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The basic idea was to build an interaction with Redstone.
One uses the generally known motor (http://www.minecraft-bauideen.de/332-Motor) and connects it with two pistons, one of which is inverted with a Redstone flare. Then one builds, as in the picture several pistons (or lamps) connected against each other. 
Here's also a simpler variation that I didn't think of until afterwards.
I don't really see the point, though.
Something similar I once built a ship to generate "engine noises". Was already very cool and has brought in some atmo.
I've done this with trucks that go back and forth all the time...
What's the point?
Engine sounds pretty cool
100% Pointless..
and the gearshift sucks too..
Beautiful computer, calculator, everything there ....but a circuit where a piston goes up and down is not feasible ..... .