This is a device to test bicycle hub dynamos/generators and its respective electrical loads. This way you can test bicycle lights and phone chargers while respecting the real live characteristics of the dynamo.

Hardware required:

• DC motor (when using a smaller one, use one with attached gearbox, something like 5:1 to 10:1)

• Bicycle hub dynamo

• GT2 closed loop belt with 2mm pitch, 400 mm total length, 6 mm width

• M5x10mm bolt + nut for the motor sled

• 2x M2x10mm bolt + nuts to fix the pulley to the hub

• 2x M3x10mm bolt + nuts to fix the small pulley to the motor.

• Lead weights to increase the moment of inertia of the dynamo

• Rubber band to fix the motor to the holder

Customizing the Freecad file:

• Change VarSet -> motor_diameter to fit your motor

• Set VarSet -> hub_number_spokes to 32 or 36 according to your hub

• Change VarSet -> pulley_generator_spokehole_dist to the distance of the spokeholes to the center of the hub

• Change VarSet -> pulley_generator_inner_big_diameter and pulley_generator_inner_small_diameter according to you hub dynamo

• change VarSet -> motor_transmission_offset to change the distance motor face - side clamp, or:

  • measure the "distance motor face - pulley inside face" and add 23 mm to get the motor_transmission_offset

Customizing the small pulley with openscad (hub_holder_pulley_motor.scad):

• change the motor_shaft to fit your motor shaft diameter

Adding weight to the hub

• Due the high cogging torque of some hub dynamos it doesn't really run smooth (5 Ohms resistor at with 3V on the motor):

• The moment of inertia can be increased by adding weights to the hub to have a smoother run and respecting real live physics

• I haven't tried that yet

Inspirations:

https://fahrradbeleuchtung-info.de/helligkeitsmessung-von-fahrradlampen (in German)

https://fahrradzukunft.de/22/steckdose-unterwegs-5 (in German)

http://www.enhydralutris.de/Fahrrad/Beleuchtung/node350.html (in German)

http://www.enhydralutris.de/Fahrrad/Beleuchtung/Beleuchtung.html (in German)