Examples of diamondoid molecular machine elements

(wiki-TODO: add animations with credits)

Strained shell bearings

These can come either with or without axial retainment.
Without axial retainments they can guide screw rods without screwing like a nut.
Guided screw rods are in the drive system for the proof of concept acetylene pump.

Gears

Prime focus: Using only protruding rows of atoms as teeth.
Note that in the case of gears the number of atoms can not be chosen to be incommensurable
and thus the waviness of the energy potential plottet over axial rotation as a fixed period and a bigger magnitude.
Still as long as no snapback occurs operatin can still be highly efficient.

Gearbox

Note the links from the strained shell axles to the unstrained plate housing being sparse with gaps in-between.
Filling it in more densely to gain more stiffness without introducing huge strains that would distort the housing plates
would probably be much more difficult than manually possible. Would require some strain minimizing auto fill in algorithms.

Note that the housing walls are made not from diamond but from silicon carbide (aka moissanite) here.

Mechanical circuit forks

Differential gearbox

A proof of concept example of conical teeth.
The problem here is that atoms only come in one size but conical teeth widen.
The the softness of atoms helps here a lot.
Note: Even if its soft on the nanoscale viewed macroscopically there
can be humongous pressures forcing the teeth together. Same for bearings.

Planetrary gearbox

The rollers in the proof of concept model are extremely small.
Designing that such that the simulation does not blow up must have been not an easy task.

Performance when loaded rather than free running seems rather questionable.
Teeth are not very deep so there might be slip-over already with light loads.

Gears with bigger teeth made from multiple atoms

Only crude models have been made that wouldn't be of practical use.
To approximate cycloid or evolvent teeth already quite large scales are necessary and
And making sure atom rows stay incommensurabe seems like a nontrivial design task.
A graphitic (or organometallc) surface cover of a diamondoid core might be an pursuable approach maybe?

Pumps

Acetylene sorting pump

A critically necessary processing step in advanced productive nanosystems
will be getting resource molecules out of solution into machine phase.

This was (to the knowledge of these lines author) the biggest molecular machine element
ever designed as of 2020 and a good while before.

Most critical on that design are probably channels and pistons.

How well has the hydrophobic aspect been analyzed?
That is the desire of acetylemne moleculed to go in those channels.
Hod critical is the diameter of these channels?

Synthesis of the somwhat non-stiff reciptocating etyne rods in this design wold for sure make
quite the nice challenge for mechanosnthetic cells.

Neon Pump

Background:
Especially in the early day molecular assembler concepts
one idea was to inflate graphene chambers with neon which
due to its high inertness might not disturb mechanosynthesis with open radicals too much.

For nanofactories just plain vacuum is most likely simpler.

This design features no channels and pistons but
rather moving pockets where grooves in stator and rotor meet.

As for why not the much more abundant argon was chosen this may be because:

• Argon is bigger and this less easy to filter from other stuff
  
• Argon is more reactive than neon and might interact more with extremely reactive open bonds.

Miscellaneous

Assembly mechanisms

An ultra compact 6DOF positioning device.
Almost certainly not a practical approach.

Possible reasons for why such an ultra compact design was chosen to be modeled might be:

• Limited computer processing computing back in the day
• A focus on the now outdated concept of ultra compactly self replicating molecular assemblers

In nanofactories one would instead use molecular mills with hard coded functionality at the lowest assemble level
and high freely programmable 6DOF assembly robotics only at higher assembly levels where much more space is available
and thus things come a little closer in looks to bulk limit designs.