Has anyone used 6 motors on a mecanum chassis. By this i mean 2 motors on each of the back wheels and one on each of the front wheels. I think this might cause an imbalance making the robot travel off course, but i was not sure.
Yup… my teams used it for sack attack.
No issue with the balancing actually.
The rotation speed is the main factor in deciding if your robot will be moving straight.
There might be a bit of “imbalance” when it is strafting though. But nothing serious that can’t be solved using sensors.
ok perfect thanks
While going straight did the extra 2 motors improve the performance in your experience?
Well… it will definitely give you better pushing power.
I would say that the advantages of a 6-motor based mecanum drive are the same as a 6-motor based omni-wheel drive.
I believe they covered a lot of facts of 6 motor X drive with this thread
https://vexforum.com/t/6-motor-x-drive/22692/1&highlight=motor+holonomic
I think some things were changed when converting to mecanums though. i think i’ve read somewhere that mecanums aren’t exactly 45 degrees, making their strafing slightly slower?
Im not sure if that is the exact cause, but the mecanum wheels do in fact strafe slower than they normally drive, unlike a 45 degree x-drive.
It would probably work fine, but if your robot was really heavy, the wheels would sink a little into the ground, and the front wheels might not turn as fast as the rear wheels, which would result in some really wonky strafing, as was previously mentioned.
To respond to the idea that mecanum wheels don’t strafe as well as an x-drive, you’re probably right. I’ve never used mecanum wheels before (hence the questions), but I have used x-drive. If you look at a generic x-drive from any cardinal direction, you wouldn’t be able to tell which way was front, unless somebody told you. When you look at a generic mecanum drive system, you can’t tell front to back, but you can tell front to left/right. I’d imagine there is some connection there with friction and whatnot. Point is, physics can’t “tell” which side is the front with an x-drive. Meanwhile, physics can “tell” which side is N/S and E/W for a mecanum drive.
One thing we tried last year was having the 4 mecanum wheels, but between the front and back mecanum on each side we also had an omni wheel so we would have more pushing power.
1200B ran this same system last year and I know their guys really liked it. I believe they used the omnis in their system to get a little more speed out of the drive rather than pushing power though.
I know with my experience with mecanums center of gravity and friction is critical. We used a 6 bar linkage at first, but our drivetrain started strafing in a U. Once we swapped to a rd4b, our center of gravity was fixed and we strafed with ease… on hard surfaces. The moment we placed the robot on the field, we underestimated sinking from the tiles and screws dragged, Significantly affecting our strafing ability. Of course, you shouldn’t have the second problem this year, but that’s a reminder to check your bearings/chain/gears/etc.