Not quite the same as either swing tip or quiver
It works when a swing tip doesn't because its not so easily disturbed by wind or current drag, staying still like a quiver
Like a quiver you tighten up to it and bend the shaft - not the spring - slightly; thus giving a drop back indication.
If there is a take that bends the spring over then the initial force required to bend the spring is the only real resistance to the fish, unlike a quiver.
With a quiver once half bent its still exerting a force trying to straighten up and applying resistance to the line.
With a spring, once 'cracked over' is the best way I can give of describing it, once you've felt the sensation you will know what i mean, then the spring kind of just gives up and it takes relatively insignificant force to keep it bent over. There is then littlefurthre significant resistance to the fish.
Someone who understands the physics of it will no doubt explain it better, but that's the effect of it, like a knee joint offering strong initial resistance but, once pushed past critical point, falling back to little or none at all.
But they are a bugger to cast with and IMHO the modern quality quiver beats them hands down frankly.
If you want to try one then it's easy enough to make, just use a swing tip and substitute spring for rubber. ie. use a rod with a screw tip end ring, screw in themetal adaptor bitwith the rubber removed, then push a tight fitting firmly coiled small spring over it (first find your old fashioned hardware shop !), then push the butt of the rod end / quiver bit into the spring. As long as its all tight that's it. Go try....
