A OpenSCAD model of 5V 4-phase 5-wire geared stepper motor 28BYJ-48, remix of http://www.thingiverse.com/thing:204734 with most dimensions using named variables, taken from measurements of a specific sample, and also some small details added (wires, and top flange protrusions). You can read more about this stepper motor at http://arduino-info.wikispaces.com/SmallSteppers***Measurements taken from this particular device: http://www.amazon.com/gp/product/B00DUSYEWY/