Penalizing mecanum wheeled robots durring alliance selection.


#1

Over the years as mecanum drive robots increse in popularity its become incresingly common for teams that seed in the top 8 to penalize 1st round picks for having a mecanum drivetrain. So CD comunity, what does your team do when it comes to mecanum drive robots?


#2

We built mecanum robots in both 2011 and 2012. We were (for give my narcissism) very good both years, and mecanums proved to be advantageous in both games.

The single only reason we didn’t use them last or this year, is specifically because other teams don’t like them immediately.

I have never seen a mecanum implementation (code etc) better than ours, but nonetheless, it is painful to be judged by stereotypes than performance


#3

We have picked Mecanum wheeled robots in the past to be on our alliance. Most notably at Arkansas in 2013 when our 1st selection (Ubotics, FRC#3507) was a mecanum wheeled robot and our alliance made it to the finals.

However the biggest impact mecanum wheels have on our pick list is with 2nd round selections. Defense normally plays a bigger role in our choice for a 3rd member of our alliance and more often than not a kit bot drive base will beat a mecanum robot when it comes to standard defense techniques.

There are teams that have used mecanum wheels very effectively but similarly to crab/swerve if you are not one of the teams doing it at high level it rarely pays off. I often advise rookie and young teams from using them on their competition robots.


#4

Last year we had mechanum wheels and were the 15th highest OPR on our field but our robot was slow and could not go under the pyramid and could only load in station and we went unpicked.


#5

Maybe meccanums are less popular in NorCal, but I didn’t have to make a decision about picking a team with meccanums all that often.

(The following is about how I helped choose picks for 100, so don’t read anything about 971 into my statements.)

For first round picks (if you are in that position, we were only there once when I was helping choose our picks), it’s often fairly obvious who the next best team is, or if not, it’s a choice between two teams. Usually, the teams who are picking from the top 8 have done their homework, and base their picks off objective statistics at least in part. Most teams that have a good shot at getting picked first have already chosen not to use meccanums, so it’s usually not an issue. But, if I was in the position of picking first, and there was a team that was clearly better than anyone else available who ran meccanums, I would pick them.

Second picks are a lot harder, because there’s a larger pool of teams that it might make sense to pick, and frankly most of the teams left over really aren’t that good. Of course, it depends on the game, but in my experience, you’re looking for a team that has a strong drivetrain and knows how to drive it, and if possible can hit auto and help with the endgame. If there’s a team with a reasonably well built WCD and good drivers left by the time that we can pick them, we’ll go for them 4/5 times. Offensive ability (which meccanum bots may or may not possess) is secondary, as the captain and 1st pick will likely be doing essentially all of the scoring. You want a good defensive team for your second pick, and for whatever reason, in my experience a well built WCD works best for that.

I don’t think there’s some vast conspiracy to never ever pick meccanum bots, but I do think (from being there in the past) that given a few roughly equivalent robots, teams will usually pick tank drives over meccanum drives. Going meccanum is usually a decision based on coolness, and teams with meccanums are often kind of wild cards. It often just feels safer to pick a team without diagonal rollers on their wheels.


#6

Great poll and thread. I am very interested to see how the results turn out. As for me, I chose “does not affect position”.

Interestingly enough, for some of the regionals I have attended, I might actually be more prone to select a mecanum bot than a tank bot for a defensive pick. The reason why is because a mecanum robot always* has 4 drive motors, while too many teams still use only 2 drive motors for tank drive. I would still pick the robot that is the best driven for a defensive pick, but all else equal, I would feel better about having a mecanum bot on my alliance than a 2-motor tank drive robot.

*Although I have heard of teams that try to drive a mecanum configuration with only 2 motors. shudder


#7

Our alliance did this at Panther Prowl last year. We could not have been more pleased with the outcome.


#8

Generally, mecanum is a major detractor when my team is assembling the pick list. However, we will pick a mecanum robot if it offers us what we need. We picked 2 at the crossroads regional. Personally, I think mecanum is a poor drivetrain solution, but some teams do it very well.


#9

For our team, if a team has mechanum wheels on their robot or not is a feature that we check, but wheels in general are a feature to consider while picking. We don’t judge just by one feature, we look at all aspects of the robot, then choose. Although our team commonly makes jokes about mechanum wheels as they don’t have the best reputation, we have yet to penalize a bot on our pick list because of mechanum wheels.


#10

It honestly depends on if the team knows the limitations (reduced pushing capability, vulnerability in open spaces,) of their drivetrain, and if they use it effectively. I’d have no problem picking a team with a mecanum drive so long as they effectively take advantage of their drivetrain and play smart with it.

