pic: A mechanum wheel that shouldn't bump around at all.

[Hawiian Cadder]

true, the method that i used to make these could be aplied to any angle of mechanum wheel. when we build them we may use closer to a 35 degree angle,when strafing speed is nessisary, and they will climb better.

[Ryan Dognaux]

Originally Posted by KRUNCH DUDE

These wheels remind me of Airtrax wheels, did you get the idea from them? I would like to see a nice set of mechanum wheels for FIRST.

Do a search for Jester Drive. 357 has been creating mecanum wheels since 2005 (actually this thread right here has some good discussion in it - http://www.chiefdelphi.com/media/photos/20664). Gives some information on the development of our wheels and our relation to Airtrax.

I've attached a few images from this year's CAD renders, feel free to check them out.

[exprg:melonhead]

Originally Posted by Ether

There is no "ideal" angle.

Many mecanum wheels have rollers at 45 degrees. This makes the kinematic (and dynamic) analysis easier. The forward and inverse kinematic matrix transformations are simple, with no trig functions or square roots.

Making the angle smaller than 45 degrees (angle between roller axis and plane of the wheel) improves forward/reverse traction but reduces strafing traction, and vice versa.

So there is no one ideal angle. It depends on the application.


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so what you are saying is that in order to to drive easily both forward and back, it would be best to have a good 45 degree?

[Rion Atkinson]

Originally Posted by Ryan Dognaux

Do a search for Jester Drive. 357 has been creating mecanum wheels since 2005 (actually this thread right here has some good discussion in it - http://www.chiefdelphi.com/media/photos/20664). Gives some information on the development of our wheels and our relation to Airtrax.

I've attached a few images from this year's CAD renders, feel free to check them out.

...

What program do you use to render those?

[Ryan Dognaux]

Originally Posted by Formerly Famous

What program do you use to render those?

That was done in Inventor 2010 by one of our students, Kyle Tress.

[Andrew Schreiber]

Originally Posted by Ryan Dognaux

That was done in Inventor 2010 by one of our students, Kyle Tress.

Ryan, do you machine your hubs from solid? I assume you cast your rollers?

[Rion Atkinson]

Originally Posted by Ryan Dognaux

That was done in Inventor 2010 by one of our students, Kyle Tress.

Interesting... I've never seen Inventor render anything that pretty... Looks like I'll have to play with 2011 some more.

[Joe Ross]

Originally Posted by Andrew Schreiber

Ryan, do you machine your hubs from solid? I assume you cast your rollers?

There's a nice description (with lots of pictures) of their 2006 process in FIRST Robots: Aim High: Behind the Design

[Ryan Dognaux]

Originally Posted by Andrew Schreiber

Ryan, do you machine your hubs from solid? I assume you cast your rollers?

The hex hubs are machined from hex stock and the outside fins that hold each roller are bolted onto the outside of the hub. This way, if we somehow bend a fin during a match (the bumps liked to do that this year), we can swap them out between matches with spares and you don't lose an entire wheel.

The rollers were cast with certain materials this year from silicone molds. The rollers themselves have two layers, a hard inner core and a softer outer traction layer. I'll see if I can get some of the students who made the rollers this year to post more details.

[Ether]

Originally Posted by exprg:melonhead

so what you are saying is that in order to to drive easily both forward and back, it would be best to have a good 45 degree?

No, that's not what I said (not even close). I'm not sure how you concluded that from what I wrote. Help me understand what part led you astray.


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[Hawiian Cadder]

nice, that is the idea with these too, we should be able to replace the arms, the main hurdle now is making the rollers so that they will fit perfectly with the bearings, can you turn urethane on a lathe?

[Brandon Holley]

Originally Posted by Hawiian Cadder

nice, that is the idea with these too, we should be able to replace the arms, the main hurdle now is making the rollers so that they will fit perfectly with the bearings, can you turn urethane on a lathe?

You sure can.

-Brando

[EricH]

Originally Posted by Ether

No, that's not what I said (not even close). I'm not sure how you concluded that from what I wrote. Help me understand what part led you astray.


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I can understand why he said that... But to ONLY go forwards and backwards, it's best to have a traction wheel. (literally, he said forwards and backwards only...)

What Ether said, in essence, was that many mecanum wheels used 45* rollers, but that other angles could be used--less than 45* puts the advantage to front/back and greater than 45* puts the advantage side-side in terms of traction. I assume that this is a correct summary. If it is not, then the original post needs to be modified, as that is where I got this from.

From that, it is easily (and logically) concluded that, for the optimal front/back and side/side traction, 45* is a better angle than many others. If that is not the conclusion that was intended, then better words need to be chosen.

[Ether]

Originally Posted by EricH

...

OK so you understood. Good for you.


Justin, what part of my post led you astray? Was it the part about the forward and inverse matrix transformations? I can explain in more detail if you are interested.


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[Rion Atkinson]

Originally Posted by Ether

OK so you understood. Good for you.


Justin, what part of my post led you astray? Was it the part about the forward and inverse matrix transformations? I can explain in more detail if you are interested.


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Honestly I would just tell him to read Eric's post. It made plenty of sense. (Now yes, yours made sense to. But there is no need to re-explain that which has been explained if it is now understood.)