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I want to build a retracting insect screen having two of the retracting “bearings” holding a rod between, and having the mesh on the rod. I’ve spent hours of research to get the name of the part responsible for retraction, but no success. Bought a dog lead, but it’s a pain to get out the part. I’m pretty sure it’s been used in a wide range of applications, so I should be able to buy it alone. Any ideas?

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    Is there a reason you want to build this yourself instead of just buying one of the many pre-made retractable screen doors?
    – brichins
    Mar 12, 2021 at 0:25
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    Well first of all, as I’ve calculated, it’s cheaper to build it myself, more flexible (my doors have weird dimensions), I can make it completely gap free, and can choose smaller hole sizes than the standard (1mm - which can let insects in that are bad for my plants). But if the difference between idea and reality will be too big, I’ll have a try with the prebuilt ones. Mar 12, 2021 at 9:00
  • The coil springs similar to what is in a tape measures will require a large diameter compared to a tension spring in a roll up blind. That’s why I did not mention them. Lawn mower recoil springs are the same and they take 3 inch diameter to retract a rope and you still need to build the pawl that stops it in the lowered position or a catch at the bottom to hold it in place.
    – Ed Beal
    Mar 12, 2021 at 14:11
  • Why not use a premade retracting screen but buy extra screen material. Glue the new material offset in both directions to the original. Use a very thin glue so it doesn’t clog the holes, maybe blow air through after affixing but before the glue dries. Viola, now you have reduced the hole size to 1/4.
    – Glen Yates
    Mar 12, 2021 at 18:15
  • @GergőHorváth Achieving a custom fit is a great reason, although I still wonder if buying a premade one and swapping in a finer screen might be a good option. I've finally accepted for my own projects that "it’s cheaper to build it myself" is only true if my time isn't worth anything, and sometimes saving a buck isn't worth losing a weekend.
    – brichins
    Mar 13, 2021 at 15:01

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Another example of a mechanism that you may be able to access or modify to your usage idea is contained in a tape measure. There a coiled flat spring steel material is simply anchored to central hub on one end and the other to the tape measure rule itself. These coil springs are setup to work almost the same as the flat coil spring on the inside of a retractable dog leash. In both cases the coil spring is able to provide return pull when the tape rule or leash is pulled out even as much as 25 feet or more.

The coil springs are actually a material that on its own really wants to extend out flat. When coiled inside a confined circular space it strives to straighten which in effect makes it try to expand to the greatest diameter allowed. When the tape rule or leash is extended the coil of this flat spring steel material becomes wound tighter and tighter to the center hub creating more pull and resulting in a smaller diameter to the coil.

The springs like discussed elsewhere here in shades and on garage doors are a different type of spring that is called a torsion spring. These are formed in a tubular manner and when under tension will desire to turn and return to their relaxed position.

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When I was a kid we had plastic roll up blinds on windows--you pull down and release for them to go up (not supposed to let go but it was fun). You see them in old cartoons flipping around.

They are called spring roller shades or roller shades. Why not get one of these and put screens on it? They range in size but may do what you want in a pre made package.

The part that is doing the retraction is the spring. Roll up garage doors have the springs in the open so you can get an idea of the type of spring.

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A "spring rod", "spring reel", or "spring roller" includes the shaft, roller, torsion spring, and catch components. Unfortunately, products which include them are usually described by their larger function, such as roller blinds and retractable leashes. Searches for raw mechanisms turn up varying results, but may lead to what you're after.

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    Also, "spring reel". Seat belt retractors are probably the same mechanism, but the use of "retractor" may be unique to that application.
    – Matthew
    Mar 11, 2021 at 15:49
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Retracting leads won't be strong enough for your purpose. They are not designed to reel the dog in like a fish! They have just enough power to retract the lead into the casing and no more.

I don't know the official name - it is probably just called "the mechanism" and described by its parts; reel, spring, etc.

There are videos showing how to open and repair them. Getting in is easy once you know the secret.

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