The chaotic pendulum is used in my classroom in our discussions of resonance, harmonic motion, and chaotic motion. With small amounts of energy, it's movement is predictable, but more energy is added the movement of the arms become unpredictable.
Homemade science is a collection of classroom tested ideas, suggestions, projects, and experiments that I have used in teaching physical science for the Annville-Cleona school district in central Pennsylvania. I am currently in my 38th year of teaching. My intention is to share these ideas with other teachers or anyone who has an interest in science. I have found that designing and building my own equipment has taught me more than any course that I have ever taken. I hope that you consider trying this for yourself.. I also share and show some of these ideas at workshops, science conferences, or inservice presentations.