After choosing the Klann Linkage, we decided to put together some sketch models of of the legs.
This made CADing the linkage easier.
We used lego gears and hacked servos to drive the linkage. With only access to three servos in total, we decided to drive the crab with two of them. The front and back halves of the crab are controlled independently of one another, which gives in the ability to turn in a tank drive fashion.
This is the prototype laser cut out of delrin, and assembled with piano wire in the joints. The servos are mounted in a makeshift fashion in this iteration of development. In the next iteration we hope to add some strong servo mounts to hold the servos in line with the gears, and bring the plates holding the legs closer together to make the crab wider than it is deep.