THE PROJECT

For the midterm project, we had to create a mechanical model from 507 Mechanical Movements demonstrating a mechanism and creating a functioning model. In this project we aimed to work through the prototyping process, moving from brainstorming, to low and medium fidelity before arriving at a final model.

The movement I worked on was #27/507 or Multiple Gearing  which is described on the website as “Multiple gearing—a recent invention. The smaller triangular wheel drives the larger one by the movement of its attached friction-rollers in the radial grooves.”

To get an idea of how the mechanism worked I looked around on google:

I also found this model which was pretty cool.

And then, I was informed there was a model in the OEDK with the same mechanism although this was from a different book which also looked similar to these designs.. 

Looking at all these different designs, I was able to gain a better understanding of the mechanism and how I could approach designing my model.

2D DRAWING

Based on the picture and the various designs above, I worked on setting the design up in Illustrator, working on building of triangles and circles to create the tracks and moving spoke. I mainly created a lot of simple shapes and combined them with the pathfinder to create the final shapes and put in the holes.

PROTOTYPE #1: LOW FIDELITY

I laser cut a small version of the design above out of cardboard. However I glued down the bearing parts that connected at the spoke to show it would fit, rather than the rolling function. It would not mesh or roll smoothly due to the gaps in the cardboard layers. However, this model displayed that the basic design would work out. From this first prototype I learnt that I would need to have a good way to align the triangles to ensure that they would create parallel tracks to allow for smooth motion.

So, for the next version I decided to etch in where the triangles were on the upper circle so they could be glued in the right place.

PROTOTYPE #2: MEDIUM FIDELITY

The second prototype was pretty much the same design where instead I accounted for using .25 inch dowels for the holes and .25 inch plywood for the different joints.

Another difference was the etching for placing the triangles and creating the tracks the spoke would roll along. 

I used hot glue and cut dowels to connect the parts together to arrive at this:

From this prototype, I realized the wood was actually 0.204 inches and recognized that all of the gaps were way too big. However, using hot glue to fill the gaps I could still make a functioning mechanism, although it wasn’t the smoothest and I did not glue them permanently in place.

Additionally from this prototype, I realized that I needed to improve the support stand and would use bearings to create a smoother rolling motion while creating a firm attachment to the spoke.

PROTOTYPE #3: FINAL VERSION

Next I worked out the adjustments for the final version. Here are the notes displaying how I decided what lengths to used and the various layers with the dowels and base parts.  I used 0.24 inch holes for .25 inch dowels, 0.370 inch holes for ⅜ in dowels and 0.204 for the thickness of plywood in the adjusted illustrator file.

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Summary of additional changes made:

1. Utilizing bearings for smoother motion while moving in the tracks
2. Plasma-cutting the spoke out of 1/4 inch aluminum instead of plywood
3. Adding a spinning design on the back that spins on the other side of the model along with the rotation of the wheel
4. Adding branches (loosely based on branching coral) on the inside of the support stands to spin along with the crank to fill the space and look more interesting
5. Redesigning the shape of the crank and adding branches to the crank
6. Adding a branch circle behind the rotating wheel as a spacer between the base
7. Making the supports a separate part that would be glued on top of the base rather than being attached with finger joints into the base. This was a useful change as I was able to adjust the placement of this part to allow for the right amount of space for motion, but not too much for wiggle room.
8. Coloring the model. I decided to go with the bright colors of orange and blue and a mahogany stain for the base.

Overall the entire process was:

1. Laser cutting all the parts in this file
2. Plasma cutting and finishing the spoke
3. Cutting dowels of the appropriate length
4. Spray painting parts and wood-staining the base
5. Gluing together parts (in the right order and alignment)

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Although this sounds pretty straightforward, there were a lot of parts I had to redo and mess around with to get the alignment of the parts correct. Additionally, the painting process took a while as I had to get both sides of the parts. Gluing also took a long time because I had a lot of small parts that had to be glued in a specific sequence. I ended up using super glue rather than wood glue for the majority of the smaller parts as it was easier to apply. I used wood glue for some of the large parts such as the wheel.

THE FINAL MODEL:

Here is the final file with all the parts below:

This process yielded the final model: