They are relatively simple. There are two axles, one which has an internal spring (I have no idea what sort) and one which is solid. The sprung loaded one has a ratchet on it that allows you to change the tension on the spring and thus the shutter speed.
The blind is attached to both axles, either glued or sewn. There is a thin cord attached to a pulley on the unsprung axle. Pulling on the cord winds the blind onto the unsprung axle against the tension of the spring in the other axle. On top of the unsprung axle is a small cog which connects to a larger gear which has a ratchet attached. The large lever on top acts as a stop against the ratchet. This prevents the blind rewinding when you let go of the string.
Lifting the lever up disconnects the ratchet and allows the sprung axle to rewind the blind at high speed. The clever part is that there are two stops on the ratchet. The first stops the blind fully open while the second winds it closed again and sets the shutter. The lever has two positions, T & I. When you move it to T the ratchet will engage both stops, so firing the sutter opens it and firing it again closes it. When you move the lever over to I it is raised and acts against a different stop (there is only one) and thus does the complete cycle in one hit.
The levers on mine have a little hole in them which the shutter release connects to. You could tap that so that a modern cable or bulb release can be screwed in place.
All of this I have worked out just by looking at them and carefully disassembling them. Having posted on the other thread I decided to order the shutter cloth from http://aki-asahi.com/store/ and see how it goes. If you look at the procedure at http://aki-asahi.net/store/html/shut...l/inst/01.html you should get the idea.
I'm not sure whether your rusty axles will be a problem. I still have to find a source for the cord. String is not an acceptable replacement, it needs to be thin and strong and the string tends to unravel. The orginal cord is woven, not twisted which seems to be the difference.
hope that helps,