Customized version of http://www.thingiverse.com/thing:1705366

Created with Customizer! http://www.thingiverse.com/apps/customizer/run?thing_id=1705366

Using the following options:

gear_thickness_multiplier = .75
pressure_angle = 30
rim_width = 5
gear_twist = 100
teeth = 48
circular_pitch = 500
double_gear_yes_or_no = yes
holes = 6
height = 20
bore_diameter = 30
hub_height_multiplier = 3
hub_diameter = 50
clearance = 0.2