While time-consuming and mind-boggling, this project was rewarding and fulfilling for me and my partner. There were many times throughout our project when we simply thought, “This isn’t going to work out.” However, we persevered and were able to accomplish our goals.
Overall, our project translates rotational motion into linear motion. We used linear motion to hoist a “Guru” as he achieves nirvana in a mountainous background, creating our “Guru in Nirvana” project.
Drafting Designs
We used the scotch-yolk mechanism or number 93 from 507 mechanical movements for this project. However, we decided to attach another gear connected to a rod to add movement. The rod rotates the smaller gear, which in turn rotates the larger gear, producing a linear motion in one plane for the T-like structure. From understanding the gears, we wanted to raise the Guru as high as possible, but that also meant we needed a gear that was as large as possible since the Guru would only increase as much as the diameter of the gear. We learned early how these mechanisms would move during our low-fidelity stage.
Low Fidelity
For the sake of focusing on the gears, we only focused on developing and determining if the gears would work for our low-fidelity project. When approaching the low fidelity part of our project, one major fear my partner and I had was whether or not everything would be held up on the board without falling down. We thought that putting gears up vertically and the T on one surface would be too heavy, and our structure would quickly collapse.
When creating the gears, we started with an arbitrary size for each. We wanted to maximize the height the T would rise, which means using gear as large as possible. We used a large gear with a pitch diameter of 8″ and a small gear to rotate it with a pitch diameter of 2″. We learned early on that the scotch yolk mechanisms work very well on a horizontal surface, but issues can arise when using a vertical surface. Specifically, whenever a rotation would occur, there would be no linear motion in the T since the T would just hang on the pointed part of the larger gear. We needed something to stabilize the T on both the bottom and top of the gear, and we needed something that would restrict its motion in the x and y. To combat this, we used caps or stabilizers, as seen below. The caps were created and stuck on the board so the T could not slide off the gear. When adding the stabilizers to the T, everything ran smoothly, allowing us to place confidence in our design.
However, several problems need to be improved for this design. Since this was one cardboard and low fidelity, many privileges could not be shared with the high-fidelity model. For example, the rods we used to connect the board to the gears easily slid out of place, regardless of how tight they were in the board. This was simply because it was cardboard, and there was little friction between the wood rod and the cardboard.
The second thing that needs to be improved on is the distance between the gears. In this model, the gears were slightly too close to each other. Because of this, the gears would dig into each other, and there would be significant resistance when rotating the gear. We need to space the centers of each gear slightly farther away from each other.
High Fidelity
In the low fidelity, we only tested the gears and did not place anything around the main board, like sides or a bottom set. We laser-cut everything for our high-fidelity model and were introduced to bearings. Having the bearings made things a lot tighter and stabilized everything further. The rod problem that caused much movement in the low-fidelity model was more minor in the high-fidelity model because of this. One thing we did need to try several times was making sure that there was a tight fit between the rods and the board we placed them through. We measured the diameter size of the bearings or rods and practiced making holes in spare pieces of wood to see what size made the tightest fit between the bearings or rods and plywood so we did not have to rely on the glue.
We also further improved our low-fidelity model by using a smaller gear for the one the T was on. Instead of using an 8-inch gear, we used a 4-inch gear. However, we failed to place the gears well, as it was not centered and did not leave enough room for the stabilizers or caps we wanted to use. Overall, while the high-fidelity model helped us visualize how our gears would be held, it did not help us in any functional form.
Final Product
For our final product, we needed to combine the functionality of our low-fidelity model and the placement strategies of our high-fidelity model. First, we used the same gears from our high-fidelity model and practiced on scrap wood to make the perfect distance to print the placement on the board for the final cut. Once we finally determined the distance required between the center of each gear, we could print the final surrounding board pieces.
After we placed everything, we needed to account for any friction that may exist in the model. For this, we needed to sand down the T structure till it went smoothly through the stabilizers. We also applied PTFE, just in case. However, because we sanded the entire thing too much, it created a nonuniform surface on the top of the T where we wanted to attach the Guru.
To make matters worse, we realized that our T was not as large as it should have been and only slightly stuck out of the stabilizers at its lowest position.
To solve both problems, I created the following box in the laser cut to fit the top of the T. Furthermore, it had a space where the Guru could connect to on top. With the following structure, the tip of the T would pick up the Guru and lay him back down on the stabilizer or cap.
Laser cut pieces
Our gears, boxes, and T were laser cut; however, we also laser cut the bushes seen below. One thing that came as a challenge was the Guru. The Guru on one piece of plywood, at any size, was too heavy and would tip over at any size of the T. To reduce the mass and inertia of the guru, we created a large-scale vector cut that reduced its weight while maintaining its shape.
Vinyl Cutting
We made flower stickers for Vinyl cutting, as seen on the bush on top. We only decided to use them for stickers and aesthetic purposes.
Water Jet cutting
We cut out the handle for our mechanical model with the water jet cutter. To tightly connect to the 0.5″ thick rod, I created a 0.47″ hole in the handle for the rod to slide into. Luckily, I did not have to sand down the rod to fit the handle, as it was already a tight fit. I filed the metal piece and sandblasted it after.
Post-processing
For post-processing, my partner and I decided to paint the bushes green, the mountains grey, and the back of the box a peach color and apply a clear coat of clear enamel. It should be noted that we initially painted the outside of the box to be brown. However, it ran out, so we applied the khaki color, which is why it is uneven.
Conclusion
Overall, the project was gratifying but also required much planning. In hindsight, planning extensively before each model would have been better. For example, meeting beforehand and brainstorming what problems we could face with our model before assembling it may have been helpful. We wish we had made the guru more robust since the Guru is vector cut entirely, fragile, and easily breakable. We also made the T larger to be glued to the Guru. Regardless, our mechanisms have good mobility and rotation, and all Gurus aside, it is perfectly working.
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materiasl | ¼” PlyWood | $14/sheet | Lowes | 1 sheet | $14 |
| ½” Al Sheet | $25/sheet | Amazon | 1 sheet | $25 | |
| ¼”Cardboard | $0.38/sheet | boxforless | 3 sheet | $1.14 | |
| ½”Bearings | $12.00/10 pieces | Amazon | 1 peice | $1.20 | |
| ⅜”Bearings | $8/10 pieces | Amazon | 1 piece | $0.8 | |
| Red Vinyl | $2.49/sheet | michaels | 1 sheet | $2.49 | |
| Khaki Spray Paint | $5.98/can | Walmart | 1 can | $5.98 | |
| Green Spray PAint | $6.48/can | Home Depot | 1 can | $6.48 | |
| Wood Glue | $4.97/ bottle | Home Depot | 1 bottle | $4.97 | |
| Labor | Laser Cutter Operator | $19.17 | ZipRecruiter. | 3 hours | $57.51 |
| Water Jet Cutter Operator | $15.00 | ZipRecruiter. | 1 hour | $15.00 | |
| Vinyl Cutter Operator | $16.09 | ZipRecruiter. | 1 hour | $16.09 | |
| Spray Painter | $17.41/hour | ZipRecruiter. | 2 hours | $34.82 | |
| Overhead | Facility Cost Laser Cutter | $12.73/hour | alphalazer | 3 hours | $38.19 |
| Facility Cost Water Jet Cutter | $19.91/hour | techniwaterjet. | 1 hour | $19.91 | |
| Facility Cost Vinyl Cutter | $5/ hour | Sign101 | 1 hour | $5 | |
| Total | $248.68 |
