This Instructable is based off of a project of mine to design a working aperture out of around-the-house materials. I had just seen an awesome set of Steampunk goggles by Gogglerman that had a very nice brass aperture in one eye. I set about trying to figure out how it had been made, and my resulting project went through two design iterations before I had anything working. I then posted that as my first Instructable.
So, instead of just editing my first Instructable, there's enough different to create a new one, which I have done. This time I'll be posting some instructions sheet downloads (in *.psd and *.pdn format for compatibility with your checkbook) and more pictures. Perhaps even a video!
Step 1: Designing your Parts
The first part is the holding and hinging ring. Since my aperture was designed for six 'arms' I set the hinge holes 60 degrees apart. If you want more arms then you'll need to reposition the hinge holes. Use this widget to calculate this angle if you are lazy like I am don't want to do the math yourself ;)
The next part (looking like a rib) is one of the actual arms that swings in and closes the aperture. Each one should encompass about 100 degrees. You'll see how the hinging and swinging pegs are attached later.
The last part here, the one shaped like the hinging ring but with notches instead of holes, is the adjuster ring. The notches will 'grab' the pins on the upper face of the arms, pulling or pushing them around the ring.