Andymark Pneumatic wheel problems

[Ether]

Originally Posted by Wiifi

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.

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?

[Oldbikerider]

Originally Posted by Wiifi

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

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.

[ehochstein]

Originally Posted by Ether

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?

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.

[Ether]

Originally Posted by Wiifi

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

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

[KrazyCarl92]

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?

[Kyle Love]

Originally Posted by KrazyCarl92

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?

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

[KrazyCarl92]

Originally Posted by Kyle Love

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

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

[s_forbes]

Originally Posted by KrazyCarl92

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

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

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

[ehochstein]

Originally Posted by Ether

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

I'll add it to my list.

[Al Skierkiewicz]

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

[Joe Ross]

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

[kingbrandon14]

Originally Posted by PizzaBoxZombie

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?

At first, we thought we had the same problem. We then strengthened the motor mount we made, and the shaking almost disappeared. Just tighten it up, or attach it better i guess ?

[thedude019]

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

[Camren]

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.

[Al Skierkiewicz]

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.