This is my first Instructable, so go easy on me, huh?
This is based off of a little project of mine. 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 was made, and my resulting project went through two design iterations before I had anything working, which I then posted as my f
Step 1: Designing Your Parts
While not the hardest part of this build, designing the parts is a crucial one. I've attached the drawings I made to design my second aperture. I mainly used a compass and a protractor to design these parts.
The first picture shows the holding and hinging ring. Since my aperture was designed for six 'arms' I set the hinge holes 60 degrees apart (360 / 6 = 60). If you want more arms then you'll need to reposition the hinge holes.
The next picture (looking like a rib) is one of the actual arms that swings in and closes the aperture. Each one should encompass about 90 degrees. (That is, the 60 degrees between arms, plus a little overlap. If you are using more than six arms, you'll need to change these as well) You'll see how the hinging and swinging pegs are attached later.
The last picture here, the one shaped like the snowflake, is the adjuster ring. This was only my second design for this part, and it didn't work so well. A revised version only had one outer 'bump' and the notches to fit over the pegs were narrower to allow less wiggle room.
Step 2: Choosing Your Materials and Tools.
This step is pretty straightforward. For all of the flat parts, I used a thin cardboard/tag-board from the back of a school notebook. Cheap, fairly study, but not hard to cut or shape.
For the hinging pegs I used a thing wooden dowel (I think it was actually a round chopstick :D )
To hold the pegs to the arms I used Zap-a-Gap. Amazing stuff, that. :D Only takes about 30 seconds to dry, and holds on like no one's business.
Finally I used a combination of scissors and a craft knife to cut the parts out (after transferring my design to the cardboard.
Step 3: Attatching the Hinging Pegs
This is fairly straightforward. Cut the dowel into segments about a half-inch in length, and glue them into place on all six arms. (So, 12 pegs are needed altogether)
It doesn't matter really which direction the arm extends off to (left or right) it just determines whether the aperture will appear to swirl clockwise or counterclockwise. Just make sure all of the arms are glued in the same way!
Step 4: Attatch the Arms to the Hinging Ring
Cut out the hinging ring and make the holes for the pegs to hinge through at the places marked. Make sure the pegs can turn almost effortlessly in the holes!
Then just slide the pegs through the holes and your arms are in place!
Step 5: And You're Done!
Just place the adjuster ring over the swing pegs and (carefully!) twist. My design closes diameter pretty well, but it tends to get caught up on itself when opening back up. Just wiggle things around a little and they should fall into place.
Step 6: Some More Pictures...
Just some more pictures. The smaller aperture (with the swirled adjuster ring) was my first prototype. It didn't work very well, and the arms caught on each other too much.