pic: Mecanum Musings

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[MrForbes]

neat design! although it looks like there's quite a stretch betwen the end of one roller and the beginning of the next....might be a bumpy ride

[Andrew Schreiber]

Originally Posted by squirrel

neat design! although it looks like there's quite a stretch betwen the end of one roller and the beginning of the next....might be a bumpy ride

I like my robots shaken, not stirred.

Looks very nice, simple, and significantly cheaper than the AndyMark ones. How much does it weigh and what will the parts cost you?

Originally Posted by Andrew Schreiber

I like my robots shaken, not stirred.

Looks very nice, simple, and significantly cheaper than the AndyMark ones. How much does it weigh and what will the parts cost you?

The weight is about .6lbs completed. I'm not sure about the total cost per wheel, but it should cost around $120-200 for enough stock to make 6 wheels.

[Andrew Schreiber]

Very nice, I will be interested in how these work out should you use them. At a nearly 85% cost savings over AndyMark (6 wheels X $96 = ~$600) and lower weight these could be useful. Keep us posted.

[M. Mellott]

Very interesting design! It's so simple, enough so that almost anyone could make these in a small shop! I'll be really interested to see these in action.

What size wheel would this equate to? Maybe 4" or 4.5" mechanum?

[Stuart]

I like this my team does another comp other than FIRST called BEST and has been looking at how to implement mecanums with the limited kit you are given, I think this might be the solution. Really beautifully simple.

Originally Posted by M. Mellott

Very interesting design! It's so simple, enough so that almost anyone could make these in a small shop! I'll be really interested to see these in action.

What size wheel would this equate to? Maybe 4" or 4.5" mechanum?

The goal was definitely to have minimal impact on machining resources (gotta save all that complex stuff for the manipulator!), and keep cost down.

The effective diameter is about 4.375. It is a little rough ride, as the design goes, so I'll be doing some incremental changes to address the problem.

[MrForbes]

What would happen if you tried to use a smaller hex for the central hub?

[dtengineering]

Nice design! It is apparent that you took practical considerations into account as the primary design factor. There was a recent thread on CD, in contrast, discussing a mecanum wheel that the designer took aesthetic considerations into account as the primary factor... but as a result the wheel needed to be made on a 5 axis CNC mill in his opinion.

I can guess which one is more likely to show up on a robot!

As for the bumpy factor in the ride, you could always (at this cost) build 8 wheels, and attach them in tandem, with one rotated 30 degrees from it's partner... much the same way you can use two omnis to smooth out the ride.

Jason

[Andrew Schreiber]

Originally Posted by dtengineering

Nice design! It is apparent that you took practical considerations into account as the primary design factor. There was a recent thread on CD, in contrast, discussing a mecanum wheel that the designer took aesthetic considerations into account as the primary factor... but as a result the wheel needed to be made on a 5 axis CNC mill in his opinion.

I can guess which one is more likely to show up on a robot!

As for the bumpy factor in the ride, you could always (at this cost) build 8 wheels, and attach them in tandem, with one rotated 30 degrees from it's partner... much the same way you can use two omnis to smooth out the ride.

Jason

I remember that thread, IMHO this wheel looks almost as nice as it. Not as flashy but it has an elegance that certainly makes it beautiful.

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

[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.

[JesseK]

For even less necessary machining, you could not mill out the inside of the hex stock, and instead thread-tap the holes where the counter-sunk screws go in. This makes it a bit heavier, but you wouldn't need a mill to make the wheel.

Then, you could also drill the KOP hub bolt-circle pattern into the side, eliminating the necessity of having to make a key way.

To take this even further, instead of counter-sunk screws you could use half-head-height machine bolts, eliminating the need to create the extra dimple after the initial hole is drilled.

Originally Posted by squirrel

What would happen if you tried to use a smaller hex for the central hub?

Not sure. Next time I boot my Mac into windows to do some CAD, I'll throw together a different version with smaller hex. But to be honest, I'm not sure I'd feel comfortable making it any smaller. The team I'm mentoring has an affinity for Banebots transmissions, so I think the goal is to keep to wheels that can be direct driven off a BB tranny.

Originally Posted by JesseK

For even less necessary machining, you could not mill out the inside of the hex stock, and instead thread-tap the holes where the counter-sunk screws go in. This makes it a bit heavier, but you wouldn't need a mill to make the wheel.

Then, you could also drill the KOP hub bolt-circle pattern into the side, eliminating the necessity of having to make a key way.

To take this even further, instead of counter-sunk screws you could use half-head-height machine bolts, eliminating the need to create the extra dimple after the initial hole is drilled.

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.

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.