Re: Best motor/gearing option to drive a shooter?
 

Did you gather any data (that you'd be willing to share) during this testing?

Re: Best motor/gearing option to drive a shooter?
 

Not that I have access to at the moment. When I get into the shop this afternoon I'll see what I can dig up.

Re: Best motor/gearing option to drive a shooter?
 

This post has some useful qualitative observations:

http://www.chiefdelphi.com/forums/sh...2&postcount=55

Re: Best motor/gearing option to drive a shooter?
 

FWIW, World's record for fastest frisbee throw was 74 mph in 1988 (citation: YouTube video from Guiness Book of Worlds' Records TV show)

Re: Best motor/gearing option to drive a shooter?
 

Note that with any no-slip one-sided design, the tip will have to be going twice as fast as the desired exit velocity, since half of the imparted velocity must go into spin. So even if we only need a 70mph launch, the shooter would need to be going 140mph.

Add in a second side, however, and that changes entirely...

Re: Best motor/gearing option to drive a shooter?
 

http://www.chiefdelphi.com/forums/sh...8&postcount=36

Re: Best motor/gearing option to drive a shooter?
 

Yesterday we were running our shooter at ~4000 ft/min (about 45mph). As far as we can tell there is no slip on the belt, so this should mean a frisbee exit speed of 2000 ft/min, or 22.5 mph. Shooting from ~130" from the wall and ~30" off the floor, we were able to hit a spot on the wall a foot or two below the 3pt goal (at the farthest) with excellent consistency, all within a few inches of each other. We are happy with the consistency and the shooter design, so we are working on getting it up to speed and making a few other improvements. We would like to shoot about twice as fast, for a nice level shot.

Re: Best motor/gearing option to drive a shooter?
 

How could you tell ? Did you take video and slow it down like 2073 did ?

Re: Best motor/gearing option to drive a shooter?
 

This makes sense to me, but I couldn't explain to a mentor why you wouldn't want to run the motor at its free speed. Why wouldn't it be consistent at its free speed? Is it just because there isn't much torque at that speed, so the motor might slow down more when it shoots a frisbee?

Re: Best motor/gearing option to drive a shooter?
 

Free speed means 100% power. If you slow down and all of a sudden need more torque, uh oh. You can't get 110% power (unlike a nuclear submarine). That's what the headroom for speed control is. "Space" for more power, if and when you need it.

Re: Best motor/gearing option to drive a shooter?
 

If you run it open-loop at full voltage, three things happen:

1) The actual speed you get varies greatly as the battery voltage changes

2) It takes a long time for the motor to spin up to free speed

3) When the motor slows down due to a frisbee passing through, the motor doesn't have much torque at that high speed and so it takes longer to recover


Gearing your shooter wheel motor so that you can get the desired wheel speed when the motor is running at less than free speed*, and using some sort of closed-loop control of speed, solves all three of the above problems. A bang-bang controller is very easy to implement and works well for this application.


* ideally at 50%

Re: Best motor/gearing option to drive a shooter?
 

No it doesn't. It means 100% voltage.

100% power (mqx power) occurs at 100% voltage and half free speed.

Re: Best motor/gearing option to drive a shooter?
 

Our circular (90) degree shooter uses and AM pneumatic 7.5 inch wheel with a 32 tooth sprocket on it and a 25 tooth sprocket on the CIM. We have it set up so the wheel is hitting just above the widest diameter of the disk and just below the widest diameter of the tire with about 1/4 inch of compression and the tire at maybe 10psi. This ensures the disk does not ride up on the tire. This puppy will hit the top of a 10 foot door at 45 feet. up down variation is about 6 inches and side to side variation is almost nonexistent.
This is just with a plywood POC. You can read that as Proof of Concept or Piece of C&^%. Whatever. Still need to add a guide on the outer rail to keep the disk from riding up on that.
We have also tested a straight shooter bot so far it is not as consistent and much less powerful even with 2 wheel powered by separate CIMs.
Still plan on a little more testing here as I think it would be easier to incorporate to the robot.

Re: Best motor/gearing option to drive a shooter?
 

You posted this identical post in three different threads.

http://www.chiefdelphi.com/forums/sh...46#post1213846

http://www.chiefdelphi.com/forums/sh...56#post1213856

It might be better to post it once and provide a link.

Re: Best motor/gearing option to drive a shooter?
 

Sounds like a direct drive to a 6" wheel would be the same.

At what motor speed did you log those shooting results?