Tennis Ball Launcher

Ok so I want to make a simple tennis ball launcher. I made a quick sketch in paint (attached). I want to know what kind of motor should I be using? Stepper? Servo? regular?. Im assuming the motor not only have to be rotating fast but it also should have high torque. any help and tips would be appreciated. thanks in advance.

cheers
SN

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Tennis_Launcher.jpg

I want to know what kind of motor should I be using? Stepper? Servo?

Can't think why you'd want to use either of those two. Not enough torque from a stepper, and probably not enough speed from a servo (or 360 degree rotation). I'd probably start with something about the size of an R/C car's (540?) motor

some how i do not think this will work you could use the arduino to release the balls and control speed and direction

I get the impression that these things usually rely on the drive wheels having significant inertia and it's the momentum of the wheels which give the balls the sharp impulse. The motor just needs to gradually bring the wheels up to the right speed and doesn't need to be especially powerful. As long as it can overcome drag and spin those wheels up to the required speed eventually, it should be OK. I don't think you should be looking at stepper motors or servos, though. I'd have thought that an ordinary motor with speed controlled by PWM would be a better approach. You probably also want some sort of speed detection so that you can control the release speed.

I guess you'll also want some mechanism to feel balls into this contraption, and if you're automating that you might end up using servos to control the ball release.

Also - the wheels need to spin in opposite directions (the way you drew your belt would have them rotating in the same direction, which wouldn't work). Instead of a belt or gearbox, though, just use two separate motors. You may even be able to get away with using a single motor (some toy disc guns work this way).

from playing tennis mos of these machines run on AC so maybe a larger motor maybe a repurposed saw could be used a relay could control the on and off function but i am unfamiliar with a way to control the speed of the ac with the arduino (if you had to a dimmer ac switch with a servo to control speed) that is if there is no electronic way to control it

Ive seen these sorts of things before.
Chr0sh is right, the wheels need to spin opposite directions. The one ive seen was for launching balls for softball practice. but it would be the same for tennis balls. One wheel is powered and the other is spun by that wheel (they touch) the wheels need to be pneumatic (like a wheelborrow or go-kart) and not pumped up hard. this allows the ball to be grabbed and sucked through and spat out.

There was a cage above it with a trap door to a wire tube that gravity fed the wheels.

the motor was a 240VAC belt drive to the wheel.

angle (and distance) can be adjusted by tilting the whole contraption.

hope this helps

If the two wheels were driven independently then you could also introduce slice or top spin by varying there relative speeds.

do you think you could accomplish that by having the wheels a varying distance apart and varying some sort of friction on the free spinning one ?

THANKS FOR ALL THE AWESOME FEEDBACK.!!! thanx a bunch

Hi guys. ok so after reading the posts and putting things together, its obvious my design was trash so changed it. thanks for pointing out the one belt rotating wont do and no need for steppers or servos. so i will be using 2 DC motors and arduino motor shields using PWM. i googled motor shield on ebay and realized there are sooooooo many. so my question is that which is the best one for a project like mine? what kind of motor shield and motors should i get? thanks again guys. regards SN

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maybe a drill motor? those are very strong I have seen people make a go kart with 2 of them.