This hip joint for walking robots can be used for metal geared servos. The other printed leg parts of the pictures can be found in the ancestor things: http://www.thingiverse.com/thing:53120 http://www.thingiverse.com/thing:51425At the moment I don't know how much weight this part can carry. If you see the printed part bending, then you can use the optional lower clamp part. I added a picture including the coxa part from tmbg's "3DOF Mini Quadruped" to compare the dimensions of my optional, experimental clamp version.Adjust the parameters using OpenSCAD for best performance. Then print the part with at least 3 perimeters.More details on surface melting: www.thingiverse.com/thing:51425 Make sure there is a small hole in the gear trap. Then heat up the inner surface with a torch tool and press a metal geared servo into that melted surface and the gear trap. To heat up the surface of the printed part I'm using an alcohol torch from Buffalo. You can squeeze that alcohol filled plastic bottle to have a tiny flame tip. Secure the servo with a screw. There should be no gap between the printed part and the servo's body. This heat method is not recommended with nylon geared servos. Resin may be a better way for nylon geared servos. Next step is to connect the leg to that printed coxa part. That end is used as a clamp and should sit very tight. Secure that end with another screw.The experimental version shows the coxa part together with an optional clamp part. Probably you will not need this clamp part. This clamp stl-file is for servos with a height of 27.5 mm.