Wheel Types: What's best, and why?
 

Hey all.

I don't know if I missed it, but I didn't see a thread specifically made to address wheel types and their effect on shooters. I've seen threads for single wheels (pneumatic, etc) but not to bring a whole discussion to it.

What type of wheels seem to work best? (Pneumatic, performance w/ tread, treaded KOP wheels (2012 or 2013), 2008 KOP wheels (gray rigid ones) or something else?

Also, why do you think this is?

On our side, the 2008 KOP wheel seems to be delivering sad results. I've seen teams use the 2012/13 KOP wheels with great success, and I'm having trouble figuring out why.

We thought 2008 ones worked poorly because they were rigid and not compressible - however, the 2012/13 ones are rigid as well, yet seem to work well on a variety of launchers.

Thoughts?

Re: Wheel Types: What's best, and why?
 

2010 wheels work fine when implemented correctly (I might have a video) but they are much less accurate then the pneumatic wheels.

The 2010 wheels are not as accurate simply because the way the tread is placed.

Tread on 2010 wheels
--ll
--ll
--ll

Tread on Pneumatic wheels
lllll
--ll
--ll
--ll
lllll

With the pneumatic wheels the frisbee can fit under the rubber and still have traction while the 2010 cannot.

Re: Wheel Types: What's best, and why?
 

Give more a more detailed description of your prototype and maybe a cause can be identified:

1) linear or curved shooter ?

2) if linear, one or 2 wheels ?

3) what motor(s)

4) what gear ratio

5) what motor voltage, current, and speed ?

6) how much compression ?

7) did you have a cover to prevent axial motion of the frisbee as it is being spun by the wheel ?

8) quantify what you mean by "sad results"

Re: Wheel Types: What's best, and why?
 

I meant 2010 wheels, actually.

1) Linear
2) One
3) CIM
4) Both 1:2.375 and 1:1
5) Don't have the means to check most of those, but it was hooked up directly to a battery and the battery voltage was about 12.75 V
6) Probably around 1/2"
7) No
8) About 15 feet with a max height of around 6/7 feet, or up to 25 feet with a max height of about 4 feet. Can't seem to get a good distance and good height at the same time. Also, it seems to be going rather slow compared to other teams shooters (meaning the velocity of the frisbee as it leaves)

Re: Wheel Types: What's best, and why?
 

I don't have a picture on me right now, but here's a video. Maybe you can deduce something from it.

http://www.youtube.com/watch?v=3fA5k...ature=youtu.be

Our best shot is the last one around 3:15; throughout the video we did various angles and minor adjustments to see varying results.

Re: Wheel Types: What's best, and why?
 

You probably shouldn't expect great performance out of a single wheel on a linear shooter, because that ultimately means you're getting less than an inch of contact area (and thus, acceleration).

Re: Wheel Types: What's best, and why?
 

Here are some random thoughts (it's getting late, turning into pumpkin):

Maybe they're out there, but I haven't seen any videos of successful one-wheel linear shooters.

Too bad you don't have any bird's-eye-view shots with a high speed video camera so we could see what the bee is doing as it passes thru. It's probably slipping badly.

Your guide rail is a nice shiny metal surface. It should be grippy in order to get more spin on the bee.

Your wheel speed may be too fast. According to some tests conducted by Team 2073, above a certain wheel speed the exit speed of the bee actually decreases, presumably due to slippage.

Try running the CIM at 10 volts instead of 12, and put some grippy tape on that shiny metal guide rail. I don't think this will get you all the way to where you want to be, but it might be a start.

You're probably going to have to add a second wheel, or go with a curved chute.

If anyone has made a successful one-wheel linear shooter, please tell us how you did it and post a video.

Re: Wheel Types: What's best, and why?
 

Why?

Re: Wheel Types: What's best, and why?
 

I should add that our guide rail has a strip of grippy kitchen liner fabric on it.

This serves to prevent the slippage of the frisbee. It seems to work rather well.

Re: Wheel Types: What's best, and why?
 

To prevent slipping. Slower motor = more time for the bee to grasp

Re: Wheel Types: What's best, and why?
 

Why not gear more?

Re: Wheel Types: What's best, and why?
 

So then what's the magic ratio?

At what point are you making your wheel too fast that the bee has no time to be accelerated, and at what point are you making it so slow that the bee won't get good spin or speed?

Re: Wheel Types: What's best, and why?
 

Has anyone tried using a thicker (as in tread width, not diameter), non-pneumatic wheel for a shooter? Given that tread placement relative to the frisbee seems to be a major factor, a thicker wheel might work better, right? My team is working on a prototype with the VEXPro traction wheels widened to 2" vs the stock 1", but I was wondering if any other teams have done so already.

Re: Wheel Types: What's best, and why?
 

because:

Re: Wheel Types: What's best, and why?
 

If you want to do speed control, your CIM voltage at the desired operating point must be less than 12 volts anyway, so that you have some headroom for control.

Re: Wheel Types: What's best, and why?
 

The goal trying to be achieved isn't more torque, it's more contact time. A slower wheel will contact the frisbee for longer, and in the end will accelerate the frisbee more.

Tl;Dr: Gearing the motor would work, as it would slow down the wheel, but it's not required since lowering the voltage of the motor is sufficient enough to increase contact time.

Re: Wheel Types: What's best, and why?
 

The goal is neither or those. The goal is faster exit speed of the bee.

The higher the acceleration if the bee, the less time it spends in contact with the wheel, and the faster the exit speed will be.

If the exit speed of the bee is slower, chances are it had more contact time, but it spent that time slipping, not accelerating.

Re: Wheel Types: What's best, and why?
 

There is no magic. What you are seeking is best determined by prototyping. You can't use someone else's answer, because many factors of the shooter can affect the result.