Hi all, we are switching to mecanum this season and I could not find any updated resources regarding the wheel sizes. Should we go for 6 or 8 inch mecanum wheels, what are the advantages and disadvantages of each?
P.S. I saw that the mecanum upgrade kit on AndyMark’s website only has 6 inch wheels and not 8, so this would mean we would have to buy 8 inch wheels and gearboxes separately, will that cause any problems (missing hardware for installation etc.)
I would HEAVILY advise you to stay away from a mecanum drivetrain. It is especially not very necessary because you can just slam into the subwoofer with a tank drive to align if needed. Mecanum makes it really easy for you to get pushed around, and is a pretty easy way to land yourself on other teams do not pick lists. There is a good reason that barely any teams have used mecanum in the past few years, and the teams that do, don’t usually perform too well.
look at 4180 last year, you don’t want that
The AM mecanum upgrade is that it’s an “upgrade” from tank drive, and only includes the wheels, so you’d need the extra gearboxes anyways even if you went with 8" wheels.
I’m going to tend to side with @clavin here. Mecanum wheels are not the best option for multi-directional motion, to put it mildly. I’m going to mildly disagree about the ease of pushing around–but only mildly. On the other hand, a lot of teams see “mecanum” and proceed to, intentionally or not, not pick those teams.
Let’s ask the question another way: Why mecanum, and what other options have you considered for solving the problem that you think mecanum will solve for you?
And to answer the question: I’d probably use the larger wheels if I could fit them in the kit frame. And that might be why they aren’t listed for that–if the gap between the side rails is <3.5", the 8" wheels physically won’t fit, let alone with their chains and sprockets. But, if they won’t fit then they won’t fit and I’d go 6".
Well we are looking for a holonomic drivetrain for ease of alignment and better control of robot during high and low speed. As far as I know there are only two options, swerve and mecanum. We really want a holonomic movement this season, is there anything else you can suggest that we can use?
Swerve. Next question!
You’re also missing a couple of options involving omni wheels, but we’ll pass over those for now as those tend to be a bit more interesting. H-drive, kiwi drive, and square drive come to mind, but they have a tendency to be mostly worse than mecanum.
I’m going to ask one question: Do you, at this time, have any form of holonomic motion in your shop, or are you just buying it now?
Nope, we are going to choose a system and place an order by tomorrow. We as a team would really like to go for swerve but are really afraid because we have just around a month for our regional and from what I have heard swerve “should be done during the off season” Is this really the case or do you think there is anything we can do to make this work in our timeframe?
Mecanum can be a budget decision vs swerve. Swerve at cheapest is $1200+ for any system out there even without motors and motor controllers.
H drive is only legal with 4 motors so it’s different than in the past with 5 or 6.
Depends on the motivation of the students and how many people you have that can follow directions. We built the modules in a day, calibrated/wired in another, put the frame together the next time and then drove it around. So 3/4 meetings? But we planned it all out in advance and did the modules as a group activity.
Edit: we did Rev Max Swerve with Neos and Neo 550s (we paid for the Motor and Motor Controller Bundle). We are in the learning phase of maintenance and that will be ongoing all year long. We also haven’t used real bar stock yet, just a wooden test chassis but it’s good enough to get field accurate odom. @brandonmcd led part of the building of the modules so might have more to say about it. Also did the calibration, and has been leading the testing
That’s really great to hear, may I ask what modules and motors you used?
Updated my previous reply, didn’t see you were asking til I was mid edit
Swerve is actually as lot easier to accomplish than most people think. 4 modules, some punched tube, and some encoders and you’re good to go. Swerve is extremely easy to build and hard to mess up. Software is a little more difficult but now with YAGSL it is extremely easy and there are many tutorials that can quide you through it. It is usually an off-season thing but I think that if you are able to get your hands on some modules it’s not as hard as you think…
The only large downside in my opinion on swerve is just the high cost of entry, but if you have the money ready I would totally go for it
Any new drivetrain should be done in the offseason. It’s the one thing that you need complete reliability on. I would strongly advise building a kit chassis if that’s what you’re familiar with, put a mechanism on it, and get as much drive practice as you can. Especially this late into the build season, lead times on critical parts can greatly delay getting a robot that works before competition.
