Introduction
In this post, we detail how we produce a physical mechanical model based on the 2 of the 507 Mechanical Movements, bringing together all of the skills we have acquired thus far in EDES 210.
Planning Stage: 2D Drawings
First, we brainstormed a mechanical model to create as a physical representation, made rough sketches of our ideas and found the crank motions to use from the 507 Mechanical Movements. Our idea was based on the idea of a jack-in-the-box with a Minecraft twist (since the movie is coming out soon), hence referred to as a “chest.” We settled on 92 Ordinary Crank Motion and 158 Reciprocating curvilinear motion, the former to raise a center apparatus and the latter to raise the lid of the chest. The center apparatus comprises a lifting arm and a stabilizer, which holds the block to be raised up and down.
Movement 92: Ordinary Crank Motion
Movement 158: Reciprocating Curvilinear Motion
Our 2D drawings can be seen below. First, we created a rough sketch of our concept. Next, we sketched Iteration 1 to illustrate how the motion would be enabled by gears and a crank. After consultation with the instructors, we sketched Iteration 2 to simplify the movement by attaching each gear on a single axle. We also sketched out a draft of Materials to determine the dimensions of each part needed to laser cut.
Low Fidelity Prototyping Stage
After creating our gears with the help of Gear Generator and preparing our materials in Illustrator to laser cut, we cut out the cardboard pieces for the low-fidelity, conceptual prototype based on Iteration 2. The gears were designed to have a 2:1 ratio of the lid and the platform lift, respectively.
Gears created within Gear Generator.
Prepared Laser Cut Files (Iteration 2).
Cut out parts for Low Fidelity Prototype.
Next, we started assembling the low-fidelity prototype based on Iteration 2. We used our cardboard chest and gear cutouts, tape, and dowels, while manually drilling holes in the cardboard to fit the dowel.
Low Fidelity Prototype.
This iteration did not work due to poor functionality of the cardboard gears as well as the lateral movement of the gears from spinning. We noticed the need for stoppers on the other side of the wall of the chest to prevent the movement of the gears. We also noticed the poor design of the center apparatus, which would cause it to be placed too high within the chest. With these constraints in mind, we designed Iteration 3, which separates the center axle into two parts to allow the center apparatus to sit at the bottom of the chest.
Medium Fidelity Prototyping Stage
Using our Iteration 3 design, we created a medium fidelity, proof-of-concept model, this time using wood gears and using the laser cutter to cut out holes for the axle. We also used hot glue to adhere the gears to the dowel. We also cut and measured our center stabilizer.
Medium Fidelity Prototype.
Medium Fidelity Prototype (2).
The gears did not line up, since we arbitrarily lined up the gears in Illustrator. We could not assemble the lifting arm of Movement 158 (the lid portion) without a hole in the gear for an axle. In addition, we were unable to complete the center apparatus without a dowel to connect the lifting arm to the block of Movement 92.
For the gears, the instructor suggested we use a rectangular block to physically measure where the gears best align (pictured below). We used this measurement to align our gear holes in the next section. For the movements, we measured and added holes in Illustrator for the respective arms as seen in the next section. Overall, our general proof-of-concept model prototype was complete, demonstrating the gear mechanisms and the concept of the movements.
Gear Dowel Measurement Tool.
High Fidelity Prototyping Stage
Finally, we sketched Iteration 4, taking meticulous measurements for each dimension. We compensated for the thickness of the 3/16 inch wood to ensure that each part would fit as intended. Using the gear measurement tool, we validated the distance between the gears and used it to align the gears within the greater chest file. We used the corresponding shapes to assemble ready-to-cut files in Illustrator.
High Fidelity Prototype (Iteration 4) Sketches.
Chest (1)
To assemble our high-fidelity prototype, we first laser cut all of the shapes of our chest out of 3/16 inch wood and ¼ inch acrylic for the front wall. We used wood glue and 90 degree clamps to attach each side of the chest. We used wood glue to attach the stabilizer to the correct position, such that the platform lift piece is horizontally center aligned in the box.
Movements (2)
Next, we double-layered the gears and the lifting arms, and started by assembling the center apparatus (Movement 92). We used wood glue to glue the gears to a .1225 inch dowel. We also assembled the lid lifting mechanism (Movement 158).
Custom Stoppers (3)
We created custom stopper designs using an Illustrator pattern, creating cool swirls to be engraved on the surface.
Hinge (Vinyl Piece) (4)
Finally, we created a hinge using billboard vinyl for the lid of our chest. We superglued the vinyl piece onto the chest, first gluing the backside in a closed position then the front side in an upright position.
Constructed Prototype
At this point, we were quite satisfied with our progress as the movements worked as intended.
High Fidelity Prototype containing chest (1), center platform lifting apparatus (2a), lid lifting mechanism (2b), custom stoppers (3), and vinyl hinges (4).
