Overview | Problem | Analysis | Ideation | Selection | Implementation | Final | Evaluation

Idea Selection and Refinement

Idea selection:
      Having generated a variety of ideas, I selected the best ideas and focused on refining them further. The boot foot (downward-slanding chisel) and chicken foot (three-toed) were the most successful prototypes. I decided to combine these two designs into a three-toed claw shape.

View Product Proposal
(document 1 of 3)

Click the link above to view a piece of technical writing simulating a proposal of this product to a manager at Ossur Prosthetics

Log book - elaboration of claw shape

The boot foot easily engages small ledgess

Chicken foot is a success

Second Prototype:
     I constructed a rapid prototype of the Eagle Claw shape using 1/8" aluminum that I cut on the band saw according to drawings I had made. I was able to bend the toes by hand using vise grips, and soon found that the final foot would have to be much stronger than this once, since Britt's weight immediately crushed this flimsy prototype.

First aluminum prototype - 1/8" sheet

Solid modeling:
     
In the ideation and exploration stages of design, I sketch ideas by hand because it is much faster than computer modelling and allows me to preserve some ambiguity. At the selection stage, it made sense to represent the Eagle Claw as a fully-defined solid model. I used SolidWorks to create this computer-generated solid model based on the drawings I had produced.
     With SolidWorks, I could simulate Britt's weight on the foot and visualize the resulting strain distribution. By altering the design of the foot, I was able to improve the foot and increase it's factor of safety.

Solidworks analysis of possible structural ribs

First aluminum prototype - 1/8" sheet



First aluminum prototype - 1/8" sheet

Assembly drawing

Rendering of final assembly

Third prototype and designing for manufacturability:
      I had to consider how the Eagle Claw concept could actually be manufactured. I considered casting the foot, turning and milling the foot from a large disk of solid aluminum, or making it from multiple parts. However, I concluded that a better way to make a strong and lightweight foot repeatably, quickly, and inexpensively would be to mill a piece of plate aluminum to the desired shape and then bend the toes downward.
     I constructed a third prototype from 1/4" thick 5052 aluminum plate, which I used to practice millling and bending. This prototype proved strong enough for Britt to jump on without deforming.

Working rotary table pattern, used for 1/4" aluminum prototype

Second aluminum prototype, used to practice milling and bending

Fixturing diagrams


Final rotary table pattern