A well programmed and driven tank will always beat a poorly driven or programmed mecanum or swerve.
It’s less the case now than it used to be. There’s one problem, though. How long does stuff take to ship from the U.S. to Turkiye these days?
You’ve got 3 weeks (plus a day or so) to a) order, b) have them arrive, c) assemble them mechanically, d) code them, and e) get some drive practice/tuning/testing. And f) add superstructure–the stuff that makes the robot score points…
Do you honestly think that you can do c, d, e, and f between the end point of b) and your event? Are you SURE?
Right. The same issue is true for mecanum. You really needed to order a couple of weeks ago, maybe even earlier, to have a decent chance with the shipping timeline. It’s not impossible, but expect to pay for rush shipping here, you literally cannot get these fast enough. Let me repeat: Pay for the absolute fastest shipping here. Time is not your friend right now. If you think it’s faster and cheaper to send an adult to Texas for in-person pickup, then you might want to do that. (A bit extreme… yes.)
So, let’s reframe the question a bit. What can we do to get you more manueverability in less time? You mentioned ease of alignment, and better control. For alignment, you can partially use the field structures. For control, that might end up being driver practice. But, let’s make it just a little bit easier.
For this, I think you want AndyMark’s 6" DuraOmni. 4 of them, at least–and you can get them with the bearing installed if that will make things easier. What you’ll do is to take your 6WD drive base and pick two opposite corners (say, front right and back left). Replace those two corners’ grippy wheels with 1x DuraOmni each. It’ll give you better maneuverability, though the tradeoff is that it might be too much (and you’ll be more vulnerable to opponents trying to spin you). If it’s still not enough, replace the other two corners. If you’re really feeling crazy, replace all 6 wheels with omnis and practice drifting–it’s been done before, but you need some speed to pull it off.
While you’re doing that, if you have the budget for swerve, go ahead and order. Assume that you won’t be able to use it before the event, but because the modules are COTS items, assembled, R302E should apply and you’ll be able to use the same units next season. And if you get lucky with the timeline? So much the better.
Money is not the issue right now. We have a friend in the US so we will ship everything to him and he is going to come to Turkey and bring them to us so we do not have to deal with massive shipping times and customs processes. Our superstructure and control system is already fully built and tested with our field elements that we have built. So when the swerve modules come (Feb 19) we would have around 2 full weeks to assemble, calibrate, code and tune them. I would also like to ad the fact that we are allowed to skip every lesson and work from 8am to 5(sometimes 7) pm every single day. With the above replies mentioning how simpler swerve has become with the addition of YAGSL, I believe we can make it in time. Please correct if I am missing something out though.
That is going to help significantly–I was wondering about that superstructure.
Here’s how I’d do it, given that.
(I wouldn’t skip every lesson unless it was absolutely necessary.)
If time and money isnt an issue I would 100% go swerve in your case. Make sure that your cad with your superstructure will be easy to mount and integrate with the swerve chassis that you will also design. MK4i’s are probably the best option on the market for most teams, if you are looking for something smaller, WCP has swerve XS and rev has MaxSwerve, the latter two have identical packaging
That is some great advice for a timeline. Regarding the gear ratio, any general rules we have to follow or just determine one based on robot weight?
Which do you think would be better for a team attempting swerve for the first time, MAXSwerve or the MK4i?
The MK4i in my opinion has been more tested and has more community support then the REV Swerve. That is what I would go with if I were you. In terms of motor gear ratios, you can base it on the robot weight. I would also recommend getting the SDS 16t pinion adapter set, that way you can always upgrade your speed if you find that you can significantly benefit from that added extra speed
edit: didn’t see lead times, go with whatever comes first