its an old idea and until my last search around two years ago I&#x27;ve found almost nothing.<p>In my infinite spare time (in retirement or something) I plan to build one of a scale large enough to launch something like a water balloon or maybe paintball payload a couple feet.  I&#x27;m well aware there are simpler and more efficient ways to toss a water balloon ten or twenty feet, but its unlike there exist any cooler ways to do it.  I would take it to the local maker faire and set it up next to the guy with the pumpkin trebuchet (every faire seems to have one of those guys).<p>It turns out that shock loads can be significant and dynamic stability is not exactly guaranteed, which makes it a cool engineering project.  Also for small ones either the payload has to be extremely small (resulting in the paintball payload) or the loop has to be extremely heavy (probably not insurance approved, although it would be cool to spin up a length of hoist cable).<p>The one thing I have found is a cat or kid toy implementation radius about one foot.  Its moderately cool.  In order to eliminate or cut down on medical bills it has some elaborate and extremely fast motor current monitoring, which is usually the downfall of the toy.<p>If you&#x27;re thinking the same thing I&#x27;m thinking, I wish you good luck.  Its a cool project idea.<p>This topic comes up almost like clockwork on HN every couple years.  Eventually I&#x27;ll have something cool to demo.