My first ENGI 210 midterm was based off of by 507 Mechanical Movements #113, the basic rack-and-pinion. I also drew some inspiration from the deconstruction lab from the beginning of the semester. One of the things we found while taking apart a printer during the lab were boards of dozens of gears. I love the idea of applying a force to one gear and watching the cascade of motion in all the others gears that results, so I decided to add some extra gears to my basic rack-and-pinion. I planned to mount the entire situation on a thicker wooden board, which I ended up standing up on a mount made of plasma-cut metal.
To begin, I wanted to ensure that I could actually make a rack that could move multiple gears in series. So, I took to Adobe Illustrator in order to create something I could test with cardboard. Xiaoyao was kind enough to share a website with me that would generate a file for a rack-and-pinion (http://hessmer.org/gears/InvoluteSpurGearBuilder.html). Although the website allowed for the customization of the size of the gear, it only allowed for one gear at a time. So, I downloaded three different rack-and-pinion files with differently sized gears and extracted only the gears themselves from two of the three files.
This resulted in a cardboard prototype that looked like this:
And it worked! The gears meshed and everything, so I assumed it was safe to begin to increase the fidelity of my prototype. I cut the same rack-and-pinion systems of gears on the laser cutter out of plywood. In terms of assembly, I began by using wood-glue to secure the two different layers of gears to each other.
After this, I knew I would eventually need a rectangular piece to be cut out of the top of the board so that the rack would have a path to move across, so I thought back to the many hours I spent using the XCarve last semester and figured that a similar machine, the Carvey, would be suitable to make this type of cut. As it was only a rectangle and not something more complicated, this process was fairly straightforward. I made the rectangle directly in Easel, the online program associated with the Carvey, secured my board in the machine, and let it do its thing.
Then, one-by-one, I clamped each gear to the section of the board where I wanted them to go, and drilled holes simultaneously through the gears and into the board, as shown:
I found some dowels upstairs in the OEDK that conveniently fit snuggly in these drilled holes, and I used them to create an initial assembly of my machine.
At this point, I needed to create some collar-ring type pieces to fit on either end of the dowels that go through each gear. My initial plan was to laser-cut these pieces, but at this point the laser cutter was not working, so I improvised. I grabbed a thick dowel, clamped it to a table downstairs, and drilled a hole down the center. Then, I used a saw to slice the dowel into as many collar pieces as I needed.
Now, for the metal aspect of this design. A conversation with both Dr. Wettergreen and Carlos our wonderful TA lead me to conclude that I could make a joint out of some metal pieces to act as a stand for my machine. Carlos helped me come up with a geometric design for the pieces, so I created their outlines in Adobe Illustrator and took to the plasma cutter. After this I underwent the same process as I did for the post-processing homework, which consisted of filing the slag off of the pieces, sand blasting them, and painting both sides. Here are some photos of the process:
I determined that these joints were not as stable as I wanted, especially because my machine involves considerably more force to move than I foresaw. So, I used some epoxy to do two things. 1. I epoxied the pieces of my joints together, and 2. I epoxied the joint pieces to a rectangular piece of wood to act as a base for my machine, as shown.
The final product is as shown:
Cost Analysis:
This time I’ve decided to calculate the cost of this item based on the costs of all the things I made in order to learn the skills necessary to make this machine.
first box homework: $27.78
Adobe Illustrator practice homework: $20 (I did not actually include cost in this blog but I’m guessing the file took about two hours to make, and my summer job paid me $10 an hour)
laser cutter box homework: $30.62
post-processing homework: $861.47
sum: $939.87
Finally I will multiply this by two, because it took basically the same amount of time and resources as the combination of all the other homeworks.
Final cost: $937.87*2 = $1,879.74
We’ll call it a nice $1999.99, because that’s easier to say in a commercial.
Shoutouts:
Xiaoyao, for being patient with me while I figured out that rack and pinion website.
Brian and Adulfo, for being good company in the OEDK in the middle of the night.
Carlos, for walking me through my confusion at basically every step of this process.
Whoever’s in charge of the music upstairs in the OEDK, because it rocks.