Unless we’re playing a full contact game like Aerial Assist. I would not pick a team that has a pure mecanum drive for a game like this. IMHO, drives with traction wheels were king, even octocanum/butterfly.

-Nick


#11

For this year’s game our team used mecanums and knew that we were slow and easily pushed. Seeing that, we preferred to have our alliance partners have a decent tank drive to not only keep our play at a decent speed, but also to have a good defense while they weren’t handling the ball. It may be a little hypocritical, but defense was a major part of this year’s game.


#12

For us it’s all about performance. It doesn’t matter what drive train a team has, so long as they effectively use it and are the best available team at that point in the selection process. If we need someone who can score, we look at the team that has best shown the ability to score the most points per match. If we need someone to play defense, we look at the team that has been able to decrease an opponents score the most. In the end, it’s all about the bottom line - can you score more points than someone else. Ignoring a team who has proven they can affect the bottom line the most of everyone available just because you don’t like a feature of the robot? We try to avoid that.


#13

I think it really comes down to how big your wheels are. In 2013 we bought big 8" diameter, 2" width wheels and were actually one of the better pushing robots out there (didn’t get picked, but that was mainly because our shooter was awful). In contrast, we used 6" diameter, 1" width wheels in 2010 and got pushed all over the place.


#14

If they are the team that best meets my criteria I pick them. If they aren’t, I don’t. This is the same logic I apply to any other team.

So, no I don’t penalize them. I just tend to rank features they traditionally lack as higher priority than the features they excel at.


#15

I have not personally been a part of selecting teams, but I have noticed that you have to have a strategy in your alliance that accommodates a mecanum drive bot. Mecanum is good for being evasive (if built and driven well) but is bad for being physical and getting in pushing matches. If you don’t have a need for it don’t pick it(mecanum drive).


#16

Automatic DNP, unless there are too many mecanum bots for that to be possible.

It’s not that mecanum wheels are inherently bad, just that 99% of the implementations we see are.


#17

If the team drives the mecanum drivetrain well, I see no reason to leave them off the list.
Then again, I don’t do any scouting.


#18

In my fantasy world I would dearly love to see Teh Chezy Pofs do mecanum just one year so they can show us all how we have been doing it wrong all this time and then maybe everyone else would stop the mecanum bashing and shut up about how mecanums are never on Einstein.


#19

I think you’ll see it when they decide that powdercoat looks kind of stupid, wires don’t care if they’re ziptied down or not, and that they should stop driver practice because it distracts from watching South Park.


#20

We’re not penalizing anybody. We’re picking robots that best complement our robot and the strategy we want to play in the elims.

In 2014, there was no place for a (pure) mecanum drive robot on our alliances. The ability to resist pushing was viewed by us as essential to forming a 3 assist cycle. Resisting pushing with traction allows for “wall” defense and also helps avoid being spun while shooting or ejecting. People argue about whether mecanum can push or not, but they’re really missing the point - pushing resistance is where mecanum robots really struggle.

There were some robots at our events that were mecanum drive that played fairly well but without traction they just could not get into and hold position where they needed to be. Setting up truss shots or passes with them was just too difficult when they could be spun by defense. In spite of this, there was just one other robot on our list between our alliance’s second pick and a mecanum drive robot at Finger Lakes.

In other years, the “cost” of a mecanum robot versus a traction robot varies. I feel it’s worth noting that more often than not the best several teams at a regional are all tank drive. In this case the teams aren’t being selected because they aren’t mecanum, but because their robots are overall better than the mecanum robots are. In addition, in the somewhat rare event that the best teams at a regional include mecanum robots, these robots tend to have well driven and implemented mecanum drive systems.

To be quite frank, I think a lot of teams that aren’t very good pick mecanum drive because they feel like the ability to strafe allows them to drive better with less practice. It seems more trivial to just gun the robot forward into a scoring zone, then strafe to where you actually wanted to be, than it is to drive in a smooth arc up to where you wanted to score. However, without plenty of drive practice, it doesn’t matter what your wheels are, you’re a lot less likely to be a first round pick at all.

In short, there’s almost no situation where all other things equal, a mecanum drive is a net gain over a tank drive for our alliance, and I’ve observed a correlation between teams choosing mecanum wheels and teams dropping down our pick list due to poor manipulator design.

Also, if you’re the kind of team that gives teams grief for making choices differently than you and assume teams were too stupid and biased to pick your obviously superior robot based on its wheels, maybe you’re not the kind of alliance partner we would want to work with?