ReChain force hydrant

Up: ReChain tensioner
Alternative name: ReChain tension hydrant

A ForceHydrant is a spot in a ReChain system that provides
access to the inner tension of one of the ReChain force circuits of that system.

A force hydrants can be used to:

• tension a force circuit after loose assembly
• detension a force circuit to perform recomposition and adjustments of the elements of that force circuit

Optional: A force hydrant could be used as a spot to extend a force circuit there (temporarily or permanently), possibly introducing a branching point in the force circuit. For a force hydrant to allow for proper extension of the ReChain frame system, it needs to be designed such that further ReChain hull segments can be added in a ReChain self centering way.

Operating the tension hydrant / Usage

(wiki-TODO: Add details here.)

Details for reliability and or nanoscale physics

To ensure no accidental loosening and slipping can happen.
Even in the case of very large numbers of tension hydrants (mol).
Each tension hydrants shall feature a ReChain positive locking mechanism that
blocks back-slip by significant energy barrier rather than friction.

For more modularity the tensioning function shall be factored apart
form the length adjustment function for the ReChain core chain.
Generally ReChain systems shall factor the ReCahin tensioning devices out of the frame systems all together.

Terminology: Why "Hydrant"

While there is no water flowing in force circuits there are some analogies to hydrants here.

Both systems feature pressure and tension:

• water is under (omni-directional) pressure
• a tensioned ReChain hull segment stack is under (unidirectional) pressure
• pipes are under circumferential tension
• ReChain core chains are under axial tension

Both systems provide public access to a bigger hidden network sprinkled all over the place
There can be many access points sprinkled over a single (potentially branching) ReChain force circuit.
Access points that all allow access to multiple of one single hidden part of the system which may be rather big.
Not all force circuits are connected to just one single big ForceCircuit
just like not all water systems of the world are connected.

Why not just one single big force circuit?

To prevent boundless detensioning.
One reason not to connect everything together into just one single giant force circuit is
that then the whole system would lose tension when the force circuit ruptures …
– either controlledly via a Re Chain predetermined reversible breaking point
– or uncontrolledly with permanent damage
Similar to a minimal unit of ReChain tensegrity
where just the absolute minimum of RepRec DOFs is constrained and
if something ruptures at just one single spot then the whole system collapses.

It's more practical to split up the force circuits into multiple smaller ones.
This stops accidental detensioning from spreading boundlessly. A boundless ReChain RUDs would be bad.

Some parts of frame systems could be tensioned redundantly by different force circuits.
Albeit at the cost of about doubled mass.
Redundant tension can remove gaps lacking pretension at the spots where forces circuits separate.
(wiki-TODO: Add a sketch.)

Design challenges:
Extending force circuits through nodes is challenging.
Nodes that shall support that need to me vastly bigger and more complex than
nodes where force circuits end and have their tension turnaround points
Multi way connections would server as mechanical differentials equilibrium the tension to all sides.
It may be desirable to have the capability in more advanced systems, but it's not needed for starting out.
Modularity does not suffer from lack of this as simple nodes without tension feed-through can be small and compact.

Why going for bigger force circuits?

• Detensioned but monolithic sections may not be as stiff as tensioned sections. (?? To check.)
  
• Quick undeploy maybe? Like quickly being able to folding stuff up would be very useful
  

… Related: ReChain foldability as a further possible design goal.

• (TODO: Are there more arguments that larger circuits are desirable?)
  

Misc / analogies

Analogy: Splitting the force circuit is a bit like
leaving out some dominoes in a standing domino row stopping the chain reaction short.

Analogy: Working on mains.
— German mnemonic in electric engineering: "allseitig und allpolig abtrennen (und erden)"
— Translates to: "Disconnect and earth all sides and all poles"
Locking the force circuit at all sides around a force hydrant
before opening that force hydrant (close the "valves" on all sides)

Related

• ReChain positive locking mechanism
• ReChain tensioner
• ReChain temporary force circuit isolation spots

Page originally created 2020-06-13 (zim wiki)