Zoidberg : First Parts

I have wanted to build a quadruped robot for a long time. I have done a number of different simpler hex configurations for fighting robots, but nothing higher than 2DOF. I had started planning many times based on hobby servos, and I have a rather large box of them from other projects, but their inherent shortcomings for robot use made me think twice about spending the money on ones suitable for the design I wanted. I considered modding my own with better control and position sensing, but scrapped that as well due to time and cost. Then I found out about the Robotis MX line of servos  It was pretty much the servo I would build, only someone else has already done the work for me. 

Zoidberg will be a 3DOF quad using MX28's. I have worked out an initial design for the legs, and I'm still tweaking the body and frame design. Control will initially be an Arbotix board with XBEE's. I want to set up a PS3 controllers with my laptop and an XBEE to send commands, still looking through what exactly I need to do this. Future goals include getting some type of vision system working on it with landmark assisted navigation.

Here is the design for the coxa of the robot.  It is an assembly of 5 parts, the center plate and 4 identical arms which bolt to the center plate.  I will begin with the arms.  There are more of them than any other single part in the robot.  

To begin with, I squared up the stock and brought it to an overall thickness of 6mm.  I used 1/4" thick nominal aluminum extrusion, which allowed me to take a few thousandths off each side.  

Indicating the center of the part.  I like to work from the center as it allows me to keep everything even throughout the machining process.  The first feature put into the parts will be the tapped holes that bolt everything together.  It's easiest to do this now while the whole part is square rather than later on when more stock is removed.  

 

Here we are all drilled and tapped.