Andymark Pneumatic wheel problems
 

As several other teams and IR3 have shown in various youtube videos, the pneumatic wheels from andymark are pretty decent shooting wheels. after recieving ours, however, we found that ours are out of balance/round. spinning at 5-6500 rpm they shake around a lot and can not achieve full potential speed.
we have since changed wheels for some more consistent and faster, but we were wondering if anyone else had tried to use them and found the same problems? and if anyone has, have you found a solution?

Re: Andymark Pneumatic wheel problems
 

We definitely have had the same issues, we haven't found a solution and moved on to other options.

Re: Andymark Pneumatic wheel problems
 

Is the tire bead seated correctly?

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That's the problem. We can't get it to seat correctly. Any tips/tricks to do so?

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yeah, ours were, to the best we could figure out, ill double check. thanks. the other problem was we still had to balance the valve stem.

I believe I was experiencing that same problem today when we were testing a prototype. The pneumatic wheels appeared to have a lot of free movement. I don't know if this is just our prototype or wether the wheel isn't seated properly.

Re: Andymark Pneumatic wheel problems
 

I believe the problem is with your speed and not the wheels. If I remember correctly, IR3 only used a cim at ~55% power.

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Is there a special method in order to seat the wheel?

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I'm trying to hunt down the source for this. Do you remember where you got it?

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I doubt Andy & Mark expected teams to try and go 125 mph with those wheels. As others have said slowing down or switching is probably the least work per performance. :)

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We tested our pneumatic wheel at 60% speed today, launching between the wheel and our wood prototype base. We experienced approximately the same range/speed as the Robot in Three Days robot.

Re: Andymark Pneumatic wheel problems
 

60% of CIM free speed?

Re: Andymark Pneumatic wheel problems
 

On a related question, does anyone know what the safe working speed is with the AndyMark wheels? I've searched but can't find anything. I'm thinking that some bursting strength calculations are necessary here.

We've been testing with some 10 inch OD "highway" treaded mobility scooter tires mounted on 4 inch go-kart wheels. At 1600rpm there is significant tread growth and they start to get unstable in balance. The two wheels also appear to feed vibrations to each other in complex ways.

I wonder what actually fails first. Would the tire tread just catastrophically fail, or would bits start shedding more gently? I suspect the former.

Graham.

Re: Andymark Pneumatic wheel problems
 

Just to bring up a couple of other possible issues...

Are the bearings installed properly (with flanges and such extremely level and tightly in place)?

Are you using a cantilevered or secured method for the wheel?

I would guess that if you could have a bearing or some other type of "reciever" for the end of the shaft, you may take some of the wiggle out of it. I do agree with some posts above that I doubt these wheels are really meant to spin as fast as many teams are spinning them. More then likely, that is the main issue, but I wanted to just bring up a couple of other possible issues.

Re: Andymark Pneumatic wheel problems
 

I can't promise that, we coded eleven buttons to control the speed. Button 1 was 10%, 2 -> 20% etc. We ran it on buttons 6 and 7.

I uploaded a video of our shooter at 1000 frames/sec http://youtu.be/7dN1thFqr7k

Re: Andymark Pneumatic wheel problems
 

A number of questions immediately spring to mind:

1) what does "60% speed" mean? 60% of the motor's rated free speed (in which case how did you measure the speed)? 60% command to your motor controller? 7.2 volts from a DC power supply? or something else?

2) what motor were you using, and what gear ratio?

3) you said "wheel" and not "wheels". Is this a single-wheel linear shooter? or a curved chute shooter?

4) were you using the same model and size pneumatic tire as R3D? or something else?

5) how do you know the speed of the R3D shooter? I couldn't find that info anywhere. could you post a link please.


edit:
I just now saw your video. Whole lotta slippin' going on as the bee exits. Have you tried slowing down the wheel?

Re: Andymark Pneumatic wheel problems
 

Great video, thanks for posting.

What surprised me at first in your video, and in other slow motion videos of frisbee shooters is how little slip there is between the disc and the vertical surface opposite the wheel.

Has anyone done AB tests with and without friction material added on that surface? I don't think there would be much difference.

Graham.

Re: Andymark Pneumatic wheel problems
 

1) 60% command to the motor controller, I can measure the voltage tomorrow.

2) CIM direct drive

3) See video http://youtu.be/7dN1thFqr7k

4) We used this wheel which I believe R3D used, I cannot confirm they did.

5) I do not know the speed, I was using the assumption from a previous poster.

The slipping is caused by not having enough tension between the wheel and the side of the arc. The wheel is as deflated as we could get it in this video. This prototype was designed for an 8" rubber wheel
so that is what caused the extra space. Tomorrow I am setting up my velocity reader, another mentor is modifying the wheel to be more effective (I don't specifically remember how) and we will be remounting the wheel closer to the arc.

Re: Andymark Pneumatic wheel problems
 

Measure the CIM current too, if you have a clamp-on ammeter... then you can estimate the wheel speed using the volts and amps.

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We have ordered some of these wheels and they will be arriving on Tuesday. Couldn't find any information on this on the Andymark website, but what will we need to fill the tubes with air?

Re: Andymark Pneumatic wheel problems
 

These typically come unassembled. So you will need to do all of the assembly of the components including airing the tubes up.

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What will we need to fill the tubes with air though? Is it going to be exactly like filling a bike tire with air?

