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:
retainer_height = 1
motor_shaft_diameter = 5
base_diameter = 20
idler_height = 1
nut_shaft_distance = 1.2
screws_disposition = 2
base_height = 8
belt_retainer = 1
nut_shape = 1
profile = 14
toothed_part_length = 6
number_of_teeth = 18
belt_idler = 1
screw_profile = 4