Creating our mechanical model was a journey with ups and downs, requiring a lot of problem-solving and clever engineering. We wanted to tell a meaningful story with our model, so we began by brainstorming what stories we could tell. In the end, we decided to tell the story of the countries that Eze has lived in and how it has brought him to where he is now in Houston, Texas. To tell this story we wanted a model that allows users to “travel the globe” as the model iteratively shows the journey Eze has taken throughout his life. With the story in place we searched for mechanical movements that would help to achieve our vision. We landed on mechanical movement #68. Initial plan can be seen in image below.
This movement allows for a partial rotation of one gear with every full rotation of the other. Our 2d drawings show our concept that as users spin a globe disc around, representing them traveling the globe, a cube with the countries on it rotates iteratively, showing each country one by one. The countries on the sides of the cube include Nigeria, the Philippines, the United States, and the United Kingdom with Texas on the top. The drawings included iPad sketches and Fusion360 renderings.
With the concept planned out, we made a low-fidelity model using cardboard. We laser-cut the cardboard to create a base box that houses our rotating wood rods, which allow for the spinning of our disc and cube. The cardboard model was far from a final model and was created to give us a 3D vision of our concept as well as help us plan our next steps.
At this stage, we began work on the next iteration of our model, which would include pieces that would eventually make it into our final model, such as our base box and cube of countries. For both the base box and the cube of countries, we used the box maker website to obtain our SVG files for laser cutting. For both, we used a kerf of 0.008” and a wood thickness of 0.2”. The final base box we ended up with was 10x4x13 inches in measurement. Our cube of countries had side lengths of 3.5 inches. We placed blue tape on our wood before laser cutting to avoid burnt edges where needed.
Other components such as our gears and rotating rods changed as we started to put our pieces together. In particular, we ran into issues with our initial gears. The first issue we ran into was due to the misalignment of our stacked gears, we noticed that when we would spin the gears they would always end up bumping into each other and hindering the overall mechanical movement. We thought that this was due to the circumference of gear B (in first image), and so we proceeded to try to sandpaper gear B to reduce its overall size. Following the sanding of the gear, we still noticed that the motion was still being interrupted, and so we decided to cut the gear down instead of sand it down.
Following cutting gear B, we still noticed that it would not spin. We put this issue down to the gears being handtraced when the adobe file was being made for laser cutting. We did some research and found a blog post from this exact class from 2017 that ran into the same issue with mechanical movement 68 (link below). Lucky for us, they had made a file of mechanical movement 68 that seemed to be properly handtraced. We took this file, adjusted the size of the gears to fit our box and proceeded to use the resulting gears for our project.
Link to older blog post: https://engi210.blogs.rice.edu/2017/09/17/stop-in-the-name-of-fitting-like-a-glove-mechanical-movement-68/
Second issue we ran into was the positioning of the two gears in such a way they were not too close together that they would touch each other and prevent rotation or not too far away that they would not come in contact with each other. The picture below shows the multiple distances that we tried using bearings as our gear and rod holders. To create the holes for the rods to pass through we drilled holes at the measured locations by first drilling a pilot hole and then using a bigger bit to create a bigger hole. We then sanded the edges to create smooth round holes.
To the right of the above image, you can see two empty bearings that were glued to the base box; that was the initial distance that we tried which failed. For the ones with wooden rods in them, we measured the radii of both our gears (respectively from their midpoints), added these values together and then averaged them. This gave us a relatively optimal distance for our two gears to sit at from each other where they could spin properly. We also placed the gears on top of the base box to allow for a flat surface to lie on, and to increase the smoothness of rotation we put washers down first for the gears to rest on to avoid wood on wood interaction.
