Auto Parts: alternator, alternator pulley, fan blade

Question
I am doing a science fair project on wind on a car.  We decided to test this by putting a fan blade on to an alternator.  The fan blade spins fast enough but we cannot get a reading in amps or volts.  We have tried various ways of hooking up the alternator to a volt/amp meter but nothing seems to work.  We also tried hooking it up to a light and a battery to get the electricity flowing.  The alternator has been tested and it works fine.  If you have any suggestions on what I am doing wrong or some way to hook up the alternator please share.

Answer
Hi John,

You need to gear-down the fan blade to have the alternator pulley spin faster. Most alternators need a 'kick' to about 3000RPM before they begin to create power which is why most fuel-injected vehicles have a quick 'rev' before the engine idle stabilizes. It's actually more complex than that, but if you are doing experiments, I'll let you find your own results. In my opinion however, you would be better served in your experiment with an older style generator and regulator assembly instead of the IC regulator in the alternator you have. A generator makes power no matter how fast it is spinning. An alternator can ONLY produce voltage on a 12volt system whereas a generator starts below 1 volt and will work to about 25volts (DC) and not have a problem with rotational speed. I also suspect that if or when you do get that alternator to spin fast enough to produce power that it will be extremely short-lived. Once the alternator starts creating power, the magnetic field it will be producing will draw-down way too fast for wind-power to compensate for. An alternator producing 10amps will require nearly 2-horsepower to sustain it's output. I'm guessing that wind-power will be fractional in comparison which is why a generator and external regulator would be your best equipment to test with.

Thanks for the question, I hope this information is helpful to you.
Kb