mecanum wheels? mecanum vs holonomic

I have a few q’s

If you are using mecanum drive do you have to have mecanum wheels or can you use omni wheels?

I heard the programming is the same is this true?

How is the friction with a mecanum drive? I know holonomic has very little friction since they are on an angle, but is it the same with mecanum? Or is it normal because they aren’t angled?

mecanum=WAY better traction and power
omni=easier to build
you cant just use omnis to mecanum, the mecanum wheels are what make it mecanum.

So I still have to make those odd slanted wheels?

yes you would have to make your own because VexLabs does not sell them
also remember that FIRST does not allow them in their competitions
search ‘Mecanum’ on this forum i think somebody posted pic’s of their mecanum wheel with dimensions

This is for FTC not FRC

as long as they are made out of vex parts they should be legal correct?

yes but if you find a way to make them out of vex parts please provide instructions, what would you use for rollers? to get the 45 degree angle?

Expend a tiny bit of your time researching this subject and you should find a clear path to what you are looking for.

Blake

I believe someone has already done that.
I also created a set, found here.

Although mecanum wheels provide more traction and pushing power than the traditional omni-wheel holonomic set up, it is still very vulnerable to being pushed.

[EDIT]sorry blake we posted at the same time![/EDIT]

One of the mentors from FRC Team 839, Rosie Robotics, designed FTC-legal mecanum wheels made of only Vex parts. Here are links to some pictures that were posted on Chief Delphi:


http://www.chiefdelphi.com/media/photos/25959

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to make the rollers I think I would use the half inch spacers. They are quite big, not the black ones you get in the starter kit.

they are from the spacer kit on this page:
http://www.vexlabs.com/vex-robotics-fasteners.shtml

as to create the angles I think either custom cutting the metal plates or over lapping the metal bars and bending them…

There are a few pictures in the gallery that are made out of what I just described I believe.

You would think that you could just use omni wheels… aren’t they the same thing? just build differently? They are made to allow all directions of movement, same thing with the mecanum wheels right?

edit: YES! The one’s the otherguy posted we’re EXACTLY what I was talking about.

There are several places where you can find information on mecanum wheels, but there are subtle differences between it and omni-wheel holonomic drive (more traction, different speeds horizontally than fwd/bwd, easier to mount, etc.)

Some of these generalizations are not always true. When discussing design related questions it is best to try to avoid statements like these.

I think further experimentation and investigation will show that these wheels have comparable amounts of traction (wheels cannot have “power”, I think you should research this term so you can understand it’s correct meaning and usage.)

Omni wheels are in many cases easier to build. It is sometimes difficult to get the rollers at 45-degree angles.

One of the main advantages of Mecanum Wheels over Omni wheels, is that you can use a chassis almost identical to a “tank-steering” chassis. The wheels axles are all parallel.

Thank you, that really helped.

What no one has really answered yet is: CAN you use Omni wheels with a mecanum drive?

you mean omni wheels in a parallel to each other formation (2 on one side 2 on the other), this would cause the robot to only be able to move sideways and not forwards or reverse

You can’t replac mecanum wheels with omni wheels and get the same result, There can only be one omni wheel on each side of a square chassis if you put them parallel to the sides, OR the omni wheels have to be angled at 45degrees to the chassis.

Here is a robot my team worked on using the omni wheels at 45 degree angles,

Yes I know that, it’s called holonomic.

You answered my question though, thank you.

Crap, so I have to make the mecanum wheels… this will be tricky.

Does anyone know what is a good holonomic code?

The one I got from cheif delphi doesn’t work quite right, one of the wheels is always spinning, and we had the code coppied exactly-- we checked over it a couple times.

I have it school, I will try and upload it later today.

Awesome! Thanks so much!!

Sorry to get your hopes up. I was unable to locate the code. I will send an email to our reprogrammer. He should know where the code is. In the meantime, Good Luck.