For our metal piece, we plasma cut a 3 inch diameter disc, angle grinded the dross, filed the rough edges and then proceeded to sand blast the piece. Following these, we downloaded an animated globe and used the vinyl cutter to place this on our processed metal disc. We then glued this piece to the rod with gear B attached to it where the disc would serve as a handle for spinning its cube counterpart. See below:
At gear C, to support the cube, we cut out three 4 inch rods with the same thickness (0.3 inches)as the single rod holding the cube in the picture above. We then proceeded to stain the model with a transparent oil based wood stain. See below:
Final model/PowerPoint slides and videos below:
Ppt link: https://docs.google.com/presentation/d/198vlvkP47eV__f-Y1WXTiTI3CpqZPYRJPFmGOPOJt3I/edit?usp=sharing
Cost/price analysis:
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials | 24”x24” Laser cutting Plywood | $169.99/12 sheets | Amazon.com | .21 (2.5 sheets) | $35.70 |
| Cardboard | $16.99/50 sheets | Amazon.com | 1/50 | $0.34 | |
| Blue tape | $6.19/roll (60 yards) | Homedepot.com | 1/10 | $0.62 | |
| Wood rods | $0.78/ rod (36” long) | Walmart.com | 1.5 | $1.17 | |
| Vinyl Sticker | $12.99/roll (12”x15’) | Amazon.com | 0.015 | $0.19 | |
| Transfer Tape | $6.74/roll (12”x48”) | Joann.com | 0.056 | $0.38 | |
| Steel | $14.93/108 in^2 | Homedepot.com | 0.065 | $0.97 | |
| Hex nuts | $18.20/box (100.box) | Homedepot.com | 1/100 | $0.18 | |
| Bearings | $4.75/bearing | Homedepot.com | 3 | $14.25 | |
| Washers | $15.30/box (100/box) | Homedepot.com | 3/100 | $0.46 | |
| Blasting Abrasive | $77.59/25 lbs | Homedepot.com | 1/50 | $1.55 | |
| Sand Paper (150 grit) | $6.98/4 sheets | Homedepot.com | 1/4 | $1.75 | |
| Oil Based Wood Stain | $13.98/qt | Homedepot.com | 1/4 | $3.50 | |
| Labor | Laser cutter Operator | $19.25/hour | Ziprecruiter.com | 4 | $77 |
| Plasma Cutter Operator | $19.89/hour | Ziprecruiter.com | 1/4 | $4.97 | |
| Vinyl Cutter Operator | $16.49/hour | Ziprecruiter.com | 1/3 | $5.50 | |
| Post-processing | $14.39/hour | Zippia.com | 3 | $43.17 | |
| Prototyping Engineer (You!) | $35/hour | Red Fox Innovations | 1.5 | $52.50 | |
| Overhead | Facility Cost (Machine Time) | $1.25/hour | Sawmillcreek.org | 7.6 | $9.48 |
| Quality Control | $13/hour | Zippia.com | 1 | $13 | |
| Design | Engineering and Development | $35/hour | Red Fox Innovations | 1 | $35 |
| Adobe Illustrator License | $263.88/year | Adobe.com | 21/365 | $15.18 | |
| Fusion360 License | $545/year | Autodesk.com | 1/365 | $1.49 | |
| Misc. | Waste and Scrap | $13.50/hour | Ziprecruiter.com | 1 | $13.50 |
| Total | $331.85 |
This project combined many prototyping techniques from previous homework and, as such, has a cost analysis that combines many of the materials and methods used in previous assignments. The cost for each aspect of our project is laid out in the table above. The total cost of materials was $61.05, many of the material costs were straightforward and were obtained from websites such as Home Depot or Amazon. There was some estimation involved, such as estimating how much wood stain we used or the quantity of sand abrasive exhausted during sandblasting. Others required some area calculations used in determining the amount of metal used for our 3-inch diameter disc and the two vinyl stickers to be placed on the faces of the disc. Labor cost was $183.14 and was the most expensive aspect of the project. To estimate labor costs, we used websites such as ZipRecruiter to find the average hourly rate for operators of different machines used in the project as well as hourly rates of engineers for the job. For the design portion we included software subscription costs for adobe and fusion360 as we used both in the design portion of our midterm. For waste and scrap we estimated that we used about an hour of our time cleaning up after each work session and equated this to time used for the management of waste generated from a project like this. The total cost came out to be $331.85 which is the most expensive of projects so far this semester. Now that the process has been refined and earlier low and medium fidelity iterations of the prototype are no longer needed the prices would be driven down in the development of future models. This would especially be true if the model was made in bulk in a factory setting.
