to stick to tank drive this year.
The practice time you will lose with your robot is just not going to be able to be overcome by the extra features you are imagining you will have. Finish early. Give your coders coding time and your drivers practice time and your whole team time to iterate and improve your robot. THAT is the way to be playing after lunch on the last day of the tournament*. Dr. Joe J. *said the guy who designed his first Swerve Drive for Ladder Logic (1998 season). Chief Delphi won 3 blue banners with CD3. I KNOW that drive trains matter. But driver practice matters more. A LOT more. |
Re: 2017 Drive Train
Disclaimer: Build a tank drive. Please. Just do that. If you are the kind of person who listens to advice on CD to make drivetrain decisions, do that.
-- That said, there's a pretty reasonable argument for swerve or butterfly drive this year if it's compact. The bumper rules limit intakes since six inches of room on each side of the drive must be backed by bumper - leaving more space for various omnidirectional drives. Lining up at the peg, goals, or human loader could theoretically be faster using a strafing drivetrain. And the full field sprints lend themselves well to butterfly style drivetrains. But I mean, if you haven't considered these drives and built prototypes long before reading this post, it's too late, and the possible small advantage they could give your team is more than offset by the development difficulty. We have a bunch of other tough tasks to do in this game, don't make it harder than it has to be. |
Re: 2017 Drive Train
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Re: 2017 Drive Train
It seems to me that people are far overestimating how hard it will be to deliver the gear. The (horizontal) margin of error is 6 inches. That's (approximately) the width of the gear. Because the hook is spring loaded, you have even more leeway, not to mention that the place you have to deliver to is directly in front of your driver station. I'd argue it was harder to line up with the chute in 2015. If your driver really can't do it, just put a camera on the robot and use that to align, but don't build your drivetrain around this particular challenge.
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Re: 2017 Drive Train
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In my experience, a field-centric holonomic drive is the easiest robot to learn to drive. Mecanum provides a good trade-off between complexity (2 extra gearboxes, a bit of learning to program) for increased maneuverability. It's also the closest you'll get to a COTS solution. Any other drive really needs to be developed in the off-season. |
Re: 2017 Drive Train
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There's this myth that mecanum is hard to program. It just isn't. (It's also incredibly easy to build. Just direct-drive four wheels off of appropriate gearboxes, and voila.) That said, straight-up mecanum will be a mistake this year. The parallels to Ultimate Ascent say defense will be *huge*, and mecanum drives don't do a good job powering through defense. |
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