Question about wheel preferences

[roboticsgoof95]

My mentors have no interest in mechanum wheels, and i love them. How efficient are they or arent they. I just want outside information about different preferencs on wheels.

[Ether]

Originally Posted by roboticsgoof95

My mentors have no interest in mechanum wheels, and i love them. How efficient are they or arent they. I just want outside information about different preferencs on wheels.

When you say "efficient" what do you mean by that?

[roboticsgoof95]

I just mean like what are the good and bad about these wheels. And what wheels could make up for the bad things about the wheels. if that makes sense

[Ether]

Originally Posted by roboticsgoof95

I just mean like what are the good and bad about these wheels. And what wheels could make up for the bad things about the wheels. if that makes sense

Not to discourage you from asking, but you might want to try the forum search feature. There have been many many discussions about this. You might be delighted to discover how much you could learn. It's worth the effort.

[roboticsgoof95]

alright thanks.

[Ether]

Originally Posted by roboticsgoof95

alright thanks.

This will get you a lot of hits:

1) Go to the forums advanced search page.

2) Set the options as shown here.

[BJC]

I'll say two things real quick, then you can go search the topic as much as you'd like:

1. If you like Macanum because they allow superior manuverability to get around defence, then do NOT use them. They are not superior in this regard and are actually MORE suceptable to defence because they can be pushed around so easily. There was a thread on CD a while ago asking for proof of a mecanum driving "circles" around a tank drive. Although there were many videos of the tanks driving circles around mecanums there was not a single video of the opposite.

2. If you like mecanums because they allow you to more quickly allign to field elements this is slightly more valid. However, the lack of traction is still probably an overpowering reason not to use them. Building a simple tank and practicing with it will yield much better results then a mecanum. (Another point: you need lots of practice to be a good mecanum driver.)

Happy searching, Bryan

[Marc S.]

Just a few pros and cons

Pros:
1. Omni-directional movement.
2. Relatively easy to build.

Cons:
1. Usually requires larger heavier wheels(than 6wd's) .
2. Harder to use 2-speed transmission(meaning more load on motors and slower top speeds).
3. Can be easily pushed(with 1 finger).
4. Requires a lot of practice to make effective.
5. Only works for offense.

[Andrew Schreiber]

Originally Posted by Marc S.

3. Can be easily pushed(with 1 finger).

I'm not a fan of mecanum wheels but I gotta call this one out. Where is your source for this?

[EricH]

Originally Posted by Marc S.

Cons:

3. Can be easily pushed(with 1 finger).

5. Only works for offense.

I don't think so.

1 finger will not push a 150-lb mecanum drive. Or a 150-lb 4wd. MAYBE a 150-lb omni-drive (with only omni wheels) in the sideways direction can be pushed with one finger.

It's more accurate to say that mecanums have lower pushing resistance and lower pushing power than X drive (where X is some other specific drive type).

Also, I've seen mecanums play effective defense. Effective defense is just as much getting in the way as it is ram and shove someone else around.

[IndySam]

It all depends on the game. We used mecanum last year because of the maneuverability and lack of defense in the scoring zone and were quite happy with them. They also aided in easy pick up of tubes. Having said that, the only way we would use them again is if the game had similar rules. The odds are probably 80% we won't use them again.



But common guys lets not over generalize on their faults.

1. Lots of practice needed to be a good driver. Totally not true. They need no more practice than a tank drive.

2. Heavy - wheels are heavier yes but you only need 4 and no chains or sprockets are required so this is also a straw dog.

3. Push with a finger - now your just making things up.

[Marc S.]

Originally Posted by IndySam

1. Lots of practice needed to be a good driver. Totally not true. They need no more practice than a tank drive.

2. Heavy - wheels are heavier yes but you only need 4 and no chains or sprockets are required so this is also a straw dog.

3. Push with a finger - now your just making things up.

The reason i say it needs more practice is because, its omni-directional. While it probably doesn't require as much practice as a swerve drive it still has the complexity of one. A 6wd yes does need a lot of practice to make perfect but it is very easy for a new driver to control. I personaly have never driven a mecanum robot so my expirence comes from swerve drives.

Yes they don't need chains or sprockets, but they are still larger and very heavy. The larger diameter the wheel, the more force you need to excelerate regardless. Add weight and the required force goes up even further.

Yes maybe claiming that someone could push a mecanum with a finger was a exaggerated. Frankly I might just be spoiled by robots that can't be pushed at all.

[sdcantrell56]

Originally Posted by Marc S.

Yes maybe claiming that someone could push a mecanum with a finger was a exaggerated. Frankly I might just be spoiled by robots that can't be pushed at all.

I'd love to see your mythical perfectly stationary robot...

[EricH]

Originally Posted by Marc S.

Yes they don't need chains or sprockets, but they are still larger and very heavy. The larger diameter the wheel, the more force you need to excelerate regardless. Add weight and the required force goes up even further.

Mecanums aren't larger in diameter than most wheels. They're larger in the axial direction. (Now, if you use 4" wheels, you might think that mecanums are larger, but most teams use 6-8" wheels.)

[BJC]

Originally Posted by IndySam

But common guys lets not over generalize on their faults.

1. Lots of practice needed to be a good driver. Totally not true. They need no more practice than a tank drive.

I have to say that I see way too many teams using mecanum drives that are opperating them like a tank drive. Mecanum drives can be effective if they are utilized properly. This requires practice. I know that 2337 does extensive driver training which utilizes a very different mindset then driving a standard tank. They practice stuff like using the opponent's inertia to assist them and peeling off of defenders; a lot of things that are nearly impossible for a tank to do because they REQUIRE the ability to move sideways. So I would say that they require a similar amount of practice for the driver to become proficent (you can never have enough practice) but an entirely different mindset. This is what most teams don't do and a part of the reason why mecanum wheels have a bad name.