Filament reel tensioner

Filament reels have a nasty tendency to spontaneously unroll their contents, resulting in kinked, tangled and broken filament. After a number of 'air prints' I decided to design a tensioner device for my Makerbot Replicator 1 Dual. The principle is simple - apply a steady frictional force to the face of the reel, thereby preventing it from unrolling.

The OpenSCAD code allows customisation of the dimensions, adjustment of the number of springs (thereby varying the reel friction) and either a