Drew Devitt is the Chief Technology Officer at New Way Air Bearings. Since 1994, New Way Air Bearings has been the market leader in Porous Media™ air bearing technology.
I wonder what plasma cutting dust or powder coating powder maybe a few specs of metal from sparks will do to the performance would be cool if it blows it out of the way
I'm amazed at how stiff the air film is, seems to defy intuition. Please correct me if I'm wrong, but is part of the secret or "magic" behind this tech the fact that the air in the gap is not only being compressed, but is restricted from exiting the gap, and this restriction or equilibrium between the the compression and "restriction" is what allows the stable/stiff air film to form? Is the restriction due to the particular viscosity of the air, or just more simply a result of geometry (i.e. too large for viscous effects to really matter). In the film, is the range of air compression still linear (following ideal gas law) or is it now exponential, and that too may be part of the magic perhaps? (less likely I think). Seems to me, and I may be very wrong, but it's as if there's a special regime of scale here where some particular physics are what's allowing the air film to be created, and exploited. Any Info is much appreciated, thanks!
@drewdevitt - I see why many applications can't/don't use them. Ancillary requirements, packaging dynamic load resistance, etc... but there are sooooo many applications where these are overwhelmingly applicable, yet aren't being implemented. Turbochargers are a fine example. Integrated air supply.
Impressed to see externally pressurised bearings in action. Donald Bently's dream come true! Though we see these bearings in TPS & ATPS and other symposiums, I have not come across them being employed in the machines I have worked on in the refineries and chemical plants. But I've worked on several AMBs and wonder if AMB, despite the hitech control systems, are more reliable than these. Could the author provide a comparison of AMBs with these pressurised bearings please?
My primary concern would be how the air bearing can handle thrust loads. If you completely blocked exhaust gasses and compressed air from getting to the back of each wheel, you would largely negate thrust loads, so that could be a solution. You would then be dealing with only the much smaller thrust loading caused by the pressure on the outward faces of the compressor and turbine wheels. These could still be substantial given the possible pressure differentials, so that would need to be handled.
Just curious. What kind of rates of contamination or clogging to the porous filters do you get from a setup like this. Can it clog to the point of impeding fluid flow, or is that able to be stretched for a very long duration with clean enough gas processing before it reaches the filter, or is that not even required. Are the filters designed to be serviced or replaceable? Mech eng here that's been looking into your videos lately, very fascinated by air bearing technology in general. Using porous material like carbon seems like the play for most designs, but I'm curious how big of a problem you tend to have with this material getting "clogged" over time.
These bearings are not plugged by particulate contamination as an orifice air bearing could be. You can pour sand or Teflon tape or the stuff that Schuff off the inside of tubing after a while into a bearing without any effect as even if the whole Plenum is contaminated it has less restriction than the porous media does. Contamination by water or oil does have an effect on the flow through the pours media running clean, dry air through the bearing will clean out water contamination quite quickly. Usually within a few minutes oil takes longer that may take a few hours.
Yes, we often make spindles with porous bearings. Yes 360° circumferential porous bearings are also a good seal although we typically use the thrust bearing position towards the contaminant side. thrust bearings have a smaller gap and generate more pressure 360° around, they act like a dry gas seal or a noncontact face seal.
This showed up in my feed a few days after watching a video by integza about a porous knife with an oxy fuel mix fed into it. The porosity was apparently the result of a defect in selective laser sintering processes that turned out beneficial. Was the bearing material made using the same sls process? It leaves me wondering if it is possible to produce something like a phase change heat pump or a heat exchanger using the same process.
Yes, we often run porous bearings using Freon as the bearing medium rather than air. This makes for a hermetic oilless contactless bearing system. It’s typically employed and larger air conditioning systems where centrifugal compressors are used.
You are ruining that granite surface plate. It’s for precision metrology. I hope that’s not the plate you’re using to measure your machined products off of
Air barings where good enough why being so retarded and adding the viscosity of water clearly that was an idea form sime morronic and retarded Marketing management Apes😂
I suspect there might be at least some market selling these to DIYers who want to improve the performance of their mini lathes, Mills, 3D Printers, XY Gantry Router Tables, X/Y Laser tables, etc. I think I've seen some such users attempting to DIY their own air bearings out of graphite.
@@EvanZalys For the stage, yes, I agree, but the bearings themselves if you type New Way Air Bearings into Google I'm seeing some examples under $200 each.
