A lean, green, yo-yo machine.

He’s green, he’s lovable, he’s roughly spherical.  He’s Mike Wazowski, and he stumbled into our hearts way back in 2001, starring in the Pixar film Monsters, Inc.  I don’t know about the rest of my teammates, but ever since I saw the movie as a child, my greatest dream was to one day hold Mike in Yo-Yo form in my own two hands.  Back in high school, when I heard that by going to MIT and majoring in Mechanical Engineering I would have a chance to build my very own Yo-Yo, I immediately trashed my other acceptance letters and swore a solemn oath:  I would take 2.008 and I would not flunk out until I had built my Mike Yo-Yo.

Pictured:  The nexus of childhood dreams.

Team B the 1 went through a number of design iterations, and ultimately settled on one that used as few parts as possible, fit together as simply as possible for ease of both manufacturing and assembly.

We wanted to get some voice samples of Mike, but Billy Crystal’s agent won’t return our calls. 

Each Yo-Yo consists of five injection molded parts (numbers 1, 2, 3, 4, and 7), one transparent thermoformed part (number 6), and one die or laser cut part (number 5).  All of the parts will be press-fit together, with the shells (parts 1 and 7) snapping onto their bases (parts 2 and 3).  The facial elements are all held in place by part 7, with the exception of the iris (part 5) that is free to rattle around inside the eye (part 6).  Essentially, part 7 is multi-functional, serving both as Mike’s face and holding the assembly together.

We chose this design to minimize the number of assembly steps and the total number of parts.  The pieces of the face align naturally together, and by pressing on the facial shell, they are securely held together with one action.  The rear is composed of two pieces to minimize material – rather than having a solid block, a hollow shell uses a fraction of the amount of plastic.

The iris (part 5) is small and of a regular shape, so we made the design decision to slice it out of sheets of vinyl or acrylic as opposed to injection molding.  This requires the production of fewer molds, and has a comparable production cost and speed to injection molding anyway.

The design should be very solid.   Even though we have a number of parts, they are all held together by a small number of press fits, enhancing stability and durability of the final assembly.

Here are some specifications.  I didn’t write them personally, but I’m told that they are very nice.

General Parameters	Parameters of Interest	Specifications
Length Dimensions	Diameter	2.5 in
	Width	2 in
	Gap Width	.125 in
	Height of Oscillations	2.5 ft
Mass Dimensions	Mass	0.12 lbs
	Moment of Inertia	0.09375 lbs * in^2

Also, it turns out that simply wishing that I had a Mike Yo-Yo isn’t enough – we actually have to come together as a team to make it.  To that end, here’s a nifty-looking Gantt chart that will guide us through the semester.