In this Instructable I will describe the process of building a mechanical iris diaphragm window with a porthole into an existing wall opening. I've always appreciated old fashioned ingenuity where the mechanics were as much art as function and a mechanical iris is a great example of this. Irises have a unique balance and symmetry and the steampunk world has taken the device to a new level of appreciation.
Several months back began creating a studio in the attic above my garage. Little by little I've been filling the space with tools, decor and computer equipment. The room had one small window on the one framed in wall. This wall is something of a focal point in the room and I've been want to do something creative with the window and a big round iris seemed perfect.
The space originally was completely unfinished with open rafters, roof and wall framing with a simple screened window built into the framing. On the exterior of the house this window is covered with louvers so even with the lights on at night it doesn't draw much attention. I began insulating and laying the sub-flooring and covering the walls and ceiling with OSB sheeting. The window was only finished on the outside so I covered the void with OSB and marked the opening. I found some inexpensive laminate flooring and used it on the floor and for a different look I covered the windowed wall with it as well.
Thanks everyone for taking a look see - please vote for me in the Full Spectrum Laser Contest!https://www.instructables.com/contest/fullspectrum2014/
I began by drawing up the project in AutoCad. I knew I'd be using my Carvewright CNC to mill out as much of the project as I could so I planned most of the parts to fit in the machine. The early design, shown in the shop drawings throughout this Instructable, used the leftover flooring as the iris framework and mechanics. The material seemed to machine well and I thought the color contrasts would make it *pop*. That was the idea anyway.
The existing window opening is 24" wide. That's a little large for a window like this. It would take a considerable amount of material for the leaves not to mention weight concerns. An 18" aperture seems a bit more practical. Plus, with louvers on the outside of the house, it's not like I have some grand view outside anyway.
I played with a few designs of different numbers of leaves. Irises can be built around an unlimited number of leaves from one (think guillotine) on up. I chose to use 12 leaves because it gave a nice round opening and the 30 degree increments work well around a circle.
The main cover shell contains the leaves and the cam. The cam ring holds the travel pins on the leaves and rotates to operate the aperture. To open and close the iris I added a partial spur gear to the cam to mate with the pinion gear mounted to the side. This way the cam plate will be enclosed under the housing cover and the small gear allows the aperture to function without having to open the porthole. The porthole cover has a clear polycarbonite Lexan window to assist in keeping out the elements.
As with most projects, things change and after much trial and error I determined the laminate had to go. There's a learning curve in using this laminate in the Carvewright. The biggest problem is it's so slick it's hard to hold in place which leads to tracking and misalignment problems. The grain patterned surface is also very brittle and chips out easily. Plus it quickly dulls the bits and will burn them up over time. Factor in various software issues, machine issues and user issues and I started running out of patience ( and laminate ). After much frustration, new software and a lot of cursing, I decided to switch to tried and true Carvewright friendly plywood for the bulk of the project. I used good grade of Baltic Birch 1/2" ply with few inner voids. This stuff stains well and looks good. Overall I'm pleased with the results. I still think it *pops*.
I'm posting the dxf CAD file here, as well as pdf files of the drawings. The pdf's should print to scale on a common letter sized sheet. Although my design changed, the CAD files should work fine if someone was of a mind to pull out the part patterns for their own uses. Everything is drawn to scale and I can only assume you could drop them straight into a laser cutter or even a waterjet and assemble them with no problem. Carvewright owners - use at your own risk!