Mechanical Design Process
Define the Problem - We met with Mrs. Benardine Ghanson and Mr. Joel Opoku of the MakeLab ACity Accra to discuss the project they were interested in implementing. They expressed that they wanted a display to encourage students to interact with mechanical engineering in the space. More specifically expressed an interest in creating a pinball machine we the tools in the space to inspire students and engage them in engineering.
Do Background Research - We researched other pinball machines. Many are arcade style and there are also many DIY versions online. From this research, we learned the ideal angle for the obstacle board, common characteristics that each pinball machine shares, and gathered some interesting ideas for obstacles and designs.
Specify Requirements - From our research and conversation with Mrs. Benardine and Mr. Joel, we were able to gather requirements for this design. The design had to be table top, and must be able to be created with the materials in the Make Lab. It had a maximum size of 21 inches by 48 inches by 7 inches. We also generated a list of characteristics such as a launcher, flippers, angled board, obstacles, etc.
Brainstorm - In our team with input from Joel we created the idea for the dual pinball machine. We also brainstormed some obstacle designs, and began to sketch what this design would look like. In brainstorming, it is important to remember that no idea is a bad idea, it is okay to be creative with a solution you are unsure will work at this stage. It is also important to include the input of as many people as possible to try to find the best ideas.
Develop and Prototype - In our case, most of our work was done remotely. This meant that we could not prototype with the tools in the lab. Instead we used SolidWorks to CAD our ideas and send them to ACity for feedback. In this environment, we were able to see how everything fit together physically.
Test Solution - While we were working remotely we could not test the full design. Testing instead happened in smaller components. We would use the rubber band and a table to make a board and experiment with how much stretch the design would need. We also developed test pieces which are small pieces of wood that allowed us to ensure all of our measurements fit together correctly without printing the entire board idea.
Repeat - Once we had tested aspects of our design we modified it accordingly. At times this meant that we had to brain storm a new idea, develop a new design, or simply do more testing. Below there are more details about many of the changes that were made a result of this process. This process continued until we were able to be in-person and physically assemble the design. From the assembly we also found more changes that we want to implement for future use.
Communicate Results - The last step in this process is to share your results. We did so by hosting a 2 hr workshop session in the MakeLab at ACity where we reviewed our design process and the techniques used with students. We also created a lesson plan for a 4-week version of that session to teach students even more about our findings. Lastly, we created this website to communicate these concepts with any student at any time or place.
Spring to Rubberband
One of the first design changes that we made was to switch our launcher from being powered by a spring to being powered by a rubber band. Many pinball machines that we researched used a spring, so this was our original design. However, from our collaboration with Joel we learned that getting springs in a specific size can be difficult. Since we wanted other MakeLabs to be able to replicate this design, we wanted to choose components that would be easy to find. This prompted us to redesign the launch mechanism to be powered by a rubber band.
Double layer of wood
In our original design, we planned to use 1/4 inch thick wood for all components. Since we were developing the design remotely, we had no concept of the strength of this wood, how heavy it would be, or how it would react with the laser cutter. Since Joel has worked with the laser cutter in this space often and is familiar with these materials, he advised that we modify all of our smaller components to use 1/8th inch thick wood. This would be still very durable and save resources. He also expressed that 1/8th inch thick wood is very difficult to laser cut, but that the larger pieces would still need the support of that thickness of wood. As a result, we modified the design to use two layers of 1/8th inch thick wood, so it would have the support of 1/4 inch thick wood and the laser cutter would not have to cut through such a thick material.
Obstacles to Peg Board
Initially, we had wanted to use recycled objects as the obstacles. We thought this could be a cool way to add some character to the design. After our original design was complete, we had a brainstorming session to find ways to improve the design. Out of this, we came up with the idea of the peg board. We wanted to find a way for student to be able to add to the design and we thought it would be cool if they could create their own obstacles using the 3D printers and laser cutter. The peg board would act as default obstacles, but would also allows students to add to this design and modify the board to make the game more engaging.
Change in Shape of Dowels Face
In our original design, the face of the launch slider was a circle to hit the ball. As this design was tested in CAD, we realized that this would have now way of attaching to the rubber band. Instead we extended the top to provide indents for the rubber band to latch too. We also added a flat bottom so that it would say upright on its own
Additions
Through this process, there were also several additions made to the design that we had not originally considered. Notably, we added a curved wall. This helped the ball to move toward the obstacles after it was launched. As we were creating the design, we realized that we would also need a place to keep all the electronics and a good way to access them. At this point we also decided that we wanted them to be visible to students. We moved the obstacle board upward to allow more room for the electronics in the frame of the display. We also added access holes to make it easier to modify the electrical board and implement the components. Lastly, we added offsets to each of the holes connecting components. This allowed the peices to slide together more smoothly.
Use of Test Piece
We used the test peices shown to the right to test how all the components would fit together. It would have been a waste of resources to test our design by laser cutting the entire thing only to find all the ways it does not work. Instead we conserved on our resources by testing the size for the connecting joints, and motor on a smaller piece of wood. This helped to inform the offsets we would need and modifications to the motor mount.
