Note: This text is a work in progress. If you find any inaccuracies or material that needs to be included, please contact us.
Concept development
Our original idea for a new suspension is based on the principle of a Chinese finger trap, which is easy to insert your fingers into but tightens as you try to pull your fingers out of it. This effect happens because the trap is made from a lattice structure which contracts on one axis as it expands on the other. Here is a two-dimensional illustration of the effect:
Fabric used in this way is said to be cut on the bias in the textiles industry. When fibers are woven on the bias into a continuous tube, this arrangement is called a braid. There are many types of braid produced commercially, and they are typically used as the basis of composite tube structures. Braided structures are very efficient at absorbing torsional and tension loads and impacts. Braided composite material is already used for the structural part of many prostheses because it is strong and can be easily shaped.
The aspect of braid that makes it potentially useful for a suspension is that it constricts under tension, as illustrated by the following diagram:
This means that the grip force of the suspension sleeve is roughly proportional to the tension load on it. There is precedent for using braid this way in the medical industry, which uses braided sleeving for orthopedic traction.
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