Ok, thanx to Ignoblegnome idea I have done my 360° servo
First i started cutting pieces of PVC, i took a bunch of screw and nuts in order to build the frame for my superservo...
but suddenly Gareth appears in my mind and say: "Use the polymorph Luke..." :O
yeah right, very easy, 10 minutes of work and it's done, very sturdy and precice.
Now i can sweep my sensor in 360° :D