Correct Motor Type

[tracerrx]

I want to create a simple "catapult" to toss a tennis ball. I was thinking of using a single DC motor, which would wind a string attached to the "throw" side of the lever, and have a spring attached to the other side of the lever. I'm looking for a DC motor, that when powered off will free spin (allowing the string to unwind quickly), releasing the catapult (spring pulls down lever) tossing the ball.

Could someone please direct be to the correct motor type that would "free spin" the best?

Thanks

[adafruit_support_bill]

I think you will find that any motor with sufficient torque will also have too much friction and/or inertia to release quickly. I think you will want a DC Gearmotor for the torque. And some sort of clutch or releasable ratchet mechanism to decouple the motor from the shaft for release.
https://learn.adafruit.com/adafruit-mot ... -of-motors

[tracerrx]

Thanks for the reply. I was hoping to be able to pull this off with only using 1 motor. I'm open to any ideas others may have! I need to "toss" the tennis ball about 20 feet.

[adafruit_support_bill]

Another simple 'tossing' mechanism to consider is similar to what is used in tennis or baseball pitching machines. Simply have a motor spinning a wheel and feed the ball between the wheel and a guide.

https://en.wikipedia.org/wiki/Pitching_machine

[Franklin97355]

Here are some other ideas.