— PROJECT NAME
ChickenClip
— ROLE
3D Design
Prototyping
— DATE
4. 2. 2023 -
6. 6. 2023
The Problem: We carry our backpacks everywhere, but placing them on the floor gathers dirt, bacteria and other health hazards.
In fact, our everyday backpacks can have as many germs as public bathroom floors!
So, we created ChickenClip to fix this problem, and keep our bags off the floor, without crowding public spaces. Keep scrolling to the process behind this sleek, efficient and affordable solution!
Alternatively, here's a detailed report about all the engineering, design, testing and results that led to ChickenClip: PROJECT REPORT PDF
Here’s how ChickenClip works:
Step 1: Take off your backpack.
Step 2: Slide ChickenClip on to a table.
Step 3: Enjoy your clean and organized space.
On your way out, simply grab your bag and get going.
Initial Free Body Diagram
A design goal based on mechanics.
Our design goal was to create a form such that we could maximize the coefficient of static friction of the ChickenClip tips, so that we could increase that component of the force and increase the lifetime of the product.
Look above!
(Play-doh-test)
This is a test we came up with to study the type of contact surface that was being created by the clip and table, so we could optimize the design for surface area.
Testing & Benchmarking
We designed the ChickenClip for a spec that we determined by doing a user study and finding the median and upper quartile backpack weight carried by college students.
This Turned out to be roughly 20lbs, so to be safe and allow for some variation, we set the target weight as 23lbs.
The ChickenClip would have to withstand this weight for extended periods of time. We also performed a load-till-failure test.
Results
After testing multiple clips to failure, we found that:
Left: Clip V1 broke at the point of contact with the force meter, this meant that we needed to move to a more robust hook design.
Middle: V2 was better performing in terms of load till failure, and this time the bottleneck was the strength of the contacts with the table.
Right: V3 was clearly the best yet, exceeding benchmarks, while maintaining similar amounts of material weight, simply because of the added “shark teeth”.
Material Selection
Part A: Outer high-friction material
Part B: Main body material
TLDR: We chose Polyurethane Rubber for the high friction material and PLA for the main body material based on a tradeoff between cost and performance-based material properties.
But here are the nerdy details anyways:
Final material choice:
For Part A we narrowed our search down to – Natural Rubber and Polyurethane Rubber as well as ‘Plastidip’, a synthetic compound that was intriguing from a manufacturing standpoint because of its high formability.
For Part B we chose PLA for this iteration, this was due to its high specific strength to material cost ratio.
Cost Structure
The PLA plastic is a total of 31 grams for the product, and is priced at $0.05/gram, or $1.55/unit.
One bolt costs about $0.27 to be made of black-oxide alloy steel, and a black-oxide steel nut is about $0.13.
The steel spring is $1.15 for one, bringing the total cost of one ChickenClip to $3.10, before labor costs are added.
Mass-ordering and production of the ChickenClip could easily bring down the overall cost by a factor of 5, to $0.62/unit, before labor costs. This means that the profit margins of one single ChickenClip would be tenfold of the base cost.
Next steps for ChickenClip!
The team is currently in the process of attempting to injection mold ChickenClip, to make it suitable for mass manufacturing!