If resources are the concern, the kit comes with a really nifty drivetrain that’s far better against defense than mecanum.
I was going to say essentially the same thing, so I’ll paraphrase:
If you have a great design, and it is well executed, and you end up at or near the top 8 in your regional/district event, then a good mecanum robot is a good robot.
If, however, a robot has performed “OK,” and is in the 15th to 25th seed zone, mecanum wheel are highly likely to prevent this robot from being picked.
It does, but many teams are making custom drives anyways. for instance, the team I mentor only used the kitbot their rookie year and have be using customs drives the last 4.
I’m a fan of the kitbot. But I also think lateral movement is a big advantage in placing and grabbing cubes. Steamworks was a good example, teams with non tank drives had a huge advantage in lining up for the peg and loading slot.
But that’s not what it is, though. Look, I’m no mecanum evangelist (mecavangelist?) but here’s a post I made in a similar thread in 2016. I don’t like repeating myself, and my thoughts really haven’t changed, so here’s that:
I don’t care how your robot moves, as long as it gets the job done well. The drivetrain is one aspect of the whole that cannot be isolated as the only factor of success. Is the drivetrain important? Yes, extremely. Is it the only important thing? No. Good mechanisms make a good robot, and the base is not the only mechanism.
Personally, I don’t like mecanum because I feel it’s too easy to bully mecanum robots, especially in a game where alignment is key. However, my team has been in a situation where, as the 8th seed alliance captain, the 2 best remaining robots were both mecanum. (this was 2014, by the way) Did we care? No. We picked them because they were the best, and they fit our strategic goals. What matters is that you’re completing tasks consistently and quickly, regardless of what kinds of wheels help you do that.Tl;dr: I don’t care if you use hot dogs for wheels. If you’re scoring points, and you fit the strategy, it’s fine.
100% this. Well said.
Pick your strategy, how you’re going to play this game. Pick your drive based on your strategy.
Make your drive train robust, give your driver lots of practice. Don’t be a team that is immobile for any part of a match because of your drive train. Seriously, this is more important than tank vs. mecanum.
If you decide a holonomic drive train fits your strategy, mecanum is probably the best choice for teams with low to moderate experience. Figure out how to use the advantages of the drive train you pick. Seriously, don’t build a mecanum drive and then drive it like a tank all of your matches.
I wouldn’t worry about other team’s opinions. If you bring the best robot to the competition, their opinion of your drive train really won’t matter.
Alright, 492. Won a district event, First seed of Galileo, made it to finals.
One thing to add on, dont bite more than you can chew. If you havent done mecanum before, dont think its just like tank in terms of both ease of use and build time. Extra driver practice will be essential if you want to use it properly.
personally I would go tank because then once you start to win you are the best suited to play defense so you keep your advantages on the tipping things as time goes on.
Last year we didn’t get picked at worlds, mostly because we had a mecanum drive. I know it seems stupid, but take into account that people picking you probably wont like the fact that you have a mecanum even if that’s why you got to worlds.
Did some team tell you that or did you just not get picked by anyone?
It’s more likely the rest of your robot that made them not pick you.
There is a small, but not insignificant, ramp in the middle of the field. Mecanums can climb ramps, but in my experience not as easily as tanks.
On the other hand, keep in mind that while you’ll use your robot for competition for a few months, you’ll be using it for demonstrations for years. There are few things more inspiring than a robot that moves in an “impossible” way.
We kept our 2007 Mecanum robot kicking around for years because even experienced engineers would look at the wheels and ask “What’s with that?” We had a little discussion about vector forces and “reinventing the wheel”. It definitely took more practice for our drivers to learn to use the benefits of the mecanum, and more work for our programmers to get it to work (keep in mind, they were using a previous generation of controller) but it was a gift that kept on giving long after the season was over.
I agree with most of the discussion that mecanum isn’t necessarily the drive I’d choose for this year’s game… but in all the analysis of why or why not, don’t forget the simple fact that mecanum is COOL (although not as cool as they were 10 years ago when you had to walk to school up hill both ways in the snow to make them work… get off my lawn you darn kids and your fancy controllers and COTS parts). Our robots are meant to inspire, and the inspiration factor of a fancy drivetrain should not be ignored.
Jason
Nothing saying you cant switch them out after the season is over though. Some work? Yes. Impossible? No.
Not all Mecanums ** are equal. Some are executed better than others.
** substitute as appropriate
- gearbox
- shooter
- swerve
- elevator
- claw
- autonomous mode software
*]…
Every year I have been part of FIRST (this is my third year, so I’m still far from knowing even a little bit), my team has had mecanums in some way. Whether it was all four wheels or just 2 (worked well for Stronghold), our robot was almost never bullied. The important part is the drive team. With an aggressive and smart driver that has some experience driving, it is difficult to simply push a robot out of the way. Both tank and mecanums have their pros and cons, so go with what you feel confident with. If your team is one of those that finishes the robot in the last days (mine usually is), then see what your drive team feels most comfortable with.
(Side note:As a scouting captain, I don’t factor in wheel type or really any robot features. I look strictly at performance.)
Another consideration re: Mecanum is a bot’s weight distribution. If the CG is generally low and stable - not a problem. This game may require maneuvering while the robot is reaching high to place something on the scale and any lateral/longitudinal movement can significantly effect normal force at the wheel. Not a good thing for Mecanum control systems.
Another factor is whether it’s centered. I don’t know if this applies to the smaller ones, but with the larger mecanum wheels I know that the rollers behave differently based on weight distribution. If weight isn’t distributed right, you may find yourself strafing when you don’t want to.
Every year I see this question and it blows my mind how much of a stigma is attached to mecanum in this community that is normally so tolerant of diversity.
Personally I’m not sold on how much contact there will be this year, but my mentality is that the drive base is just another design choice you want optimized towards the role you want to play. I’d first pick a unicycle if the team showed me the theory-crafting, laid out their strategy, and proved it with their performance during a competition.
I understand bringing an unpopular opinion to a debate can be uncomfortable. I’ve been there. 2015 I ran through all the rules, strategy, Q&A, research and I had to swallow my pride and go to my team and say “So I’m being 100% serious right now and I need you to hear me out, and I even hate myself for saying it but I believe mecanum is the right choice. I do have some concerns but they can be put to rest with some testing.” (We ran the tests and mecanum did fine)
That was an awkward conversation for me but we ended up running mecanum that year and at the end I don’t feel like we regretted that decision (of course that is me speaking for other people but that is the consensus I got).
YO students, if you have a serious idea or question **BRING IT!** Anyone who can't keep an open mind to it really shouldn't be sitting at that table. This is a time for discussion not disrespect.This is the case with mecanum wheels in general. Mecanum wheels work based off of having a resultant force vector that is actually on a diagonal; going straight forward, the x-components cancel out and y-components add. When strafing, certain wheels go forward and certain wheels go backwards so that the opposite occurs. However, the magnitude of these forces is due to the reaction of friction, so less weight on a wheel = less friction = components that might not actually cancel out. This can be compensated for by adjusting to weight distribution in code, but is not ideal IMO.
Unless your the captain with meacs doing 6 gears a match with your eyes closed. But, yes not all teams want to judge robots logically by on field performance and scout teams individually so if you do meacs you better do them well to control your own destiny.
Now for this game, I wouldn’t do it because of the platform and traction issues / control challenges driving on poly carbonate/plastic. We’re doing a tank drive and we don’t just shy away from meacs because we can do them well.
I would just like to say dont use mechanum for countles reasons in this post. However, if you must Gear for SPEED you want to go bloody fast.