About this 3D model

This is a drop in replacement for the Ultimaker, though it should prove useful on other printers with belts with an X/Y moving head, such as the makerbot (it is all parametric: belt, rods, bushing etc) It also embeds a novel and precise belt tensioner thanks to a sliding banana. No? Really! Just have a look at the "exploded" STL view to know why! Nb: these are for the Ultimaker gantry rods, so 6mm for the two central rods, 8 mm for the outer with a bushing of ~11mm (outside diameter). But the source can be adapted to other diameters (probably not smaller though).