This Knex automata is based on a scotch yoke mechanism which is being used to operate Randlett's flapping bird. You can also use this to operate other moving origami pieces that are operated by pushing and pulling on the origami construction.
You can learn more about a scotch yoke at https://en.wikipedia.org/wiki/Scotch_yoke
Let me know what you think in the comments below and I hope you build it! Also check out my "Year of the Pig" origami automata at https://www.instructables.com/id/Knex-Origami-Automata/
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Step 1: Here Are the Parts You Need
Step 2: Build the Origami Support Frame
Step 3: Build Motor Cage
Starting in this step and through the following steps, we're building the motor, shaft, and yoke assembly starting at the bottom and working our way up, installing one layer on top of the other.
Step 4: Build and Install the Motor Shaft
Construct the motor shaft using a red rod and two purple clips. Install the shaft by pushing it all the way through the K'nex motor and into the bottom white connector. Finally, push the lower purple clip so that it rests against the bottom motor assembly as shown.
Step 5: Build and Install the Shaft Support
After building and installing the shaft support as shown, adjust the upper purple clip of the motor shaft so that it rests against the upper white connector.
Step 6: Build and Install the Crank
Step 7: Build and Install the Scotch Yoke
In building the scotch yoke assembly, notice that the grey connector rod is going through the holes of two red connectors. Also notice that three purple clips will clip onto the grey connector rod. In contrast, the bottom red connector rod goes through the holes of its two purple clips. The straight orange connectors also clip onto the grey connector rod. In this way, the yoke can slide back and forth on the red connector rod but moves the grey connector rod.
When installing the scotch yoke onto the motor assembly, the crank pin (blue connector rod from the previous step) should feed through the yoke as shown.
Step 8: Add Support Feet to the End of the Motor/Yoke Assembly
Step 9: Attach the Motor/Yoke Assembly to the Origami Support Frame
Step 10: Attach Origami Flapping Bird to the Origami Support Frame
Use tape to affix the origami bird to the two purple clips as shown.
Step 11: And We're Done!
Please share with me any other ways that you find to use this build. Also, please feel free to suggest any improvements. Again, hope you have fun building this.