INSANE Ball Launcher For My Dog


Background


5 years ago, in 2016, my wife and I adopted our first Puppy, Piper. Piper is now all grown up and many things about her have changed, but one of the things that she has loved to do since she was a baby, was to play fetch with her favorite ball. Whether it's raining or snowing, 105 degrees or -10 outside, the moment I let Piper outside to go potty, you can bet she'll grab her favorite ball and come drop it at my feet. This is undoubtedly one of my favorite things about Piper, but as I near the end of my twenties, I can already start to feel my shoulder disapprove of the constant ball tossing. I know, I know, Tom Brady is damn near 50 years old and he can still throw a football. Well, I'm no Tom Brady (nor do I want to be), so I started looking for a better solution.

Inspiration

I know there are already solutions out there to help with throwing a ball for your dog, like those long flinger-sticks, but as an engineer and a general over-doer of things, I decided none of those would cut it. Instead, I went back to my childhood for inspiration. When I was a kid, I loved playing with Hot Wheels. I had countless cars, tons of track segments, and I even had some of those track shooters that would launch the cars along the track using two spinning foam wheels. Now, I'm not sure why my brain went to the Hot Wheels track launcher instead of a baseball pitching machine, considering I played baseball much more recently than I played with Hot Wheels, but the overall idea is the same. 

Build

Now that I had my idea, the easy part was over. After several failed designs, and numerous electronics swaps, I finally had something that ALMOST worked...


First, I tried using some old brushless motors from a failed drone project a few years back, with some plastic tires from an electronics kit I got off Amazon. I was initially hoping that the high RPM of the drone motors, combined with the admittedly small weight of the wheels would generate enough momentum to launch a racquetball at least a fair distance. Unfortunately, the motors simply didn't have enough torque to send the ball anywhere and ended up almost completely stopping every time I pushed a ball through. They were able to launch the ball about 10 feet, but I was hoping for more dramatic results. 


To get around this, I switched the brushless motors out for a pair of brushed DC motors that are intended for a Racing RC Car. These motors came with a lot more torque at the cost of some RPMs, but they should still be able to get up plenty of speed to really launch the ball. So, after redesigning the entire project to accommodate the new motors and speed controllers, I fired it up and... I almost took a flying, spinning, rubber tire to the face.


It turns out that the new motors definitely generated enough speed and torque for this project, in fact, they might provide too much speed and torque. As soon as I got the motors up to speed to attempt a ball launch, one of the rubber tires saw an opportunity for freedom, and seized it. The cheap rubber that the tire was made of allowed it to stretch out just enough to slip off the wheel and go flying in the direction of my face. Luckily, it missed by an inch or two, but it definitely prompted me to wear safety glasses for the remainder of the tests. 

To address the rubber death frisbee issue, I decided to scrap the use of those wheels altogether in favor of a single, solid, 3d printed wheel. This change came with two clear benefits, and at least one drawback that became evident when I tested them out. As far as benefits, the printed wheels eliminated much of the vibration caused by the rubber tires, as they weren't evenly balanced, nor were they intended for high speeds. The printed wheels also eliminated the risk of rubber damage to my face, but it turns out some sort of rubber was most likely necessary to get a good grip on the ball.

Whenever I tried pushing a racquetball through the launcher, the printed wheels struggled to get a grip on it, cause them to build up friction heat on the ball before launching it forward. This resulted in a lovely burnt rubber smell every time I launched a ball, and the white PLA even started to smooth out from the repeated attempts. These new wheels, although not completely successful, still added about 10-15 feet to my launcher, which is admittedly much less than I was hoping for. 


Conclusion

In the end, my super over-engineered ball launcher could send a racquetball about 25 feet, with some added distance after the bounce. This is far from what I was hoping for, but considering the engineering hurdles I had to jump just to get to where I am, I'm gonna call this project a semi-success. In the future, I hope to find a better wheel design that will allow me to actually launch some distance, but for now, I think I'll have to keep playing fetch the good old fashioned way.


Check out the video for this project at the link above, and make sure to reach out or comment if you have any suggestions for how this project could reach it's full potential! Parts and some other useful links can be found below, otherwise see you next time!

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