Hello my team is looking for some help with mecanum drive systems. We have not designed one recently and we don’t know what has worked best for teams in the last few years. I’m mainly looking for the technical things (what transmission, wheels, and reductions).
Any help is appreciated.
Regular gearboxes that gear down to increase torque are what you’ll want. If you have no torque you won’t be able to strafe. You need mec wheels and want to put them in an X pattern with their treads. The wheels are expensive so I would recommend getting the good ones so that you don’t break the slightly cheaper ones.
An important thing is that Mec drive takes a ton of power. Running sideways and driving a lift or something would be pushing your power limits.
Also coding will be a little more complicated than just a regular tank drive system.
My first advice will be to build the kitbot but if you are deadset on it.
Vex has you covered, build this.
We did it in 2015 and it was perfect.
Reduction is figured the same way as for a traditional drop center, just recalling that you have four drive trains instead of two, so one CIM on each wheel is equivalent to two CIMs on each side of a skid steer.
Wheels: I have only used the AM 6" Mecanums, in 2014, no complaints. The important things are to make sure you get wheels which will handle the load (with a safety factor of 3x or more preferred), and to make sure the rollers spin freely; tight or sticky rollers will greatly increase the work your motors will do to strafe.
Before you get too far into this, consider how much strafing you really think you’ll do. If all you want this for is to make 3-5" adjustments to line up with a port, consider putting your manipulator on a lateral slide instead of making the whole robot that manipulator. Mecanum can’t transfer torque among the wheels in the same way a skid steer does when accelerating; you don’t really realize how important that is until you don’t have it.
Our team (3974 E=mcD) has had great success using mecanum drive (2013, 2015 and 2017). Using this drive system we reached the finals of 4 district events and qualified for Championships twice.
I recommend that you pay close attention to the weight distribution on your robot. Mecanum drive works well when all wheels are supporting equal amounts of the robot weight. I have seen many unbalanced mecanum robots perform poorly.
Also…. The rollers on mecanum wheels can break, so purchase at least 2 wheel replacement roller kits. You will need one for the right side wheels and one for the left side wheels.
Weight distribution with and without the game pieces too not just by itself. Recycle rush our turning got weird as our stacks got bigger less of an issue this year but yeah.
Thanks for the information! Would there be any reason to use 8" mecanum this year?
Would you recommend andymark or vex’s wheels for this year’s game?
My team has had good experiences with AndyMark’s “HD” mecanum wheels. We tried Vex’s wheels on a practice robot and had trouble with them, broke off several rollers, and AndyMark’s standard mecanum wheels have a similar design. For me personally, I would stick with the HD mecanum design if/when my team does mecanum again.
I can’t recommend vex vs AM, never having used Vex. Happy with the AM wheels with rollers between plates.
6" is probably OK, but 8" might have less difficulty with the ramp into the HAB. Edit: Especially with the KoP chassis, as mecanum wheels mount about an inch higher than the skid steer configurations, meaning the chassis is an inch lower.