Mechanical Space Model by Rachel and Thomas | ENGI 210: Prototyping and Fabrication

For the final project, we were tasked with creating a working mechanical model using 2D techniques like laser cutting, water jet cutting, and vinyl cutting. We drew inspiration from the website 507 mechanical movements and chose #55 ( http://507movements.com/mm_055.html ).

Our initial idea was to have one large inner gear, one medium driving outer gear, and two smaller outer gears that were connected within the large inner gear. This way, the three outer gears would spin within the large inner gear. We decided that our project would mimic the solar system ( somewhat) with the middle driving gear as the sun and the other two gears being planets.

After our initial first draft, we realized that our solar system would be much more accurate if the smaller outer gears would revolve around the medium driving gear. We decided to take the jump and go with this route.

We decided that we would instead have three smaller outer gears that would follow a circular path around the central driving gear, while rotating.

Our first steps involved determining the diameters, and teeth numbers for all of the gears. This process was relatively easy thanks to the help of geargenerator.com. We also created designs for the planets that we were going to add to the small gears. Then we determined the dimensions of the entire model, including what we called the backboard and the base. This was a bit trickier to figure out because we had to create the circular path for the small gears to follow. We decided to make the gears two layers of laser-cutting-plywood thick (⅛” each) and the backboard four layers thick. We also decided to laser cut our name plate. We added the mechanism number, our names, and the semester/year.

Unfortunately some of the wood cut perfectly while other parts did not, so we ended up having to redo parts of the cut.

After this, we cut out a vinyl sheet filled with stars so we could use the negative to spray paint stars on our back board.

We moved on to water jet cutting where we cut out small comets to attach onto our large inner gear for aesthetic purposes. For the functional water jet cut piece we implemented a piece of aluminum as part of our crank mechanism.

We moved on to gluing the pieces of wood together. All of the gears were easy to glue together with some wood glue and clamps. The backboards required a little more thought. We realized that in order for our model to work, we would need to have a way for the smaller gears to be held upright without sagging forward. To remedy this, we decided to put dowel rods through the small gears, and at the end of the rods, add a circular piece of wood. Then we could add additional layers in between the backboards that would allow for the dowel rod to move along the circular path and have a supporting backing. In total, the entire backboard consisted of 6 layers. We then glued the backboard together in two separate parts. We realized then that gluing the two parts of the backboard together would have to be our last step.

We then worked on creating the smaller gears. We had to epoxy the bearings on the inside of the gear, and cut and glue dowel rods of the appropriate length. Finally we glued the circular backings on the ends of the dowel rods. We also cut and glued a dowel rod through the middle of the central driving gear. We also glued the large inner gear onto one of the backboard halves.

After we finished gluing the majority of our parts together, we worked to sand down the rough edges of the gear teeth and the surfaces of all the parts we needed to spray paint. This was probably the most tedious part of the project. After sanding down and taping down the gear teeth, we went on to spray paint our parts.

This part was a bit more fun as we got to be more creative. Our spray paint design took on the look of a galaxy, with a first layer of black spray paint with hues of dark green, light green, and blue. We ended up spray painting the backboard parts and the base in this galaxy theme. After the paint dried, we added the vinyl sticker and taped off the rest of the board so that we could spray paint on our stars.

For the planets we ended up “finger-painting” with some of the red acrylic paint mixed with the yellow spray paint for one of the planets. For “earth” we were able to first spray paint it blue, and then use a q-tip to add the green paint afterwards. Finally for the last planet we used pink and blue spray paint, but mixed the colors around with our fingers. We added the final touches with a q-tip. For the central driving gear, we opted to use yellow spray paint to mimic the sun. We then used a protective “crystal clear enamel” spray to coat all of our pieces.

Once we finished all of our pieces it was time to assemble. Our final assembly ended up being very time consuming as fitting in the gears along with putting the base together ended up being more difficult than anticipated, especially because we had previously glued the planets onto the gears. We ended up having to cut the planets off with a saw, assemble, then glue them back on.

In conclusion, our grueling efforts paid off as our final model worked out exactly the way we wanted it to, not only succeeding in performing the mechanical function but also being aesthetically pleasing.

Video of Mechanism: IMG_2178

Rachel and Thomas Final ENGI 210 Project Slides