Mecanum Drive Train
 

Hi, we are planning on using a mecanum drive train this year and im not 100% sure on how to set it up. if anyone can help me that would be great. thanks

Re: Mecanum Drive Train
 

First, don't commit to a drivetrain until after kickoff. It's the worst thing you can do. Prototyping is fine, but planning before Kickoff is asking for the GDC to outlaw that design, or designing a game (or kit) so that it won't be the best.

Now, setup: 4 motors, 4 gearboxes, 4 mecanum wheels, and a fairly standard 6WD/4WD frame. Rig one motor to each gearbox, and arrange the wheels in the frame so that the tops look like either an X or an O. (Both will work, but the X pattern on the top resists spinning better than the O.) Connect the gearboxes and turn it over to the programmers so they can figure out the coding.

Re: Mecanum Drive Train
 

If you're going to build a new (as in new to yourself) drive system, you must first know how it works. A good whitepaper that discusses the kinematics of a mecanum can be found here: http://www.chiefdelphi.com/media/papers/1836.

Read it, learn it, know it. It will will help in your planning. Also, do a quick CD Media search for pictures of mecanums to get your brainstorming going.

Oh, not to mention the break-through 6wd-mecanum suspension, but here's a good example. And then there's 488's prototype mecanum.

Re: Mecanum Drive Train
 

we build our own omniwheel drive system from scratch including wheels but i believe you can order mecannum wheels off of FIRST.

Re: Mecanum Drive Train
 

Actually, its Andymark that sells them.

http://andymark.biz/mecanumwheels.html

Re: Mecanum Drive Train
 

If your team is completely unfamiliar with how a mecanum system(or for that matter any other drive system) works then I would highly suggest that you do not try it during the build season.

A good drivetrain is (usually) paramount to having success during the season, and it becomes that much more difficult if you need to learn that drive system during the build season.

I would also echo EricHs' warning. Don't lock yourself into a drivetrain (or any other robot part) until you understand the challange given at kickoff. To do so could possibly lock yourselves into a design that may not work.

Re: Mecanum Drive Train
 

You can find lots of examples of mecanum robots on Youtube. To get started, search for "1346 mecanum" and you'll see the one we built a couple years ago.

While I would suggest that you heed the advice about not committing to a drive train until the game is announced, there is absolutely nothing wrong with preparing to build a mecanum once you know it will match your team's game strategy. The worst thing that will happen is that you will learn a lot about mecanum (and other omni-directional) drive systems.

There are a GREAT many forums here on CD discussing the benefits/disadvantages of mecanums and tips/techniques for building them.

Jason

Re: Mecanum Drive Train
 

thanks for all the help. regardless we are going to prototype a drive system sometime hopefully in the next month. i've read about how they work and everything but i guess i wont be exactly sure until i see it. and what is the best way to attach the wheels to the gearbox and what is the best gearbox to use

Re: Mecanum Drive Train
 

Sprocket and chain is the best, though some will prefer direct drive. The best gearbox is a relatively fast one; mecanums don't transfer power in the same way as a 4WD. (Hint: Toughbox, unmodified, is/can be too slow even on a 1:1 ratio to the wheel.)

Re: Mecanum Drive Train
 

so is there any gearbox that would be best. or would we need to modify any gearbox we get

Re: Mecanum Drive Train
 

you could use the banebot transmission, they are pretty fast(when directly driven to the wheel) although reliability is an
issue

Re: Mecanum Drive Train
 

Try 9:1 banebots. Thats what 1675 used this year with 6" mecanums and they were pretty quick.

Re: Mecanum Drive Train
 

I've been discussing Mecanum with my team as well and completely agree that committing before the 4th at bare minimum is an extremely bad idea in the sense that it could just not work for the game or at the very worst GDC could outlaw it. =/

however, [as is the case with my team *currently*] not even thinking about it do parts/labor/programming needs and the fact we've never done it before is... well, just an excuse. Nobody did it before they did it ya know? that's plain logic. If anyone remembers any of 279's robots, they can see that tank drive with an occasional perpindicular omni has been used EVERY year since Jake in 2001. I think, being our 11th year, it's time to try something new, but nobody's willing to commit the resources. I'm pretty sure that even though 6w with a larger or offset middle wheel has been the driveline of champions the past few years the mentors on my team will still not consider an alternate driveline. my question to CD is who wants to help me/us do something differant assuming something doesn't develop before... say december?


