For our 3rd prototype we used smaller rollers but wrapped them with rubber self-fusing splicing tape for traction. They seem to work the best so far and it clears the ground well enough. Three more are to be fabricated soon and mounted on a robot. Hopefully it works!
so, Kevin, how do these wheels work?
here’s the video
http://www.selectric.org/nerds/robots/vex/vexmecanum01.wmv
maybe Kevin could describe what’s going on here?
Umm… well, lets see. It’s definitely not working correctly! (probably because the front two wheels have their rollers set at 10-15* less than the other two)
For those of you too lazy to watch the movie (which is only about 30 sec by the way), all 4 wheels are mounted on a simple robot and the holonomic code was downloaded to the microcontroller. It runs just peachy in tank drive mode, but once you start trying to strafe or move in any other direction, it moves in strange and mysterious ways (again, probably due to the lack of accuracy when mounting the rollers on the front 2 wheels). Also, the shiny-slick tiles don’t help either…
It may help to give it a suspension; from what I’ve seen on here they are almost essential for mecanum drive trains. Just build two halves of the robot and connect them on a metal shaft, might help it keep it’s wheels on the ground. Also, try to make all of the wheels the right shape if you can.