Help with Omni wheels?

[IndySam]

Originally Posted by tawnos23

I would suggest to buy metal omniwheels instead of the plastic ones. Our first year with omniwheels we bought the plastic ones, and they broke to pieces during the course of a regional.

We have used AM plastic wheel for the last two years. In 4 regionals, 2 IRI's, 1 championship, and hundreds of hours of demonstrations we have never had a single failure.

[Armando Gonzalez]

Although mecanum wheel provide excellent mobility and a relatively fast movement speed, the system to make them work weighs too much. Each wheel weighs about 2.5 pounds + 2.5" CIM Motor + transmission = alot of weight simply to make the robot move

[kristenliz_28]

our team was considering using omni wheels, but it would be hard to herd/move the balls out of the way. Of course, I guess the reason to use omni wheels is so you can juts go around quickly

[Andy Baker]

Originally Posted by tawnos23

I would suggest to buy metal omniwheels instead of the plastic ones. Our first year with omniwheels we bought the plastic ones, and they broke to pieces during the course of a regional.

Yes, that first year, I thought that it was a good idea to put a 10% fiberglass fill into the black polycarbonate. While that made the tensile strength higher, it was lower rated on the Izod impact rating. The fiberglass mad the material brittle, and when teams hit the side of the 1 point ramp in 2006, the wheels broke. The result of these breaks were improving these wheels and creating the aluminum omni wheels.

So... last year we had black polycarbonate with no fiberglass filler, and that resulted in zero complaints about breakages.

If I had to pick which omni wheel to use on a FRC robot, I would choose the 6" aluminum omni wheel, and use an Omni Spacer to make them a dualie omni wheel. That is a sweet setup. The polycarbonate wheels are nice, and can handle 2 bearings, but the aluminum wheels take up less space (they are thinner) and they are repairable. The only negative about the aluminum omni wheels is that they only have the ability to have 1 bearing mounted to them, that is unless you add on an extra hub.

Andy B.

[ebarker]

Originally Posted by Andy Baker

So... last year we had black polycarbonate with no fiberglass filler, and that resulted in zero complaints about breakages.

Last year we used the plastic polycarbonate omni wheels and we are a very happy customer. Zero problems. In fact we are ordering more for this year tomorrow.

[Richard Wallace]

Originally Posted by Andy Baker

...

If I had to pick which omni wheel to use on a FRC robot, I would choose the 6" aluminum omni wheel, and use an Omni Spacer to make them a dualie omni wheel. That is a sweet setup. The polycarbonate wheels are nice, and can handle 2 bearings, but the aluminum wheels take up less space (they are thinner) and they are repairable. The only negative about the aluminum omni wheels is that they only have the ability to have 1 bearing mounted to them, that is unless you add on an extra hub.

I agree dual 6" aluminum omniwheels are sweet. In '06 my team spent a lot of effort building our own, so it was nice to have the option of buying them from AndyMark last year.

Our '07 chassis used single 6" aluminum AM omniwheels on the corners of a 6WD kitbot, and kit AM wheels in the middle with one CIM per side -- not a defense-oriented drivetrain, but nice for maneuvering. To get around the single bearing limitation Andy mentioned above, we mounted the inboard bearings in the sprockets that drove each omniwheel. This required boring out the center hole in the sprocket to 1.125", which is a relatively easy lathe operation in a standard 3-jaw chuck if the tooth count is a multiple of three.

[Zoysiamo]

In 2006 I helped create an omni drivetrain for team 859 using the poly AndyMark omniwheels, only to have the roller mounts (around the circumference of the wheel) shatter several times on the ramp. Other teams had better luck with small caster-style wheels such as from omniwheels.com or mechanum (angled roller) wheels.
At least without ramps this year's game should be easier on omniwheels.

[Bob Steele]

We used the AM plastic omniwheels last year with absolutely no problems.
We will have to replace the rollers because in the course of 2 regionals and the championships, we wore them down...

this year we are going to a new idea.. using two of the poly wheels staggered to produce a wider wheel.

Please take a look a the attached jpg ... we are direct driving the omniwheels with Dewalt transmissions...

This is a holonomic robot....

[Armando Gonzalez]

what are the benefits of direct driving the omni wheels instead of using two normal wheels and two omni in the front?

[qwertyuiop[]\]

In my years of robotics i havent found an advantage to driving omniwheels other that more power.

[artdutra04]

Originally Posted by Bob Steele

Please take a look a the attached jpg ... we are direct driving the omniwheels with Dewalt transmissions...

That is going to be one really fast robot!

[sweetie_pi]

i have never used omni wheels but my team is thinking about it. What is the difference between metal and plastic wheels on the carpet? Does one work better than another?

[EricH]

Originally Posted by sweetie_pi

i have never used omni wheels but my team is thinking about it. What is the difference between metal and plastic wheels on the carpet? Does one work better than another?

Quick answer: metal wheels are not allowed. All the omni wheels in this competition have plastic rollers. So the main difference would be weight, I think.

[Darunada]

Originally Posted by tawnos23

I would suggest to buy metal omniwheels instead of the plastic ones. Our first year with omniwheels we bought the plastic ones, and they broke to pieces during the course of a regional.

WE shattered a junky plastic one all over the field tw years back... and another one demonstrating post-season. The ones currently on the robot aren't very "omni" as most of the small wheels are locked in place by what I assume is a crushing force of the omniwheel plastic colapsing.


That said, last year we used these: http://andymark.biz/am-0097.html
with excellent results, and we will use them again in the future...

[T3_1565]

I wouldn't say mecanum wheels are better than omni wheels, they are quite different and transfer power differently to the movement of the bot, but I wouldn't call them better, I find the biggest thing about having a strafing bot, is to make sure your driving practices, and uses all the advantages the wheels give you (too often do I see a bot with mecanums or omnis being driving like a 4wd bot, I dislike it lol)

for the record omni and mecanums have slightly different pros and cons about them and depending on how you want to drive it or how skilled your driver is at controlling them, ethier one could seem "better" than the other for your team, I personally perfer omns over mecanums!