Measure the wind, a 3D printed anemometer

Finally we know what Sherlock Holmes was carrying around all the time… it was an anemometer, the picture clearly proves that. With the smoke of his pipe he determined the precise direction of the wind to make an accurate velocity measurement.

Whatever how you want to catch the wind, it might be handy to be able to measure its strength.

This contribution has three printed parts and a small DC motor. When the shaft of the motor is rotated, no resistance by internal magnets should be felt. Except for small PC fans (where magnetic resistance is clearly felt), most of the smaller DC motors are O.K.
Test the motor with the fan by blowing and checking the voltage.
It will probably read about 1.5 Volts.
The distance of the mounting holes for the motor can be chanced in the Open SCAD file at the indicated place.

Rather than implementing electronics, which would bring this gadget out of reach for most of us, it has the two motor wires connected to a universal meter.

Calibration.
Ready for calibration? Get in the car, hold the instrument outside the window and ask the driver to call out the speed. Note the speed and the voltage. Do this for a variation of velocities but make sure that you respect the speed limits. At home, the values are plotted in Excel to give you a perfect calibration curve. Don't expect a straight line, DC motors generally show an S-curve.

Tip for use: Who blows 35 km/hr at a party of your kids.