Simple Machines Toy Project

In the toy project, I worked with Kate Lee and Sara to build a cat car. We went through a lot of drafting and revision to get to our final product. Below your will find different artifacts from this project.


Project Proposal

.pdf version (Optimized for viewing)

.html version (Basic, no load time)


Process Photos


Group Bio

Eric Harmatz: Eric Harmatz has attended the COSMOS at UCSD during the Summer of 2008 to enrich his engineering/math/science skills. While there, he worked on electrical and software engineering in embedded systems and worked on the programming for a simulation of a traffic intersection.

Kate Lee Newcomb: Kate had an internship with SeaBotix over the summer in the Quality assurance lab, where she learned some basics about workshop, engineering and testing. She was even able to improve some of her analytical skills and knowledge through this experience. Through this internship her eyes were opened to the possibilities of the engineering field. She was also inspired to continue in her pursuit to go to college.

Sara Brant: Sara had an awesome summer vacation. She went to Camp Rock and learned how to surf, wake board and 14 miles mountain biking. She also did a hip hop performance at camp with her crew. She met so many amazing people and had a blast at camp! She did a dog walking business during the summer and went to the beach at Torrey Pines with her family and her friends. The last week of summer she went to a spa in Mexico, she played tennis, danced, did yoga, and other sports activities.


Brainstorm Drawings and Explanations

Click on each working drawings to view the High Resolution Version

Our orginal idea for the mice moving up and down.

Original idea for overview of cat car.

Propolsion system and overview of cat car.



The Mockup


Final Working Drawings

Click on each working drawings to view the High Resolution Version


The Prototype


Key Questions


Final Model Material List

* Approximately Two (2) 2 by 4 sheet of Birch Plywood

* 10 Thick Rubberbands

* 5-7 Bristles from Broom (for whiskers)

* Non-Toxic Paint (Orange/Black/Blue)

* Nails for the Nail Gun


The Final Model



Kate Lee's Reflection: Throughout this project, I have been tested through the creation of the mechanical toy. Some of the areas I have been tested are teamwork and cooperation, knowledge of simple machines as well as my resourcefulness. This has been a really great experience and it has helped me learn a lot about simple machines and how a few can create many outputs. I have also learned that great effort being put into a project will usually create an amazing product.

What I have learned through this project of simple machines I believe will benefit me in the future because I will be able to create better and cooler projects with the understanding of how things work. The reliability of our toy is high due to the limited number of parts used to create outputs. This was a change from our first design which had many pulleys and gears. Another thing that I think was important to understand was how to use power tools to effectively get a job done. Lastly, this project brought out and honed my project skills by challenging me so I had to rise to the challenge and use the skills.

Eric's Reflection: This project presented many hurdles for our group. We started off with the idea for a "Cat Car", which turned into a "Cat Train". I have learned the engineering design process and practical applications for the process. At the beginning of the process, I wanted to just go ahead and build our final wooden model, and then fix it from there. However, the design process dosen't work that way.

We started with a cardboard mockup, where I learned that I would have a serious problem in getting the tail to move. After the mockup, we worked on the prototype. The most important thing I learned during the working prototype is to always take into account the width of the blade when you are measuring wood to cut on a saw. That is why the prototype wasn't even. After the protoype, we totally revamped the idea and made one section instead of three.

Our final model works because of the engineering design process. If we wouldn't have gone through the steps, we wouldn't have caught the problems with the tail movement and propulsion. I will stick with this design process in my future engineering endeavours.

With regards to mechanics, I learned about gears, gear ratios, levers, and cams. I found out through trial and error that cams with small deviations of the curve don't work as well as bigger cams. I learned about gears and how to calculate gear ratios through our comprehensive quiz.

If I could change anything, I would have been more careful when doing the tail section to start so that we could expedite the final process and get everything done on time. Luckily, the deadlines were extended so that we were able to meet the revised deadline.

I am pleased with how our final project turned out and am excited that we got it done on time. I love how the paint job turned out and hope that the kid who gets our toy will appreciate it for years to come.

Sara's Reflection: One of the main points that I have learned from the cardboard mock-up was the size of our toy. It was a great visual perspective of our toy to give ourselves an idea of what we needed to work on. It also helped me with how to make the three outputs move our three objects.

During the working process, our group and I went through lots of critiques from cat train to a cat car model. From the working prototype, my group and I created pulleys to operate the mouse and the bottom mouth of the cat. We decided to use the car model for our final because we wanted to make the toy sturdy and durable for the kid who will play with the toy. Also, we wanted to make a simple mechanical toy to operate all of the three outputs. I learned how to make a triangular smooth cam, learned how to make a lever to move all of the three objects of our mouse, cat tail, and the tongue. It was a simple mechanical idea for our toy to operate our three outputs.

From this experience, I have learned how to make cams and pulleys for our toy. Another teaching technique was the gear and pulleys test which was to solve the equations.

The only thing that I would change would be painting the cat and the mouse more realistic.

I am very pleased that our group had put lots of effort into our working hours: during class, after school, during break and weekends to get our toy done. We all worked together as a great team.



The information presented on this Digital Porfolio represent Eric Harmatz. Any views, opinons, morals, and comments are property of Eric Harmatz and do not necessarily reflect the views of High Tech High or any of it's subsidiaries.