I am looking to build a wind turbine to produce energy with an alternator from a truck as the power plant. Now, I know that the alternator needs to normally spin 2X to 3X the speed of the motor, but is there a way that any of you guys know how to make is so I'm producing 12V of power with significantly lower RPM's? Any suggestions? Input? I was thinking of making some sort of makeshift transmission, using a large gear behind the turbine, and gearing it down to a smaller one, and getting smaller to the alternator. But then I get to the question, will the wind and blade combination be enough to move the gears? Just a hobby project, no rush.

 

Keep in mind my only experience is college level physics, but my concern would be that if you geared it up to spin the alternator faster, that would increase the torque required to turn the blades. A pully and belt arrangement might provide less resistance and require less maintainence than a gearbox, also may be easier to assemble.
But the best way to know is to try it an find out. Sounds like a fun project.