Mecanum or 6WD

[,4lex S.]

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.

[ThirteenOfTwo]

Originally Posted by ,4lex S.

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.

[DonRotolo]

6WD for 2 reasons: First is pushing power, second is "we've never done Mecanum before".

[Ryan_Davis]

Originally Posted by BrendanB

You can have a max of 4 cims plus the motors included in the kop.


I would go with 6wd over mecanum in a heartbeat. Mecanums as mentioned have no pushing power and you won't be driving as fast around the field either. One problem with throwing the tubes to the center is you are increasing the chance for your opponents to grab it especially if you are the weaker drive. Yes there is some advantages with the lateral movement in front of the rack, but I'd take speed and pushing power over that.

A properly built 6wd and 8wd will have a turn radius of zero and waste no power.

The rules say:

<R45> Motors specifically permitted on 2011 FRC ROBOTS include:
A. all motors, actuators, and servos listed in the 2011 KOP Checklist,
B. an unlimited number of COTS servos with a maximum power rating of 4W ,
C. one or two CIM motors in addition to
those provided in the KOP. This means up to four CIM motors and no more can be used on the robot

[dodar]

Originally Posted by DonRotolo

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.

[GGCO]

It's a pretty board statement, but from my experience I'd have to say 6WD because a macanum bot will get pushed around easily.

[Charmander]

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

[Charmander]

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

[Chris is me]

I'm going to disagree with teams that go "mecanum = agility". Every year I see so many teams who say "oh we should be agile so we need a mecanum drive" and it drives me nuts.

First, agile is a very vague term. Mecanum has a specific kind of motion it can do that 6wd can't. The real question is do you need that kind of motion?

Second, it is very easy to underrate the "agility" of a 6wd system. It can turn easily on a dime and drive very well in that fashion. The only thing it can't do is strafe.

Essentially, the trade off is strafing sideways or resistance to pushing / pushing power. Which is more important?

[Ether]

Originally Posted by ,4lex S.

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?

[mathking]

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.

[Cyberphil]

Originally Posted by Chris is me

I'm going to disagree with teams that go "mecanum = agility". Every year I see so many teams who say "oh we should be agile so we need a mecanum drive" and it drives me nuts.

First, agile is a very vague term. Mecanum has a specific kind of motion it can do that 6wd can't. The real question is do you need that kind of motion?

Second, it is very easy to underrate the "agility" of a 6wd system. It can turn easily on a dime and drive very well in that fashion. The only thing it can't do is strafe.

Essentially, the trade off is strafing sideways or resistance to pushing / pushing power. Which is more important?

I see the same exact thing! It makes me confused. I would not consider mecanum more maneuverable also. The only trade-off is pushing power to strafing.

Well stated.

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

[Jeffy]

Originally Posted by ThaineP

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.

[Ether]

Originally Posted by Jeffy

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.