Cat and Pinion
Yesterday, our rack and pinion project was due for my EED 111 course. The purpose of our rack and pinion project was to introduce us to the concept of translating rotary motion to linear motion. This motion can then be applied to later projects in the course and in the future.
All the groups presented their rack and pinion with their own unique twist. For my group and I’s rack and pinion we made a CAT and pinion ;). We were inspired by another students project where they designed a rack and pinion that, when in motion, looked like a lobster claw opening and closing. Unfortunately, I didn’t save the website and can’t share it with you here. Our group wanted to do the same concept but with a cat wagging its tail.

The first step I took towards designing this project was getting the gear and rack. I used an online gear generator to give me a gear and rack dwg file that I could then open in AutoCAD. From here, I downloaded a cat silhouette image from google and imported it into the same dwg file. I used the spline tool to then trace the outline of the cat. Then, I moved the image to the side and separated the tail from the body of the cat. The silhouette of the cat’s body would act as a sort of cheek that would sandwich the gear to the rack and keep it together where as the tail would be on the gear. These cheeks have half inch dowels at the bottom, middle, and top of the cat.
At first we were only going to do the cat design, but Mike (our professor) suggested to put in a mouse element. So my partner, Nikko, chose a mouse silhouette and used the same spline tool to trace the image. We figured it made the most sense to just add the mouse to the rack so there were less pieces to glue together.

We used the laser machine in the UNLV Library’s makerspace. It worked pretty well. However, the wood most likely had some knots in it because the machine wasn’t able to cut out all of our pieces completely. Once the machine finished cutting, Nikko had to go back and cut some pieces out.
We used quarter inch plywood that we had to buy from the makerspace (the makerspace doesn’t let you bring your own materials to cut in the laser machine). We then used two layers glued together for both the gear and the rack. This gave the design a bit more strength and ensures that it wouldn’t be as “floppy”. (We had that issue with our last project…)
Overall I am super proud of our working cat and pinion. You are able to move it either by rotating the tail or pulling the rack. It came out very cute and our classmates and professor really enjoyed it.
Even though the assignment has already been turned in, I still want to improve it a bit. For example, because of the dowel through the cat’s head, the tail isn’t about to ‘wag’ or rotate more, bringing the cat closer to the mouse. This could be fixed just by the placement of the starting position of the gear. Another thing I may try is changing the tail design to not be as long or find a different way to stabilize the head of the cat without using a dowel.