Turning Knob
We then created a knob for the user to manipulate the model. We decided to use a 0.5inch diameter dowel for the handle, which connects to our smaller dowel on the big gear and operates the mechanism.
Creative Piece
For our inside creative piece (to be lifted), we decided to assemble a 4x4in Creeper (Minecraft mob) head. We cut out wood and glued together a cube that would become our creeper head. Each piece was spray painted with green spray paint, clear coated, spray painted again, and clear coated again. We then designed the face of the creeper and cut out adhesive vinyl to attach to our head.
Creative piece (creeper head).
We sanded down the outer surface of our chest with the orbital sander and by hand, as the wood felt rough to the touch and there were many areas with an excess amount of wood glue. We had to be careful not to break any of the existing connections and stoppers.
After this was completed, we glued our creeper head to the platform lift piece.
High Fidelity Prototype containing creative piece.
Front panel
We also decided to create a custom front panel with an acrylic pane for the user to see the mechanism inside.
Improvements
When we constructed our high fidelity prototype, there was a limited variety of dowels, and we chose to use ⅛ in diameter dowels for our mechanism. The next day, a larger variety of dowels arrived and were available in the OEDK, but we decided to keep our thin dowels as they were functional at the time. The problem is that these dowels are so thin that they can barely hold under the weight of our creeper head. The creeper head is also so heavy that our original mechanism felt less smooth and struggled to lift it. In the future, this problem could be mitigated by using thicker dowels to begin with or using a lighter material to construct the creeper head. Unfortunately, for this project, we didn’t have many options in terms of materials as we were limited to vinyl, wood, and metal.
Final Product
While testing our prototype, the chest started to fall apart due to our aforementioned shortcomings. Due to the weight of the creeper head, parts of our machine started bending under the weight. This is because the dowels that we used were too thin. Also, our mechanism was no longer as smooth as before, creaking on the left side as it struggled to lift the head.
So we remade our product!
Making the chest (again)
Following the steps of our High Fidelity Prototype, we changed the main axle to be a ¼ inch diameter dowel instead of a ⅛ inch dowel. In addition, we changed the front panel to have a slot for a hand. Since the weight of the creeper head brings the entire chest up while turning the knob, the user is required to hold the chest down while turning to operate the mechanism.
Metal Piece
Although we weren’t required to have a metal piece, we cut out ¼ inch aluminum pieces using the Water Jet cutter for decorative ingot pieces and for the chest latch. The ingot pieces can be considered functional since their intended use is to be counterweights to prevent the chest from raising up. The larger chest latch piece was sand blasted for a smoother finish, while the ingot pieces were purposely kept shiny.
Aluminum Pieces.
Post Processing
We stained the top, sides, stoppers, and handles of the chest to get the appearance of a polished, finished chest.
Final Product
Final Product.
Video
Improvements
- Using a larger dowel to begin with, as previously mentioned.
- The left side of the center apparatus needs an additional stabilizer for the axle. The user feels friction while turning the knob due to crooked movement of the center apparatus.
- Post-processing could have been improved; the acrylic was slightly cracked during handling and the staining is uneven.
Cleaned Workspace
We made sure to clean the laser cutter after every use and cleaned off our work table after our work was completed.
[insert image of cleaned laser cutter and cleaned work table and cleaned water jet]
Bill of Materials
Total Cost:
Labor – 77 Hours
- Unskilled laborer wage ($15/hr)
Wood – $12.53
- Panel – $12.03 ($36.08 for full panel)
- Dowels – $0.50 for 5 dowels ($9.99 for varied set of 100)
Sandpaper – $20.46
- Assorted Grit – $1.80 for 3 sheets ($14.99 for 25 sheets)
- Orbital Sandpaper – $0.78 for 1 ($5.47 for 7)
Vinyl – $9.23
- Adhesive Vinyl – $0.73 for 1 ft ($7.99 for full roll)
- Billboard Vinyl – $8.50 for one tarp ($16.99 for two tarps)
Spray Paint – $13.98
- Green Spray Paint – $6.49 for 1 ($13.98 for 2)
- Clear Coat – $6.49 for 1 ($13.98 for 2)
Wood Stain – $12.98
- Ipswich Pine Classic – $12.98 for 1 qt
Aluminum – $3.17
- ¼ inch Aluminum Sheet – $18.89 for 6×12 inch sheet
Material Cost: $87.46
Labor Cost: $1,155.00
Total Cost: $1,242.46
Conclusion
We felt that the project was difficult, especially since the quality of the final product and mechanism don’t truly reflect the time we sunk into it.
We thought we could finish with our high fidelity prototype, but we could not get the mechanism to work as intended when we attached the turning knob, and had to make the difficult decision of remaking the piece. This made the weekend before the deadline especially rough, with both of us spending 90% of our time awake in the OEDK (or 47% of the elapsed project time in just two days). Nonetheless, we felt proud and relieved when it was all over. More than making a chest, this project was an exercise in patience and acceptance.
