After the zombie apocalypse, survivors found themselves forced to return to a 19th century lifestyle which relied on such items as brass, leather, wood and steam power. The Steampunk lifestyle is now the only way to survive.
You don't know what steampunk is? Check your pulse. No pulse? But you can still read this? That means... oh my God! You're a ZOMBIE!
The Stirling Engine
(An alternative to steam power)
Although steam power is the engine of choice for steampunk, the stirling engine is an alternative form of power that is consistent with the steampunk concept. Invented in 1816, it is an idea nearly as old as the steam engine. While steam engines use steam to move a piston, a stirling engine uses a temperature differential between two cylinders to drive two pistons. Do an internet search for "stirling engines" and you can learn a lot about them. Wikipedia has a fairly good article explaining them. Also, while you probably would not try building a steam engine at home, a stirling engine (at least a small one for show) can easily be built out of items you probably already have laying around the house. YouTube has a lot of videos showing stirling engines that people have built at home.
This discussion about stirling engines is not intended in any way to downplay steam engines, but simply to make the reader aware of at least one alternative type of engine that seems to fit into the steampunk universe.
ConTemporal 2013 - Steampunk Convention