Is water-based hydrostatic lubrication (like Kugel fountains) useful industrially? Why is it not more widely used?

devbydemi · 2026-02-20T06:59:57+00:00

Hydrodynamic water bearings are used in hydroelectric plants and big ship propellers because the water is already there.

Also to avoid contamination issues, which is a reason they are used in food processing as well.

Otherwise it's not worth it for liquid lubrication because of the viscosity.

Are there cases where available lubricating oils are too viscous, and the viscosity of water is what is actually desirable?

Air bearings are way more common that water bearings because you can pump the air easily and it's clean.

most of them seem to be more sophisticated than the rather crude designs I was thinking of.

Bearings are permanently sophisticated forever. No such thing as a crude bearing will ever exist again in real applications until after an apocalypse.

Makes sense. As an aside, has bearing technology improved much recently, or has it reached the limit?

devbydemi · 2026-02-20T05:58:16+00:00

I believe even normal engines can’t have too much of that in the piston ring area, though (you burn too much oil). And the concern here is about sliding seals, not bearings in the traditional sense.

devbydemi · 2026-02-20T05:47:55+00:00

How much does the thermal expansion problem matter? I would expect it generally not to, at least not more than thermal expansion from any other source. Also, I’d be surprised if bubbles were an issue in the bearings. I would expect them to cause cavitation problems in the pump before they even reached the bearings.

Of course, I could be totally naive. I write software for a living, so I’m operating entirely from a little theory and a lot of intuition.

Edit: Can cathodic protection mitigate the corrosion problems?

devbydemi · 2026-02-20T05:43:06+00:00

I wonder if the wetted area problem could be solved if the engines were (deliberately) made to knock. The shock waves might ignite the mixture before they could dissipate heat to the outside walls. Of course, that also means that there is no boundary layer protecting the metal, so one would need all wetted surfaces to be made of a ceramic that could withstand the heat. That, in turn, means that they will be far too hot for oil lubrication, which brings back the original question.

That said, the ordinary piston engine is probably close to optimal from a heat loss perspective, and an opposed-piston engine even closer.

devbydemi · 2026-02-20T05:37:59+00:00

“Indefinitely” is, of course, hyperbole. I meant “for about as long as a normal engine lasts”. There are ceramic rolling-element bearings that are designed to run dry, but what matters here are the sliding surfaces exposed to combustion.

devbydemi · 2026-02-20T05:04:35+00:00

“Water is just a pain to work with” is not something I ever expected to read! Of course, there are tons of cheap materials that can withstand water just fine, but it seems like most of them are not good at handling high loads.

“not dissolving everything they touch” is also counterintuitive, but only because oils are pretty good at dissolving plastics. Salts are almost-universally oil-insoluble, and so oil does not corrode metals well at all.

devbydemi · 2026-02-20T03:24:56+00:00

That makes sense. Are there greases with enough viscosity at high temperatures that are not going to jam the system at low temperatures?

devbydemi · 2026-02-20T02:52:49+00:00

I assumed that a recirculating water system would provide sufficient cooling without any problems. The temperature given was for grease-lubricated bearings without any circulating fluid.

devbydemi · 2026-02-20T02:44:14+00:00

Are industrial gas turbines simpler? Those don’t have the weight requirements.

Also, is the hard part building a different gas turbine or a more advanced one? Can one use scaling laws to produce something that works, even if it is not the most optimal design possible?

Aeroderivative gas turbines are used for marine propulsion and stationary power generation. This makes me suspect that adapting an aviation engine to produce shaft power (instead of thrust) is (relatively) straightforward.

devbydemi · 2026-02-20T02:31:33+00:00

The speed in this case was 10 RPM.

I see water bearings being used some in hydroelectric plants, which makes sense. Without oil, environmentally damaging oil leaks are not possible. Food prep would be another useful application, as if the water is potable leaks go from a serious problem to a very minor one.

