Get someone to help you make this one. Using a hammer and a nail, poke a hole into the bottom of a large tincan. Wind one coil of a large thin wire spring (a slinky works too) into the hole and glue it in place with Shoe-Goo ™ or hot glue. Wait until the glue sets, then hold the can and let the bottom tip of the spring bump into a hard object. A gravel road works well.