The main question for me regarding the air bearings is how much load they are ready to take in comparison, for example, with sliding guides. Will a air bearing lathe be able to remove a large layer of metal, or it will be only applicable for finishing or grinding?
We may spindles that can carry tons of load. We can definitely make spindles that are appropriate for heavy, cutting most diamond turning machines, though, where air bearings are typically used. Relatively light cuts, but result in super accurate mirror finishes.
Not here to spew doubt, but my concern here is not the bearing material, well, the porous matrix to be precise, the air is the bearing material in a way, but my concern is not the capacity of the matrix to withstand the hot side, my concern lies more in the direction of the fact that as an air bearing, sure, its somewhat cooled by the air itself, but the shaft is no technically suspended, contacting absolutely nothing, as per the function of the air bearing... In such conditions, the hot side, which can get real damn hot, will heat up the impeller, thus through it, it will heat up the shaft, which being steel, will expand... How much can the ceramic or whatever matrix used, contend with steel`s thermal expansion without it becoming an issue... Being isolated, the heat can only rely on the air current to cool it somewhat, which i dont see as being adequate to cool down, what is supposed to be an ultra high precision shaft-bearing-bore system, and maintain the clearances, which as you state, should be minimal, both to run an air bearing sys, and to as you say, improve the efficiency of the turbo itself... Oil is troublesome, but it themally couples the shaft with its rotors and bearings to the housing of the turbo, which often has extra routing for engine coolant, which makes it quite a decent thermal sponge... Without oil, you dont just lose the cooling provided by the oil, but you lose the fluid coupling that allows the shaft to quickly shed heat and maintain its tolerances... Speaking of tolerances, if you run air bearings, they require pretty high precision, or minimal tolerances... One side is cold, which will when running reduce the clearances on that end, and the other is hot, which will loosen the clearances on that end... The shaft being insulated by air, will undoubtedly suffer from that situation even more, so how do you plan on contending with that issue? The healthy turbo range is quite varied, and the clearances have to be adequate for both support of the componentry and for adequate sealing and free running... With oil, that is less of a problem, as it has some properties that are greatly reduced or not present with the air as a bearing film medium... Im not outright denying the idea or calling it a scam, i just see some aspects from the technical standpoint which rise some questions... Not just that, but speaking of heat and tolerances, you said the thrust clearance thermal growth can be eliminated... I dont see how... The shaft is going to be heated up through the hot side rotor, no matter what you do - the air bearing air flow cooling wont be enough to impact that... That in turn will render your shaft longer, regardless of its shrinkage on the cool side... cool side is not too cool, but hot side is extremely hot, which is bound to extend and expand the shaft during running... That will affect your thrust clearances without a doubt... And again, the shaft being suspended in air, not being actively cooled by a liquid, will not benefit from any housing cooling system... You can run liquid nitrogen as coolant through the housing(ridiculous, but im just giving an overkill situation) and it will cool the housing(thus reducing your clearances on the bore - matrix surface, but the isolated shaft wont benefit from it, it will only be heated up by the hot side and minimally cooled by the air flow and the cold side... An air bearing is not an air motor, which greatly benefits from cooling air, the bearing relies on high pressure and relatively low flow, so its self-cooling capacity is quite minimal... Which normally isnt a problem, as there is no contact or friction to induce heat which would have to be lowered... Air bearings are amazing, as a machinist, i love the concept, just as with hydra-bearings, but as a machinist, i know that some things are not used in some scenarios, exactly because of their inherent benefits that in some situations turn into absolute detriments... You know, ice skating is cool, and ice`s properties that allow you to skate are amazing, but they really fucking suck when you are trying to just walk or drive... As said, i dont want to call shit out as anything, but i do have some concerns, and those have been written down above...
I appreciate your comments. Especially the ones concerning thermal growth. Actually, the shaft will expand more than the poorest media so the clearance is reduce in the hot area and expand in the cool areas, especially in cryogenic Turbo machinery. 90% of turbo chargers have a shaft that’s less than half an inch in diameter and most of those are on the order of a quarter inch so even with large temperature swings the thermal growth is not great. Also the turbo chargers heat up quite quickly because of the hot exhaust gases, so we just leave enough clearance to accommodate the growth which happens quite quickly. The ultra fast pull up and efficiency improvements by avoiding oil shear drag are huge improvements for turbo chargers. Plus, there is no oil to Coke improving the reliability and longevity of turbocharged systems.
