I need an example for an article. Can anyone think of a modern product whic h uses plain bearings in a demanding application? I'm not talking about the extremes (like dental drills and steam turbines), but more common applicat ions such as supporting lathe spindles and engine crankshafts. It used to b e common to have plain bearings in these machines, and some were incredibly durable, but I haven't seen any in a new product for a long time. Are ther e any examples, or have they been entirely displaced by standardised ball a nd roller bearings?
The front wheel bearings on my Poulan Pro light garden tractor/mower (Husqvarna, Craftsman, Electrolux) are just sleeve/flange:
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A really unusual bearing application was the use of wood for the bearings in an hydroelectric power house turbine in Michigan's Upper Peninsula. It was installed around the mid 1930's and as far as I know is still in use. It was some odd type of wood. It ran wet, in the water going through if I recall correctly...
ich uses plain bearings in a demanding application? I'm not talking about t he extremes (like dental drills and steam turbines), but more common applic ations such as supporting lathe spindles and engine crankshafts. It used to be common to have plain bearings in these machines, and some were incredib ly durable, but I haven't seen any in a new product for a long time. Are th ere any examples, or have they been entirely displaced by standardised ball and roller bearings?
The large majority of IC engines use plain bearings, and always have. Honda 's experience with motorcycle engines in the '60s is instructive. They used roller crankshaft bearings until their development work actually showed le ss friction was developed with the latest plain bearings and lubricants. II RC, the first engine for which they switched to plain bearings was the 4-cy linder 750, in the late '60s.
Be careful with a couple of points about plain bearings. "Hydrodynamic" bea rings are those in which the rotating shaft drags lubricant around with it to maintain a film. The pressure of the oil supply in this case, as in auto mobile engines, has nothing to do with the film. It's just a supply for the oil to get *into* the bearings.
"Hydrostatic" bearings are those in which oil is supplied at much higher pr essure and the film is maintained by that external pressure, even if the sh aft is not rotating at the time. Thus the "static" part.
High-speed milling and grinding spindles in some of the more exotic machine tools look like plain bearings, but the film in their case is air -- pneum ostatic. There also were pneumodynamic bearings used in toolpost grinders b efore 1925 or so. They ran hardened-and-polished steel spindles, running in hardened-and-polished steel bushings, at up to 10,000 - 12,000 rpm. There was no external air supply. They just dragged air around dynamically, like a car engine does with oil, and the air created a lubricating film when the spindle got up to speed.
You're dealing with a potentially complex subject. Good luck!
hich uses plain bearings in a demanding application? I'm not talking about the extremes (like dental drills and steam turbines), but more common appli cations such as supporting lathe spindles and engine crankshafts. It used t o be common to have plain bearings in these machines, and some were incredi bly durable, but I haven't seen any in a new product for a long time. Are t here any examples, or have they been entirely displaced by standardised bal l and roller bearings?
'Sounds like lignum vitae. They were used for a lot of bearings in the past , including steam engines and water wheels.
Off the top of my head that sounds right. Something went amiss and caused it to dry out, seize up. They fixed the water problem, broke it loose again and it continued in operation. I use to talk with the man in charge of the operation ~20 years ago. He had long retired but still kept in touch with his old employer, fellow workers. At that time it was still in use, even after that mishap.
ich uses plain bearings in a demanding application? I'm not talking about t he extremes (like dental drills and steam turbines), but more common applic ations such as supporting lathe spindles and engine crankshafts. It used to be common to have plain bearings in these machines, and some were incredib ly durable, but I haven't seen any in a new product for a long time. Are th ere any examples, or have they been entirely displaced by standardised ball and roller bearings?
The center bearing on the Garrett Airesearch air cycle machines on a Boeing 767 is a plain bearing. Basically a backwards turbocharger that expands hi gh pressure/volume engine bleed air to cool it for the ship's cabin. Very h igh speed operation. Uses the incoming air as a lubricant film in the beari ng. There are Teflon ribbons between the bearing surfaces to prevent damage until full pressure and support takes place after the inlet valve is opene d.
