Maximizing the in-line CoF of Omni-wheels
 

Has anyone ever tried adding custom tread patterns to omniwheels in order to maximize front-to-back CoF while retaining free lateral motion? Could you theoretically use custom rubber treaded rollers? I would love to hear of and see examples of people trying this, if it's been attempted at all.

Re: Maximizing the in-line CoF of Omni-wheels
 

I was thinking about using rubber rollers with plastic hubs on the omnis, but you would have to make them yourself.
Following.

Re: Maximizing the in-line CoF of Omni-wheels
 

I've never heard of this done, but building the rollers wouldn't be to hard, Polyurathane would work in that application (same type of material as colson wheels). However, I'm not sure it would be worth your time to develop this type of Omni-wheel unless it had significant benefits (which I don't see).

Re: Maximizing the in-line CoF of Omni-wheels
 

Why wouldn't this be beneficial? It could give you significantly better traction with almost no additional weight.

Re: Maximizing the in-line CoF of Omni-wheels
 

Significantly better than what? AndyMark lists a forward COF of 1.0 for their 6" dualie omni wheel.

Re: Maximizing the in-line CoF of Omni-wheels
 

Significantly better than omnis with standard rollers. Even if you could only get the COF to 1.1 or 1.2, that would be 10 or 20%. Looking at the difference of the two different vex versawheels (http://www.vexrobotics.com/vexpro/wh...sawheels.html), the W tread adds an additional 20% compared to the DT tread. You could probably get a similar increase by adding a pattern to the omni rollers.

Re: Maximizing the in-line CoF of Omni-wheels
 

I might be concerned about the depth of the cuts. If they were too deep, you definitely could run the risk of chunking out the rollers.

-Nick

Re: Maximizing the in-line CoF of Omni-wheels
 

Yeah, I think that I would get bigger rollers (anyone know how?) and trim them down with the cuts.

Re: Maximizing the in-line CoF of Omni-wheels
 

Most omnis have rollers with rounded edges, that is, they try to follow the arc of the outside of the wheel to minimize bouncing as the robot drives. If they were kept square, it's possible that they could dig into the carpet at the edges, and still drive relatively well (because the carpet would compress to compensate).

Re: Maximizing the in-line CoF of Omni-wheels
 

All things equal, it would, but given how Omni's behave in a pushing match against another robot that isn't dead center. It would likely negate much of the gain that would be seen. (i.e. they break loose/slide in a direction away from the pusher, effectively rendering the friction gain useless)

Given the amount of time that would be put into building these (taking apart the wheels, rollers, testing,ect.), I think a team interested in Omni's could easily design something else that fits the bill better (Such as Butterfly) and be much happier with the results.

Re: Maximizing the in-line CoF of Omni-wheels
 

Back when mecanum wheels were still new to FRC, at least one team tried getting better grip with patterned rollers/rubber coatings on plastic rollers. As I recall, it wasn't fully tested, but there was an improvement. (Though as I recall, the biggest improvement came from adding the rubber, so that's out with AM wheels.)

Re: Maximizing the in-line CoF of Omni-wheels
 

3D print a master, make a silicone mold, poured urethane rollers.

Screw trimming, just model it in there initially.

Re: Maximizing the in-line CoF of Omni-wheels
 

I think with the right wheel configuration there's a way to solve some of the pushing problems. I need to think on this one a bit.

The benefits of this is that it would be a direct swap out for a normal omni drive, so you would only need basic testing in the offseason. With butterfly and similar drives, there is a LOT more weight involved and it has to be custom built for each robot. Plus, you don't get a lot of push power in mecanum mode. So IF (big if) a modded omni could be omproved it could offer an advantage over butterfly drives.

Re: Maximizing the in-line CoF of Omni-wheels
 

Butterfly is Omni, Octo-canum is with Mechanum.

I see the gains to be made here, I just don't think post-manufacturing modification is a very efficient route to go in this application. I'm also not convinced it would be very helpful just because of how the Omni's react to lateral loads.

Re: Maximizing the in-line CoF of Omni-wheels
 

You're assuming that you are configuring the omnis in a traditional manner. I think ther emight be a way to get them all nice and on the ground (maybe with thingy-which-name-escapes-me with springs)
Post-manufacture, I agree, is somewhat dead because the rollers can only be modified so much. Swapping out the rollers with polyethurane with a delrin hub might work if you were to modify an existing wheel.
I've never assembled an omni before; is it possible to take the rollers off?

Re: Maximizing the in-line CoF of Omni-wheels
 

Has anyone tried these?


Is there a common understanding as to what this means?

Re: Maximizing the in-line CoF of Omni-wheels
 

Which wheels are you referencing? The link is broken for me. The Omni's that site has seem interesting, but very expensive compared to Vex Omni's

By Traditional, he likely means Omni's in the 4 corners of the robot and each wheel direct driven by a CIM.

Look at Kiwi drive, it doesn't help with pushing either.

Re: Maximizing the in-line CoF of Omni-wheels
 

Well,
either 4 omnis in the corners or one omni in the center. With these configurations, the extra COF might not help due to one or more wheels not touching the ground fully. You would need suspension (that's the word I was looking for!) or a different setup that hasn't been used to maximize ground contact with all wheels and escape spinning issues.