Read this:
http://www.fieldlines.com/story/2008/2/4/0350/64735
As wdyasq informed me, this would be a Rankine cycle engine, like a steam engine with a working fluid different than water.
I also recall a Do-It-Yourself (DIY) "Belize Butane engine" You might Google it to get some small scale ideas.
Best of luck. -Ron in 105F SoUtah
"Most people miss opportunities because it often comes dressed in overalls, and looks suspiciously like work" -Edison
