Mecanum in FRC2020?

Don’t

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My team ran mecanum last year. Highly do not recommend it for 2020. Mostly due to the risk of defense, but also passing over the RP climb, as it will never survive. I see why it’d be helpful with targeting, but it isn’t worth it.

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So I’ve seen one person post a video with activity. Looking to see the next robot video with full speed and full “robot load”

So I have data points.

I have folklore from 5 other posters. Facts not folklore. Physics vs psychic guesses. Math before maybe.

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At least two of the replying teams ran mecanum as recently as last year and though they did not elaborate on their reasons they said unequivocally that mecanum is a bad idea based on experience, which is not folklore or psychic predictions. I understand the desire for data but there are many data points over many years. My team has built three mecanum driven robots since 2015; one was used in Recycle Rush, one was a practice bot, and one was for outreach. We used the AndyMark standard wheels, the AndyMark HD wheels, and vex wheels. The HD lasted the longest but we still broke rollers in competition. The number of rollers and wheels that were bent or snapped on the other two types from running a full weight robot over minor floor bumps (not steel 1" tall rectangular tubes) was incapacitating. I am of course aware that there are successful robots that use mecanum, two of my favorites are 2996 in 2014, and 3478 in 2019. I would still not recommend using the wheels this year, the risk is very high.

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And I’d move your post into the fact category since you have lots of details on what you did, wheels used, failure points described. You have a metric ton of information about what you did and the results.

Elaboration can move folklore to data. I’m always on the look out for posts that has the data to back up comments.

Mecanum = bad as the only information doesn’t get a second glance.

Maybe the 5 prior posters will come back with the specs on the robot, wheel info and how it (didn’t) work out. That way we can all learn.

Nice post, but you’ve been around since sprockets were just ore …

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The Drive Base in the video weighs ~150 lbs. There are lead bars on top of each rail. Ill take the video of the full speed test today. I am not advocating for or against mecanum. It depends on the individual teams strategy. I was just curious about the ability for a mecanum robot to cross the boundary.

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Oh my gosh, that’s lol. And probably true

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I can clarify some things.

In our 10 years as a team, only once have we picked or advised a pick of a mecanum bot, or been on an alliance with one (2014 Center Line, if you’d like to know).

The only world champion to my knowledge that has used a mecanum drive was 1671 in 2015.

We built a mecanum drive in 2015 and 2017 (octocanum in 2017). In 2017, we believe we would have been better served by building a tank drive because while mecanum wheels look cool, in practice they don’t help all that well, especially with power consumption. In 2015, we threw them on halfway through the year to compensate for a lack of driver’s practice with lining up with the feeder station. I still believe if we drove a tank drive with more practice we would have been much better served. Tank gives more precise control over your robot, and isn’t as susceptible to being pushed wherever a defensive bot wants to push you (loading zone, anyone?).

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(I’m going to poke you since you are a mentor and have been around a long time. Don’t take it personal. )

How did that choice work out? Were issues in the match related to their drivetrain or did other things happen?

So what happened in 2015 around the drive base? Did it work/fail? What were the downsides of your matches? How did the game play integrate into the robot?

Tell us about your bold move to move to the octocanium drive in 2017, was it all you wanted it to be? Were there other issues around the robot that made the drive choice not the best?

Nice idea, change the base to match the driver skills. And did that work out? Was the ability to strafe a few inches to the right / left give the driver better control to pick up the load?

Were you often pushed off track because of defense bots or was driver control the central issue.

How much practice time did you get? Were drivers sometimes able to get to places or was it mostly just a mess. (Side note. I run parent sessions where they can drive the robot. What they think is “easy” on the sidelines becomes an awkward 6th grade dance with them at the controls) (Note: I’m banned from driving for a team due to my amazing ability to drive the robot into the only support column in the practice field. Twice)

So a drive with the ability to strafe and translate gives you precise control as all the mecanum and swerve teams will tell you. I agree with your point on defense. OTOH I’ve seen swerve robots pivot around a tank drive, broad side it and move it out of the way.

Keys seem to be driver skills.

Thanks for the post. What you wrote helps. We are all looking for facts and similar situations to make comparable decisions around.