What exactly is the definition of a "plain" bearing? Bronze bearings are still used all the time in all kinds of things. They are great for fast prototyping mechnical assemblies. Does a nylon bushing count? How about acetal? How about teflon impregnated acetal? Is cast iron on cast iron in a mill a plain bearing? Does it only count if its unlubricated? Do modern exotic materials count?
With the range of materials available today I would be curious to know...
There are lots of simple mechaical devices that have a steel rod pushed through a hole in a thermo plastic body. Is that a plain bearing? Or does that not count because there is no third mechancial bit?
Is a plain bearings still a plain bearing if it "accidentally" operates like an air bearing?
I need an example for an article. Can anyone think of a modern product which uses plain bearings in a demanding application? I'm not talking about the extremes (like dental drills and steam turbines), but more common applications such as supporting lathe spindles and engine crankshafts. It used to be common to have plain bearings in these machines, and some were incredibly durable, but I haven't seen any in a new product for a long time. Are there any examples, or have they been entirely displaced by standardised ball and roller bearings?
A plain bearing, according to Machinery's Handbook, has no rolling elements. So even the flat way surfaces on machine tools are plain bearings. So I would say that the hydrodynamicically supported ways in a milling machine is a demanding application. At least some if not all F1 engines use plain crankshaft bearings. I would say that's pretty demanding. Maybe that's too extreme. On the other hand, there are all sorts of plain bearings sliding on round rods in all different types of positioning applications. Many of these bearings have aluminum shells with a thin synthetic lining, Rulon for example, that are very low friction and can carry very high loads. IGUS is one company that makes these types of plain bearings and they have all sorts of examples on their website. I have nothing to do with them except that I have used their products. Eric
Well, every bicycle chain (or other chain drive, for that matter) uses dozens of plain bearings, one at every pivoting joint. They're remarkably reliable, considering the environment.
I've got a nice Cameron Precision sensitive drill press, which I got new sometime in the 1970s which has plain bearings on the spindle. It goes up to pretty high RPMs. The spindle ends in a JT-0 and mine came with a 1/8" Albrecht chuck on it. to give an idea of size.)
And -- as far as I can tell, they still use the plain bearings. (they look like sintered bronze style, not hand-scraped bearings.
Ehre is the page which shows mine as the first photo, excep that mine does not have the clear plastic belt cover.
Scroll down far enough and there is a link for contacting for questions -- so you could verify whether they still use the same bearings that way.
Well -- the MGA (1956 to I think around 1964) used needle roller bearings for the clutch pilot, and the throwout bearing was a graphite ring in a cup applied to a hardened steel ring..
The needle roller bearing was not an assembly, but rather a cluster of needles which you put in place with some grease to hold them until the input shaft pilot was into place.
I had the eyesight and fine motor skill for that kind of detail when I was young. I could read the States' names on the Lincoln Memorial on the back of a $5 bill.
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With a magnifier I can still splice the ends of 0.015" solder together.
Got one of those too. They just discontinued the classic looking model for a newer design. My guess is they ran out of castings or motor parts from decades ago. While way newer than yours, it has plain bearings as well. With a little practice I was able to drill through the widest part of a brass key for about a 30x width hole with good straightness. There's no play that I can measure, and they claim speeds up to 30,000 RPM are OK. Small bearings can run fast, so there probably isn't any real sorcery behind their bearings other than there's some hand fitting going on at the factory where they take out all the play. The original motors are real screwy, so there's no loss if they ditched those for something better, even if it doesn't match the look of the original.
Really accurate, oil-lubricated plain bearings in normal sizes can run with a clearance as small as 0.0002" or so, which is more or less the resulting spindle accuracy at modest speeds, as on a lathe.
However -- and this is a big however -- when they turn at really high speed s (and your description sounds like this is a high-speed spindle), the cent ering force from the hydrodynamic action can be very high. In other words, they can run a heck of a lot closer than their nominal clearance.
Ball bearings, of course, can run with zero clearance when they're preloade d. But they present other problems when the speeds get high. The centrifuga l force (here come the nit-pickers...) overcomes the preload and the acc uracy of the spindle or shaft declines. That's why they use ceramic bearing balls in high-speed spindles: they're lighter, so there's less force fight ing against the preload.
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