Week 7

     During class this week, we presented our midterm presentation. This included a summary of what has been up to this point, as well as future testing and actions to be taken. Our presentation was slightly different than most other groups', as we will not have as much testing to do (since we are unable to take our project to space or perform bed-rest studies). Therefore, much of our presentation focused on the redesign that we are working on, and how it will be incorporated into the current prototype. Further details about the redesign may be seen below and in the previous blog post. An example of one of our slides may be seen in the image below.

This is one of the slides that was included in our midterm presentation.

     The rest of the week, we ordered parts that will be used in our redesign, such as pins (for holding one of the brass weights) and ball bearings. The redesign consists of two brass masses spinning in opposite directions. These will be spun by the motor and a gear system, and held in place by a large "arm" on the leg brace. The reasoning behind this is that the opposite spin should cancel out the forces (and thus the wiggle) around the leg. This would result in force only being transmitted along the z-directions, or along the bones of the leg. (The CAD images for this overall system may be seen in the previous week's blog post.)
     Isaac also worked on the MasterCAM for milling the second set of brass weights this week. Dr. Hekman agreed to meet with us and help us use the CNC machine in Bourns Lab again. We were using the same piece of brass stock before, as the remaining brass was just long enough to machine our new parts.

     We experienced an issue during milling however, where one end of the brass stock was not supported as well as we had believed it to be. This left one end free to move around during milling, which caused one of the new brass weights to be cut incorrectly and unusable for our purposes. We were able to cut one of the new weights out successfully (see the image below), but will need to purchase more brass in order to mill the second one. (One advantage to buying new brass stock, however, is that we can get the thickness that we want, rather than having to face off a large portion of the brass.)

The successful brass weight that was created. This part was easier to mill than the original, since the entire piece was the same height.

     We also sent our redesigned leg brace (with the large arm to support the gears) to Josh Park for 3D printing. The leg brace finished printing successfully late during the week, but we were not able to test anything as we are missing the second brass weight. The motor casing had also been sent to Josh for printing, but will not be available until next week. Additionally, the gears for the redesign were 3D printed from SLS nylon from an outside source (Jake's parents), which should be stronger than if they were made out of PLA (as is the leg brace). These may be seen in the images below. 

The redesigned portion of the leg brace. The large "arm" will hold/guide the two spinning masses. 

The gears to be used in the redesign.