Sorry to bring this thread up again, I’ve just been busy with robots and I was writing this reply on my laptop.

2014 Center Line we ended up as Finalists from the 6th seed, partially due to the defense our alliance played. However nobody really played defense on the mecanum robot until the finals, which is where we really stalled out (and if you are somehow able to find discussion of 2014 CL, that event was a big mess all around that really was an anomaly for FIRST events in general. The refereeing was extremely controversial, the semifinals were 2v6/5v8, and finals was 6v8). So to answer your question, there weren’t really any issues with their drivetrain. However, it may have partially been the reason we didn’t win the whole event.

To really get into our whole process in 2015 would take longer to write down than I would expect anyone to care about, but in short, we made a very… stupid(?) design decision early in the season (if you want to see the decision, look at our matches from Traverse City vs our matches from Center Line), and never got the robot really working the way we wanted, so we weren’t able to really get any good driver’s practice. Then after our first event when we went unpicked, we tore down our robot over lunch and rebuilt it and ordered mecanums so that we could compensate for lack of driver’s practice with our new design to help with lining up with the feeder station. It worked, but we were not good by any means, and in a game like 2015 where being a feeder station robot meant you didn’t have to do a ton of heavy driving, we didn’t end up having any major issues. In addition the lack of defense made it an easier decision to make.

2017 I was an alumnus in school in Indiana when the team was building the octocanum. However, I ended up being our drive coach at MSC that year because nobody wanted to drive coach, and I was home for spring break. We got to MSC because

a) we went to the Center Line district, where if you could score gears at all, you were getting picked,
b) we won a district as a defensive bot picked second round because of the traction mode. (In addition we won Chairman’s at that event, but we qualified on points before winning Chairman’s).

To explain a little bit more what I know about, the octocanum sucked battery like no other drivetrain I’ve ever seen. In addition, they spent all season tweaking it because we hadn’t prototyped it preseason. There was a few matches at MSC where we would run gears all match and then when it came time to climb (our climber was on the side of our robot, so we had to strafe to hit the rope), we’d be browning out when strafing. I would go as far to say that the mecanum mode didn’t really help our team at all, and drive practice with a tank drive would have helped tons towards being a competitive team.

We believed a lot of issues with our alignment would have been solved by getting adequate driver’s practice, because having finer control of the robot and driving up to the peg/feeder station properly the first time will save you more time than driving up crooked and strafing.

In 2015 and 2017, I believe we had less than 5 hours both times. The drivers were able to get places, however it wasn’t as efficient and as strong of driving as a tank would have been that year. (To reply to your side note: I drove our 2014 and 2016 robots and was Operator in 2015, so I understand how difficult driving is)

I strongly disagree with mecanum giving you more precise control, simply because strafing sideways is usually much slower. Swerve has the same speed in all directions and also has some funky moves you can pull off with it (pivoting around one wheel to get around defense like a pick and roll), and I wouldn’t disagree that swerve gives you more precise control (although I would say that it takes longer to build/implement and there’s definitely a cost/benefit associated with it), and if you look, my team started prototyping a swerve this offseason so I’m not fully against holonomic drives in general :slight_smile:

I will add that I fully endorse FTC teams to do mecanum, and have endorsed my own FTC team to do it. The defense scene in FIM FTC is virtually nonexistent, and middle schoolers aren’t as good of drivers in the limited timeframe that they have to practice as I’d like.

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Thanks for the great detailed reply!

We did this and it works fine

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We went off the level two in the last match of the onseason and it went fairly well.

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Lighter weight robot maybe, or maybe it was our weight was more concentrated over the wheels that broke. I’m not sure.

Mecanums any year…

@JackN

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Don’t do it!

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@Austin_Plummer how did the full speed test go?

Here’s the video of the test. Robot weighs about 150 pounds and top speed is about 10.5 feet per second. The bar I’m using is square edge so it is probably a little worse for the robot than the real field would be. Inspection after didn’t find any damage and it still drove normal. While I wouldn’t want to do this to the robot match after match the wheels held up and it is possible. If you do decide to go with mecanum I recommend you do cycles through the trench to avoid defense anyway but you can definitely maneuver over the boundaries.

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