I built several of these from scratch after realizing that pegboard is already set up in the right pattern and dowel pins fit into peg holes perfectly.
I demo'd it at a STEM fair and everybody has a great time. It makes a ton of noise and a great visual demo. I even ended up learning a bunch about hopper theory because I had to 3d print a hopper to feed it and it kept jamming.
I forget where I first read about hopper theory but I was fascinated to discover that so much analysis has been done on the dimensions of such a simple device. It makes perfect sense in retrospect given all the industrial and agricultural applications but it's one of those little corners of the world where you would never guess the pains engineers go to understand and optimize it.
I demo'd it at a STEM fair and everybody has a great time. It makes a ton of noise and a great visual demo. I even ended up learning a bunch about hopper theory because I had to 3d print a hopper to feed it and it kept jamming.