Homemade Stirling Cycle Engine

Video found on my phone of a totally homemade (out of scrap tins and bits etc) Stirling engine, it has an alloy cast piston, which was cast in a tube and then machined primitively on a drill. It took a few lunch hours at work to make and is totally pointless but none the less worthy of a share. Satisfaction of it actually working is rewarding however! This is why I always Need a project, my mind wonders down some pretty pointless paths otherwise!