Grippy Mecanums

Is there a way to make a grippy mecanum wheel? I know they are usually low traction rollers, and use those rollers to obtain omni-directional movement, but is there any way to add more traction to the rollers, while keeping the fluid, omni-directional movement?

Thanks!

[IndySam]

The rollers themselves are not low friction.

The AndyMark rollers use a rubber compound that sticks to carpet quite well.

I have also seen custom wheels that use very sticky urethane.

A typical mecanum wheel will have a lot of traction in the forward direction, in fact I have seen mecanum bots push standard bots around.

Originally Posted by IndySam

The rollers themselves are not low friction.

The AndyMark rollers use a rubber compound that sticks to carpet quite well.

I have also seen custom wheels that use very sticky urethane.

A typical mecanum wheel will have a lot of traction in the forward direction, in fact I have seen mecanum bots push standard bots around.

Then why are mecanums considered "low-traction" wheels?

[Kevin Ray]

Originally Posted by SuperNerd256

Then why are mecanums considered "low-traction" wheels?

This is because most people who say this are merely miss-speaking. What they are actually referring to is the ability of non-powered wheels to roll. For example if an macanum drive bot were to be pushed from the side (straffing) it would "roll" as though it had no traction.

[IndySam]

Originally Posted by SuperNerd256

Then why are mecanums considered "low-traction" wheels?

They're not by people who understand them.

In a pure pushing match they perform well. They can suffer from gearing problems because they generally have to be geared high for good speed and are rarely used with shifting gearboxes so they can suffer when it comes to power.

Originally Posted by Kevin Ray

This is because most people who say this are merely miss-speaking. What they are actually referring to is the ability of non-powered wheels to roll. For example if an macanum drive bot were to be pushed from the side (straffing) it would "roll" as though it had no traction.

Originally Posted by IndySam

They're not by people who understand them.

In a pure pushing match they perform well. They can suffer from gearing problems because they generally have to be geared high for good speed and are rarely used with shifting gearboxes so they can suffer when it comes to power.

That makes more sense. Thanks!

[Katie_UPS]

If you look at a mechanum wheel or an omni wheel, they have rollers. They achieve omni-directional movement through the manipulation of force vectors (which Ether will be able to explain far more eloquently than I will). The reason they are considered low traction is because the rollers on the wheels are not powered, and so the robot is resting, essentially, on tiny un-powered wheels, which are far more push-able that powered wheels.

The reason mecanum/omni robots can sometimes win in a pushing match is that if the pushing force is parallel with the axis of rotation, then the rollers aren't spinning (and so as the angle of the pushing force approaches parallel to the axis of rotation, the less the robot can be pushed).

I hope that helps

EDIT: It's already been answered, but I hope that adds.

[jblay]

Originally Posted by SuperNerd256

Is there a way to make a grippy mecanum wheel? I know they are usually low traction rollers, and use those rollers to obtain omni-directional movement, but is there any way to add more traction to the rollers, while keeping the fluid, omni-directional movement?

Thanks!

Make a swerve drive setup.

In all seriousness though the real issues with the mecanum wheels in terms of pushing are this:
-They aren't 100% effective at transferring power, a lot of it is lost. This forces you to have to gear higher to be able to go at a reasonable speed which makes you less capable of pushing. It is difficult to do a shifting gearbox with mecanum wheels because each wheel has it's own gearbox and shifting gearboxes are quite heavy.
-They are easily pushed sideways. They are designed to do this so that you can strafe, but most of the time when pushing is done it is not done front of pushing bot to front of bot being pushed but front of pushing bot to side of bot being pushed.

Hope this helps. As a team that used mecanum wheels last year I would advise against them because when the eliminations roll around and you are facing defense, being able to be pushed sideways easily really hurts your chances and it makes winning very difficult.

[Ether]

Originally Posted by Kevin Ray

For example if an macanum drive bot were to be pushed from the side (straffing) it would "roll" as though it had no traction.

Not.

[Kevin Ray]

Originally Posted by Ether

Not.

I meant to say, A non powered macanum would roll.

Originally Posted by jblay

Hope this helps. As a team that used mecanum wheels last year I would advise against them because when the eliminations roll around and you are facing defense, being able to be pushed sideways easily really hurts your chances and it makes winning very difficult.

Trust me, I'm not going to use those things ever in my 4 years as an FRC student. I'm just curious about them, why they are considered "low traction", and how one could manipulate them to make better traction.

Thanks all!

[Grim Tuesday]

Get in contact with team 357, Royal Assault. They debuted Mecanums for FIRST usage, and if there will be a Mecanum robot on Einstein, it will be them.

[EricH]

Originally Posted by Kevin Ray

I meant to say, A non powered macanum would roll.

No, it wouldn't. You're confusing mecanum and omni.

Mecanums do not roll sideways easily. They go front and back. They'll go at a 45 degree angle if you only have one. But sideways, especially if you've got all four on the robot, not so much.

[Kevin Ray]

Originally Posted by EricH

No, it wouldn't. You're confusing mecanum and omni.

Mecanums do not roll sideways easily. They go front and back. They'll go at a 45 degree angle if you only have one. But sideways, especially if you've got all four on the robot, not so much.

You are right. They are not Omni's. We've used both. Though they don't roll easily, they do roll. Try pushing a macanum bot sideways when it is not powered. What I was trying to explain to SuperNerd256 is that a macanum bot in most orientations would roll off the tilted bridge with no power applied to prevent it. And, while we are at it, given identical gearboxes and friction coefficients of wheels, macanums would lose in a head to head with conventional wheels. This is possibly what SuperNerd256 was referencing.

[EricH]

It's a lot easier to push a mecanum, unpowered, forwards and backwards than sideways. There are four aligned axes of rotation instead of 4 axes at 90 degrees to each other.

As for the rest, read the thread and hope Ether doesn't come in and apply physics to show you exactly how wrong you are.