Best motor/gearing option to drive a shooter?

[Ether]

Originally Posted by clandry94

From what i've roughly calculated that would give around a 2,000 rpm output.

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

Would this be enough to launch a frisbee a reasonable distance?

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.

[clandry94]

Originally Posted by Ether

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.

Is this exit speed in feet per second?

[JohnSchneider]

Originally Posted by clandry94

Is this exit speed in feet per second?

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

[clandry94]

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.

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).

[Ether]

Originally Posted by clandry94

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.

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

[Djur]

Originally Posted by Ether

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

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

[Ether]

Originally Posted by Djur

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

Who said they are running it at full voltage ?

[ehochstein]

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

[Ether]

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 ?

[Aren Siekmeier]

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.

[Ether]

Originally Posted by compwiztobe

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.

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

[Aren Siekmeier]

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.

[smclean1969]

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.

[Ether]

Originally Posted by smclean1969

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.

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.