How I built a hot air engine almost entirely from junk. I've wanted to build one of these ever since discovering stirling engines in about 2003. Spending the weekend making things in Steveastrouk's workshop gave me the opportunity to make the precision parts I'd need, and I knew most of the engine was going to be made of improvised materials, so decided to see if I could make the entire thing out of scrap or unwanted materials.
If you aren't familiar with how Stirling engines work, there are plenty of resources online- the Wikipedia page
is a good place to start.