Assistance with Mecanum Wheels
 

My team has just purchased mecanum wheels, yet this will be the first time our team has diverted from the standard chassis. Yet no one on my team knows anymore about mecanum wheels than what you can get off of wikipedia and youtube.

Could teams more familiar with mecanum wheels provide more information for me?

Specifically, I was wondering:
1. Would a mecanum set with gear boxes of the same ratio as the standard wheel design output the same speed as a standard wheel design?
2. I've read some teams feel a suspension is required? Is this true? More info?
3. Has anyone had any success with encoders regarding the 6" andymark mecanum wheels?

Any more info, suggestions, comments, thoughts, ANYTHING, etc is greatly appreciated!

Thank you!

Re: Assistance with Mecanum Wheels
 

Team 357 would have no problem with helping out. We have been using "Jester drive" which is a reliable mecanum wheel drive system. We have been using it since 05'.To answer your first question the wheel will spin at the same rate BUT there might be a little slip in the rollers depending coefficient of friction and speed at which you travel. Second, a suspension is HIGHY recommended. In order for the system to perform at its highest ability all four wheels must be in contact with the floor. We found this out the hard way in 05'.Thrid, Encoders should work on any wheel because it reads shaft revolutions. For some inspiration visit www.airtrax.com. If there are anymore questions u can pm me. Or post again.

Re: Assistance with Mecanum Wheels
 

When you search CD for mecanums, also search for mechanum and meccanum, two common misspellings of the word. You should find a very helpful white paper in there somewhere.

We did mecanum last year with the AM wheels each coming off a Banebots 12:1 gearbox, with no suspension... but a fair bit of flex in the frame. Although our drive system was not as smooth as some of the other mecanums, I don't believe that was due to a lack of having a suspension... not a big deal on a flat playing surface, but not having our drive code fully optimized and PID loops fully tuned.

The Banebots gearboxes and encoders (with divider board) worked great, but the programmers still had a real challenge getting all the wheels to work together in a usable fashion. You may want to consider using a gyro to control for rotation rather than basing all your movement calculations on the encoder feedback. We tried both, went with the encoders only, but in retrospect could perhaps have benefitted from using a gyro.

Now that we have the robot back at the shop, though... and on an uncarpeted, not particularly level cement floor, the lack of suspension is a real pain... it makes it difficult to show people just how cool mecanum is.

Congratualtions on choosing a really cool drivetrain design, just try to keep other systems simple enough that you have a couple of weeks to practice and fine tune everything. Mecanums are not only more complex to program, but also require the driver to re-learn everything they know about robot driving in order to take full advantage of it.

Jason

Re: Assistance with Mecanum Wheels
 

Thank you both so much for your responses.
One new question - has anyone had any success using the 6' mecanum wheels with the KOP chassis?

Re: Assistance with Mecanum Wheels
 

I'm not sure of their size (I'm a programmer!), but 1675 used the mecanum wheels available from AndyMark last year with the kit chassis.

Re: Assistance with Mecanum Wheels
 

team 42 has used mecanum wheels in the past without suspension and a completely solid frame, the result was them bowing and rubbing against the frame the rest of the match... of corse this was also the result of us jumping entierly off of the 3 or so foot end ramp, instead of going down the ramp:p

(the ramp i speak of was the "aim high" start ramp)

Re: Assistance with Mecanum Wheels
 

Thanks once again for your responses. I've read about every thread here on CD regarding mecanum wheels. In several instances people refer to some public code for the mecanum drive - and in several other threads when people ask the thread seems to die.

Is this a myth? Is there anyone out there gracious enough =) to share past mecanum drive code?
Thanks,
1466

Re: Assistance with Mecanum Wheels
 

Last year we (1379) used the AM 8" wheels with the BaneBots 12:1 transmissions. We had 4 wheel independent suspension which worked great except the springs were a little softer than we would have liked. It's nice to be able to drive the robot over a 1x4 laying on the floor during demos with no problems. This year I understand they are going with a much stiffer suspension due to the cornering requirements of the game. The Mecanum drivetrain does not work very well unless all 4 wheels are in contact with the floor. Unless you are 110% sure that you will get no bending or warpage in your frame during the "vigorous interaction" between robots (or the far wall of the field that you can't quite tell how close you are to it from the driver's station in the opposite corner), make sure you have a way to ensure that you can keep the wheels on the floor in the later matches.

This post is where we got started from in terms of code: http://www.chiefdelphi.com/forums/sh...13&postcount=4

Good Luck!

Re: Assistance with Mecanum Wheels
 

I couldn't find the information exactly, i don't know where it went to. However mecanum wheels can hit high speeds, probably higher speeds then normal wheels since due to the rollers generate less friction while moving (the tend to produce more horizontal friction which allows them to turn like they do.) I know we hit between 10 - 15 mph with our robot last year and it had mecanum wheels. As for suspension i would say its a must regardless of what type of wheels you use if you don't want to wreck your robot like i did to ours last year due to no suspension.(destroyed entire floor, snapped the 120 pound tested fishing wire we were using for lift and it wrapped around the axle of one of our wheels and caused considerable damage. It wasn't a pretty sight. That and the time when we crashed into the cafeteria wall at full speed, knocked a few tiles of the wall and bent the axle.) Point is... regardless... put the suspension on!