Springy bend

[X1]

   Almost a rope-made spring, this bend is very secure knot, easy to tie (*) and to inspect, symmetric in form ( when it is not loaded), which I had never seen before - or I do not remember seeing it before. I wonder if it could possibly be used to absorb a sudden strong pull, that would had been devastating to a more compact, more "rigid" knot. I believe it deserves the name " Springy bend", indeed. 
   ( In order to prevent an early, easy "closing"/compactification of the knot when it will be loaded, we have to dress it pulling the standing ends AND the tails as hard as we can.) 
   ( *) By properly retucking the fisherman s knot, for example - although there are many other ways.

[X1]

   Trying to make the bend presented at the previous post a little shorter and more compact, while retaining its peculiar "springy" character, I arrived at the bend shown at the attached pictures. The "spines" of the Pretzel-shape-looking interlinked overhand knots are now crossed, so the two standing ends are closer together, and the knot is shorter.

[kd8eeh]

It is also good to note that any simple crown sinnet will have a springy quality, as will some other sinnets, in certain ropes, like a simple crown sinnet i have used in the wires for exceptionally long headphones.

I have described a very simmilar knot (in tying method and function) although i believe it is slightly different than what you show.  The springyness is in the fact that the knot tries to twist as loaded.  I have attached pictures of this knot and a slightly stronger (i think) version, with an added half knot to secure the tails better, and reduce total bend in the rope.

[X1]

the knot tries to twist

 I do not think that the behaviour of the "springy" knots is as simple as you describe - but I can not offer any detailed explanation either. Beyond the elastic resistance to torsion (twist), it has also something to do with the fact that the ropes are not "ideal", i.e. their cross section can be deformed up to a certain degree, and that, during this deformation, the rope behaves like an elastic, not a plastic material. In a world with "ideal" ropes, there would be no "springy" knots...