@@drewdevitt Most glad to hear back from ya! Great, glad to hear your analysis of the system... As said, i was speculating, i know that the growth ain`t much, but being that i am not the one designing this nor researching the specific materials and applications, i still am lacking specific insights into performance of this system, especially on the long run and in the ``field``... Sure, oil/grease shear is a major drag contributor, no doubt there... Hell, even air has shear of sorts, or rather, a sort of molecular friction when it passes near something, so yeah, switching from lubricant shear to what is essentially a jig grinder spindle with the ridiculous bearing efficiency is a major deal... As said, i didn`t come to shit on this, on the contrary, i was curious and unsure as to how well the system would operate ``not on the clean room table``... As a machine fetishist, i am aware that the field and clean room perform a lot differently, so i had to ask... And now i am glad that i did... I wonder what is the running, full temp - clearance of the spindle in those bearings, or the shaft in this case... Cant be far from a micron of few, in which case, i wonder what`s the clearance of the same part when cold... Hell, i would love to see the dynamic graphic display of the system fluidity and fluctuation as it goes from 0-100, or rather from env. temp to full operating conditions... That would be a damn cool sight with modern cad display capacities of computers... At any rate, i wish you all the best and you have my kindest regards! Steuss
Japan patented a sandblasting technique using rubber as the blasting agent to create small round indentations on the metal surface. The size of the round indentations are just the right size to trap air between a shaft and housing, essentially creating this same affect without having to pump air through it. I’ve been looking for the parents since the 90’s. I believe it was discovered by FUJI. They pioneered enclosed sandblasting machines and techniques that were over shadowed by the primary business of film. I believe it was Fuji. Someone please help and or correct me. Because I’m still looking for it he data and the patents
Thanks for your comment. There are fundamental differences between aerodynamic gas bearings as you are describing with the sandblasting technique and externally, pressurized gas bearings. so they are completely completely different sets of teachings and claims inthe patent literature. The basic idea of hydrodynamic or aerodynamic bearings were first described by Kingsberry and Mitchell, respectively in the United States in England at almost the exact same time.
I found intrest in these when I got into Computed tomography. The Phillips CT scanner I currently run works on an air bearing. I think it can make a full rotation in .3 seconds.
I think it makes a rotation in point two seconds in production machines. Philips is still a customer of ours for computed tomography machines in the development, back around the turn of the century We had a 2 m diameter rotor go 500 RPM with over a ton of rotating x-ray equipment on it. That’s less than point1 seconds per Revolution and over 100 m/s surface speed
@@drewdevitt I don't doubt that it can make that rotation faster, my interface only allows me to select that minimum . 35 second rotation speed for image acquisition.
Hey Drew, hope you have a minute for a curious viewer: Do air bearings cope well with water (or oil) spilling onto the static surface of the bearing? The 1974 paper published by the Oak Ridge plant puts forth that keeping moisture out of the gas supply is quite important and generally emphasizes cleanliness, and yet seeing this video, I wonder if porous media air bearings could be at ease in an environment with cutting fluids going all over the show... Couldn't find anything on your website answering this exact question, yet, so thought I'd ask. :)
Hi Yes, the air bearings are so good at keeping water and coolant out they can be used as seals. Here you can see an example of pouring water directly between bearings supporting a 100mm dia shaft at 7500 RPM. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-0SPwPxYHeRs.htmlfeature=shared
Compressor wheels with flat backing are outdated designs, reason they are nit flat is you are trying to push as much rpm into the wheel as possible, and with raised back the rpm can double in some turbos so you want to avoid flat backed compressor and Turbine
Impellers with flat backs and our externally, pressurized gas bearings running on them reduce clearances that are typically required between the impeller and the rest of the state or housing. Turbo chargers should spool up quickly. The oil shear at high speed is a surprising drag on the ability of turbo chargers to spool up, this has a much bigger effect than the geometry of the impeller.
@@drewdevitt I think what he was trying to say is that the superback design is necessary for structural integrity of the compressor wheel at high speeds. It is not about sealing of any kind. However, even a superback design could obviously implement a flat area or whatever is required for sealing.
Here's a snarky comment from the peanut gallery: the 2 cutouts at the end of the shaft couldn't be why it's turning to face those cutouts up, because it's happening too quickly. That missing amount of metal couldn't rotate that heavy shaft so quickly. This is really, really cool video. I had no idea 'air bearings' existed- or that they could work so well. I'm imaging things like a free piston linear steam engine/generator that would need no lubrication and would be wear-free.....
