Question about wheel preferences

[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.)

[IndySam]

Originally Posted by Marc S.

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.

I'm not trying to say whether they are better or not or when they should be used, I'm just tiered of the assumptions and rumors that are tossed around.

You say they need more practice but you have never driven one. You say they are very heavy but totally discount the weight and extra complexity you need for six wheel drive.

I just want everyone to know that when you state facts you better be sure of them.

[Cory]

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.

Everyone knows Truck Town is the only team that can't be pushed

[sanddrag]

Originally Posted by Cory

Everyone knows Truck Town is the only team that can't be pushed

Especially the 2003 one, before the ruling.

[Andrew Schreiber]

Originally Posted by sanddrag

Especially the 2003 one, before the ruling.

Gosh was that a good looking robot. They did so much research on what tread to use. I was going through one of 68's cabinets last year and found about a half dozen tread samples (12+ treads each)...

[Clinton Bolinger]

Originally Posted by Cory

Everyone knows Truck Town is the only team that can't be pushed

Didn't Truck have Mecanums this year?

So does this mean the Mecanum are un-moveable in the right situation?

-Clinton-