My Automobile Airspeed Indicator

Sometimes I wonder what is the airspeed of my van. You might think this is not that important. You might be right about that. But I DO drive a van (a Volkswagen Vanagon) with the aerodynamics of a barn door. So the airspeed affects my car more than it does most cars. And I think it is cool.


So I took apart a pager and removed the tiny electric motor that makes it vibrate. I pried off the weight that actually causes vibration to happen. Then I made a tiny propellor from a model airplane's propeller and some clear plastic. I made a mount for the motor from a small piece of plastic, and then I JBWelded the bracket to a clamp I made on my lathe. This bracket fastens to the Vanagon's antenna, which is right at the front of the van where it can catch a nice, steady stream of oncoming air. The coup-de-grace is the wiring for the motor. I had to drill through the motor mount to get a wire into reliable contact with the motor's case. The other wire is soldered to a screw that contacts the back of the motor.


I led the wires from the antenna through the driver's side wing vent window. From there, I alligator-clipped them to my voltage meter. I can watch the voltage go up on the voltmeter as the van's speed increases and the little generator catches air. It doesn't register much below 15 mph, and I imagine that it would fly apart above 80 or 90 mph. But the van doesn't go much faster than 80 mph.