This is an adapter I made for my canon 7d with macro bellows. It allows you to slide a strip of film through a cardboard gate for photographing. The film is illuminated by a flashlight shining through a piece of frosted Mylar.
Here is a short film excerpt that uses this rig. The film is made by making short video clips through this device, joining them all together and speeding up the clip, so it is purposefully jumpy.
I was needing a pulley head on motor to pull a string and so I made this little add on. I was able to get a nice tight fit by scanning the gear on a flatbed, doing little work on the levels to yield a higher contrast image and importing that into rhino3d as a background. As long as I lined the background image up to a properly scaled circle ( measured the gear with calipers) I was able to get a general profile for the teeth and just duplicated them in 360degrees. It took two tries to get one which would fit.