2/6/15 & 2/10/15: Windlass Project
My new partner, Angel, and I started on our new project: the windlass for a well. The device had to span over a 12cm "well" (just a gap between two tables), and use a hand-powered crankshaft to lift a "bucket of water" (1 liter of soda). We drew multiple sketches of what our windlass might look like and took a pause many times, adjusting to the unfamiliarity of the term. These are our compilations of our main sketches.
Our initial favorite idea was the third sketch from the top. We could stack up all the Delrin pieces We started measuring out all the pieces of structure from a 500cm^3 sheet of Delrin we were limited to, and realized we had to change our plans. It used up too much material, especially since each Delrin piece was 1/8'' thick and we had a target height of 15cm. We ended up with making (or attempting to make) a Styrofoam model of the 3rd sketch from the top: the trapezoidal stands with a rod running through them. It seemed like a sturdy structure and would hold the 1 liter bottle well.
2/11/15 & 2/13/15: Styrofoam Modeling and SolidWorks
However...
The cut outs of these squares have remained in this bag since (almost) the beginning of their creation. Angel and I came in to cut out a Styrofoam model, and we were never able to stably put all the pieces together. After learning the multiple ways of attaching Delrin, we thought that we could use the piano wire and the drill press to attach them more easily when we actually cut them out in Delrin. We were advised not to complete this model, and thankfully, we didn't. It would not have been an efficient way to use or materials, or time.
We revisited our models, and came up with the first sketch! A build-on from our previous sketches, we wanted a simple model in which we could still run a rod through it and have our little wheel. The triangle would also be more stable than the rectangle because it would not topple over easily. The pulley itself needed space for the string, so we thought of stacking the inner circles together to create more space, using a total of 4 separate circular disks. Keeping in mind the multiple ways of attaching Delrin, we made tabs at the bottom of our triangular foundations to connect on a horizontal base, so that it wouldn't wobble under pressure. Not only would this structure be much more time efficient than the first model, but it would also use much less Delrin (approximately 400cm^2)!
We spent most of class time cutting out our Styrofoam model...which had adjustments of its own.
Hinges and plates! We originally wanted our triangular structures to be secured by a tab, but what it wiggled back and forth? Side to side? We created four hinges for our model and the blank squares were additional cut outs from the Styrofoam to represent the plate we would make in SolidWorks. As for where the bushings would go, we would want them on both sides of the wheel and both sides of each of the triangular foundations. The handle also needs to be secured, but since we would piano wire the handle to the rod, bushings wouldn't be necessary. The hinges and the attachment of the wheels would also be secured by piano wires.
Moving on to the SolidWorks, we created each piece and saved them. The next day, we would be printing out test pieces and using Assembly to complete our design.
2/14/15 & 2/16/15: From SolidWorks to Product
These were rough snowy and laser cutting days. We designed our SolidWorks parts already and used some time the next afternoon to link them through the Assembly portion of the SolidWorks. The pieces had fit together and all the measurements were accurate in the design, but as we know from learning how to connect Delrin together, we would need to print out test pieces slightly smaller in dimensions in order to achieve tight and loose bushings on the rod, and tightly fitting tabs and notches. After a few runs (and much waiting!), we finally had successful tight tabs and notches, and loose and tight bushings. We tested the tab and notches twice, and tested the bushings three times before we obtained a tight fit. The loose "bushings" were needed to figure out the radius of the holes at the top of the triangles, because we didn't want them too tight. They needed to be stationary and not be spun by the rod when it rotates. Besides the triangles, everything else would need to have a tight fit.
Ready to print! We were able to use the laser cutter on Monday to print out our first product on one sheet of Delrin (1/8''). We decided we would only need two hinges (to lessen the materials), and added more holes to the triangles to run more of the rod through it. We wanted to create a more stable and stronger structure by adding the rods. Although we printed a total of 12 bushings with the idea of using all of them for extra support for the handle, wheels, triangle, we didn't end up using all of them.
