Project Overview  |  Proof of Concept  |  Final Design  |  Fabrication  |  Testing and Results  |  Meet the Team  |  Acknowledgements

Project Overview

The Cart Stopper is a device aiming to solve a common, and potentially costly, problem the average shopper has when unloading a cart. Whether it be the weather or the slope of the parking lot, Carts are often found drifting away from us once it is too late to act, likely to be aiming straight for one of many cars in its vicinity.

The Cart Stopper is a handy tool that will keep carts of varying sizes immobile and stable, while the user unloads their cart into their vehicle. The Cart Stopper is a circular device no more than 8 inches in diameter that is meant to be quick to use, clean, and store for later use, while adding no additional safety hazards to the shopping experience. The cart stopper also has the ability to be used with a variety of cart shapes and sizes, making it a useful tool for utility carts as well.

This project belongs to the consumer industry, specifically targeted towards the physical shopping experience involving a store front. The competition in this industry is extremely marginal, but does include some contenders. Caster wheel locks and some patents for shopping cart locks are called out in our patent search. Considering that there is practically no competition in this field only ones that are semi similar, we have determined that we are ready to enter this market.


Proof of Concept

A device that would prevent a shopping cart from wandering off in the parking lot would be beneficial. Not only would the device help keep the cart in one spot for ease of use of the cart, but it could also prevent damage to cars. This device would need to fit many cart styles for each stores cart type. It would need to support the load from the cart under high winds, and high slopes with heavy weight within the cart. Not only would the device have to be strong, but it must also be light and usable enough for anyone that uses a shopping cart and a car. The system that is used to secure the shopping cart must require less than five instructional steps and be able to secure the cart in less than a minute. The purpose of this device is to prevent damage that the cart inflicts upon parked cars.


Final design

In shopping centers across the United States, customers must unload their shopping carts while also keeping the carts stationary by themselves. For a variety of reasons, a significant number of shopping cart related claims are reported yearly to insurance companies. Abandoned carts left in parking lots by customers after being used along with uneven parking lots are some of the attributing factors to this damage related dilemma. This results in expenses to the both the insurance company in combination with the store in the form of damaged carts, damaged customer property, man hours required to resolve the situation, an extreme inconvenience to the customer and law suits from customers whose cars are damaged by free carts. This Project is an add-on silicone-rubber Flat-top-cone shape mechanism by which allows the costumer to conveniently unload their products from the shopping cart with complete immobilization along with a worry-free mentality in which their shopping cart will remain stable until they no longer require it. This device would utilize the existing consumer-based shopping cart design platform without any additional add-on parts. Instead, this product is designed for the consumers convenience where the neglect of a brake or damaged shopping carts stability will no longer be an issue.




For the fabrication process, making a cast mold would allow for simple recreation of the cart stopper. Plaster is an ideal material for this project as it has extremely malleable properties in its unhardened (semi-liquid) shape and can withstand very high heat when dry. Therefore, making this the ideal process to produce our product. Below are the steps entailed in the production process of the cast.

  • Step 1: Materials:
    • 3D Printed Cart Stopper (Desired duplicated Object)
    • Plaster of Paris
    • Water
    • Hot glue stick
    • Sealant
    • Molding Clay
    • Mold Release
    • Plastic container for mixing
    • Plastic container for mold
  • Step 2: Constructing the mold perimeter.
  • Step 3: Using the clay, create a base layer to set object.
  • Step 4: Generously apply mold release to the object and firmly press into clay base.
  • Step 5: Mix the Plaster of Paris and Water mixture, then pour into mold.
  • Step 6: Let cure.
  • Step 7: Apply sealant to cast.


Next, you will find the steps needed to replicate the production model of the final design cart stopper.

  • Step 1: Materials:
    • 100% Silicone Type 1
    • Mold Release
    • Caulking Gun
  • Step 2: Apply mold release into cast indentation.
  • Step 3: Pour silicone into cast carefully avoiding air bubbles.
  • Step 4: Allow time to cure.
  • Step 5: Remove Cart stopper from cast
  • Step 6: Remove excess material from cast mold.


Testing and Results

Final Test Trial – Cart Stopper


  1. Test your product and include the results.
  2. Discuss your test plan.
    • The test plan for Team 3 was to use the product varying the amount of weight in the shopping cart from empty up to 200 pounds in increments of 50 pounds at a time starting the max grade of 10%. The testing criteria similar to how we tested the proof of concept, with the only difference in the PoC was the horseshoe was tested up to 17% grade.  After researching common slopes around the United States we found not many roads exceeded at 10% grade, which is why Team 3 chose that value to be the max grade.


  1. How did you test your product?
    • Our product was attempted to be tested to failure but over 10% grade with 200 pounds our product did not fail, which is an extreme grade not likely found anywhere in a parking lot. In a hardware store, we recreated a 10% grade, loaded the cart with varying amounts of sandbags. We tested up to a 200 pound load, in 50 pound increments, with the cart being stable and agitated.


