I play with different educational manipulatives for a living. (Visit www.weirdrichard.com). I am using servo motors with various ft robotic projects. My boss asked me to demonstrate different ways to integrate an INEX servo motor with fischertechnik components.
One obvious solution would be to drill a hole in the servo's X-horn radial arm. With a larger hole, you could easily integrate elements with axles, studs, or rivets.
Examples at ftcommunity.com:
I decided for this project, I could not alter (no cutting or drilling) the servo or its X-horn arm.
There are two sets of issues. Integrating the servo into a frame, and transmitting turning action to a drive train.
Step 1: Integrating the Servo Into a Frame
(I have different servos laying around my office, and the holes seem to be ubiquitous in a variety of models).
I was able to fix the servo motor using assemblies of:
*Clip Axles/Clip 5s/Building Block 7.5s.
*Clip Axle 20s/Building Block 7.5s.
*Axle with Clips/Building Block 7.5s
*Struts and Plugs.
I noticed that the holes on a Parallax servo have an open side. Using this design, I could fix the motor using Rivets.
An example by stefanft:
(Also note: He alters a Cog Wheel to fit on the servo itself).
Step 2: Transmitting Motion
I removed the X-horn, and inserted a horn mounting screw. (Typically the radial arms are held in place with a small screw, but in this example the screw was missing. I used a screw from a Parallax servo). I was able to integrate a:
Using a longer screw, I would be able to mount a Building Block 15 with Counterbore, or a Flat Hub Collet and a Hub Nut (and a range of gear and cam elements) onto the servo.
Conclusion: You can integrate third party servo motors into original fischertechnik robots!