A linear servo for HiTEC HS-645MG Ultra Torque metal gear servos capable of lifting ten pounds, with a 50mm reach. After searching thingiverse for a robust, 3D printable linear servo, I found several with very fine teeth which would not provide enough holding force and would require tight tolerances. Furthermore, the 3D-printed gears had nothing to prevent slipping on the servo axle. I designed my own last night using a HiTEC MG servo and created a gear with holes aligned to the HiTEC servo horns. It can work with any HiTEC servo of this size. The metal gears just make it stronger for robotics and less likely to wear out.
5-16-2017 Fixed three hole positions in the servo horn gear. The HiTEC Servo Horn Wheel has three rings of holes arranged in groups of three, ten degrees apart from nearest neighbors, at radial distances of 7mm, 8.5mm, and 10mm. Previous gear had only three holes in the 8.5mm radius ring and nine holes in the 10mm radius ring. Also added a bevel to the screw holes on the gear. Also added 1/8-in screw holes to the ends of the LINEAR ARM for more attachment options. I also widened the clearance for the gear in the fixture. Servo position may be adjusted by adding washers to servo mount screws if needed.
Added a square servo horn mounted gear. Most HiTEC servos come with a square horn (but not the HiTEC HS-645MG), simplifying the gear attachment to one screw.
Makerbot TrueBlack ABS at 230 degrees C, with Kapton tape over table at 110 degrees C