  1. How many times did your team test the product?
    • The Cart Stopper was tested a total of seven times. Team 3 set up a ramp that exceeds the maximum slope one would encounter in a parking lot.  The testing was done with an empty cart to fully loaded cart at a 10% grade, with weight increments of 50 pounds at a time.  Once an additional 50 pounds was added from the previous test, a team member would bump into the cart to make sure it held.


  1. Did it do what it was designed to do?
    • Yes the product was able to hold a loaded, standard shopping cart stable. The product will hold the cart in place even if moderately bumped into.


  1. Did it fail to do what it was supposed to do at any time in your testing?
    • No, our product did not fail. Held steady at every test weight interval.
  2. If your product failed a test explain why it failed and how did your team come up with a fix.
    • N/A


  1. What problem does your product solve? How is it going to make things easier for users?
    • Stabilize a shopping cart for customers convenience. This product allows for effortless stability once cart is placed in the center.


  1. How do users feel about this product?
    • They love it! Highly anticipated. Team 3 noticed many parents found this product useful, and during innovation day there were multiple parents who wanted to buy the product to be sure their kids while unlocking the car to put the kids into the car.


  1. Does the products design match its purpose?
    • Yes

Testing Notes:


Trial Number Weight (lbs) Did it hold?



0 w/ bump




50 w/ bump




100 w/ bump




150w/ bump

9 200 Y
10 200 w/ bump Y



Meet the Team



 Reuben Thomas Osofsky is a Senior Mechanical Engineering student at the University of Nevada, Reno. Born and raised in the California Bay Area. Reuben will be graduating the Spring of 2018 with a Bachelor’s of Science in Mechanical Engineering. Reuben is currently working as a Mechanical Engineer at Orbis Technologies, and upon graduation plans on continuing his career with Orbis or taking a job offer with Royal Dutch Shell Global.





Owen has worked for a drone delivery company for the last three years, where he leads manufacturing and engineering integration, as well as product testing. The most challenging engineering problem that he has been a part of is successfully making the first FAA approved drone delivery on American soil. He has applied my ability to use analytical techniques during the construction of this drone, which can carry a payload for miles and able to deliver it to a very specific GPS location. This drone is now housed in the Smithsonian National Air and Space Museum. Owen has lived many places including New Mexico, Arizona, and South America. He moved 11 times before ending up in Reno 8 years ago. Owen’s plans after graduation are to continue working with his current employer on pushing the limits of drone delivery. Eventually, he will come back to school for a masters in business administration.




Garrett Forman is a senior at the University of Nevada, Reno working on his Bachelors in Mechanical Engineering. He also has completed two minors, one in business administration and one in mathematics. Throughout his college career, he has performed well in a team setting as his group took first place in the hovercraft competition freshman year. Garrett excelled in the topics of thermodynamics and manufacturing process. He designed a spin top that could spin for upwards of eight minutes in his manufacturing processes class. Garrett is the treasurer of NRAP, a club on campus, and has done numerous volunteer projects throughout his years at the University of Nevada, Reno. Garrett has had multiple internships while working on his degree. One of the internships Garrett had was with Enel Green Power North America. He worked as a geothermal engineer and ran efficiency testing on the geothermal power plant. He used his skills in thermodynamics to improve the plant’s efficiency throughout the hot summer months. Garrett is from Danville, California; a town in the San Francisco Bay Area. Garrett plans to use his mechanical engineering degree to go into the field of renewable energy. He is passionate about improving the energy crisis facing this country.


Ryaan is a Mechanical engineering student, currently completing his final year of studies at the University of Nevada, Reno. Although he was born and raised in the San Francisco Bay Area, Ryaan spent his high school years in Dubai, UAE. Having shown great interest in the future of the automobile, he would like to pursue a career in the automotive industry, working towards cleaner and more efficient commuter vehicles. He spent a summer in a town outside of Paris, called Grigny, working for France Craft, a French electric vehicle manufacturer, assembling, testing, and maintaining street-legal electric vehicles.






Matt Crispino was born and raised in Reno, Nevada.  The toughest part of perusing a mechanical engineering degree has been understanding the material then completing all assignments and turning them in on time for each class while staying prepared for test and quizzes.  Another challenging but rewarding aspect has been learning how to use certain computer programs such as Matlab and Solid Works.  Accomplishing so much in school has given confidence to be able to find resources to solve problems, such as fixing something that broke around the house whether it be a television, vacuum or washing machine.  Current goals include finishing college career, finding an internship, staying active and healthy, and making money to be able to travel. After graduation goals consist of traveling, finishing a build on a project car and finding a prospering career with a prestigious company.