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how are fluid bearings made? Answered

i was looking at fluid filled bearings and wanted to try and make one i just cant understand how they are filled and how they can rotate without leaking any ideas on how they are sealed?

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steveastrouk (author)2009-09-01

One way is to use ferrofluids, and retain the material using strong magnets. In many fluid bearings, there are "labyrinth seals" which hold liquid in place What do you want to make ?

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sharlston (author)steveastrouk2009-09-01

i always wanted to try make a fluid bearing any idea how i can make one? i have acces to lots of bearings and a giant workshop

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steveastrouk (author)sharlston2009-09-01

I have plenty of ideas. What do you want to make one for ? A car engine is full of them.

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sharlston (author)steveastrouk2009-09-01

i just wanted to make one but i dont have access to a car engine just a hole lot of nsk bearings and a giant workshop

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steveastrouk (author)sharlston2009-09-01

Well NSK don't make fluid bearings do they ? A fluid bearing can be all sorts of things, the simplest is just called a journal bearing, or it can be called a hydrodynamic bearing. In other words it doesn't work until its moving. Occasionally you can find hydroSTATIC bearings, which have high pressure oil injected into them.

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sharlston (author)steveastrouk2009-09-02

nsk make roller,ball and tapered roller any idea how i could fill a nsk inner and outer raceway up with oil without leaking?

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steveastrouk (author)sharlston2009-09-02

That's not how a fluid bearing works. Look up "Journal Bearing" Steve

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sharlston (author)steveastrouk2009-09-02

ok so theres theres 2 race=ways qith oil or grease inbetween?

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steveastrouk (author)sharlston2009-09-02

Well done. the outer is usually made of a castable metal called "white metal" its got a lot of tin in it. The inner is usually polished steel. The lubricant sits between the two., and as the shaft spins, it rides up on the oil film. So what are you going to use it for ?

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sharlston (author)steveastrouk2009-09-02

its a school project so if i get a beariing then get raceways then fill with grease?

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steveastrouk (author)sharlston2009-09-02

Nope. If you want a demonstration one, make it in clear plastic. This one is a particularly expensive one
http://www.usdidactic.com/images/produktbilder/04028000/Datenblatt/04028000%202.pdf

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sharlston (author)steveastrouk2009-09-02

so the bearings get a constant supply of pressure

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steveastrouk (author)sharlston2009-09-02

No, in the hydrodynamic bearing, it makes its own as you start to spin it. A hydroSTATIC bearing is pressurised (and harder to make) Ideally your radial clearance would be about 25um, and you have shallow pressurised pockets inside the outer bearing, coupled with capillaries to very high pressure fluid.

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Yes, that is the way; I saw the first example in the '70s, here in NZ. And it was running from a bottle of nitrogen gas. Soon after I made my own, at my place of work, and used compressed air as the lube. You have slight pockets in the outer bearing to introduce the air, a small clearance between shaft and bore, that clearance depends on the veracity of the flue, oil, more clearance, air, less clearance But the minimum clearance at the 2 outsides of the bearing, to reduce loss of the lube fluid, you should not consider it efficient if the fluid is running out of the bearing flat out. That one bottle of nitrogen ran the bearing for 2 days of 10 hours as a display. The flywheel over the bearing was machined from steel, about 350mm diameter, one spin with the hand, it continued for 15-minutes, when the revolutions dropped below a certain point, the wheel just stopped, it was explained that the cushion of gas had collapsed, it needed a certain speed, to draw the gas right around the bearing, it only needed a small amount of gas to replace losses. And in fact, it’s not a lube so much, as a supporter, which meant that starting the bearing, you needed extra force, to begin it floating If you check out machine tools, large milling machine tables are floated using such a process, you might think it is a hovercraft system, but no, its like a bearing. I think some machine tool spindles like center less grinding, use such bearings

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I make one now that works at zero rotational speed. Its all about the design of the gas feeds to the bearing plenum.

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sharlston (author)steveastrouk2010-01-31
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sharlston (author)steveastrouk2009-09-02

sorry i had to reply to this message becuase the chain got too long and i couldnt see the reply button is there a constant supply of pressure and fluid to the bearing?

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