As part of our off season, we are hoping to investigate holonomic drive using mecanum wheels for our FTC robot.
It appears there are 4" mecanum wheels from VEX and AndyMark. Which do you prefer and why? Are there others that are better?
It seems either wheel design comes with its own set of issues when mounting the wheels onto hubs and axles that can then be mounted on TETRIX channel. Which is the most reliable/durable approach? Which requires the least machining and customization?
What “parts list” should we start with if we go with the VEX wheels? What would be the list for AndyMark wheels? Obviously, we want to stay FTC legal.
Vex, your going to have to design some sort of bracket and hubs to connect to their wheels.
Andymark, the wheels from them were ment for an FTC bot, and have the hole pattern already for an axle hub, so those would be the easiest to mount. Granted, I have heard teams have been snapping the rollers off of these with semi-normal use.
There is one last mechanum wheel out there that I have seen being used, but the cost of them is through the roof, which you probably dont want to be having to buy for an off-season project. These are really stong wheels though, as the structure is made of metal and not plastic. And again, with this one, you would have to make/print some sort of bracket and hub.
For testing purposes, I would go with andymark. Thats what we are doing. Even though we will probabaly stick with the regular 6 to 8 wheel tank drive for competition, as when you get to the World Championship level, you need that torque and defense, otherwise you will not have fun.
5026 Tesla Coils currently use the Nexus mechanum wheels and they make a big difference. You will see them at World this year. You can see their design on their Facebook page. https://www.facebook.com/5026TeslaCoils
Team 3507 Robotheosis has posted in a a prior thread on this topic:
We went with the VEX wheels and they performed exceptionally well.
They have a better urethane formula than the Andy Mark wheels for traction purposes, and they were extremely durable and strong, despite their plastic hub.
We had the most mechanically sound mecanum drive in the state (Illinois), and in two matches during autonomous, we even became pinned under the balance beam while continuing to drive forward. we lifted the entire bridge, going up on only our rear wheels and started sliding it across the floor. No damage to wheels, axles or any part of robot.
We refuse to use Tetrix axles as their inferior strength is an insult to good engineering design. After drilling and reaming out the square hole VEX wheels to 3/16" +.001, the grade 8 10-32 cap screws were used to capture the wheels between a nylock nut outside and the Tetrix hub adjacent to our sprockets inside. The four holes of the Tetrix hub were used as drill guides to drill holes into the VEX wheel plastic ( partially thru), so that over long 6-32 screws would then penetrate into & engage the plastic hub and help transfer torque. Shoe Goo urethane adhesive also bonded the sprocket/hub assembly to the wheel hub. Wheel runout was kept very minimal by selecting the straightest screws (all were pretty good), and the unthreaded bearing zone was polished (not much needed).
We won our first regional as captains of the winning alliance, and at state we were 2nd place after qualifying rounds. Because we also do FRC and we are a small team, we did no work on the FTC robot for the 2 months between regionals and state. I have no doubt we would have won state had we spent time tuning performance and practicing during this period.
We were most consistent flag winder, largely from our better lateral positioning with the mecanum drive, and we were able to double hang after a completing a flag wind. Next year we plan to implement a four-wheel independent suspension to further improve the mecanum drive train.
hi does anyone have the teleop code they used to drive their mechanum drive for robotc or labview i would appreciate it.
We don’t or at least not yet. Last year we used labview this year were using RobotC
i understand i used labview last year but quickly realized that robotc has more power.