Just a quick and dirty illustration of an idea I had for an electro-mechanical engine.

It uses a battery (A) just like a regular DC motor. A distributor (B) regulates the flow of electricity to contact points and into one of several Nitinol springs © which compress into a tight coil once an electric current is applied.

This in turn causes the spring to pull up on a rod (D) analogous to the pushrod in an internal combustion engine (though these function more by pulling than by pushing), thus turning the crankshaft. If you know how an internal combustion engine works the rest should be self-explanatory.

Nitinol is a fascinating alloy. It is a memory metal, which can be machined into a pre-determined shape. When bent out of shape, it can be returned to its original shape through the application of heat or electricity.

Nitinol exerts tremendous forces when it returns to its original shape; it is my hope that this design would actually use electricity more efficiently than a traditional brushless motor.

I'm not much of a fabricator and I can't find any documents on the life cycle of nitinol so I don't know how the cost of replacing the springs would be. I do know that Nitinol springs can be purchased online so all the parts should be reasonably easy to either make or buy.

Nitinol springs: http://www.motiondc.com/products/spring-products/82-nitinol-springs

A Nitinol engine developed in the 70s:
http://www.youtube.com/watch?v=oKmYqUSDch8