Element J: Documentation of External Evaluation

Introduction

When revising our design we have to look at our suggestions and criticism and be able to implement and improve upon ideas for our design. Compiling all our suggestions and future plans is important to allow us to move forward and create a plan for the evolution of our design. We are able to focus on which pieces of information are more important and essential to the design process.

Working with Dr.Gold

On Sep 26, 2021 Dr.Gold told us about Uneek shoes by Keen (Figure 1) which she liked for being comfortable and have a good arch. She however did not like the fact it was open toed. We liked them for the arch and agreed that the open toed design was non ideal since it didn't protect the astronauts feet

On Sep 30, 2021 Dr.Gold sent us a source from Glenn Johnston about TPU, a 3D printed rubber (Figure 2). While we didn't use this process, we eventually used a mold formed from a CNCed piece. Both of these processes allowed for a CADed piece to be created.

On Dec 6, 2021 Dr. Gold suggested possibly using mabas that pinches on shoe laces to keep them tight (Figure 3). While we found this a plausible solution, we didn't like that the mabas had a small surface area making it more difficult to grab onto and they require fine motor skills in the finger.

On Jan 6, 2022 Dr. Gold suggested to us to use a harness that hold 5/6th of our weight to simulate gravity on the moon (Figure 4). This suggestion was greatly beneficial since previously our only idea to test lower gravity was using a pool and letting the buoyancy of the water push us up.

Preliminary Design Review

Our Preliminary Design Review was on 11/17/21

In our preliminary design review the main criticism was that we said that our shoe would weigh 4lbs. The reason why we had that point was it would slightly increase the normal force and thus friction of the shoe, and that it would put more work on the astronauts lessening the affect of muscle and bone atrophy. However we were unable to specifically justify the cost of having it weigh 4lbs using our research. Glenn Johnston also mentioned that we should look at a silicon caulk for the sole of our shoe (Figure 5).

Critical Design Review

Our Critical Design Review was on 2/11/22

At our critical design review some critiques were made on some of our tests. The main criticism came to the harness test that we did as it was incredibly limited. We had little flooring and the harness we used was in a fixed location so the data we took was based on the gait of a single stride. We discussed our plans on doing a varied weight test which we have now done already and discussed how washable the shoe was. How machine washable the shoe is was a pleasant surprise as we didn't plan on making it washable, our design just coincidentally was washable.

Mr. Ballentine critiques

Mr.Ballentine is an AP physics teacher at Glenelg High School.

Mr.Ballentine said that during the pulley test we need to make sure that the string was attached to the center of the shoe otherwise the shoe would would begin to rotate which would mess up the experimental setup (Figure 6).

Mr.Ballentine mentioned that the forces we were measuring was outside the range of the spring scales they had, so we might have had to put the spring scales (Figure 7) next to each other so the force would be distributed between the scales allowing them to measure higher forces

Mr.Ballentine said that we needed to get a protractor so we can measure the angle of deflection of the electroscope (Figure 8) to get a numerical measurement for the amount of static electricity.

The main advice he gave us was to have many many trials. He said that the tests we had were solid tests and that we need to have large and varied amounts of data will give us a complete picture of our data.

Mr. Gerstner critiques

Our engineering development and design instructor Mr. Gerstner gave us several key pieces of advice when it came to the development of our shoe.

Mr. Gerstner suggested to us that we could use the CNC machine to cut out the shape of our sole (Figure 9) and use that as a base to create a vacuum formed mold that we can pour liquid silicone into and create that will solidify and create out sole.

Mr. Gerstner suggested that during our static electricity test we take humidity measurements using a sling psychrometer (Figure 10) since the humidity in a future lunar habitat might be different than on Earth and humidity helps dissipate static electricity.

Mr. Gerstner suggested that we look at exercise mats and vinyl flooring as a new possible floor material since they still have that higher friction but are easier to clean.

Moving Forward

Moving forward in our design process we plan to make some big changes to our design to move from having the best possible friction to a more feasible and usable design. Our first major step in this process is revisiting our floor suggestion. Currently our floor suggestion consists of the same material as our sole. This was an intentional design plan because there is very little static electrically generated between two of the same materials. The problem with our silicone floor is during testing and over time our floor pad accumulated dirt dust and grime. When we tried to clean our floor pad the material made it very difficult to clean and never got rid of all the particles. This was a problem because the friction of the particles against each other would cause static electricity and decrease our static friction by forming a layer between the silicone. So we decided to change our floor material. Currently we are looking at gym weight mats. We liked that most are durable and easy to clean while still being able to provide a good grip for weightlifters. So we have acquired some to test and depending on the results of redoing our coefficient of friction and static electricity it could become our new floor material. We also will be looking into using a different pourable rubber silicone for our sole, we found while the sole performed well in our tests the sole was to flexible for comfort and durability, so testing higher durometer silicone will be necessary to determine whether or not it would be worth losing some of our coefficient of friction to have a more sturdy sole.

Conclusion

Using the criticism we received we have or plan to implement these changes into our design and make some smaller changes while keeping the design mostly. We plan to make the floor out of some material with a higher durometer to help with cleaning and maintaining it. We also plan to make the shoe a bit thinner around the foot. These changes come from the critiques we received from our reviewers and our tests.