It really works! This is a working model of a Stirling Cycle Engine.  It is sometimes referred to as a heat engine or a hot air engine.  When the top is filled with ice water and tealight candles are placed under it, the engine will run for 10 to 15 minutes. The engine will stop when the ice melts or the candles burn out.

Almost all of the parts are 3D printed. Additional supplies needed will be two aluminum beverage cans (12 oz or 330 ml), 1.5 mm carbon rod (from your local hobby store or an online store), epoxy glue, and RTV silicone sealant. 

Looking for a smaller Stirling engine? Check out the Working Stirling Engine.

Here is video of the engine running:

Here is a video describing the engine: