Mecanum Demo-Bot Recommendations?

[James3245]

Thanks for input everyone - very helpful!

[Richard Wallace]

Originally Posted by Poseidon5817

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?

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.

[Allison K]

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.

[R.C.]

Originally Posted by Thayer McCollum

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.

Did you get the new updated rollers?

http://www.vexrobotics.com/vexpro/mo...um-wheels.html

Look under Mecanum Wheel update

[Poseidon5817]

Originally Posted by Richard Wallace

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.

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.

[adciv]

Originally Posted by roboruler

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

Ah, but they already have them in house and the FRC controller interfaces nicely with the roboRIO. While over kill, the FRC controller is the cheaper/quicker option.

[Thayer McCollum]

Originally Posted by R.C.

Did you get the new updated rollers?

Yes, R.C. we were using the updated rollers. The robot they were on was from 2015's game. I would expect that they broke because in 2015 my team had a large number of problems, and that directly correlated to how well our robot was built. And so, if we had built our drive-train properly the problem would have been avoided. Let's just say (and OP make note of this) that putting your gearboxes underneath your frame members, held on with 6 inch 10-32s is a REALLY bad idea. So OP when building a mecanum drive give your wheels and gearboxes their needed support, and if you're not going to, give them some kind of suspension. So R.C. we were using the updated rollers but I don't blame VEX at all, and should have made that clear, we were just using them very improperly.

[Ryan_Todd]

I'm surprised that nobody has mentioned this yet, but one of the biggest reasons to use mecanum wheels on a demo bot is for the shock-and-awe factor! In that regard, 4" or even 6" wheels are a bit small-- this makes it harder to see what's going on and how the wheels work.

I would personally suggest 8" wheels for this application, although 10" mecanum wheels aren't a bad choice either. AndyMark offers both 8" and 10" varieties, and I can personally recommend them for their durable construction-- although I will definitely admit that the VexPro mecanums are easier on the eyes.