Rock-tumbling in reduced gravity?

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Discussion Overview

The discussion revolves around the concept of improving the sphericity of small steel spheroids intended for use in a low-gravity environment, specifically through a rock-tumbling process. Participants explore various methods and designs for achieving effective tumbling in reduced gravity conditions, considering both theoretical and practical implications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests using a rock-tumbling method with grit to enhance the sphericity of the spheroids, considering the noise implications in a space station environment.
  • Another proposes extending the tumbling operation from the station to achieve higher G-forces, questioning the technological level of the society in the scenario.
  • A participant mentions that a 2-meter diameter tumbler could potentially provide around 3g of force at typical tumbling speeds.
  • There is a suggestion to use a standard tumbler design placed in a 1-G zone on an arm extending from the station, with vibration isolation to mitigate noise.
  • One participant critiques the initial manufacturing method, proposing that forging would be a more efficient approach in real life.
  • Another participant raises the feasibility of using WWII-era workshop tools for creating the necessary machinery for forging the spheroids.
  • Concerns are expressed about the limitations of low-tech workshops and the sourcing of raw materials for manufacturing the rods used in the spheroids.
  • There is a discussion about the RPM settings for the tumbling pots and the arm frames, with one participant suggesting that differing RPMs could be beneficial.
  • A participant elaborates on the mechanical design of the tumbling apparatus, including the use of drive belts and tension rollers to manage torque and slippage.
  • Another participant clarifies the source of the bar stock used for the spheroids, indicating it is salvaged from structural components of the habitat.

Areas of Agreement / Disagreement

Participants express various ideas and suggestions regarding the design and method of tumbling in reduced gravity, but no consensus is reached on the best approach or the feasibility of the proposed solutions. Multiple competing views remain regarding the technology and methods discussed.

Contextual Notes

Participants highlight limitations related to the technological capabilities of the hypothetical society, the efficiency of different manufacturing methods, and the practical challenges of sourcing materials in a space environment.

Nik_2213
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Protagonists need to 'improve' many ~10mm OD 'mini-musket-ball' spheroids' sphericity.

They've been made by chopping 10mm steel rod stock to 2/3 cm lengths, zapping to molten with eddy-current coil in inert atmosphere, the now-round blobs allowed to cool along a low-g drift-line.

But they're not quite 'even' enough. ( Note: NOT intended as ball-bearings... )

So, partially-immersed 'Rock tumbling' with grit would seem the way to go.

Space-station environment ranges from near-axis tidal / micro-gravity to approx 1/3 g (spun), but the latter, habitation area would not be happy with the noise...

Best I can think of is akin to a fun-fair ride, akin to a 'Waltzer', where a pair of drums ride between ends of two rotating arms, are belt-driven so they rotate at similar RPM to the arms, on parallel axes....

Any better ??
 
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I would say that you could put the tumbling/milling operation on an extension from the station for higher G-forces. How advanced of a space faring society are we talking? Relatively near-term, or something more akin to The Expanse?
 
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So, making a deployable structure to carry the tumbler units out to a high gravity area is not going to be an issue. I’d say use a fairly standard tumbler design and just… basically put it down in a 1-G zone on an arm extending from the station? You can put them on vibration isolation mounts to mitigate the noise.

If you’ve ever played Elite: Dangerous, there’s a few stations with setups like that, sticking out well away from the rest of the spin station. Long-time players call them “noob hammers” because new players either don’t know they are present and can destroy their ships, or they think you can dock with them and then get smacked.
 
Nik_2213 said:
They've been made by chopping 10mm steel rod stock to 2/3 cm lengths, zapping to molten with eddy-current coil in inert atmosphere, the now-round blobs allowed to cool along a low-g drift-line.
I understand the necessity of a really cool manufacturing scene, but in real life any sane engineer would just go with forging. Lot less trouble: time, space, energy.

 
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Thanks, Rive !!

How you'd contrive that real-neat forging 'mill' pair is an interesting problem:
Could it be done using eg the big mill/drill & lathe tooling of a WW2 'Battleship' work-shop ??
 
??

Old style workshops were fine for (relative) small work (everyday maintenance, repair) only. Not tooled for bigger works or for complete machinery builds. But for 10mm sized balls, I think even those workshops would be able to produce something temporary, low production rate machinery.

But in a SciFi setup these days, at least a decent sized metal 3D printer would be included and that would solve most of the problem.

BTW1: if you only have a low tech workshop, then where does the raw material (rods - well, rather: wires) coming from? How/where is that manufactured?

BTW2: that mill is not really 'neat': for anything precise (ball bearings) it's just the very first step. It just fits the description of 'spheroid' :wink:
 
Nik_2213 said:
Best I can think of is akin to a fun-fair ride, akin to a 'Waltzer', where a pair of drums ride between ends of two rotating arms, are belt-driven so they rotate at similar RPM to the arms, on parallel axes....
Same thing I came up with. I quibble that I don't see why the RPMs need to be similar. Just put one RPM at the ideal rocktumbling setting and the other at the ideal "gravity".
 
Hi ! I specified 'similar', as this would let the two tip-mounted tumble pots turn at sorta-default 50~~60 RPM, while the twin ☍ arm-frames rotate at similar 50~~60 RPM, providing 2½~~ 3 g (apparent). By using drive-belts and perhaps-differing drive-pulley sizes, only one (1) motor would be required, turning the arm-frames' horizontal axle,, so no cabling / slip-joints etc to tumble-pots...

This arrangement would also allow easy up-grade to drive eg four (4) tip-mounted tumble-pots ❌...

Both the 2-arms and 4-arms set-up would surely be fitted with sprung tension rollers to control drive belt 'creep'. Some slippage and torque-limiting would be beneficial as, even with frames given an initial 'swing', toothed drive-belts could throw too much start-up load on the low-powered drive....

( Per our labs' old swing-out centrifuge, sufficiently balancing opposing baskets was easy, but essential. Sadly, a benighted Tech's 'Hung-over Monday' gaffe 'danced' the old machine from its chocks and off table. The five-decades younger machine, laded with safety features, which replaced it would 'fail-safe' without even closer balancing... )
 
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Oh, sorry, the bar-stock ?
Salvaged from 'many' 10mm mild-steel tensioning bars used to cross-brace hab partitions. Like office-area framing, not pressure-holding bulk-heads. 'Privacy' and 'Smoke Limiting' is all....

Threaded ends cut off and saved as 'studs' against need.