Re: Omni wheels?
 

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

Re: Omni wheels?
 

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 :D

Re: Omni wheels?
 

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.

Re: Omni wheels?
 

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.

Re: Omni wheels?
 

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. :]

Re: Omni wheels?
 

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....

Re: Omni wheels?
 

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

Re: Omni wheels?
 

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

Re: Omni wheels?
 

When you say they are more affective, is that just for versitility in moving the robot (more or less why they are designed this way) or are they also affective for top speed?

Re: Omni wheels?
 

I have only seen one advantage of powering omni wheels, to climb things like in the 04 game.

here is a picture of my old hs bot from the 04 game with my omni wheels in the front so we could turn easily and climb the steps without a problem. it was really fun to watch actually.

Re: Help with Omni wheels?
 

Our team has been thinking about using an omni drive but we have a question. How do you figure out how fest an omni drive will go. Our team knows how to calculate the speed if all the wheels are strait, but how do you account for the omni wheel slipping?

Thanks

Re: Omni wheels?
 

That is going to be one really fast robot! :ahh:

Re: Help with Omni wheels?
 

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?

Re: Help with Omni wheels?
 

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.

Re: Omni wheels?
 

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.