Hello,
In the off season, or before the Las Vegas regional, we would like to explore the idea of mecanum wheels. What is the best way to drive these wheels? We were thinking of using the BaneBots 56mm Planetary Gearbox with the CIM motor. The BaneBots shaft would go directly into an Andy Mark 1/2" universal hub which would be attached to a wheel. Would this be a good idea or should we go with a chain driven design, we have had bad experience with chains.
we are using mecanums this year. we found that it is soooooooo much easier to mount directly and just avoid chain alltogether. good luck!
We learned that you need two universal hub on each or you get this weird wobbling action. I guess your using AM mecanum wheels, right?
Be sure to support both sides of the shaft. cantilevering the banebots may not be the best idea…
Suspensions are also useful. do a CD search on that too.
drop me a PM if you have any questions.
Thanks
Yes, we were thinking of using the Andy Mark mecanum wheels.
And by the looks of your picture there, team 384, you used a custom gearbox. Would it be more efficient to make our own, I know it would be a space saver. On a side note, where did you get your material for your frame? It is so awesome, hope you make it all the way! Great design.
We are using the AM Mecanums direct mounted to 12:1 Banebots 56mm trannies. They work great… we probably have an hour or more of driving in now, and while the backlash in the trannies is getting greater and greater, they are still working. The 12:1 ratio results in a fairly fast robot, but if you’re building an omni-drive that is what you want… to out run, not out push your opponents. We are going to keep our eye on this however, as right now we have only run the robot at about 50% of the final weight. As we add mass we may want to increase torque a bit… as it is we spin the wheels before we stall right now, which means we have more torque than the wheels can handle.
We have found that using encoders and closed-loop speed control greatly improves your handling… while I hesitate to call it a necessity, you probably really, really want to think about adding encoders. I believe the gyro may also help with directional control.
The banebots encoders and divider cards work great too, however there is one complication that can ensue… the BB trannies can develop sufficient end play that as the shaft slides in and out of the gearbox the encoder disc rubs up against the encoder optics and shreds the sensors. At least that was our analysis of the problem. To solve this, if you notice too much end play in your gearbox you can pull the gearbox apart (Banebots users should be pretty good at this by now…) and pull out the inside bearing on the shaft mount, and machine a spacer to keep the inside and outside bearings sufficiently far apart that there is no room for end play because the shaft shoulder and circlip are both tight against bearing surfaces.
You will also want to be VERY sure that you support the BB trannies at both ends, rather than cantilevering the wheel off the tranny alone.
Many threads will say that mecanums require a suspension system. We have a rolling drive train that demonstrates that a suspension is not required… however we have intenionally left a great deal of “flex” in our kitbot frame and paid attention to trying to make an equal distribution of weight to each wheel. The mecanums, as you might suspect are more sensitive in this regard than a traditional 4wd or 6wd drive train.
If you are looking for more info on mecanums, try also searching for common mis-spellings such as “mechanum” and “meccanum”. There is good info in the CD white papers section.
The BB trannies are an acceptable option for direct drive of mecanum wheels, and should BB get on top of manufacturing tolerances and quality control they will be a great option… although in some ways having a “rough and ready” gearbox that needs tweaking does provide a good learning experience on how planetarys work.
See you going sideways.
Jason
awesome, thank you to everyone who has posted, your advice has helped a great deal.