The Bird Box aka (Middle Finger Assist)

There is a blank and an embossed version of the case. The blank version prints with all the pieces at once with no supports.  The embossed case needs to print with the lettering facing up and needs support and a brim.  I've included the GCode files to print either model at once as well as the files for the individual parts. 

Assembly:

Place the sprocket in the slot in the rounded end of the bottom piece and put the large gear on the top of the sprocket. There is a flattened side that aligns them

The small gear with the attached crank slides onto the pin

Then snap on the top and select a detachable top to your chain 

next just feed in the chain and turn the handle.

I printed this in PLA at 0.2mm layer height with 3 perimeters to make the small crank and some other thin areas strong.

More than the model itself, the chain is the thing I love about this.  My last design used a gear and rack system that had some space limitations so I wanted to create a chain and sprocket to see if I could overcome this. The Parametric chain can be sized by changing 2 parameters; The “Hole Diameter”controls everything but the width, which is a separate parameter.  There are some limitations on size before the model breaks in Fusion360 but it can be customized quite a bit.  Feel free to customize and use it in your own design, or just print as many links as you need from the files. There is a chain - individual links can be copied and moved 12mm (at the current size, smaller or larger links will need to be spaced accordingly), a snap on link, and a link with an insertable pin to connect the chain together or place interesting objects on the end like in this design.  I've included the F3Z and step files.