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.

[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.

[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.

[DELurker]

Originally Posted by 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.

Actually watched 357 shed half of a mecanum this season at Philly. As another team that uses mecanums, 1370 had tremendous success as a defensive bot, pushing other bots around the field. While mecanums do have their limitations, they are nowhere as bad as their reputation will lead you to believe.

[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.

[MichaelBick]

Originally Posted by Kevin Ray

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.

You could implement some type of brake, electronic or physical. Either way, traction is only half the problem most teams have with mechanums. When strafing, you have less than 100% power and speed off a traction drive(I believe close to 60%). Therefor, in many situations a traction drive can get to the same place as a mechanum in equal or less time, even if there is a turn involved.

Originally Posted by Kevin Ray

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.

Kevin's right; That's what I'm referring to.

[Andrew Schreiber]

Originally Posted by SuperNerd256

Kevin's right; That's what I'm referring to.

Except Kevin is wrong. I've tried pushing unpowered mecanums sideways (software testing for 2337 in 2010). I was physically unable to push the robot sideways. Along the diagonals was a different story though. Still not easy but most definitely easier. None of this involved any sort of fancy software which would enable the wheels to hold position.

As for grippy mecanums, if you ever get a chance talk to 357 about their process. Their wheels have quite a bit of grip and they are one of the few teams I've seen use mecanums well.

However, I am a firm believer in the theory that if you are pushing with a mecanum wheeled robot you are doing it wrong.

Originally Posted by Andrew Schreiber

Except Kevin is wrong. I've tried pushing unpowered mecanums sideways (software testing for 2337 in 2010). I was physically unable to push the robot sideways. Along the diagonals was a different story though. Still not easy but most definitely easier. None of this involved any sort of fancy software which would enable the wheels to hold position.

As for grippy mecanums, if you ever get a chance talk to 357 about their process. Their wheels have quite a bit of grip and they are one of the few teams I've seen use mecanums well.

However, I am a firm believer in the theory that if you are pushing with a mecanum wheeled robot you are doing it wrong.

I know Kevin posted twice, so maybe we're reading separate posts. I'm agreeing to http://www.chiefdelphi.com/forums/sh...1&postcount=14

Mainly the part about the mecanums rolling off a tilted bridge if the power was disabled, and how they aren't as good in pushing matches.

And I agree 100% on your last statement.