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I think I'm gonna need this one for some of my creatures who need power magnification.

The basic idea is simple, I wanted a biogenic spring that can withstand tensile stress, store and quickly release as much kinetic energy as possible. How could that work?

I'm unsure if resilin would work at the sizes I intend the springs to be.

Basically, they're supposed to be used by large fliers to launch themselves into the air where they'd have enough clearance to flap their wings and speed to produce lift.

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  • $\begingroup$ How long does the spring need to function? Seconds? minutes? Hours? $\endgroup$
    – DWKraus
    Jan 26, 2021 at 1:21
  • $\begingroup$ @DWKraus Since this is a tendon, a lifetime, but with constant repairs. $\endgroup$ Jan 26, 2021 at 1:22
  • $\begingroup$ And what is the work the spring needs to perform? Jumping? Throwing? Eviscerating claw? $\endgroup$
    – DWKraus
    Jan 26, 2021 at 1:23
  • $\begingroup$ And i meant, how long after storing the energy does it get released? $\endgroup$
    – DWKraus
    Jan 26, 2021 at 1:24
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    $\begingroup$ How high do you need to jump? An impala can jump as high as 10 vertical feet just using regular old tendons and muscles; so, you may not need anything all that special. $\endgroup$
    – Nosajimiki
    Jan 26, 2021 at 1:47

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No Genetic Engineering Required

The Red Kangaroo can reach up to 90kg in size and over 2m tall when standing upright. They're able to clear 9m horizontally or almost 3m vertically in a leap. When hopping, their Achilles' tendons store about 70% of their potential energy.

That said, most real-world flight-capable birds are able take off from the ground with no genetic engineering required. They raise their wings all the way up to the top, then hop into the air as they bring their wings down. By the time they reach the bottom of that first wingbeat, they're already high enough that their wingtips can clear the ground: https://www.youtube.com/watch?v=CJHP6dPjuGY

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Archery Bird:

Okay, this is mostly for fun, but if you have a flying animal who needs to suddenly launch themselves in the air with a spring mechanism, why not?

The Archery bird's beak is long, stiff, and it can dislocate it's lower beak, then lock it back into place sideways using great force applied by small wing hooks. additionally, the beak has a long tendon it periodically regrows that attaches to the ends of the beak. This tendon is snapped taut when the beak is in it's sideways position.

The need for the bird to get airborne in dense foliage means it can't just flap wings - it would hit vegetation. climbing, for some reason, is risky. Maybe poison predators, or carnivorous plants. So the archery bird strips down a small tree or bush, hooks it's tendon over the top, and uses it's wing hooks to pull down on the taut tendon. when enough tension is applied, the bird fires itself upwards like an arrow from a compound bow.

If you care to be REALLY creative, the bird can also use a gland that exudes glue to attach it's own feathers to sticks either sharpened or tipped with a special piece of eggshell. It's a living bow. So the bird has a hunting behavior it can use from high perches to strike prey at a distance and avoid whatever nastiness makes it unwilling to climb up trees. It flies to the ground, swallows the best parts of the prey, then strips a tree and launches itself back into the sky.

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Your tendons may not be the best spring material but whatever you use, a high water content will reduce the recoil velocity of the material. Perhaps you can consider using muscles instead. Hummingbird wing muscles are composed exclusively of fast oxidative-glycolytic fibers (type IIa), with giant mitochondria occupying ∼50% of total volume. They respond incredibly fast, but require a very high energy fuel and lots of blood supply. In fact hummingbirds could not even hover if they didn’t have flower nectar as their fuel. I do think muscles would serve better here than a tendon because muscles naturally mend themselves quickly. Using a spring-like tendon still requires powerful muscles to charge them up. This means you have three systems: Charging muscles, skeletal frame, and tendons. It will in all cases be heavier than using raw muscle power.

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Insects can store a lot of energy. Grasshoppers for example, so maybe some inspiration there. Although scaling with size can be an issue.

From a paper in the journal of experimental biology, “Take off speed in jumping mantises depends on body size and a power limited mechanism”

In the catapult mechanism, used by insects such as grasshoppers, fleas and froghoppers, energy produced by muscle contraction (muscle force×distance) is generated slowly and stored by deforming a cuticular ‘spring’. The spring then recoils rapidly, releasing the stored energy and delivering considerable power (energy/time) to the legs, which propel the insect into the air (Bennet-Clark and Lucey, 1967; Patek et al., 2011). As mass increases, these insects will have a greater amount of available energy but will also have correspondingly larger opposing inertia. An equivalent increase in both available energy and inertia will thus result in the take-off velocity (and thus the maximum jumping height) being independent of mass. This relationship was formulated as ‘Borelli's law’ in the 17th century (Borelli, 1680) and summarised by Bobbert (2013).

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