ReChain force hydrant

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50px This page is part of the ReChain project.
Short for Rebar CoreChain Systems.
For an index of all pages of this project, see the category page ReChain.
This article defines a novel term (that is hopefully sensibly chosen). The term is introduced to make a concept more concrete and understand its interrelationship with other topics related to atomically precise manufacturing. For details go to the page: Neologism.

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 sketches of possible designs here.)

★ (1) Press the tensioning mechanism against the tension hydrants positively locked nut THPLN thereby
– (1a) first (by slight push) engaging the end effectors DOF to the still locked nut, and only then
– (1b) second (by further push) unlockinng the THPLN from its ReChain hull segment (to which it was locked to).
The purpose here is to never let anything go uncontrolledly free-spinning out of machine phase.
This finishes the transfer of the control of the THPLN from its lock-state to the enforcedly controlled effectors DOF
The THPLN may still be hard to turn as it is under heavy load. Thus the next step is NOT attempting to turn it. But …
★ (2) Screw the tensioning mechanisms nut TMN (other than the THPLN) onto the over-standing thread
★ (3) Use the tensioning mechanism to pull on the TMN thereby removing the load on the THPLN making it easily turnable.
– Yes this (intentionally) briefly increases the inner tension even if we desire is to reduce or remove inner tension.
★ (4) Turn the (now load-less) THPLN to either incerase, decrease, or fully remove the tension (that will later result).
★ (5) Do the steps in reverse (3)(2)(1b)(1a). Reload THPLN, TMN uncrew, lock THPLN, decouple THPLN.
In case of removal of all tension (and adding some slack) structural disassembly state can proceed in the now fully detensioned state.
For additional slack to not destroy machine phase:
How the additional slack distributes may be managed by weak springs (macroscale) or vdW forces (nanoscale).
Machine phase being preserved means that an open loop control robot
still can know where everything is without any senses at all.
Non need tor camera (macroscale) or touch probing (nanoscale).
And no need for the associated compute intelligence.

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.

Factoring apart of sub-functionalities

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.
There is no point in leaving huge mass and volume of a tensioning mechanism in the frame system that fulfills no further purpose.

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:

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

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

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