Using 10 old school MG995 servomotors, I have designed and build a 10 degrees of freedom bipedal gait in order to study humanoid-like walking, running and jumping algorithms for robots and push it to the next level.
I started with the design of a 3D printable holder for the MG995 servomotor aiming at two goals :
1) rendering MG995 rotation axis more robust.
2) enabling the easy creation of fully-actuated joint chain thanks to an innovative assembly design using only one screw per joint. Its solidity is due to the sliding fixation.
Next step is to assemble two legs and join them to a body parts which contains a power electronic board and a Raspberry Pi to drive the servomotors.
I hope you'll be able to use it and learn a lot on robotics with it.
Step 1: What You'll Need :
1) 10 MG995 servomotors ( maybe these ones : http://www.amazon.com/Tower-Pro-MG995-Metal-Torqu... )
2) a 3D printer in order to print those models that you'll required to build your HaRo.
3) 10 STHC (PLAT) M3x10 screws in order to fixe the joints. And obviously a screwdriver in accordance.
4) 10 screws that fit in the MG995 servo attach (delivered with the servos, usually).
5) servomotor extension wire cable ( that you can bought here : http://www.amazon.com/Leegoal-10pcs-320mm-Servo-E... or do them yourself)
6) a Raspberry Pi board (with WiringPi installed : https://projects.drogon.net/raspberry-pi/wiringpi... or any other piece of software that would enable you to use PWMs on your Pi ) or any other microcontrollers with which you'll be able to drive your servomotors.
7) something to power your servomotors with the required 6V, maybe 2 to 3 LiPo batteries.
Finally, this bipedal robot may cost you not more than 100$, accounting for all of the above including the 3D printed parts (given that you only pay for the materials...).
Step 2: What Is to Be 3D Printed ?
Thanksfully, almost everything :).
Here is the list :
1) 2 foot, one right ( PiedSupportBasPivotAxeColinearRight.stl) and one left ( PiedSupportBasPivotAxeColinearLeft.stl ).
2) 4 90 degrees joints ( the one that suits you the most between those two : joint2xMotorDiff90Deg.stl and joint2xMotorDiff90DegTHICKER.stl, given that this last one is thicker in the middle so that you'll be able to cut it in the middle while generating your gcode on CURA, for instance, and thus you'll have to print two of those cutted parts and then glue them together with the 90 degrees angle. That way, the part will be easy to print for your 3D printer, without any sopport prints of any sort ).
3) 4 lower parts of the servo holder ( SupportBasMG995v5.stl ).
4) 2 lower parts of the servo holder with the inverted fixation system ( SupportBasMG995v5INV.stl ).
5) 2 upper parts of the servo holder ( SupporHautsMG995v6.2.stl ).
6) You may want to 3D print a body part that will be able to assemble nicely your two robotic legs... Coming soon...
Once they have all been 3D printed, you'll intuitively find how to assemble all those things.
You'll just have to use some screws here and there between the 3D printed parts that compose the joints and between the servomotors' attach and the lower part of the servo holder.
And that's it, you're done.
Have FUN !