For the midterm, we each picked a simple machine to make from a book of choices. I chose to create a fast return actuator, which uses a narrow channel that a crank is fed through in order to rapidly turn a wheel. This can be seen here. This allows for quicker turning of the wheel and precision, as the handle is forced through a limited path due to the arm in the middle. While this does make the machine stiff or rigid sometimes, when turned correctly it rotates the wheel quickly.

To begin, I first designed the different parts in Adobe Illustrator, using shapes such as rectangles and circles to make the large pieces, and smaller circles in order to map out the holes for the dowels to fit through. I also created a base and backboard for the mechanism to fit onto, and put  the words “Fast Return Actuator” on the base.

The first challenge came in translating the design into dimensions that were appropriate for the laser cutter as well as the dowels available. The dowels were available in standard sizes from 1/8″ to 1/2″, but the original designs called for some very strange dowel sizes, such as 5/32″. To solve this, I standardized the holes to either 1/4″ or 1/2″. In addition, the design called for various holes in the dowels themselves to be drilled in order to thread another dowel through which would serve to provide limits to the movement of the first dowel, much like the toothpick method we learned in class. However, I did not like the aesthetics of the toothpicks, so I also made various rings which would be placed on the ends and glued into place:

The second challenge came in the thickness of the wood. The laser cutter could not handle the 1/2″ thickness of some of the pieces, so I made two copies of those pieces and glued them together. For the base, I glued three 1/4″ pieces together in order to obtain a stable base.

After printing these pieces and gluing them together and creating a semi-finished mechanism which worked, I was unhappy with the overall size of the machine, especially compared to the ones created in previous years. As a result of this, I decided to go back into my original designs and double them in size. I figured this would not be difficult to remake since I had done it already.

I re-cut everything in the laser cutter and proceeded to finish some of the pieces. To change the color of most of the pieces I went with a simple stain which darkened the wood and provided a nice color. For the main wheel, I planned to make it into a sort of roulette wheel of alternating black and red color. However, upon returning from spring break, I found that all the black spray paint had been used. I decided to settle on a just a simple red coat, which proved to be a slight challenge especially on the sides which had been charred due to the laser cutter. Ultimately after a couple coats it finally cooperated, and I was happy with the color. I debated on using Sharpie to add numerical values to the wheel, but after testing its look on another piece I thought I looked too unprofessional and clean and decided against it.

Assembling the rest of the machine was simple, and just required a few days of gluing parts together with clamps. However, the final challenge came on Monday, when I assembled the final piece. One thing I did not account for was the added instability of the larger wheel. In the smaller version, the wheel spun neatly and did not wobble, but in the larger version spinning it too quickly would lead to the wheel rattling too much. I know how to fix this, but I unfortunately had no time to redo the dowel as it would require another day of gluing. I would simply place another wooden ring around the outside of the wheel. I already had one on the inside to ensure it was able to turn, but another ring on the other side would enhance the stability greatly. In addition, the machine feels stiffer than the smaller version, but as long as it is turned in a nice rhythem, it operates nicely. These were the only two mechanical things I would change in a future design. I would also like to spray paint the black onto the wheel in the future, and the wheel is easily removed because of the lack of an outer ring. This outer ring design worked well for the bottom piece, as it keeps it turning straight and prevents it from wobbling:

Additionally, I decided to make the turning rod removable just to added another human dimension to the machine. The turning rod can be stored on the left side of the base, but it could easily be permanently attached to the wheel and through the middle piece using glue.

Other than the instability caused by the lack of an outer ring, I was pleased with the final version, and would only make other minor aesthetic changes to the machine later.

Thanks for reading, Tim.