Re: Andymark Pneumatic wheel problems
 

Yes, if you have standard Schrader tubes on your bike.

http://en.wikipedia.org/wiki/Schrader_valve

Re: Andymark Pneumatic wheel problems
 

I'll add it to my list.

Re: Andymark Pneumatic wheel problems
 

These tires are not balanced as that is not needed in normal operation.

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In today's Lunch with Andy episode, he mentioned adding weight to balance the valve stem.

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Re: Andymark Pneumatic wheel problems
 

just wondering has anyone had a problem with the wheel braking under a high rpm because we ordered pneumatic wheels and we were testing with a placation wheel and the tread broke off the wheel so is it possible this can happen with the pneumatics wheels

Re: Andymark Pneumatic wheel problems
 

Here is what I for see as the problem. Lets take in consideration the pneumatic tire of a automobile. It spins usually 1500 rpm and is meant to travel at speeds 100mph. The rim of the tire is meant to seal at the bead just right and have a place where you can balance the tire. because not every rubber tire you get off the assembly line is the same one. Now lets look at the Andymark pneumatic wheels, They have a simple design with a rim a tube and the tire. teams are spinning these wheels at complete excess of what they were designed to do. these tires cant be balanced nor do they 100% seal to the bead. Now if a team were to just by the tire from andymark and scale down a CAD design of a real life rim and buy some weights from Napa or any other auto parts store. then you will get a properly balanced wheel.

Re: Andymark Pneumatic wheel problems
 

Luke,
Let the centrifugal force be with you!
If you plan to use any wheel in a high RPM mode, you need to be sure that the surface (tread, tire, tube) are rated for that RPM. Spinning devices can have tremendous energy and when they self destruct they impart that energy to their surroundings, be that robot or human.

Carmen,
Automotive wheel weights need to be designed for the tire rim they will be used on to prevent them from escaping. Your 1500 RPM calculation is close to an average 15" wheel at max rated tire speed, which for most cars has already exceeded the point at which vehicle stability has been lost. If a team were to go down to the their local auto store and bought some of those weights, I am fairly certain they would be ejected from the wheel prior to full speed.

Re: Andymark Pneumatic wheel problems
 

Our tire that we put the tube in refused to seat correctly, even after the hub was coated with a little water/soap and pumped up. I think its just part of the wheel coming off the line.
Our other wheel we put pool noodle in, and it seated pretty well and was pretty well balanced, but wasnt solid enough.

Our motor mount is pretty much all screwed down, and the wheels are supported from both sides.

The answer from everyones' replies seems to be that these wheels just are not rated for what we were all trying to make them do. i think most teams saw IR3 using them and jumped to the assumption that we made ourselves, which was that they worked, and worked great. And as IR3 showed in the videos, they do- to a point. Stated somewhere above is the (so far) unproven statement that they were scaled to 60%.

Team 225 has moved on from these wheels, and it sounds like most other teams have as well. Good luck to all of you finding replacements, and if you get really stuck, pm me- we have a few ideas that we can share.

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Pizza,
The filling of the tube is what is needed to seat the tire on the wheel. In some cases, as you fill the tube, you may need to compress the outside diameter of the tire to get it to seat on the wheel. Once it appears to be seated then you can fill it the rest of the way.

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Has anyone done an analysis (using the high-speed videos or any other method) of how much slippage there is between the shooting wheel and the disc? In other words, by the time the disc is exiting the shooter, has it accelerated enough that the two surfaces are no longer rubbing?

And if you do have this answer, then:
1. What material is on your shooter wheel?
2. What size is the wheel?
3. How fast is the wheel spinning?
4. How much travel does the disc have with the wheel? (90 degrees, etc.)
5. How much compression are you using?

Re: Andymark Pneumatic wheel problems
 

1. Rubber AM Pneumatic wheel with extra mass (saw blade grinded down)
2. 7.5" - No air inside of the tire
3. 80% controlled via programming
4. 90 degrees
5. Not much, the frisbee sits under the wheel and on top of our wood prototype, it follows a track around (c-channel).

I'm still compiling some data and I hope to post it later tonight. I'll include multiple pictures of what our prototype looks like, how we load the frisbees and (hopefully) some velocity measurements.

I do not have a clamp-on ammeter as my college will not allow me to borrow theirs, so I will not have current readings. However I will post voltage readings.

Re: Andymark Pneumatic wheel problems
 

What control algorithm are you using?

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Thanks for the data.

80% of what? What motor are you using? If we know the free speed of your motor, and if you're running it at 80% voltage, then we can estimate the speed of the wheel (subtracting a bit because free speed is idealistic).

Re: Andymark Pneumatic wheel problems
 

Team 225 has successfully solved this problem by removing the inner tube from the tire, and replacing it with pool noodle. This provides a strong, springy, balanced wheel that spins beautifully.

Good luck!

Re: Andymark Pneumatic wheel problems
 

We found that part of the problem was that as the wheels rotate, the valve stem is pulled outwards by centrifugal force, making balance much worse.

We solved this by putting a zip tie around the valve stem and the bolts holding the wheel to the hub. After that we had no problems and the vibration level was quite acceptable.

By the way, frisbee launching speed does not seem to be linear to wheel speed. We found that our best launching speed came at about 3000 rpm. Probably each shooter is a little different though.