2" Mechanum Drivetrain?

The 2" mechanum wheels were recently made legal by VEX. Do you think it would be a good idea to make a 600 rpm 2" mechanum drive?

Edit: Also, does anyone know how the Versa adapters work and how I could attach this wheel to a VEX axle?

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It would be interesting to see if these would work in a drivetrain. They are much narrower than the 4" mecanum and would save a lot of space.

The versa adapters are not easy to use, adding bulk and unnecessary complexity. Perhaps there is a way to screw a gear directly to the wheel, using the screws provided with the mecanum.

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NONONONONONONO,

from what I’ve heard, these things absolutely SUCK at everything. The plastic digs into the tiles, making it unusably for a drivetrain (or so I’ve heard), and they just suck.

I would think this is true considering how low the plastic is and how in line it is with the wheel.

I would stick to intakes with those.

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You do not need a VersuHub like you use for the flex wheels. You just need the small VersaHex adapters which are conveniently listed with the mecanum wheels.
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However, I might recommend using the metal VersaHex adapters from the flex wheels page.
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But I would probably recommend against using just four of them as is. You might have better results using eight wheels instead to spread out the load so the plastic does not dig into the mat as much. It would definitely still drive and strafe fine, but it might make turning a little funky, I’m not really sure though.

Also keep in mind that 600rpm on 2" is equivalent to 300rpm on 4" which for a four motor drive is
really pushing it and should probably only be used on a six motor drive which gets funky with mecanums anyways.

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not really. Using this website, which is extremely useful when planning bots,

A 200 RMP with a gear ratio of 60:36 (reasonable ratio) or 0.6 (333 RPM after gearing) and 4" mechanum wheels gives a speed of ~3.97 MPH. a 600 RPM and 2" wheels would have a speed of ~3.57 MPH. To match the speed of the 4" drive, you would need a gear ratio of 0.892 which is an awkward ratio. inclonclusion, the 2" drive would be slower.

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werent vex 4” mecanums really poorly designed too, and just weren’t thought out well? If so, jeez can Vex just do some designing there, mecanums need some love.

Yeah, the 4" mechanums are pretty poorly designed from what I’ve heard/seen. I might be wrong though, but they do cause quite frequent-ish hot motors under heavy use. That might be because the motors themselves being too weak, but the wheels always seemed sluggish to me for some reason.

On a side note, the 2" mechanums would probably be really great for an intake(ik it’s already mentioned), especially on the edges of the intake where you want the discs to go inwards. So the one upside, I guess, would be controlling which direction the discs go without physical guide rails. I remember my old FRC team using mini mechanums to guide balls into the center of an intake passively with them.

My students tried them this year and they didn’t work.

A couple of observations:

  1. The flanges supporting the ends of the rollers set REALLY close to the tiles.
  2. The rollers do not have much surface area in contact with the tiles.
  3. A heavy robot will cause the flanges at the ends of the rollers to dig into the tiles, making strafing impossible and making them utterly pointless.
  4. A VERY lightweight robot MIGHT be able to make them work; my students have not tried that…
  5. The other possibility (much more expensive and complicated) would be to use more than one wheel per corner.

Based on simple arithmetic, a 600 RPM 2" drive is equivalent in speed to a 300 RPM 4" drive; fast but not utterly outrageous.

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Would grinding down the flanges make it dig in less?

Theoretically yes, practically no. there is not a lot of plastic between the end and the pinhole for the rollers. so you could grind some off but not enough to solve the issue. You will also weaken the wheels and risk ruining the wheel if you go to far.

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I see a potential use for these as a passive wheel spinner. Put them on the side of the robot and drive past a spinner.

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What makes these wheels better than a traction or Omni-wheels, which are thinner.

Because these wheels will be able to spin the spinner given motion parallel to it given the nature of the roller slant. Completely passive.

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Could a thinner omni wheel not do that?

Y’know how the mechanum wheels have rollers angled at 45ish deg?

As it drives past, it will spin itself as it tries to roll across, in turn, spinning the roller. It would take some time tuning, but it could work.

Ignore that I posted this at 4:20 am

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Ok, I’m an idiot. thanks for explaining

I am pretty sure I saw this in team 60A before

And I would assume the robot will use a mecanum/x-drive. IMO it’s easier to chain a spinner to an intake, so during auton you don’t have to move.