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View Poll Results: Mecanum or 6WD
Mecanum 90 40.36%
6WD 133 59.64%
Voters: 223. You may not vote on this poll

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Unread 09-01-2011, 16:10
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Re: Mecanum or 6WD

"throwing tubes to the center" is an advantage to mecanum because it is a shorter distance from where the tubes are picked up to where the grid is. Thus, more time is spent placing tubes on pegs and less time is spent traveling. The forums have stated again and again that 6WD is faster in a forward, reverse direction than mecanum.
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Unread 09-01-2011, 16:21
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Re: Mecanum or 6WD

Quote:
Originally Posted by Charmander View Post
"throwing tubes to the center" is an advantage to mecanum because it is a shorter distance from where the tubes are picked up to where the grid is. Thus, more time is spent placing tubes on pegs and less time is spent traveling. The forums have stated again and again that 6WD is faster in a forward, reverse direction than mecanum.
If i were on the other team, I would be stealing those tubes that are "in the open".

As per speed, in the forward direction, mecanums, (for the most part) act as any other wheel with lower traction would. Therefore, if it were geared the same way and the wheels are the same size, and your wheels do not slip on acceleration, a 6wd, 8wd and mecanum drive will be the same speed forwards and back.
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Last edited by Jeffy : 09-01-2011 at 16:22. Reason: typo
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Unread 09-01-2011, 17:09
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Re: Mecanum or 6WD

As per the posts so far....

Speed: Equal
Maneuverability: Mecanum
Traction: 6WD
Difficulty in Design: Mecanum
Power Consumption: equal

Is that it? Do mecanum and 6WD have different acceleration rates?
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Unread 09-01-2011, 17:20
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Re: Mecanum or 6WD

Quote:
Speed: Equal
Maneuverability: Mecanum
Traction: 6WD
Difficulty in Design: Mecanum
Power Consumption: equal
I disagree with difficulty in design. The programming, as well as driver training is a much greater requirement for a good mecanum system (I have built an omnidirectional system before, and I say this even considering the availability of example code). The maneouvrability is also a lot tighter than you would think (strafing is not as much of an advantage as most people think). In the end, with a well designed system, it is driver skill, either way.

If I recall, 80%+ of championship Einstein robots have been tank drive over the years.
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Unread 09-01-2011, 17:46
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Re: Mecanum or 6WD

Quote:
Originally Posted by ,4lex S. View Post
I disagree with difficulty in design. The programming, as well as driver training is a much greater requirement for a good mecanum system (I have built an omnidirectional system before, and I say this even considering the availability of example code). The maneouvrability is also a lot tighter than you would think (strafing is not as much of an advantage as most people think). In the end, with a well designed system, it is driver skill, either way.
First: I think he was saying difficulty in design is greater for mecanums.

Second, I think that when the safe zone is only seven feet long (minus the 16" pegs for <6 feet), strafing could actually be really useful, especially since an effective defender will just body block in front of where they know you're going to put the tube. With a mecanum you can sort of get in from anywhere and sidle over, with tank that takes quite a bit longer.

Third, I agree that while each system is stronger than the other in certain respects neither is inherently superior.
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Unread 09-01-2011, 18:54
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Re: Mecanum or 6WD

Quote:
Originally Posted by ,4lex S. View Post
The programming ... is a much greater requirement for a good mecanum system (I have built an omnidirectional system before, and I say this even considering the availability of example code)
What part of the programming of mecanum did you struggle with?



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Unread 09-01-2011, 19:24
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Re: Mecanum or 6WD

We have done 6WD and mecanum, both have advantages. I do think that given the depth of the scoring zone, a mecanum drive could be a big advantage. Furthermore, while mecanum drive robots are easier to push around, I have found them to be more difficult to block. The ability to always be able to move directly away from a blocker is very nice. It makes it much more difficult to continuously block the robot.

All that said, the best drive train we have produced was probably for Rack 'N' Roll, a 6WD with omni wheels on the "front" (read: the end where the tube is dangling) and the other four wheels (aft and a little aft of center) were traction wheels. That year we geared for torque over speed, which served us pretty well. The base of our arm gave the back end a lot of traction, but the whole thing spun really close to in place.

Side note: If you choose to do a one speed mecanum system you have to give yourself enough torque. We had quite a few problems in Overdrive with motors overheating because we didn't have enough torque when strafing.
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Unread 09-01-2011, 17:48
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Re: Mecanum or 6WD

6WD for 2 reasons: First is pushing power, second is "we've never done Mecanum before".
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Unread 09-01-2011, 18:38
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Re: Mecanum or 6WD

Quote:
Originally Posted by DonRotolo View Post
6WD for 2 reasons: First is pushing power, second is "we've never done Mecanum before".
More reason to try it. This will be our team's 7th FRC season and we have done 6wd for each year, but we are heavily debationg 6wd vs. Mecanum.
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Unread 09-01-2011, 18:47
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Re: Mecanum or 6WD

This drive system team 2404 used is interesting... it has many of the characteristics of the mecanum drive system.

http://www.youtube.com/watch?v=pZf1-...eature=related
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Unread 09-01-2011, 18:49
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Re: Mecanum or 6WD

This drive system 2404 is testing is interesting. It has many of the pro's that mecanum wheels have.

http://www.youtube.com/watch?v=JqJK0E9Jpmk
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Unread 09-01-2011, 19:54
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Re: Mecanum or 6WD

How about Mechanum6? It could be like this:

\\\ ||| ///

\\\ ||| ///

So that there are six wheels, where the front and back pairs are Mechanum, and the center pair is straight Omnis. It seems like it could be possible, so it may not work.

Just an idea.


Thaine
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Unread 09-01-2011, 20:32
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Re: Mecanum or 6WD

Quote:
Originally Posted by ThaineP View Post
How about Mechanum6? It could be like this:

\\\ ||| ///

\\\ ||| ///

So that there are six wheels, where the front and back pairs are Mechanum, and the center pair is straight Omnis. It seems like it could be possible, so it may not work.

Just an idea.


Thaine
like this?

I assume it would allow you enough traction to effectively push other mecanum bots, but thats about it.
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Unread 09-01-2011, 20:35
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Re: Mecanum or 6WD

Quote:
Originally Posted by Jeffy View Post
like this?

I assume it would allow you enough traction to effectively push other mecanum bots, but thats about it.
Maybe they needed the omni's to assist rotation since the mecanums are mounted incorrectly.


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Unread 09-01-2011, 20:59
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Re: Mecanum or 6WD

A. Yes, like that.

B. I haven't build a Mechanum drive before, so humor me.

I was thinking you'd get the strafing ability as well as extra power and speed from six wheels.
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