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Mechanical Iris construction, does anyone know how?

S

Shadowspawn

[H]ard|Gawd
Joined
Sep 17, 2002
Messages
1,870
The title says it all. A tube style case I am trying to design would be perfect if I could close off either end with an iris; however, my research into how to construct a working iris has resulted in very little help. A couple of animations and a ton of camera reviews have been my only results. Does anyone out there understand the mathematics of an iris, or better yet, have a tutorial on how to create one?
 
This may or may not help, but if you go to one of those big keithcen centers that sell all the kitchen utensils, you'll see a device for making tea I think. It looks like a big flower when it is open, but it closes kinda like an iris, into a small compact "pot" that you can fit into a pot of boiling water.

It is made of perforated metal, but you may get an idea or 2 from it at least.
 
SarverSystems said:
This may or may not help, but if you go to one of those big keithcen centers that sell all the kitchen utensils, you'll see a device for making tea I think. It looks like a big flower when it is open, but it closes kinda like an iris, into a small compact "pot" that you can fit into a pot of boiling water.

It is made of perforated metal, but you may get an idea or 2 from it at least.
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Are you referring to a steamer?
 
A more precise term for what you're wanting is 'iris diaphragm'. Unfortunately I don't have easy access to that information anymore, since school is no longer in session, otherwise I'd just grab the info from the photography department.
 
Look about 1/2 way down on this page , and you should find a decent idea of how to do one. Hope it's good enough to explain it for ya. :D
 
Dude, Nivram, thats a great diagram. It gives me alot of ideas. I would only need to motorize the upper ring, probably with a servo. The mathematics of it are still unknown...things like the angle of the slots on the upper ring, width of the blades, etc.

Those things I can probably figure out with trial-and-error. At least I know the inner curve of the blades are the same diameter of the rings now.

The strainers always seem to be mentioned when discussions like this come up, although I haven't seen anyone figure out how to pull it off.

Really I'm surprised nobody has done this yet. With all of the talent out there, it seems that something like this would be a natural for what we create.
 
Make the blades out of something like construction paper (or cut them out of manilla folders). That will save you a lot of materials until you get the blades right.
 
Well, Ill need to make them out of something sturdier to be able to make them movable...Ill need something that I can mount guide pins in, that won't crumple, otherwise I won't know if the guide slots are right. I'll be working on it when I can - unfortunately Im stuck in the middle east for a little while longer. Doesnt stop me from playing with ideas, making plans.
 
Thats an interesting way of doing it. The mechanics of it are, in some ways, simpler, while more difficult in others. For instance, the valve may only be 1 inch thick when closed, but the thickness is going to be quite a bit larger when opened. But it is a simpler construction, without any of the complex math.
 
let me know if you need machining services for this beast! i just need drawings!
 
Shadowspawn said:
Thats an interesting way of doing it. The mechanics of it are, in some ways, simpler, while more difficult in others. For instance, the valve may only be 1 inch thick when closed, but the thickness is going to be quite a bit larger when opened. But it is a simpler construction, without any of the complex math.
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All of the pictures I looked at appear to stay the same size when opened - I don't think the example pictures are accurate in that regard. I'm gooing to have to hunt one down just to satisfy my own curiosity now.
 
Well, you may be right. If the rubber tube was stretched out, it would be bigger, but I suppose it doesnt need to be, it would just be a collapsed tube, with only a slightly restricted opening, then fully restricted when twisted.

I still think, for looks and style, the blades would be the right way to go. After all, these will be on the outside of the case and would look sloppy with a collapsed rubber tube just hanging there when its opened.
 
Shadowspawn said:
Well, Ill need to make them out of something sturdier to be able to make them movable...Ill need something that I can mount guide pins in, that won't crumple, otherwise I won't know if the guide slots are right. I'll be working on it when I can - unfortunately Im stuck in the middle east for a little while longer. Doesnt stop me from playing with ideas, making plans.
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I meant for prototyping, they would be sturdy enough. And the pins should be on the rotating ring, not on the blades. The blades just have holes for the pins.
 
Nah bro, the guide pins need to be mounted to the blades, because they slide in their slots on the drive rings. I knew what you meant - and I'm talking about prototyping too. While construction paper would work for determing blade sizes, to work out the mechanical issues (angle and length of the slots on the drive ring, position of the anchor and drive pins, etc) everything will need to be a bit more solid - the paper would just rip. I dunno, maybe cardboard, or I may just have to bite the bullet and make a prototype out of metal.
 
I disassembled a VHS (big and old) camcorder's lens a couple weeks ago and the blades did not have pins. They hinged on pins at their ends and were moved by pins on the rotating ring. You can make it any way you want, but putting the pins on the blades is more trouble.
 
I'm having a hard time picturing that. Because the blades move inward, the pins have to slide in some sort of slot. Was there a slot on the blades? Any pictures?

Perhaps a slot wasn't used, but some sort of flexible arm?
 
The pins are fixed to the blade, they then stick through and run in the slot in the rotator ring. As the ring is rotated, the blades are forced to move as the pin slides through the slot, hinging on the second pin which is fixed to the base plate and the blade..

Thats my take on it anyhoo...
 
Shadowspawn said:
I'm having a hard time picturing that. Because the blades move inward, the pins have to slide in some sort of slot. Was there a slot on the blades? Any pictures?

Perhaps a slot wasn't used, but some sort of flexible arm?
Click to expand...
Yeah the holes in the blades that interfaced with the rotating ring were slots, but they were not very long.
 
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