|Mojo3 - printed leg covering original sketch
Side by side, the first printed parts are next to the original conception. The upper right piece is the 'leg'. The leg has a bearing in the top to transfer the weight of the robot. there is a 'control arm' that will connect to the servo. At the base are two connectors, that allow the 'arm' to move up and down. I call the connectors 'trap' - short for trapezoid, the shape created from the four fastened points. Finally, the 'arm' is made of the base, connected to the trap, and the fore-arm, which will touch the ground. The fore-arm can slide on arm-base. There is a spring in the fore-arm that will absorb some of the motion of the leg and ensure good ground contact.
|Mojo3 - Leg first draft print, next to original sketch.
Thinking about the next step of the development, there will need to be a 'Serial Elastic Actuator' (SEA). This SEA is basically a spring, that provides a 'compliance' with the ground, but allow for the arm to be pulled up, allowing for the leg to lift and be moved forward. (Here is a link to my previous designs SEA v5.)
From the design of the fore-arm, above, it occurred to me that there may be a simpler design option for the SEA. In essence, the fore-arm is a SEA. The next phase of design will have a new SEA that is attached from the arm-base to the hip of the leg. below you can see this new component in red on the CAD design. Let us see how this works.
|Mojo3 - potential new style of SEA