Over the past few weeks..

We have finally finished testing all the different balls and trying different way of slicing the balls so that they stay securely on the chain.

Unfortunately, all the balls except the Wiffle ball had major issues staying on the chain and not popping off under the pressure of our "drop test".

Here is a Pugh chart that summarizes our conclusions:

We were therefore forced to add another component to our design - that kind of ruins the simplicity of the idea - which is velcro. The addition has helped the ball stay on the chain and so it actually works now, which is great.

We glued velcro on to the racquetball, bouncy ball, and Wiffle ball. We then took a trip to CRI for feedback. They seemed to like the Wiffle ball, but didn't think it would be sturdy enough to withstand repeated drops. They liked the pliability of the racquet and favored it. However, after further testing we confirmed that the racquetball was too easily ripped at the holes and would not work. 

Wiffle ball testing at CRI

We decided to run with the Wiffle ball, since it was the only one that could hold up. Since CRI didn't like the "feel" of the ball, we experimented with different textures to make the plastic Wiffle ball seem more like a rubber ball. However, the PlastiDip we used to coat the ball was messy and took away from the aesthetic of the original prototype.

We asked Larry about the best way to attach the velcro to the ball and he suggested we glob a bunch of glue-gun glue onto the velcro strip and then press it onto the ball until the glue squirts out the sides. Then when the glue dries, cut off the access with a Xacto knife. This method worked great, and we have clear edges now. 

Our presentation is ahead, and we are almost done making 6 replicas of our final prototype!

Final Prototypes + Meeting with Jaden

On Wednesday we finalized our ideas and came up with a couple of sacrificial concepts before our meeting with Jayden.

Also, the 3D printed part I modeled last week is finished printing, and we added in the bolts just to have a finished prototype even though we scrapped the idea. The size and spacing of the holes were pretty accurate which I was happy about, and I learned a lot about SolidWorks and modeling through the process.

Final HandleStopper permanent attachment prototype.

The second prototype we showed Jayden was a sacrificial idea. It made use of magnets and wood to keep the cord in place. The cord would be sandwiched between the two pieces of wood, holding it in place. This idea was not practical for a few reasons. First, it was really difficult to get the magnets to align properly. Secondly, even if they were aligned, they didn't have the strength to stop the momentum of a dropped chain.





Another idea that utilized magnetics was the prototype Alex had been working on for the past few weeks. After adding foam padding to the inside, it didn't fit over the cord as well as perform. It also didn't pass our "chain drop test".

We also went back to the original idea of simply slicing a sphere in half. We modified a red plastic ball and fitted it over the erg chain. It worked surprisingly well and didn't fall off even after we let go of the handle at full resistance (10) while sitting on the erg seat. Jayden liked the idea of the sphere the most out of all our prototypes, especially since CRI can make their own using balls such as tennis balls.

Sliced sphere prototype

 After our meeting we have decided to move further with the sphere concept. We ordered a bunch of spheres and will cut/drill, and test them over the next week. Our goal is to have a few viable ball options before our visit to CRI.

Variety of balls ready for testing

Prototyping Part 2

Alex and I have made good progress with the prototypes. We have sent both ideas to CRI for review. 

This past few weeks we have been ordering parts, making 3D models of our prototypes. So far we still have two different concepts we have been working on separately, but by next week, after we receive feedback from community rowing, we should know which concept we should invest all our time to.

Our first idea is to make a simple stopper that prevents the chain from snapping into the machine. Alex has created a prototype out of wood and magnets.

Prototype of Idea 1 in wood

The idea is that the two pieces will "clamp" the chain and act as a border so the chain doesn't retract and damage the erg.

Sketch of Idea 1

Before making the prototypes out of wood, Alex and I tried to 3D print them but we were having issues with that process. The built plate wasn't heating up properly so the plastic wasn't sticking. We aren't sure whether that's an issue with the printer settings or with the model.

3D models made in TinkerCAD

Our second idea was to create a cord stopper that also  made the process of replacing the handle easier. The stopper would stay on the machine and allow the handles to be interchanged without any tools. One side of the stopper would hold the chain and the other a bolt that can attach to any handle needed.

 

We 3D printed the model and it came out fine, but there were a few issues with the underside of it. We also had to scale it down to make it easier to print. We will be printing a final model this week.

Sketch of Idea 2

 

 Overall we are in good shape and it's just a matter of hearing CRI's feedback to that we can move forward with a final product.

Rob Wood Seminar

I really enjoyed Rob Wood's talk. I think the projects his lab are working on are interesting and I learned a lot of new things during the seminar. I didn't know that microrobotics had come so far, and didn't expect the variety of prototypes they had already built. The production process of folding or "snapping" the pieces into place with one gesture was, I thought, a really creative and ingenious idea. I wish he had more time to go into more detail about the design of the MEMS and the actuators. 

