

Super-Efficient Free-Piston Engines Could Replace Traditional Gas and Diesel Engines - MikeCapone
http://www.treehugger.com/files/2008/10/free-piston-engines-efficient-plug-in-hybrid-cars-electric.php

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DabAsteroid
Here is the original article:

<http://www.technologyreview.com/energy/21442>

Caption: _Piston power: In an unconventional engine design, a rod with a
piston at either end shuttles between two combustion chambers. Magnets at the
center of the rod move past metal coils (orange) to create an electrical
current._

I usually call these crankless engines.

    
    
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_Free-piston engines aren't new: they were invented in the 1920s. But the
increased recent focus on hybrid cars has led a growing number of research
groups and automakers to start research programs to develop the technology.
Unlike in conventional engines, there is no mechanical connection between the
piston and a crankshaft (hence the name free-piston). Since the design allows
for improved combustion and less friction, the engines could be far more
efficient in generating electricity than either conventional generators or
newer fuel-cell technology._

