Best motor/gearing option to drive a shooter?
 

Using a linear shooting system what would be the best way to drive those motors? By looking at Andymark I noticed the Double Doozy assembly http://www.andymark.com/product-p/am-0629.htm for the AM 9015 motors and then the http://www.andymark.com/product-p/am-0449.htm gearbox. From what i've roughly calculated that would give around a 2,000 rpm output. Would this be enough to launch a frisbee a reasonable distance?

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

You won't know for sure until you slap the thing together and toss a frisbee. Also, a "reasonable distance" might be anything from 2 feet to 40 feet. It depends on what "reasonable" is to you. Check your game strategy.

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

That truly depends on how far and what goals you are aiming for. Just to give you an idea, watch the robot in 3 days video about their linear shooter. They are using a CIM geared up to roughly 8,000 RPM (if I'm remembering correctly they are gear up about 1.5:1 and a CIM standard is around 5,200 RPM). You also have to consider the pressure you are applying to a disc and how much that affects the speed of your shooter. I would suggest looking through all the legal motors that you don't plan on using for other things and see what you can find. A good place to start can be the BaneBots motors. Many of those motors have a very high RPM output and have many options to how you can apply them for your needs.

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

Is consistency important to you? If you run it at free speed, there's no headroom for speed control.


What's your wheel diameter?

Theoretical frisbee exit speed in mph (no slipping) is given by

pi*d*s/2112

"d" is wheel diameter in inches.

"s" is wheel speed in rpm


If there is slippage between the wheel and frisbee, the exit speed will be lower.

If there is slippage between the chute and frisbee, the exit speed will be higher.

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

Is this exit speed in feet per second?

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

I believe he has it listed in miles per hour. Just do some unit conversions.

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

That would give an 8,000rpm, 8inch wheel (exactly like robot in 3 days) and exit speed of 95 MPH. Seems a tad fast for a frisbee exit speed.

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

Just to throw it out there, the MiniCim actually spins faster than the CIM motor (free speed 6200 rpm, compared to the CIM motor's 5310).

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

question:

answer:

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

Not saying you're wrong, but where did you get the 8000 rpm number from ?

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

5200 rpm CIM geared at 1.5:1 => 7800 rpm. He rounded that up.

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

Who said they are running it at full voltage ?

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

Before we can answer the question of the best motor/gearing option, we need to determine the ideal exit speed.

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

Does anyone have any data (actual measurements) for the following?

1) what effect do different shooter wheel speeds have on frisbee flight path (e.g. height at the target distance) ?

2) how much does your shooter wheel slow down when a frisbee passes through it ?

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

Your best bet to determine any of this is to put together something with a launch speed in the desired ballpark and test the desired shot. Then you don't need any math beyond knowing how things scale. We have run all of our tests off of a UPS (uninterruptible power supply) so that we can adjust the voltage to get the desired launch speed. Knowing this speed makes it much easier to design the final mechanism, and we haven't needed any frisbee flight models, only repeated testing.

Of course, we are not simulating any shooter spin down with a UPS, but as already mentioned, leaving headroom for speed control should take care of this.

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?

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

Sorry didn't think about the link idea.
I'll do better next time.
Thanks

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

At full battery voltage and no speed control.
Ya, it's primitive but it works. We will be looking into PID or bang bang later.

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

The larger diameter provides a slightly longer contact path.

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

It's a great post though. The problem is, it's going to be difficult following the discussion. You've already got responses in two threads.

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

We were looking into gearing up our CIM motor to 6000-8000rpm and running an 8in pneumatic wheel. Originally we were looking to gear up a toughbox but after realizing that they only seel 12-14 teeth gears for CIM motors, we'll probably just use belts and sprockets

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

FYI, Team 2073 found that above a certain wheel speed, the frisbee exit velocity actually decreased.

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

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

Something for the 8000 rpm, that's assuming free spin, which isn't accurate for a motor under load conditions. The CIM has to turn the wheel, so it's going to be something less than 8000. It won't be an amazing drop but 7000 - 7500 is probably more reasonable.

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

Could be a lot less than that if the wheel is generating vibration and windage.

Hint: measure the CIM current with a clamp-on ammeter. Then estimate the CIM speed from the voltage and current, as shown here.

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

This is definitely interesting, though they're using (from what I can tell)
8" Plaction Wheel from AndyMark while we're using a rubber wheel which may be turned to better fit the frisbee so I guess we'll have to build the belt/sprocket mockup before we can really test what the effective speed is.

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

http://www.chiefdelphi.com/forums/sh...40&postcount=7

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

Anybody planning to buy 8" pneumatic and run it at 8000 rpm read this thread:

http://www.chiefdelphi.com/forums/sh...d.php?t=111118

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

Is there anyone considering using dual banebot 550's to drive their shooter?

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

Yes.