Strandbeest

This is a slight remix of @nraynaud's Strandbeest Robot. This one differs primarily in that it was designed to be a semi-autonomous using basic obstacle avoidance running an Arduino Mega and various sensors. Differences from the original: 1. The connector is 20% wider in order to make room for the updated battery holder. 2. The battery holder was redesigned from scratch in Wings 3D in order to allow mounting of an Arduino Mega to the underside and a custom proto board holding the sensors to the top. It was also redesigned to house 4 x 603450 batteries (2 pairs in series to provide 7.4v). A dovetail connection was added to the front in order to mount an IR sensor as it was too wide to pass through the connector opening. Also pre-cut a hole in the front to mount a 9g servo. The sonar holder screws into it for 180 deg distance detection. 3. IR mount for a Sharp GP2Y0A02YK0F (sparkfun.com). 4. Sonar holder for a HC-SR04 (generic). 5. 2 holes in the rear for dpdt switches. 1 switch controls the vin from the batteries to the arduino and the other breaks the ground to the motors. In this way, I could still work on the code and not have it trying to crawl off the table. Notes on the build: 1. Wow. This was my first 3D print project and my first robotics project. I will say this. You had better have a LOT of patience or a LOT of determination. I had the latter. 2. I'm guessing that the number of bearing this thing requires has turned a lot of people off to making it. Yes, there's about $30.00 worth of 3x7x3mm bearings in there. The biggest issue I'm having is getting them to both fit and not keep popping out. In some cases I had to heat them up with the soldering iron and press them into place. 3. I decided on brass for the hardware. This created a problem as @nraynaud's design called for flat sided threaded bolts and/or rods. Apparently these just don't exist is brass so I had to get creative. And it seems that 25mm M3 screws don't exist either. In the case of the cranks, I