If you have no data on the anemometer, you will have to calibrate it somehow, in order to actually measure wind speed.
Strap it to your roof racks and go for a drive? Seems the easiest way to me if you don't have another callibrated sensor handy to compare with.
A hand drill would be easier
How do you work out wind speed from there if there's no easy way to correlate wind speed with RPM (from mauried's observation, above)? In the car you have your speedo, so I figured on a still day any RPM in the anemometer while driving at a constant speed on a straight road is directly relatable to the road speed?