Balancing a Pneumatic wheel

[F22Rapture]

We've got 2 6" Andymark pneumatic wheels on our shooter, and we were having some major issues with vibration due to the air spigot throwing off the weight distribution. We removed the innertubes entirely and filled them with bubble wrap which helped some, but it still vibrates badly because the tire doesn't seat particularly well without inflation. For teams that are using pneumatic shooter wheels, what did you do to balance them?

Also, did anyone find a different type of wheel to be superior?

[SailorDad]

We are using a single 8" pneumatic wheel and the team taped a few small nuts/bolts into the spoke opposite of the filler tube. Works fine.

We were running the tire without an innertube but discovered it flattened out too much and it was difficult to get a good grip on the disk.

[ksafin]

We used 1/4 oz tire weights from Harbor Freight - they're adhesive backed and worked like a charm!

[Brandon_L]

Two long bolts on the holes opposite of the air nozzle, with washers stacked on them. Our sweet spot was 9 washers on each bolt, give or take a few for others depending on bolts/nuts and such.

Am I the only one that watches lunch with Andy?

[JohnFogarty]

Step 1: Take the inner-tube out.
Step 2: Fill the tire with pool noodle which has been cut in half.
Step 3: Thank your friendly M'Aiken Magic mentor from South Carolina.
Works like a champ, promise.

[Andrew Schreiber]

Originally Posted by ksafin

We used 1/4 oz tire weights from Harbor Freight - they're adhesive backed and worked like a charm!

Remind me to wear my kevlar vest to any event you're at.

Seriously, don't forget to take into account that these wheels are running at speeds they were NOT designed for. Make sure anything you attach to them can handle the speeds.

Do what we did: Just take the tubing out! Literally. Just the hub and the rubber tire. No inner tube. It works beautifully.

[ksafin]

Originally Posted by Andrew Schreiber

Remind me to wear my kevlar vest to any event you're at.

Seriously, don't forget to take into account that these wheels are running at speeds they were NOT designed for. Make sure anything you attach to them can handle the speeds.

Well we've probably run the shooter wheels, in total, for over 2 hours of run-time and nothing has ever gone wrong (this is actually an insane amount of time considering robots are typically not run for very long times).

When you couple the strong adhesive and with the centripetal force of the wheel, there's no way these puppies will fly off.

[Boe]

I know team 3130 removed the whole inner tube and replaced it with pool noodle and had great success with it.

[Ian Curtis]

Originally Posted by ksafin

Well we've probably run the shooter wheels, in total, for over 2 hours of run-time and nothing has ever gone wrong (this is actually an insane amount of time considering robots are typically not run for very long times).

When you couple the strong adhesive and with the centripetal force of the wheel, there's no way these puppies will fly off.

Something to consider is that the way most teams practice is not indicative of an FRC match. Their is significantly more vibration, impact, and otherwise dynamic loading that the robot will see during a match compared to the loads it sees when you drive around picking up frisbees without the full contact of a typical match. Any field reset volunteer could tell you about the buckets of stuff they have to pick up off the field.

Originally Posted by Justin Shelley

I believe those are the smaller wheels, not the pneumatic. If someone is spinning that pneumatic wheel over 4,000 RPM then the are lucky they still have a wheel.

I think many people are running tires at 1:1 off a CIM and just assume they are getting close to a no-load free speed. If they were to put a tachometer on it I bet they would find their true rotation rate is significantly slower.

[Alan Anderson]

Originally Posted by Justin Shelley

I believe those are the smaller wheels, not the pneumatic. If someone is spinning that pneumatic wheel over 4,000 RPM then the are lucky they still have a wheel.

The TechnoKats robot this year uses the pneumatic tires from AndyMark. I think the operator typically calls for 3000 RPM, but it can go to 5000 on command without trouble.

Originally Posted by Ian Curtis

I think many people are running tires at 1:1 off a CIM and just assume they are getting close to a no-load free speed. If they were to put a tachometer on it I bet they would find their true rotation rate is significantly slower.

The final output wheel on the TechnoKats shooter has a Spinbox in "overdrive" configuration on a MiniCIM motor. It definitely exceeds 5600 RPM when run full power (the cRIO stops getting a good signal from the encoders above that rate).

The wheels are well balanced (though there is still enough vibration to matter) and there is a shield in place to keep debris from flying out if something comes apart at speed.

[team222badbrad]

Here's how I did it:

I also used stick on lead weights for RC airplane balancing, but I simply did not trust just double sided sticky tape to hold them inside the wheel.

I stuck the weights on where they needed to go and then I used 30 minute epoxy as the final balancing "weight". This also helps to secure the weights in place.

http://www3.towerhobbies.com/cgi-bin...&I=LXK204&P=ML

The fourth picture is what happens after you spend time balancing the wheel and the tire decides to spin the tube inside the wheel resulting in an unbalanced wheel...

[jimwick]

We found that the valve stem was being pushed outward by centrifugal force.

So we put a zip tie around the valve stem and the bolts holding everything together. Seems to work well. Has been reliable.

We are only running about 3000 rpm. We are not trying for real long shots.

[Brandon_L]

Originally Posted by jimwick

We found that the valve stem was being pushed outward by centrifugal force.

So we put a zip tie around the valve stem and the bolts holding everything together. Seems to work well. Has been reliable.

We are only running about 3000 rpm. We are not trying for real long shots.

We did the same but with a few wraps of a fishing line

[z_beeblebrox]

Originally Posted by jimwick

We found that the valve stem was being pushed outward by centrifugal force.

Had same issue. Elegantly solved with strategically placed duct tape toroid.