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.

[Justin Shelley]

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.

I think if the weights will work on sport bikes that they will be fine on a robot wheel a 2006 yzf r6 has a top engine rpm of around 21,000RPM. The sixth gear reduction ratio is 1.074. Dividing 21,000RPM/1.074 will produce the RPM of the rear wheel. This comes out to be 19,553RPM. I don't think the shooter wheel is hitting that speed lol Now i realize you may do the math and realize nobody ever drives that fast but when the bike is doing 250MPH, people do drive that fast on the track, the rear wheel is spinning at abut 3,703RPM which is faster then any shooter wheel is spinning. So Andrew you are just fine using wheel weights

[Andrew Schreiber]

Originally Posted by Justin Shelley

Now i realize you may do the math and realize nobody ever drives that fast but when the bike is doing 250MPH, people do drive that fast on the track, the rear wheel is spinning at abut 3,703RPM which is faster then any shooter wheel is spinning. So Andrew you are just fine using wheel weights

3703 < 5000 So I'm not seeing your point. I know one of my wheels is geared close to 7500 rpm. Now, I'm aware I'm not hitting that speed but I'd be willing to bet you that it's well above 3700rpm. And frankly, I don't care if it "should" be safe. I care that it is. I care that teams took some time to put in safe guards to prevent shrapnel hitting people because I'm selfish and I enjoy the use of all of my limbs.

[Alan Anderson]

Originally Posted by Justin Shelley

I think if the weights will work on sport bikes that they will be fine on a robot wheel a 2006 yzf r6 has a top engine rpm of around 21,000RPM. The sixth gear reduction ratio is 1.074. Dividing 21,000RPM/1.074 will produce the RPM of the rear wheel. This comes out to be 19,553RPM. I don't think the shooter wheel is hitting that speed lol Now i realize you may do the math and realize nobody ever drives that fast

That's well over 1200 miles per hour. I don't think the wheel itself would survive, much less stick-on weights.

but when the bike is doing 250MPH, people do drive that fast on the track, the rear wheel is spinning at abut 3,703RPM which is faster then any shooter wheel is spinning. So Andrew you are just fine using wheel weights

Based on reports I've seen here, some frisbee shooters are spinning their wheels at 6000 RPM or higher. 5000 RPM seems common. Whether or not you use wheel weights, if you're running a wheel at several thousand RPM, you'd better have an effective containment system to protect the outside world in case something spontaneously disassembles itself.

[Justin Shelley]

Originally Posted by Alan Anderson

Based on reports I've seen here, some frisbee shooters are spinning their wheels at 6000 RPM or higher. 5000 RPM seems common. Whether or not you use wheel weights, if you're running a wheel at several thousand RPM, you'd better have an effective containment system to protect the outside world in case something spontaneously disassembles itself.

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.

[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.