Has anyone had any experience with the vex mecanums? More specifically the 6 inch wheels for our drive train. How do they hold up to the stresses of competition? I see that andymark has mecanums but have the vex’s been sufficient for you guys?
I don’t have experience with those wheels, but I’d also recommend you consider whether Mecanums are really the drive train you want to go with. See this thread and specifically the linked post.
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I have no personal experience with these mecanum wheels, but the field this year is perfectly flat with no bumps of any kind, so the wheels should last just fine. Luckily mecanums are quite affordable these days, so a few spares would not hurt to have on hand.
Are you looking to use mecanum wheels to help you align for scoring more easily? What was your justification for these over a traditional 6 or 8 wheel tank drive for this game?
Best of luck!
Ask anyone that was on 4180 during rapid react and they will warn you about the vex mecanums. Likely they will warn you by screaming “oh god no don’t do that!” as the color drains from their face. It was bad.
But also, you probably should reconsider using mecanums anyway (just please buy the all metal ones if you do!)
To simplify the issue…
Tank:
-Strong and defendable
-Sturdy
-less manuverable
Mecanum:
-manuverable
-breaks really easily (rollers bind and break)
-literally no chance for good defense
Swerve:
-Both manuverable and defendable
-expensive
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Also, imo, mechanums are generally not the route you want to go for drive trains : )
Vex mecanum wheels for driving are bad. They break very easily and arent very smooth to drive.
You want the andymark ones for sure. 4 or 6 inch.
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We’ve done a bunch of mecanum drivetrains over the years, but not since 2019. The Vex 6" wheels were on our 2015 machine. The early versions failed at the blades that support the rollers. The new ones do not, but the rollers do tend to bind up over time, and then mecanum no longer drives like mecanum.
I also need to point out that a mecanum drivetrain will get you on some no-pick lists, regardless of the rest of the robot due to the inherent traction limitation.
I know there is a lot of down opinions on mechanums but if you can’t afford swerve I see a use for them in this game for aligning for amp placement or aligning for source pickup. Especially if you still want an off the front/back intake for ground pickup. Easy horizontal alignment takes something other than tank and everyone loves swerve but it is expensive.
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We used the 4in vex mechanum wheels last year and experienced many failures.
YMMV
We used the AndyMark mecanum last year they were terrific. Not one roller failure. From build thru competition we ran on carpet only. We now use they bot for demos and training on concrete floors in our shop and ran it retty hard wih no significant wear. They are a little pricey but well worth it if you plan to go this route. If you can’t go swerve its a good alternative. In this photo the wheel setup is different than what we eventually mounted, we chaged the mecuanum pattern to better work with our programming.
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Consider lead times in your drivebase construction as well. Presumably, your team can have a driving Andymark drive base by next week if you know your chassis dimensions now. Mecanum would mean a couple weeks for the wheels, a week for construction, then you have to figure out how to get it to strafe properly.
That’s half of build season for a drive base. Now your drivers aren’t going to have the time to take advantage of the upsides of mecanum. So they’ll drive it like tank most of the time. It might seem to be worth it for the alignment to the source, but I might argue that a mechanism such as a wide intake or ramp could alleviate that problem in a way that doesn’t compromise your ability to drive well across the field.
Mecanum is good if you’ve built and programmed it before, there were many teams before COTS swerve who specialized in it and did well. The key is doing so before the build season.
They can work, but not that well, at least for the six inch wheels. I cannot necessarily fault the wheels for any of the major drivetrain issues we had while using them, but they do not seem to roll smooth. There is an audible rattle and physical vibration when rolling along a hard floor. For context, Andymark wheels (not sure which ones exactly) seem to roll smoothly on the same floor.
Not sure which one it was, but there was a match where the rattling was picked up by the announcer’s microphone.
I cannot fault the durability of the wheels. They held up for one regional one off-season event and other uses. That is not exactly impressive or anything, but we broke other things by driving over the cable protector so they will not break if you look at them incorrectly.
Would not recommend the Vex clamping single reduction gearbox for 6 in wheels. It is geared for 4 in wheels and will leave you unable to strafe.
The AndyMark were srurdy but there was a lot of design work that went into it we made a butterfly fly system for the climb and some defense last year not to mention all the machining we did on a Bridgeport end mill and Waterjet cutting. All of that came we a weight penalty we had to overcome. The weight of the chassis was 65 lbs. So we drilled out a lot of holes. But it drives well.
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