I remembered something that I had read during the discussion, which was about the relationship between quantum physics and transistors. I can't remember the details, but I read that transistors can only get so small before quantum physics comes into play, and they stop working (something about the electrons not being stopped by the "gate"). The theory was that when transistors became this small, Moore's Law would end and we'd have to come up with materials other than silicon to create transistors. The Schon scandal was related to this topic because Schon had claimed he made transistors out of organic dye. Although, I guess this is applicable to the nano scale and not micro scale. Either way, I'm curious to know if they have faced any similar difficulties at such small scales. 

I also found it interesting that so many different departments collaborated to make the projects possible, and that it has a lot to do with understanding the biology of whatever organism they are simulating.

Final Project Community Rowing

We want to create a cord stopper that will prevent the cord from retracting into the machine as the handles are being switched out.

Our design specifications are as follows:

- Easy to remove (<20 sec).

- Does not damage the erg.

- Is sturdy/reliable and holds the cord every time.

Materials: Heavy metals, rubber, magnets?

Parts list?

Schedule:

3/18 - parts list/materials

       - basic prototype/concept

       - meet up after exam, finalize materials list

3/30 - have prototype mostly done

       - meet up outside of class to see where we are with prototypes and what needs to be done between Monday and Friday

4/1   - finalize prototype, hopefully end the class with two or more prototypes almost/ready for presentation

       - test prototypes

4/3   - present to class

       - discuss critiques, identify weak points,

4/6 - commit to design, narrow down to one design

4/8 - begin final product, think of variations according to feedback

4/10 - continue working on final product, think of variations accoring to feedback

4/13 - test product

4/15 - prototype testing at CRI

4/17 - discuss critiques, identify weak points, work on final product

4/22 - make changes to final product design

4/24 - continue working on the final product, test product

4/27 - test product,

4/29 - (Ruhlman Conference) final adjustments

Testing plan:

- Figure out how to safely test without ruining the machine.

- Place stopper on the erg chain, check for correct width and strength of stopper/mechanism.

- Use erg with attachment in place to test for compatibility.

Prototyping Part 1

Alex and I are off to great start. We've decided to tackle the one-handed handle project. We both made sketches of handle ideas and then compared our ideas. We both had similar concepts and decided to work off of Alex's sketch, which was more clear.
 

Initial concept sketch

We then began the process of making a rough prototype out of sheet metal, scrap wood and foam board. The initial model is not accurate at all because at that point we were still vague on how we were going to exactly idealize the design. In order to get a better sense of our direction, we wrote up questions to ask CRI. We also sent them our initial sketch for their opinions.

Our next step was to take a trip to the KSC to take measurements of the erg machines. We also looked up different clamp designs to brainstorm how to attach the handle to the cord. We looked at rod-latch systems such as those found on camera mounts and music stands. Those types of latches tend to be very easy to mount/unmount. These are the clasps we found:

Clasp options

Some options are more refined products and others are pretty industrial looking. After testing them out, we can incorporate features from multiple products to create the ultimate clasps for our handle.

I'm working on learning SolidWorks so that we can create a better prototype that has features that will be reflected in the final design. We are trying to standardize the handle as best as possible, while also working with the curvature of the handle for a secure fit.

3 Ideas

The three problems Alex and I picked were the following:

1. The one-handed handle that is hard to attach to the erg.
2. The arms, shoulders, and torso seat that could be adapted for arms and shoulders users.
3. A device for the pontoon that makes it easier to attach the pontoon to the boat.

For all three categories, we set a timer for 5 minutes and brainstormed ideas during that time. We then sorted ideas into categories and made a corresponding Pugh chart.

We first brainstormed ideas for the one-handed handle. We divided our ideas into three categories: "Attach to cord", "attach to handle" and "new handle". We chose "attach to cord" as standard and based off of our ratings, chose the handle attachments as the best option.  The handle attachment seemed the most practical and least costly. It is also easy to remove and is therefore very adaptable.

Some of our sketches when brainstorming

By the second round, which was the AS seat adaptation, coming up with ideas was a lot easier in 5 min. It seems like it's not ideal to brainstorm two completely unrelated concepts in a row because all the ideas we had for the handle were pretty mundane, but once we got to the seat, the ideas were a little more far-fetched. Although that is a sign that the process was working.

We divided each of our ideas into the categories: "boat attachments","seat attachments" or "new seat". We chose "seat attachments" as standard and determined that building a new seat was the best option. Despite expenses, building a new seat would improve upon reversibility, adaptability and comfort. We were also most passionate about this approach.

Pugh Chart for the seat

Our last problem to brainstorm was the pontoon attachment to make it easier to flip into the water. We also generated ideas that fit into three categories: "pontoon attachments", "boat attachments", a whole "new pontoon", and pontoon attachments with "sensors". Designing a new pontoon was ruled out almost immediately when compared to the standard of "pontoon attachments". The "sensors" category had some great positives, but was ultimately ruled out due to cost, do-ability and maintenance.

Brainstorming for the pontoon flipper

It was great brainstorming for all these problems. Alex and I had chosen the same projects to begin with, so we started off on the same page. In the end, I think we were most passionate about the one-handed handle. It is a problem with a lot of flexible solutions and potential. The hardest part will be to rein in all our thoughts to come up with one solid, manageable approach.