pic: "Omni Grenade" Wheel

[Stu Bloom]

I am definitely interested an any CAD files you have available. If you can "publish" them - and post to the white papers it would be greatly appreciated!

GREAT looking wheels!!

[D.Fahringer]

Originally Posted by Stu Bloom

I am definitely interested an any CAD files you have available. If you can "publish" them - and post to the white papers it would be greatly appreciated!

GREAT looking wheels!!

Thanks, I will get the files together, and zip them up.

Here is the Mold and drill fixture used...the brass sleeve (not shown) fits on the center pins. The drill fixture assures a good hole location every time!
The holes were finished with a flat bottom before tapping. The 5/16-18 tap was modified to get thread all the way to the bottom. The bolts were faced on the ends and completely bottom out in the hole.

[artic_raven]

looks like a good idea. but what will happen if you are forced into a pushing match? those wheels look like they will turn like no other but whats the coefficient of friction? turning isnt the only thing that you have to look out for.

[Cory]

Originally Posted by artic_raven

looks like a good idea. but what will happen if you are forced into a pushing match? those wheels look like they will turn like no other but whats the coefficient of friction? turning isnt the only thing that you have to look out for.

They aren't using them for a FIRST project. And rubber has a pretty high coefficient of friction... you're going to have a problem with durability though, more likely.

[Max Lobovsky]

Its "soft polyurethane", not rubber, if I'm not mistaken. Soft or not, polyurethane definitley is not as good as some nice rubber treads. I wonder if a finer tread pattern, rubber coating, or a different material can be used to make the rollers.

[D.Fahringer]

Originally Posted by Max Lobovsky

Its "soft polyurethane", not rubber, if I'm not mistaken. Soft or not, polyurethane definitley is not as good as some nice rubber treads. I wonder if a finer tread pattern, rubber coating, or a different material can be used to make the rollers.

Two points well taken...Pushing vs steering: I would want to use omnis on the front and good pneumatic treaded tires on the rear, the steering input would for the most part revolve around the rear wheels. The other point about using rubber: I like the thought of being able to use real rubber. It would be neat to have little air-filled omni rollers with real rubber tread too, but we have to work with what we have, and soft urethane is workable, you have probably seen the clear pencil erasers... thats how soft a compound I would be wanting to use. When you push with the front of your robot most of the traction is at the rear wheels, when pushing with the rear at least you are getting reasonable traction out of your Omni wheels. Different tread patterns are possible of course, I had considered using the black rubbery adhesive they use to seal windshields in cars. I would coat the inside of the tread pattern part of the mold and let it set up then assemble the mold and inject a harder urethane to make a soft reinforced treadded roller.


As for not being used by a FIRST team....it certainly was designed to be!

The goal was to make this prototype and present the construction tools and techniques to New Horizons Robotics Team 122. Teach the Team 122 students about the current prototyping methods used in the current day industrial world. The wheels were to be built completely by the students on the team during the build season except for running the waterjet machine. The wheel was accepted by the mentors and students but the teacher would not because it was not a Team 122 student concept.
This year all concepts, designs, construction, must be that of the students only. I realize that all teams are run differently, at least Sam Elzarian has learned a lot about these current rapid prototyping techniques, and about Omniwheels as well!

IT would need to be tested to see how durable the wheel would be...robotics is hard on wheels and just about everything else. One good thing is that if you bent an axle bolt it would be so easy to replace.

I assembled all the CAD files and Stereo lithography files, it comes to less than 50 megs...where could I store it to be used by the FIRST community?