16-07-2012 21:54

PAR_WIG1350

Re: pic: More fooling around with mecanum wheels

Yes, a three inch mecanum wheel would be a bit ridiculous, a wheel of any type smaller than 4 inches is rare in FRC.

On another note, you should consider how you are mounting these. Mecanum drives do weird things when any of the four wheels lifts off of the ground so some sort of suspension is recommended.

16-07-2012 22:10

Tom Ore

Re: pic: More fooling around with mecanum wheels

Yes - it's not a serious proposal. Just got to thinking about it and wondered what it would look like.

16-07-2012 22:12

MattC9

Re: pic: More fooling around with mecanum wheels

Have you tried shifting with mech's befor?

16-07-2012 22:21

Tom Ore

Re: pic: More fooling around with mecanum wheels

We did a mini-octocanum drive last year and had mecanums with fixed raised wheels for climbing the ramp in 2010. We've never done a shifting version. (The mini wheels were 2" diameter Colsons.)

16-07-2012 23:24

Gregor

Re: pic: More fooling around with mecanum wheels

What is mini-octocanum? Is it standard octocanum with smaller "tank" wheels?

17-07-2012 03:39

Tom Ore

Re: pic: More fooling around with mecanum wheels

Yes. Since we wanted a wide robot there wasn't much room for the second set of wheels. We tucked 2" diameter Colson wheels in as close as possible to the 6" mecanum wheels.

Here is a picture of the module. It worked really well except for being rather heavy. (The frames were aluminum not Lexan.) If we did it again, we'd work on bringing the weight down.

17-07-2012 03:49

GRT808

Re: pic: More fooling around with mecanum wheels

What CAD software is this?

Personally, I am interested in what you did you color the bearings. I haven't been able to make them look like the shiny metal bearings you have.

Very nice render!

17-07-2012 04:55

Tom Ore

Re: pic: More fooling around with mecanum wheels

We use Creo. I made the bearings chrome. The other parts are aluminum, steel, brass, plastic, etc. Creo has lots of material choices and then choices for each material. For example, under the aluminum choice you can pick brushed, anodized blue, anodized red, cast, matte, polished, satin or scratch. The room for rendering is set to glossy white plastic.

17-07-2012 06:58

Nemo

Re: pic: More fooling around with mecanum wheels

Tom, you're the man. You make some really sweet models, even if you're just fooling around with some of them.

17-07-2012 11:53

JesseK

Re: pic: More fooling around with mecanum wheels

If the wheels were 2.5" instead of 3", I'm not sure why this is infeasible at a first pass. I think this design would be robust enough for a FRC bot on a flat field under 2 conditions: 1.) The lexan that supports the outer edge of the dead axle were replaced with C-Channel and 2.) The robot frame only mounts to the C-Channel.

3"x1.5" C-channel with 0.2" leg thickness would work great. The added ounces of the Aluminum C-Channel would be offset by leaving the gearbox plates as polycarbonate. All robot impact forces resolve through the C-Channel, and the polycarbonate only needs to be strong enough to rigidly cantilever the CIM as shown.

17-07-2012 12:16

Ether

Re: pic: More fooling around with mecanum wheels

Hi Tom,

I'm interested in the rollers.

Could you post a spreadsheet (or a text file) of the roller contour profile (roller radius vs position along roller axis). Thanks.

17-07-2012 14:50

Tom Ore

Re: pic: More fooling around with mecanum wheels

I generated the profile in CAD. I took a 3" diameter circle and projected it onto a plane tipped at 45 degrees. Then I played with the roller center line to get a roller size that fit nicely. I set the width of the roller so that the end of one roller was in line with the start of the next roller.

17-07-2012 21:29

GRT808

Re: pic: More fooling around with mecanum wheels

Is this with Creo Parametric? How long did it take you to render this? As for the bearings, did you color them entirely chrome? Or did you color them any additional colors (for example, different faces different colors, etc).

17-07-2012 22:05

Tom Ore

Re: pic: More fooling around with mecanum wheels

It's Creo Elements/Pro (Wildfire 5.0). I didn't time the render but I believe it takes maybe 45 minutes or an hour. I do a draft render first that only takes a couple of minutes and if everything looks good I put all the settings to maximum for the final render. The bearings are just chrome but other parts have multiple colors. If you look closely at the nylock nuts you may be able to see the nylon inside the nut.

17-07-2012 22:13

GRT808

Re: pic: More fooling around with mecanum wheels

Amazing render, I've got an assembly of a transmission and I'll try that chrome color to the bearings thanks!