Mechanical Movement

In this project, my teammate, John Reko, and I will be building a simple machine using one or more of the motions presented in Henry Brown’s 1868 book 507 Mechanical Movements. As Rice’s mascot is the Owl, we will be using the following movements (and some derivatives) to make an owl that flaps its wings.

92. Ordinary crank motion – We will use this to convert rotational motion from a hand crank, the”power” for the system, into vertical motion to drive the wings up and down.

131. Geared crank – This machine will run in “reverse”, so that driving the shaft up and down “flaps” the green lever, to which we will attach wings.

100. Quick return crank – A rodent (mouse?) will be attached to the end of the blue crank to give it irregular motion. This will give the model the impression of a hunt – the owl is chasing the mouse as it flies and the mouse is scurrying back and forth to get away.

An early drawing of the flapping mechanism and owl and mouse structures are shown below. An underlying gearset will drive each of these motions.

  

Here are this images we chose to base the owl around. The first we used for the wing outline, the second for the body. Snowy owls were used to give greater contrast to the background and with shading within the owl.

From these and our initial drawings, we developed the following 2D model, both for the owl and for the mechanisms and the box to support them.

Prototype 1:

We used the laser cutter to print the functional parts out of cardboard and assembled them with hotglue and masking tape. The proof-of-concept worked, and we could flap the wings with the gear and cam motion.

Prototype 2:

Using more wooden gears. cranks and cam rods, we built a more realistic working prototype.

This revealed quite a number of shortcomings in our design, including:

• The front slot for the mouse crank too narrow
• Wing gears improperly aligned
• Wing crank too wide and too long.
• Supports needed between the two “halves” of the owl

The underlying concept, however, worked flawlessly, and we proceeded to the final high-fidelity prototype with these changes.

Prototype 3: 

We laser-cut the remaining pieces out of wood and plasma cut the mouse crank out of metal: This had two purposes. The first is that the gray metal will lend itself nicely to it’s new life as a mouse. The second (and more important) reason is that a screw or post will slide with less friction in a metal slot than it would in a wood one.

 

We assembled the box and added a vinyl sticker to make the mouse more mousy. Then after staining and oiling everything, we glued it all together! Voila!

A video of the owl working: Google Drive Link

Slides for project grading: Night Owl Slides

Review and Analysis:

This project turned out amazingly. The cranks work smoothly and the wings flap very naturally.

However, after oiling the raster didn’t appear as dark or accented as I had hoped. The body split into two is also rather odd, and if I could redesign it, I would probably put them closer and move the gearing to the outside of the body in some way.

Price Breakdown:

• 2-3 sheets of laser cutter wood ~ $6
• 1/8 inch steel ~ $10 for entire plate
• Bearings x 8 ~ $5
• Machine Time:
  • ~2h laser cutter – $100
  • ~20 min plasma cutter – $20
• Time (14 hrs) × 2 people ×$15/hr ~ $420

Materials Cost: $21

Total Cost: ~$560

Lessons Learned

Delegating asynchronous work – John and I quickly learned how to split up the work and utilize our team effort well. After the first day, we delegated both design and build tasks, and communicated interfaces between them and the necessary changes and updates on each of our ends.

Clearly demarcating prototypes – It was so much more efficient to build a prototype, list the things that worked and didn’t work and build another, than to keep changing little things on the same model. It also gave a concrete sense of progression as each successive model improved in quality and functionality.

Plan time for glue/finish drying – One thing we drastically underestimated was the time the glues, stains, and paints we used would take to dry. This led to us accidentally polluting the “clean” pieces of wood when we accidentally touched pieces we thought were dry, and some less than ideal fingerprints on the rastered pieces as well as the project still having wet parts at the class showcase.