pic: Mecanum Musings

[jwfoss]

that mecanum looks really good, reminds me alot of the WPI wheel from 2005 except a little smaller. Do you have a view directly from the side so we can see the complete arc of the rollers?

Originally Posted by jwfoss

that mecanum looks really good, reminds me alot of the WPI wheel from 2005 except a little smaller. Do you have a view directly from the side so we can see the complete arc of the rollers?

Sure, let me grab a render real quick. I'll edit this post in a minute with it.

There's two renders here: My 1.0 ultra-cheap design, which is with 6 rollers. It's outer diameter is around 4, 4-5 inches. Next is the 8 roller one, a bit smoother, and a little bit larger with a effective diameter of 6 inches.

[Alan Anderson]

Originally Posted by Andrew Schreiber

Jason, would mounting two of them like that really work? I mean I suppose it would but has anyone ever done it with Mecanums?

I've driven a platform with doubled AndyMark mecanums, and it works just fine. It almost looks like they were designed to be able to be mounted that way.

[Andrew Schreiber]

Originally Posted by Alan Anderson

I've driven a platform with doubled AndyMark mecanums, and it works just fine. It almost looks like they were designed to be able to be mounted that way.

Ok, thanks, Ive just never seen anyone do that.

[lbarger]

Great design. Do the nuts and bolt ends miss the carpet? You may want to look into tapping one end of the c-section and countersinking the clearance on the other. Then you could use a flat head screw and match the length of the screw to the c-section width. Then you should be able to avoid any hardware overhang and further reduce the weight. Typically you should have at least three full threads for any bolted joint.

Keep up the great work and please post your final version!

Originally Posted by lbarger

Great design. Do the nuts and bolt ends miss the carpet? You may want to look into tapping one end of the c-section and countersinking the clearance on the other. Then you could use a flat head screw and match the length of the screw to the c-section width. Then you should be able to avoid any hardware overhang and further reduce the weight. Typically you should have at least three full threads for any bolted joint.

Keep up the great work and please post your final version!

No, there's plenty of clearance for the hardware holding the rollers to the C channel. I'd really prefer to not take any more material out of the C, as the goal here was to go cheap and easy (hence going with aluminum from McMaster. If I go to something stronger (like a higher strength alloy), Then possibly I'd work on lowering the profile a bit.

I'd love to post the final version, but for me all designs are a work-in-progress. Maybe I'll post some renders side by side with a real thing if these actually get built? It's all really up to the team for what they'd like to build. I am just a mentor, anyway.

[rutzman]

Originally Posted by Speedfiend

I am just a mentor, anyway.

Just a mentor? You say that like it's unimportant...

Originally Posted by rutzman

Just a mentor? You say that like it's unimportant...

I understand the importance of the position, but I see the limits in the spot. I'm here to teach students about engineering and smart decision making, not win them a competition. If that were my job, you'd be seeing a lot more designs up here that I "planned" on making, and justification on why they're the best.

Instead, I spend my time designing and planning parts and mechanisms with the intent of showing students that there are more possibilities than the most complex (high school students seem to be good at finding the most difficult solution first...) and expensive option.

A mentor should teach the team, not BE the team in my opinion.

[rutzman]

You're completely right. My apologies for getting off topic.

Originally Posted by Speedfiend

Also, for the rough ride concerns: Once I make the wheel wider, and thus the rollers longer, the wheel actually smooths out a good bit.

How wide do you think the wheel would have to be to give a smooth ride?

Originally Posted by rutzman

How wide do you think the wheel would have to be to give a smooth ride?

About 3 inches wide, then it's pretty much smooth.

Here's a render of the latest revision. It's little bigger (effective diameter of 8ish inches), and uses more machining resources. to shave weight off.

Once I hit a revision that i feel comfortable putting on a robot, I'll be hosting the CAD for anyone that wants it, with only one rule: if you make it or modify it, you also have to put the CAD up. It's time to bring Open Source to robotics, folks.

[MrForbes]

can you render it with a viewpoint that's much further away, so the view of the side of the wheel is "flat"?

also....open source is nice! we did some this past season, I know we inspired a few teams

Originally Posted by squirrel

can you render it with a viewpoint that's much further away, so the view of the side of the wheel is "flat"?

I'm not understanding this, sorry.You're asking for a view that's in orthographic, not perspective, and from a "front" of the wheel view, or a "side" (front being looking at the narrow view, what I have in the middle there, "side" being the one on the left)?

[MrForbes]

side view, as in looking at the side of the robot. The view in the left of your picture above. Change the perspective to infinite, so you can see how "round" the wheel is.

[Brandon Holley]

Originally Posted by Speedfiend

About 3 inches wide, then it's pretty much smooth.

Here's a render of the latest revision. It's little bigger (effective diameter of 8ish inches), and uses more machining resources. to shave weight off.

Once I hit a revision that i feel comfortable putting on a robot, I'll be hosting the CAD for anyone that wants it, with only one rule: if you make it or modify it, you also have to put the CAD up. It's time to bring Open Source to robotics, folks.

I've spent some time designing mecanums (on a smaller scale), and I have my own method, but I was wondering if you would share the method you used to create the curvature of the roller. Specifically in CAD terms (I'm very familiar with any CAD system), what you did to ensure your roller curve was as effective as possible.

Thanks in advance!
Brando

[D_Price]

The only question i would ask would be if they were to be bumped into would they break easier or would they still have enough strength.