Btw, this is my first post!!! so a little about myself: My name is Nick Burmeister, though most call just call me Burmeister. I'm a Second Year student on Tech Fusion - 279. I was the 2008 Driver and Student-head of building driveline.

Re: Mecanum Drive Train
 

Maybe you should suggest to your mentors that they come around CD sometimes and see the various ideas that get floated around. I've seen some crazy ideas, like omnitracks. (omniwheel on a tank tread) Who knows? They might have some ideas themselves.

And, of course, this is probably one of the top 3 most helpful places to a FIRSTer. #1? The FIRST website. #2? (tie) CD and The Blue Alliance (TBA).

Re: Mecanum Drive Train
 

i've showed all of the students on the team the various drivetrains that are on CD and some of the mentors.

Re: Mecanum Drive Train
 

Show the mentors as well as the students.

Re: Mecanum Drive Train
 

Sigh... reliability is not an issue with the CIM planetary gearbox from Banebots. At least no more so than for any other gearbox used in FRC. There was a problem with their first batch of trannies, which, unfortunately, got shipped out as part of the KoP two years ago. Banebots went to great expense and effort to fix the problem in time for competitions and has further improved their product since then. Unfortunately it is the nature of (many) people to remember the initial problem, rather than the excellent committment to service and subsequent improvements that Banebots has made. We were one of the first teams to identify a problem in the original KoP trannies, and have since taken advantage of the free upgrade that BB offered to ALL FRC teams and have been running BB trannies on our mecanum for the last two years with no issues.

In fact BB trannies, or other direct connect transmissions (where the wheel is mounted directly to the output shaft) make for, in my experience, the most reliable drivetrain as the most common point of failure... the chain or belt... is eliminated from the system. Just make sure the output shaft is supported on the outboard side of the wheel!

An additional advantage of the BB trannies is that you can order them in a wide range of gear ratios, and can convert from one ratio to another (with some limitations) if you aren't happy with the performance.

Yep. There was a problem with the Banebots trannies two years ago that was quite disruptive. But it is hardly fair to question the reliability of the current trannies given the fact that BB stood behind their product, solved the problem in short order, upgraded over 3,000 trannies for free, and has since improved them even more.

Jason

Re: Mecanum Drive Train
 

i agree with that. our rookie year we had the banebots as kop gearboxes and we loved them. our robot was pretty quick that year. we are probably ordering them again this year

Re: Mecanum Drive Train
 

I know, but thats not all i was considering. has anyone every seen a toughbox fail?

Re: Mecanum Drive Train
 

No. However, you can't use them in their unmodified state as mecanum gearboxes and expect speed and maneuverability to be the best. I've seen that firsthand. There are modifications that can be done to improve speed. I don't know how effective those would be when used in a mecanum drive.

Re: Mecanum Drive Train
 

i agree. last year the toughboxes were really slow. reliable but slow. and i dont think you can speed the up all that much

Re: Mecanum Drive Train
 

You could, in theory, get a wide range of speeds out of a Toughbox; the easier ways to get that range of speeds tend to involve factors outside of the gearbox itself. (Wheel size, sprocket choice, etc.)

Re: Mecanum Drive Train
 

Or, you can try something like this. For a 6" mecanum, a roughly 1:1 out of the Toughbox wasn't enough last year.

Re: Mecanum Drive Train
 

WOW,

Re: Mecanum Drive Train
 

Or you can try AndyMarks new planetary. Had one in my hand Saturday, real sweet. 3.7:1 would work well with the 6" mecanums.

Re: Mecanum Drive Train
 

Last year we had used the AndyMark 8" Mecanum Wheels along with the AndyMark Toughbox gear boxes

One thing I didn't see anyone mention, is that when you mount them mount them in a square, so as in the distance from the middle of the wheel is the same front to back as it is left to right, it makes it easier come programming and movement. It makes since when you think of it, the rollers are mounted at a 45 degree angle.