pic: Mecanum Musings

[Akash Rastogi]

Woah, the assembly for these looks incredibly easy! Great design.

[M. Mellott]

Originally Posted by Speedfiend

There are definitely many revisions that could be made to seriously reduce machining time, but this is really just a 1.0 wheel. I'm debating changing the milling operation on the hex to be entirely one sided, so the "dishing" of the wheel would be done in a single Mill op. I'll have to do some FEA tests to see how the strength would stack up...

I think what you have here is just fine. If you're using a CNC mill, the same program would be used for both sides, so there could be time savings there. Another option would be to incorporate a spoke pattern something like our 4" tread wheel design. It might help if you plan on making the wheel wider.

[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?

[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.

[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.