Week 6: Revisiting Past Designs
Jack S -
Hello everyone and welcome back to my project! This week, I mainly focused on the soft actuators and pump layout.
The first thing I did was test out my older pump design using two actuators, with gloves acting as balloons. If you’ll remember from last week, I had planned to swap out this design for a much larger and clunkier one because I was having trouble inflating both balloons at the same time. Luckily, once I used gloves and placed them inside the actuators, the difference in pressure needed between the two balloons drastically decreased, and I was able to inflate both actuators simultaneously.
Just as a reminder: each actuator consists of a strain-limiting layer—in this case, fabric that was either sewn or hot glued into a cylinder. Inside that, there’s a bladder of some sort, whether it’s a balloon, disposable medical glove, or something similar.
I was really happy with this result, but after running the pumps for a while to see the maximum stiffness I could achieve using the gloves as balloons, I ended up popping one of the gloves inside the actuator. Normally this wouldn’t be a big deal—I could just swap it out for a new glove—but since I had sewn and glued the fabric surrounding the glove, it was really difficult to replace. I would have had to make a whole new actuator.
Naturally, I wanted to fix this issue, because in my final design, it’s possible for balloons to pop from time to time, and I want it to be easy for the user to replace. I had an idea to have two rings, with one ring glued on to the fabric cylinder itself and the other glued to the air hose (positioned further up the line compared to the balloon). I can then screw the fabric ring onto the hose ring, which will cover the balloon and seal everything up nicely. This way, I can easily remove and reattach the fabric portion whenever I need to swap out the balloon.
Originally, I was thinking about using hose materials for the rings. Many garden hoses, especially at the point where they attach to the faucet, have two rings that work similarly to this. However, there are so many other common household objects with similar threading that I figured it’d be unnecessary to buy a relatively expensive (and likely heavy) hose valve.
After considering a few different household objects, I decided to repurpose a basic screw-on soda cap. I accomplished this by sawing off the entire cap area so I had just the cap and the threaded section it screws onto. I then cut a hole in the cap, glued the fabric cylinder on, and glued the threaded section onto the hose.
Now I have a simple, lightweight, and replaceable actuator design that works well with my pump system and lets me easily swap out balloons whenever I need to.
This week I also continued soldering and cleaning up my wires. I made the mistake of leaving a valve on while hot gluing one of the actuators together, and when I noticed it was damaged from overheating I had to order another. I also ordered some heavy duty velcro straps, which I plan to use to connect each actuator to the glove.
Thank you for reading!
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