Deliverable 1

Model and Notes on Assembly

Here is a face view of the yo-yo, showing the bow-tie element. 

   Our design is composed of six main elements: the white injection-molded yo-yo body, a ball bearing, a black injection-molded bow-tie, a  black injection-molded retaining ring, a pair of nuts, and finally a clear thermoformed window. The main feature of our product is that the bow-tie is free to spin independently of the main body, which will show through the clear plastic window when the yo-yo comes to a stop in the user's hand.

Exploded view showing hidden components.

   The exploded view shows the components that will be hidden from the user, and also shows the order in which the parts will be assembled. The bearing is press-fit to a boss on the yo-yo body, which is screwed into the other half via set-screw and an embedded hex nut. The two nuts shown are press-fit into the bow-tie from the rear to increase its inertia, and then the whole assembly is press-fit to the OD of the bearing using a pocket on the rear of the bow-tie. The window is then put into place over the bow-tie, with its flange resting upon a lip molded into the body. Finally, the retaining ring is pushed into place, creating a press-fit between itself and the outer edge of the body, and trapping the flange of the window, securing the whole assembly together.

   The product as a whole satisfies the parts number requirement and also the injection molding and thermoforming requirements. Parts to be injection molded were designed to have near-constant thickness to facilitate even cooling without dishing, buckling, or warping defects. This was especially important on the bow-tie, where the underside comprises entirely of intersecting ribs that form the pockets necessary to install the counterweight nuts and bearing, and also the body, where care was taken to ensure that the shelf for the window and retaining ring did not compromise the wall thickness. Parts were also designed to maintain their shape whilst cooling, for example we added supports to the central boss of the body part so that it would stay perpendicular to the floor of the body pocket to ensure that the bow-tie would be free to spin. Lastly, all parts were designed with tapered faces so that they would not grab the core of the molds used to produce them, thus increasing the speed of our production. Quality, Cost, and Rate dominated our decision-making process during the design of these parts.

Table of Specifications

Specification	Value (with units)	Measuring Method
Yo-Yo Diameter	2.500 ± 0.005 inches	Digital Caliper
Yo-Yo Outer-Gap Diameter	2.368 +0.000            - 0.005  inches	Digital Caliper
Yo-Yo Inner-Gap Draft Angle	2 ± 2 degrees	Digital Caliper, tangent of two sides
String Gap	0.075 ± 0.005 inches	Digital Caliper
Yo-Yo Width	1.700 ± 0.005 inches	Digital Caliper
Yo-Yo Cavity Diameter	2.092 ± 0.005 inches	Digital Caliper
Bow Tie Max Length	2.046 ± 0.005 inches	Digital Caliper
Bow Tie Inner Diameter	0.375 +0.000            - 0.005  inches	Digital Caliper
Inner Shaft (for ball bearing) Width	0.125 +0.005            - 0.000  inches	Digital Caliper
IDE of Ball Bearing	0.125 +0.000            - 0.005  inches	Digital Caliper
ODE of Ball Bearing	0.375 +0.005            - 0.000  inches	Digital Caliper
Yo-Yo Wall Thickness	0.1875 ± 0.005 inches	Digital Caliper
Retaining Ring Outer Diameter	2.378 +0.005            - 0.000  inches	Digital Caliper
Retaining Ring Inner Diameter	2.175+0.000           - 0.005  inches	Digital Caliper
Window Extrusion Outer Diameter	2.185+0.005           - 0.000  inches	Digital Caliper
Mass of Yo-Yo	0.166 pounds	Scale
Volume of Yo-Yo	4.10 inches cubed	Mass/Density
Max RPM of Yo-Yo	142.29 RPM	Tachometer sensor
Inertia in X and Y direction	0.0952 pounds*inch2	Calculations
Inertia in Z direction	0.1345 pounds*inch2	Calculations

Gantt Chart

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