I built a crystal radio receiver. http://joshburker.blogspot.com/2014/01/building-crystal-radio-receiver.html I built and printed this model instead of using a cardboard toilet paper tube for my radio coil because the plastic offered more strength. Also, my Thing-O-Matic cannot print tall enough to print the tube as a single model. I printed the tube in two parts and glued the ABS plastic together. This thing was made with Tinkercad. Edit it online https://tinkercad.com/things/0KXg4ibAaxK You could combine the two models to make a single tube for printing. Or you could build your crystal radio with a toilet paper roll. The important thing is that you build a crystal radio.Printed in ABS on a Thing-O-Matic at 5% infill. Glued with Testor's model glue along top edges of the models. Instructions on how to build a crystal radio are available on the Internet. I wrote a narrative of my build with a parts and tool list. http://joshburker.blogspot.com/2014/01/building-crystal-radio-receiver.html