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?
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.
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.
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.
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.