Build Suggestion: Automatic Dog Ball Thrower.

Something along the lines of this perhaps ?

https://www.youtube.com/watch?v=4PcL6-mjRNk

That's an awesome robot tosser for indoors..... my lab cross is an outdoor dog ....

How about this one then ?

https://www.youtube.com/watch?v=s7AOy1DbvYw

This is a much better option. Do you think Ben could put some Heck-yah in it but still make it something  we can make at home?

Some enhancements might be to:

• have some sort of range and direction limit controls so as to avoid the greenhouse/neighbours pond.
• dog tracking mode so that it always launches away for the dog for maximum exercise or  toward the dog if it likes to jump and catch the ball.
• garden chair mode to allow the dog owner to interact and operate it from the comfort of their chair using a mobile device.
• auto loading from a bucket. If you can train the dog to return the ball to the machine then great, but I suspect a lot of dogs will return the ball direct to the owner, so you probably just want to be able to toss the ball into something like a bucket which then reloads the machine.

Another option is portability. Being able to take it to the off leash park would be awesome.

Multi-ball capability would be chaos in the field - multi-ball pinball with dogs.

How about an integrated camera view as well if it is being operated by phone app....

A data logger option to count how many balls have been tossed and returned.

Well, you know, Ben's really into his pinball machines...

You may encounter a lack of power problem when it comes to portability for the off-leash park.

Here is an episode of 'Scrapheap Challenge' (Series 11 / episode 8) where they attempt to build tennis ball mortars

https://www.youtube.com/watch?v=CrZQZOni4Zg

which may give an indication of the amount of power generally required to launch a tennis ball any distance.

May have to start off with something like a tennis ball practice machine.

https://youtu.be/6G70jm5eR_E

This may be more like what I was thinking but it would have to be  in a different  form  so the dog could drop the ball into the bucket easier and the working  parts would be enclosed for protection from the elements and safety for the dog.

I'm not looking to send the ball more that 15- 20 meters anyways.

Nice find. That looks surprisingly effective given that the slingshot mechanism is being driven from a cordless drill motor. I think the tennis ball practice machines generally either use counter rotating wheels or compressed air to launch the balls.