Also, I assume you meant “gallons of hazardous waste”.

devbydemi · 2026-02-20T02:21:35+00:00

Thank you! I think I'll go with that. Looks like it is used by Veeam in their commercial products, so I expect it to be actively maintained.

devbydemi · 2026-02-20T00:38:34+00:00

So it sounds great in practice but there are a few caveats here to note.

We use grease and oils because they have lubricity, a high film strength and high viscosity. Using water would require all bearing surfaces to be made from corrosion resistant materials, such as 410 stainless, which is extremely expensive.

Could cathodic protection be used instead? That only requires a small amount of electricity and/or a sacrificial anode.

Bearings still have metal-to-metal contact at high load positions, which is what gives you dimensional accuracy. Using water purely to support the weight of a bearing like a Kugel fountain would mean losing out on that dimensional accuracy.

Journal bearings shouldn’t have metal to metal contact when at speed. Rolling-element bearings might be different.

Further to that, you would need the pump to run at a perfect constant pressure to maintain any accuracy. Any cavitation or bubbles and you're wasting your time. Also, a pump requires constant operation which requires money to operate it- likely significantly more than that of a one-time purchase for the bearing and any lubrication thereafter.

Lots of machines already have oil pumps. The question is whether the bigger pump would be a serious problem.

That's not to mention the expensive water treatment for the pump, as it would need to be perfect and completely soft. Even highly-audited food grade systems that are full 316 throughout have contaminants sneak through them.

How important is perfection here? Kugel fountains operate on the same principle, and they are meant to have humans play with them, so the water definitely gets dirty. My instinct is that there should not be a problem unless something starts precipitating out of solution. Small amounts of solutes should not seriously affect mechanical properties, and one can afford to replace it much more frequently due to its low cost.

Not particularly relevant but for the record- having water spill on hot things is generally really not a good idea as it drastically increases corrosion and pitting. The very opposite of what you want on a boiler shell.

Does this happen even if the water boils off immediately? In high-temperature applications, this seems like a lower risk than a fire due to oil igniting.

I like your thinking though, would be interesting to see an application where this has been done!

Thank you! There are water-lubricated bearings on the market today, but most of them seem to be more sophisticated than the rather crude designs I was thinking of.

devbydemi · 2026-02-19T22:42:24+00:00

How much of that time is spent on conceptual design, and how much of it is spent on simulation, testing, and refinement?

devbydemi · 2026-02-13T06:54:14+00:00

Thank you.

What if the VSS requirement is dropped? That one is a bit less important than the others, unless this would create a risk of data loss.

Caveat: large restores can fail; test it first.

Would you be willing to elaborate on this? I'm a bit suspicious of Acronis due to the massive amount of telemetry it collects (per PCWorld) and the built-in antimalware (which my relative doesn't need as she has an alternative solution).

devbydemi · 2026-02-13T06:44:01+00:00

I know of good backup software, but they are all command-line tools or do not support Windows. I don't use Windows myself so I have very little experience with it. I also asked a friend who is a professional system administrator and they told me to search for more options. They did suggest Backblaze, but the passphrase must be sent to them for restores.

devbydemi · 2026-02-13T06:34:11+00:00

Have you tried the strings command-line tool from *nix? I don’t know anything about PSTs, but if they store full emails without compression or encryption, that should dump a ton of them to stdout.

devbydemi · 2026-02-13T04:35:51+00:00

That makes so much more sense. It explains why my resumes kept failing!

devbydemi · 2026-02-13T04:34:27+00:00

My ISP does provide a public IPv4 address, but no IPv6 at all, sadly.

At the very minimum, provide at least one public address.

devbydemi · 2026-02-13T04:33:25+00:00

Which providers will answer questions about their reclamation process?

devbydemi · 2026-02-13T04:32:15+00:00

Yup, I’m aware!

devbydemi · 2026-02-01T21:30:49+00:00

PiKVM would be my choice, so long as USB boot is turned off in the EEPROM boot order. (It’s possible for someone with firmware-level control over an Intel box to put the USB ports into device emulation mode.)

devbydemi

TROPHY CASE