We picked the Whitworth quick return mechanism as the mechanism to drive the retracting claw we wanted to implement for the project. For the first hands on project, we 3-D printed a crude model of our Whitworth quick return mechanism prototype to simulate the pull motion of the climber robot. To get determine the proper link lengths for our mechanism, we used the sketch feature in SolidWorks. Setting relevant constraints for each link allowed us to model and visualize the motion of the mechanism in Figure 1. Once we nailed down these link dimensions, we then created part files for each link that referenced this sketch.

Figure 1. Reference Sketch

Prototype

For our initial prototype, we designed a double-sided Whitworth return mechanism that allows for alternating retracting motion. In terms of independent movement, we intend to attach a motor onto the center gear to spin the rotating arms.

Figure 2. Prototype 1

Kinematic Analysis

Whitworth quick return Mechanism - The Whitworth quick return mechanism is a six bar mechanism designed to change rotary motion into reciprocating motion. This mechanism was chosen because of its cyclical motion and was very main component of our robot’s arms. Below in Figure 3 is a picture of a quick-return mechanism showing the motion of it.

Figure 3. Whitworth-Quick Return Mechanism

Mechanical Engineering. (n.d). Quick return mechanism. Retrieved December 4, 2016 from http://mechanical-engg.com/gallery/image/800-quick-return-mechanism/

We ended up using two quick-return mechanisms to model the alternating motion of the arms grabbing the rungs to move itself upward. In Figure 4, the kinematic analysis of one of the return mechanisms is shown, detailing the motion of the driving bar and the resulting motion of the arm moving forward as well a Table of some of its values.

Figure 4. Kinematic Analysis: Position vs Input Angle

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