Iteration 1

Our first iteration was a basic Watt’s linkage made out of cardboard cutouts and plastic twist ties. The purpose of this iteration was to play around with ideas we found online.

Figure 1. Cardboard Watt's Linkage Model

We discovered from this that there will be challenges with joints colliding with each other, preventing full rotation. We ultimately decided to continue with the Watt’s linkage but proceed with a more stable iteration. To do this, we planned how each of the links would be connected to each other.

Figure 2. Linkage Connection Sketch

Iteration 2

With guidance from the TAs, we decided that bolts would make the assembly of the prototype easier. Now knowing how each of the links will be properly connected, we created a small laser-cut iteration of a Watt’s linkage. One solution we tried to explore was layering the links. To apply this solution to our mechanism, we created two of each link and assembled them incrementally inwards, ultimately sandwiching the output link. 

Figure 3. Basic Laser-Cut Iteration

Iteration 3

We discovered through this iteration that there would be collisions between the links and the grounds, preventing full rotation of the input and output links. This iteration ruled out the layering solution. Moving forward, we decided to try and find a solution through CAD. After many ideas, we found one that worked: creating two ternary links that rotated in parallel. The CAD for this design can be seen below.

Figure 4. Functional Prototype CAD - Isometric View

Figure 5. Functional Prototype CAD - Top View

By press fitting the ternary links onto a grounded shaft, the ternary links will rotate simultaneously, fulfilling the same purpose as one ternary link.