Brainstorming, Design, and Iteration!

Last lab, our team started brainstorming for our yoyo:

Clare had lots of great ideas already sketched out:

steampunk...

time turner...

 avatar...

We discussed what our goals were for the semester and for a potential yoyo.
We all agreed that an ideal yoyo is:

• Awesomely designed!
• Easy to assemble.  We don't want to spend hours and hours putting our yoyos together.
• Robust (we don't want them to break)
• Quality (shoddy parts=sad assembly time)

While we all loved Clare's steampunk theme, the thought of moving gears seemed daunting and time consuming.  Emma came up with brilliant idea of...
A Compass!

The compass maintains the same aesthetic as the steampunk watch, but has only one moving part and still takes advantage of the circular shape of the yoyo.

Clare drafted up the compass face in Illustrator.  We are going to waterjet the faces out of aluminum!

 

Illustrator Design

We met up at the MechE Lounge to discuss the general plan for the yoyo mold design and to divide up the rest of the tasks among us.  We decided that our own personal yoyos should include real magnetic compass needles (the 44 others will have plastic needles).

 

Sketching to clarify design of components (Injection molded body, snap ring, and needle.  Thermoformed clear plastic window.  Waterjetted aluminum face feature) as well as how the nut and set screw are fit in the assembly.

Beckett and Kate were CAD leads for the body part, James took on designing the needle, Connor consulted with Dave on how to best thermoform the window feature, and Emma was in charge of spin calculations and team organization.  Clare continued as team Illustrator master, assisting with the needle drawings.

Modeling!

We iterated through several yoyo designs, essentially choosing between "one compass with a two sides" or "two compasses made into a yoyo".  The slim profile won out.  

 

Three design iterations.  We decided on the left-most design, for its slim profile and more cohesive design.

Dimensioning!

After CADing with keeping depth of the nut/set screw, part thickness, and critical dimensions in mind, we made engineering drawings.  When dimensioning, we kept our press fit features in mind (instead of +/- .005 inches for press fit parts, the exterior parts were -.005" tolerance and the interior were +.005" to ensure that parts will not fall apart.   Here are some examples:

 Body

 Gear Detail for Needle

Thermoformed Window

Full assembly

Below is a neat table of our specifications for the Yoyo!

Item	Dimension	Target Value	Tolerance	How to Measure
Assembly	Total Mass	.15 lbs	± 0.02 lbs	Scale
	Max Diameter	2.464"	± 0.003"	Calipers
	Max Rotation Speed	800 RPM	±150 RPM	Tachometer
	String Gap	.15"	± 0.005	Calipers
Compass Face	Outer Diameter	2"	± 0.005"	Calipers
	Thickness	.0625"	± 0.005"	Calipers
	Inner Hole Diameter	.25"	+ 0.005"	Calipers
Compass Needle	Ring Outer Diameter	.44"	± 0.005"	Calipers
	Ring Inner Diameter	.25"	- 0.005"	Calipers
	Max Height Dimension	1.69"	± 0.005"	Calipers
Extrusion Pole for Needle	Outer Diameter	0.23"	0.005"	Calipers
	Inner Diameter	.20"	0.005"	Calipers
	Height	0.22"	0.005"	Calipers
Cap for the Extrusion	Max Diameter	0.37"	0.005"	Calipers
	Inner Ring Diameter	0.15"	0.005"	Calipers
	Height	0.10"	0.002"	Calipers
Thermoform Cap	Max Outer Diameter	2"	+ 0.005"	Calipers
	Cap Outer Diameter	1.76"	+ 0.005"	Calipers
Yoyo Body	Cavity Diameter	2"	- 0.005"	Calipers

Now that we are done designing our yoyo, the next step is to design our molds for thermoforming and injection molding.  This upcoming week will be busy: CADing and dimensioning drawings of the molds, writing our machine code to minimize machining time, and writing up a manufacturing plan.  We're up the challenge! We even made a TeamGantt so make sure we are on track when making these Yoyo's! 

Signing off,

Team 2.00yoyo