Mecanum Demo-Bot Recommendations?

Our team has never built a mecanum drive base.

We’d like to add build one for demonstration purposes.

What is CD reader recommendations for:

-size of wheels
-vendor of wheels
-a frame that can be bolted or riveted - easy to see what is happening when bumpers removed
-a gearbox that makes both assembly and maintenance easy

Looking for a robust solution that can also be visually understood by visitors.

Thanks!

Hey there! Our team has run mecanums for a long time now and here are my recommendations:

Size: 6in wheels (nice in between size)
Vendor: Vex (they make really nice plastic wheels. We even had mecanums this year and didn’t have have a single roller break ever. This included going over the Rock Wall full speed.)
Frame: modified kit chassis. We ran a modified kit chassis in 2014 and a modified version of that in 2015. You really want a square base for mecanums.
Gearbox: toughbox nano. These are really nice because they are easily moddable and easy to maintain. They also fit really nice on the kit chassis.

You could try using VersaFrame combined with Clamping Gearboxes, both from VexPro. We used the clamping gearboxes from VexPro in 2015 and they overall worked pretty great. It keeps the base simple, and VersaFrame is a relatively cheap, low resource option.

True. I didn’t want to recommend something I had never used. :slight_smile:

It’s probably cheaper and easier.

I would recommend 6 inch VEXpro wheels:

The 6 inch variety isn’t very expensive but is still big enough to see them working well enough. Also a smaller wheel means less gearing.

I think either a modified KOP chassis or a Versa-frame with the clamping gearboxes would work great. You’d probably need to make a guard around the gears to avoid potential for harm.

You could also try a Andymark Nanotube chassis:

Consider using the Tetrix components for FTC. Smaller, typically cheaper, and you can still interface with FRC motor controllers.

Using a FRC motor controller that is capable of 60 amps continuous seems a little wasteful for a tetrix motor that can’t even draw 1 amp at max power output

That’s what we did for a demo project. We went with 4" AM Mecanums. Ran that drive train for a year of demos, including several sponsor presentations, outreach events, and football games.

We used the Vex products, including the Single Reduction Clamping Gearbox - easy to put together, held up very well and overall very happy with the results.

You can get the Vex BOM and other info here: http://www.vexrobotics.com/vexpro/examples-guides#VC

Here’s a video of ours in action: https://www.facebook.com/167378876696706/videos/696466343787954/

I remember seeing that picture when you first posted it! If you don’t mind me asking, what were the reasons you went with the AndyMark 4" mecanums instead of the VexPro ones? Durability?

I recommend AndyMark Nano Tube for mecanums.
http://www.andymark.com/product-p/am-0968
I also recommend only using your mecanum bot on carpeted surfaces. Sometimes the rollers leave black marks that can be a bit unseemly, and they’re aren’t too friendly with gravel/asphalt.

VexPro has details about a very simple Mecanum drivetrain on their website.

It would meet all of your design criteria, albeit being a bit pricey.

We have used the Vex clamping gear box with 6" mechanums. it works well. We used a belt second stage. Detailed on Vex’s web site bottom of page. The single stage isn’t enough reduction. The cost of the Vex clamping boxes add up by the time you add bearing, gears, belts, and so forth. We have also used Andymark’s nano gearboxes with the wheels mounted directly to them. Stock gearing in them is a little slow with 6" wheels.

How crazy are you looking to get? Way back in 2010, we build a “demo” bot with 15" mechanum wheels. It was quite the fun project as we had to make everything custom. It even has a torsion beam suspension! It’s great in the sense that it’s a great all purpose robot, and can climb almost anything (barring you have enough power). Downsides are its expensive, heavy, and requires quite a bit of juice!

TLDR; Big wheels are cool, but expensive.

We have had VEX mecanum wheels break on us. It seems like everyone else has had a good experience with them so take my advice with a grain of salt. AndyMark mecanums are more durable. The VEX ones look really cool but the way the rollers attach makes that attachment pretty weak, we busted three rollers off different wheels all in that same spot. So we now have AndyMark mecanums on our bot and they have held up much better. I don’t know why the VEX ones broke and I trust VEX’s quality in most things but I prefer AndyMark for mecanums.

Thanks for input everyone - very helpful!

We went with AM HD (am-3067) mecanums because they have aluminum plates instead of plastic bodies. Their 100 lb. per wheel rating is about double that of the 217-3644/45, which are listed as “conservatively rated for a 200 lb. robot.”

I believe VexPro’s ratings are conservative, because I know several of the engineers there and trust their design skills. However, based on their construction, the AM HD wheels seemed like a safer choice. We did not know in advance how hard we would be working that chassis.

Pictures of one of our demo bots top view and corner view. We are in the process of developing a full set of twelve robots out of the VEXPro parts (twelve different styles of drivetrains with interchangeable manipulators). Each robot is 20" x 20" for portability and ease of use in small-ish spaces.

The mecanum one pictured was a summer day camp project for an 8th-9th grade group. 4" VEXPro wheels with clamping gearboxes. I think they are 11:72, but might be 12:72. Runs just fine on both tile and carpet and has been durable enough for demo purposes (we haven’t specifically tried to break it). If we hadn’t scavenged the control board for another project I’d show off the nice LED underglow too.

Did you get the new updated rollers?

http://www.vexrobotics.com/vexpro/motion/wheels-and-hubs/mecanum-wheels.html

Look under*** Mecanum Wheel update***

All right, those are all good points. With it being a demo bot, you won’t always being driving it on the soft carpet surface, so it makes sense that you would want to have the stronger wheel.