parameterised fan hinge for 'Print Cooling Fan System for MakerFarm Prusa i3 and i3v'

I have a J-head on a makerfarm Prusa i3 8" - the fan duct from http://www.thingiverse.com/thing:351280 looked perfect, so I printed it, only to find out that the fan shroud would hit the build plate. Instead of modifying the fan shroud, I decided to redesign the fan bracket in OpenSCAD, as it would make it easy to customize it again when the need arises.

I printed it at:
- 0.4mm layer height
- 3 perimeters
- 1 top, bottom solid layers
- 20% rectilinear infill
- no support material