Mecanum Wheels
 

Does anyone have instructions on making mecanum wheels? Or a source of cheap mecanum wheels? The ones from Andymark seem really expensive...

Re: Mecanum Wheels
 

i cadded a set of mechanums that i calculated would cost less than 50 dollars a piece, but they require a 5 axis mill, and some casting work, i could dig out the cad files if you like. if you want to know all the math involved in making them, here we go:

the most important thing to do is to understand that the profile of the roller is a partial ellipse, where the short dimension is the diameter of the wheel, and the long dimension is the diameter of the wheel divided by the sine of whatever angle the rollers are at (usually 45) after that bit of math there is really not much to designing fully custom mechanums.

http://chiefdelphi.com/media/photos/35738

http://chiefdelphi.com/media/photos/35738

here are the renders of the mechanum wheels that i did, the blue one should cost around 50 dollars, (depending on what casting compound is used for the rollers.

Re: Mecanum Wheels
 

No sorry, but i'm curious why are you looking at mecanums?

If you want to do an off-season project mecanum might not be the best system for you and your team.

Re: Mecanum Wheels
 

There aren't exactly a lot of sources of mecanum wheels in the FRC size range. AndyMark is the biggest (and to some extent, the only) one.

You may want to get in touch with 357 (or, the Behind the Design books from the 2006 and 2007 FRC seasons); they've got casting their own down to a fine art.

Or, if you can find someone who can build them directly with a direct manufacturing machine, that might do it. Just watch out for FRC cost rules--the material can get pretty expensive.

Matt, offseason is the best time to do mecanum. Not during the season. 330 spent 2 offseasons prototyping a set before giving them a chance to make a competition robot in the build season.

Re: Mecanum Wheels
 

It's for a shifting drivetrain project. It will have mecanum for speed and agility and tank for brute strength (with traction wheels) and the ability to switch between the two.

Re: Mecanum Wheels
 

357 has a pretty impressive setup. Michael Crane is probably a good contact person from that team to ask about how they make their own.

Re: Mecanum Wheels
 

Nice!!! that sounds sweet!

well i did some searching and the robot shop has some for about 85 for a 4 pack (for the alum. hubs and 75 for plastic hubs) but the O.D. is 2.125. You might be able to do some prototyping with them using vex parts then decide if you want to drop 400 for the AM ones. Our team has done a pure mecanum drive for the last 2 years (we will not go back to it, but the AM heavy duty ones work really well).

Heres the link for the robot shop ones

PS if i did come off as negative, i just don't like a pure mecanum drive.

Re: Mecanum Wheels
 

http://www.thingiverse.com/thing:2473

http://hackaday.com/2010/04/28/print...um%C2%A0wheel/

if you have a 3d printer you could always scale a set of these.

Re: Mecanum Wheels
 

I've seen 357's casting method up close and it's pretty awesome, though I don't see most teams being able to do it. 357's wheel body is also it's own work of art - which again is pretty difficult to make, imo.

I 3D printed a set of Mecanum wheels back in '07/'08 and there's no way they'd stand up to the abuse of an FRC robot.

Not really sure why the OP doesn't want to use AM Mecanums, at $222 a set they seem like a steal.

Re: Mecanum Wheels
 

There is that. I'm pretty happy with the AM HD Mecanum wheels.

Re: Mecanum Wheels
 

I was assuming they were expensive for mecanum wheels; they seem expensive for the materials that go into it. But if they're the best option available, I'll take it.

Also I don't think the printed wheels would survive if we were to use them.

Re: Mecanum Wheels
 

I have made a set of mecanum wheels that were not for FIRST robotics but used in a high capacity application and the machining of them does not take too much work but more a good deal of time. I can speak more on the machining of the hubs than how to make the rollers because I used a neoprene rubber for the rollers with a nylon core and the neoprene was just too soft. As well as there are much better ways to make the rollers than how I did (CNC Lathe).

As for the machining of the hub I did it in a 3 step process where I started with a 6x6x1in block of aluminium and the first operation I cut out the profile of the wheel hub, the center bore for a FR8 bearing and a 6 hole pattern at 1.875". Then using the 6 hole pattern I used it to mount it to a fixture which stood the hub up vertically and I then used that to cut the fins and drill a hole that I would a #10-32 set screw in. I did 6 fins so that they would line up with the hole pattern and it just made life simpler. I rotated the part to cut each fin one at a time. Then I had another fixture which held the part at a 45 so that I could fillet the corners of the fins and drill a 1/4" hole for the axle of the rollers. The part was also rotated on this fixture for each fin.

I have also uploaded some pictures of the manufacturing process here:
https://picasaweb.google.com/j3ffr3y...eat=directlink

Hope that helps.

Re: Mecanum Wheels
 

nice photo.

Did you use ball, roller, or journal bearings for the rollers? Can't tell from the photo.

Re: Mecanum Wheels
 

The bearing surface is nylon on a 1/4-20 bolt (the nylon rolls on the shank of the bolt and not the threads) And between the neoprene roller and the fin there is a Hard Fiber washer from mcmaster

Re: Mecanum Wheels
 

When the roller is axially loaded toward the fin, is the neoprene rubbing against the Hard Fiber washer ?