Customized version of http://www.thingiverse.com/thing:16627

Created with Customizer! http://www.thingiverse.com/apps/customizer/run?thing_id=16627

Using the following options:

nut_shaft_distance = 1.2
m3_nut_flats = 5.7
motor_shaft = 12
additional_tooth_width = 0.2
m3_nut_hex = 1
retainer_ht = 1.5
teeth = 20
idler_ht = 1.5
profile = 3
additional_tooth_depth = 0
pulley_b_dia = 30
idler = 1.5
retainer = 1.5
no_of_nuts = 2
m3_dia = 3.2
nut_angle = 120
m3_nut_depth = 2.7
pulley_b_ht = 8
pulley_t_ht = 10