Servo horn extension for 18T

Strong servo horn extensions that fit over typical 18T aluminum servo horns that come with many common larger (80kg) servos like the DS5180.

I designed this to maintain the strength of the metal spline connection (keeping the aluminum, rather than relying on printed plastic) while providing a long extension.

Arm radii (distance from center of hub to each linkage hole):
52mm, 60mm, 68mm

Thickness of the arm is 8mm. The "recessed" version is recessed on the bottom around the linkage holes. Recess depth is 4mm, so plastic thickness there is 4mm, recess is 4mm, overall height is still 8mm.

Hole sizes: all holes are M3. I've left them a bit tight in case you want to thread into the plastic.

I printed with

• 1.5mm layers
• 1.2mm walls, i.e. 3 walls at 0.4mm
• gyroid infill at 30%
  and they're quite strong and stiff. Increase wall thickness and/or infill percentage to increase strength.

Similar extension for 25T size can be found here:
https://www.thingiverse.com/thing:6750263