Customized version of http://www.thingiverse.com/thing:1812136

Created with Customizer! http://www.thingiverse.com/apps/customizer/run?thing_id=1812136

Using the following options:

toothed_part_length = 6
base_diameter = 20
belt_retainer = 1
number_of_teeth = 72
retainer_height = 1
motor_shaft_diameter = 5
belt_idler = 1
nut_shape = 1
screws_disposition = 2
screw_profile = 4
idler_height = 1
profile = 14
base_height = 8
nut_shaft_distance = 1.2