Failure Test
Laser-cut hanger #1 felt a bit flimsy, so we wanted to see how much force it would take to to fail and where failure would occur. The floating side was loaded, increasing the force until failure. Failure was somewhat gradual: there was a surprising amount of deformation and the wood could be heard cracking long before ultimate failure. The break occurred on the connected side, just above the inside fillet along the grains of each ply of wood.
Fig. 1: Hanger 1 after loading the floating end to failure.
Based on these results, the team realized we needed to add material to the weakest location and removed stress concentrating hooks on the bottom for laser-cut. The following shows simple stress simulations we utilized to find any weak spots in the geometry when loading the floating end.
Fig. 2: Hanger #1 Stress Simulation with High Stress Shown on Diagonal Member
Final Design
After the team’s stress analysis, we modified our current design to be stronger and thicker overall. In doing this, the hanger will be able to withstand heavier articles of clothing (see below).
Fig. 3: Final design Stress Simulation with Wider Members and Lower Stress than Hanger #1
Fig. 4: Final Hanger Design
Fig. 5: Hanging Pants & Jacket
Fig. 6: Jacket Hung Utilizing Integrated Coat Hook
Manufacturing
Possible manufacturing processes include laser cutting, water jet cutting, and sand-blast finishing for high volume production; band saw, jigsaw, and sandpaper finishing for low volume production. We used a laser cutter and sandpaper on birch plywood for an approximate unit cost of $2, including a 2’x2′ piece of wood, sandpaper, and free laser cutting from the prototype lab.
Fig. 7: Laser-Cut From Single Piece of Birch Wood
However, for long-term, high volume production, the team believes this per unit cost will decrease as a result of the simple design which is highly integrated, requires no assembly, and can be formed and finished with very few operations. In processing the stage between design to fabrication, the team would take into account long-term investments such as tooling, labor, raw material, overhead, etc. While fabrication planning for this product is beyond the scope of this class, the team is confident that with additional time and product iterations, the product has the potential to be fabricated en masse for a lower unit cost.
Sustainability
The hanger is relatively sustainable in both manufacture and disposal, compared to wire or plastic hangers. Wood is renewable and decomposable; the scraps from cutting out the hangers can be used to cut out other products, or be turned into particle board; old hangers can be mulched, composted, or recycled.
User Test
We constructed a mock-up closet comprised of a square-profile bar in a stand and had people unaffiliated with the team hang up several types of shirts. The trials included hanging a t-shirt, athletic shirt, and dress shirt with only one hand using a standard hanger and also with our design.
The following was performed by an unaffiliated user who performed all trials with the same shirts.
Standard Hanger (One-hand average) vs. Our Design (One-hand average)
Standard Hanger Time: 17.9 seconds per shirt
Our Design Time: 7.6 seconds per shirt
Our hanger design allowed the users to hang the shirts in less than half the time of the regular hanger.
User Feedback
“The hanger worked great! Since I hate folding my shirts, it was nice to find a hanger that’s easy and quick to use” – Seth S.
“While I like the hanger design, I wish I didn’t have to replace my closet bar and that it worked with my existing closet” – Andrew M.
“The weight and material of the hanger feels expensive” – Carrie B.