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Rise Robotics had discovered an alternative approach to the spring. Using cut pieces of fiberglass and rope working in parallel, this new modular spring method is 8 times lighter than an equal performing classically wound steel spring.
Such a novel component was poised at becoming a game changer for weight reduction & efficiencies in mechanical systems. As far as adoption of new component family goes, reliability is the #1 concern. Demonstrating its reliability and limits requires time and resources. An Instron machine was required.
The Specific Spring box made, shown in the video above, nicknamed the "Flight Source", was tailored for making a portable mechanical trampoline that athletes could leap off of. This Flight Source spring is rated for 14kN (3147lbf) with a 14mm deflection stroke. To demonstrate its safety margins, we pushed the Flight Source Spring to 160% its rated maximum load. It failed at 21 kilonewtons. That's an astounding 4,721 pound-force! That is more than your average sedan.
As we were demonstrating the stability of the architecture, we made a realization that a passive spring is limited by what could actuate it. A passive spring (like a tendon) can only return energy put into it, and an actuator (like a muscle) can generate limited power. But if used together in series, mechanical power amplification becomes possible with less effort. We call this Series Elastic mechanisms. In nature, it appears as Tendons and muscles.
A spring will bend and store energy in the form of strain energy when a force is applied to it. When the force is released, the spring releases its stored energy without losses.
Series elastics help actuators (muscles) produce power beyond the actuators capacity. Activities like walking, running and hopping would not be possible without the concept of series elastics. Or more technically, "a way of metabolic energy conservation by attenuating muscle power production, and amplification of muscle power production." -wikipedia
The Flight Source Spring is the Mechanical equivalent to an Ultra Capacitor and there is no off the shelf actuator component that takes full advantage of this new spring. We should either make a lower performing spring, or discover a better actuator. We think it is pretty clear, a better actuator alternative is needed badly.
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