pic: Why aren't omni wheels like this used?

[Ether]

I couldn't find any data for polycarb-on-nylon friction. I suspect it's not pretty.

[GeeTwo]

Originally Posted by Ether

I couldn't find any data for polycarb-on-nylon friction. I suspect it's not pretty.

I concur. However, in many cases where omnis are used, the goal is either to allow a long wheelbase robot to turn (tank with 2 or 4 omnis), or to allow fine strafing adjustments so that a robot can line up on a game piece or a target after forward motion has completed or nearly completed (H/slide drive). In both of these cases, "not pretty" is still a whole lot better than "solid wheels".

I can certainly see roller friction while applying driving torque being a real problem with kiwi (three omni wheels in a triangle) or Killough (four wheels in a diamond configuration) drives. I almost suggested kiwi (implicitly using duraomnis due to our game's KoP) to one of our intramural design teams today; I'm glad I held back.

[T^2]

Originally Posted by Ether

I couldn't find any data for polycarb-on-nylon friction. I suspect it's not pretty.

Nationwide Plastics has polycarb-polycarb at 0.52 (unspecified, but I'd guess static) and Engineering Toolbox has nylon-nylon at 0.15-0.25 (static). Polycarb-nylon might be somewhere in between. Not too bad, really.

[pmckinnon]

The concept of these wheels are quite good as they provide close to a full concentric circumference, however they are complex to manufacture. A greater choice of dual and triple row omni-wheels are more readily available such as those by Vex, Andymark and Rotacaster Wheel which can provide better traction and better or equivalent ride quality.

[nate12345678]

These are both fantastic omni ideas. I personally think any omni other than the standard "strait sized" omni would be a huge improvement. We are using the practice bot's drive train from last year, and replaced traction with omni wheels. Only downside, the bot can't be driven in the huge back lot outside.