Though, not only in part because we didn't need them, but also because we couldn't use them. Unfortunately, the laser cutting was not perfect with its cuts and we had to force out some of the parts. We got out some sandpaper afterwards and tried to sand away all the ragged edges, but some of them were thick or the sides were bent. Thankfully, all of the parts of our main designs made it through safely, and we had enough bushings that were able to fit tightly on the rod. After we put our product together, we were happy that parts had all fit nicely together, but there were functions that weren't quite working.
2/16/15, 2/17/15, 2/20/15: Improvements
The key function of the windlass is to lift up the one liter bottle, and our initial product needed some modifications. None of our attachments were permanent, so we were able to dissemble the parts easily. The two primary issues with the product were 1) the wheel and 2) the handle. We had yet to piano wire the handle to the rod, and our attempts to lift the heavy one liter bottle made the wheels turn in the opposite direction as the rod. We needed to figure out a way for the wheels to remain completely intact with the rod.
At first, we were hesitant to attach the materials with piano wire. If we did, we would be running the piano wire vertically through the thickness of the Delrin into the rod. After successfully running the piano wire through an extra bushing on a rod however, we came up with two ways to secure the whole wheel together: 1) to attach a small rod through another set of holes in the disks and 2) to piano wire the two smaller circles directly onto the rod. The small rod fit perfectly after we printed out the set of circular disks, and we were able to piano wire both of the small circular disks onto the rod. The larger ones would be held together with the small ones with the short, extra rod running through all of them. At either end of the larger circular disks, we placed tight bushings to securely hold the wheel in place on the rod.
We left a bit of the wire sticking out from the smaller disks because we decided we could tie a small noose on the string and secure it on this piece of piano wire so it would not fall out.
As for the handle, piano wiring was slightly more difficult (even when it already is!). We tried piano wiring our initial handle, and it cracked. Printing out another handle and being more cautious of the position of the drill, we were able to successfully connect our handle to the rod. The beginnings of the piano wire process was shaky because the piano wire kept falling out of the hole, but since matching the drill bit to the correct piano wire size, the process ran more smoothly!
Best of all...our product works! It was able to lift up the bottle pretty sturdily!
2 Plates: 3x7 cm^2 x 2
2 Triangles: 14.5x3 cm^2 x 2
2 Large Circles: Pix5^2 cm^2 x 2
2 Small Circles: Pix3^2 cm^2 x 2
1 Handle ~ 16 cm^2
6 Bushings (Pix2^2 - Pi) ~ 56 cm^2
Total: approximately 415 cm^2 of 1/8'' Delrin sheet
Engineering Analysis: The primary rod of our windlass at the top was subjected to beam bending, and we were careful not to have it too long. The physics of beam bending determines the amount of stress the "beam" or in our case, the rod, can handle, and takes into account the Moment of Inertia (I), Young's Modulus (E), the weight of the load, and the length of the rod (d). The longer the rod, the more likely the beam is to bend, which is the only variable we can control, since we are restricted to Delrin and our objective is to lift the one liter bottle. The triangles were also subjected to beam bending, since they experience the stress at the top from the rod, but we were careful not to have them too short either, because the structure would become unstable if the triangle is narrow. Overall, our structure was very sturdy, since there were supporting plates and tabs at the bottom, extra rods running through the triangles, an appropriate width for each triangle, and an almost even distribution of weight across the rod.
Concluding Reflection: We realized that we did not need more rods to go through the triangles in our structure, because it was already sturdy enough. They would be nice to ensure stability of our structure though, and as for the hinges, they did not make it to our improved product. They hadn't made it to our initial product either, because we were not able to piano wire it to the plate. We had technical issues with the drill bit when we first started putting our product together, and if we had more time, we could have included the hinges to ensure the stability of our windlass when we use our handle. It was also inconvenient to crank the handle as well, because we had to continuously apply pressure in order to crank the bottle upwards. If there was time, we could have created a long, rectangular handle, or heat staked another piece of Delrin to our existing handle to create a crank. To add additional support (although it is already sturdy), we could have distributed the load evenly throughout our design by making our triangles arches instead. Our design could have been made more convenient to use, but in conclusion, it is efficiently functional in completing the task.
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