Hi, I was just wondering what is the purpose of the mecanum wheels, how do they work and are they worth the $400 for the set of 4, also if the sell them somewhere else cheaper than that could you give me the link?
Mecanums have some nice maneuverability. They are able to strafe, for example. (you can find some videos of it on YouTube)
However, mecanum wheels will be weak for pushing power and can slide around.
You’ll likely be pushed around a lot on the field if you use them
Where have you looked?
Also make sure you know what size you need. Don’t use mecanum wheels just for a cool factor. Mecanum wheels are great for maneuverability, but when it comes to pushing they are worthless.
My team used mecanums last year and they worked well for sliding into place at the feeder station. However, they were terrible when we tried to cycle and were pushed extremely easily. This year may not be the best for mecanums simply because of the lack of safe zones - you can be pushed at any time with nowhere to retreat.
The choice is completely dependent on your team’s strategy. Is your shooter reliant on consistent positioning? If so, you may not want to use mecanums because of the pushing issue.
In this game the only big advantage I see for them is with catching the ball from the truss, so unless that’s a big part of your strategy, I wouldn’t get them. Another downside to them is that they’re quite heavy.
Mecanum work well if they fit your game strategy. You can get a full set for much less then $400. Vex pro sells a set of 6" for 159.99 http://www.vexrobotics.com/vexpro/wheels-and-hubs/mecanum-wheels.html
Also, in my experience the vex wheels preform much better then the andymark equivalent.
Try VEXpro. They have very affordable yet durable mecanum wheels. The other posters are correct in assuming that unless you are trying to catch, mecanums might not work well this year… However** don’t believe they are easy to push**. We had to play defense with our mecanums last year in matches when our shooter failed and were fine. We could block lots of teams. I know this is contrary to popular belief, but a properly done mecanum drive base can in fact be very strong.
For anyone that wants to question our pushing abilites, we have video…
Mecanum wheels, neglecting friction in the rollers, have an effective coefficient of friction that is a factor of sqrt(2)/2 reduced from that of a traction wheel made of the same material. You can verify this yourself by drawing a free-body diagram of a set of mecanum rollers in contact with the ground.
Whether or not this translates to “being pushed all over the field” depends critically on context (robot weight, weight/drive of opposing robot, weight distribution, manner in which you’re hit, etc).
My team has used mecanum wheels for the last three competitions, and each time we had great success with our drivetrain.
The system is meant to give a robot high levels of maneuverability, and when it is allowed to move at high speed, it creates a formidable opponent. Having the range of motion provided by a mecanum drive can allow a driver to jump out of the way of onrushing defenders, all while maintaining a scoring opportunity
When discussing pushing and mecanum, it should not be forgotten that the goal of this drivetrain is maneuverability, not brute strength. Due to this, a pushing match with a robot designed for pushing will be lopsided. But that does not mean that this drivetrain is easy to push. I have seen our past mecanum drives stop six wheel drives dead, and win pushing matches. When we use mecanum, we maintain a balance of speed and pushing power, and ensure we are not compromising one for the other.
This quote sums the entire discussion up, and is good food for thought. “Mecanum drivetrains, like every other, have advantages and disadvantages” - Mr. B
I have a quick question about mecanum wheels. Can they be placed in a trapezoidal configuration?
Has anyone tried this before? How well does it work?
Could you describe the configuration you are thinking of? Do you mean something like this:
where the ] are wheels and you have the front wheels in narrower (or the back wheels)?
Our team used the VEXpro wheels last year, and I was very pleased with them. They lasted 2 competitions and multiple fundraisers until they started to fall apart. They are also quiet and light compared to the Andy Mark versions we have used in the past. We also had to be purely defensive in one competition and managed to place high because our mecanum drive allowed us to out-maneuver our opponents and get in front of them to block their shots.
I encourage anyone and everyone who thinks that they understand mecanum physics to read the whitepaper given here: http://www.chiefdelphi.com/media/papers/2759?
Yes. Something very similar to this. The back wheels would be about 12in apart and the front about 24in apart. The front and back wheels would be about 30in apart.
Last year we used Andymark mecanum and this year we were looking at the vex pro mecanums, and a couple of our main mentors were worried about them cracking because they are plastic. Did you have anything that looked like it was about to crack or anything like that?
Our team has used a mecanum drive train for the last three years and we’ve had a lot of fun with them.
As the robot driver for the past two years, I can assure you they’re wonderful to control, and driving becomes a lot easier with mecanum.
Controlling the a mecanum-powered robot is a lot like moving a character in a first person shooter video game, which I’d assume many students are familiar with already.
Couple a mecanum drive train with gyroscope technology and now your robot can always move relevant to the driver (No matter the orientation), which in my personal opinion makes controlling the robot even easier.
While a downfall may be that you lose a lot of pushing power, the versatility gained to out-maneuver the defense matches said downfall quite well.
Our VexPro mecanums have held up well. They survived one regional and some off season demos with no problems, and in our shop we typically run them on concrete. We are planning to use them again this year.
Yes, our VEXpro wheels did crack, but that only happened this past December at a fundraiser where we were showing off our robot. We went to two competitions last year and had several other fundraisers and expos before they broke. I believe they are durable enough. You shouldn’t have to worry about cracks during competition. I believe they also sell replaceable wheels for the mecanum if any of them seem to have significant wear or break.
Mecanum wheels are very nice for alignment of your robot even when the driver has not had a lot of practice time. I would imagine this year aligning your robot in order to gain possession of a ball would be important to some teams. Practicing gaining possession in a real-game situation is difficult for a lot of teams, so mecanum can be handy here.
Also, I always throw in my vote for don’t believe that mecanum can easily be pushed around. Wait…am i part of the majority on this vote?? :yikes:
At the moment, my team is not a fan of using mecanum, unless it is undeniably the absolute and only way to win matches. With mecanum wheels you can lose up to 50% of your power when doing moves like strafing, whereas with swerve drive, all the power is used more efficiently. Mecanum wheels are indeed expensive, and I don’t think that they’re worth the price unless you are absolute that they are the best choice. From my experience here in the Californian bay area/central valley, the best teams stick with drop center six wheel drive treaded wheels. Why? They are inexpensive, offer the best traction, best pushing power, least complex in programming and build, easy to fix, and provide all the maneuverability necessary. Name one team that has made it to the Einstein field using mechanum wheels. None, because this has never happened in FRC history, but hey, there’s always a first, and it could be anyone!
If your philosophy isn’t all about winning, then have at it with the mecanum wheels! Mecanum robots are really fun to drive, too. Still, they are a pretty penny, but 100 bucks per wheel isn’t a bad deal. I’m not saying that you can’t win with mecanum wheels, many regionals have been won by these types of drive bases, but what I’m saying is that treaded wheels in general are a better choice in my opinion. Treaded wheels are also LIGHTER! And that could be the difference between passing and not passing inspection if you cut it really close with your other robot components.