On Tue, 6 Dec 2016 10:15:11 -0700, "Bob La Londe"
wrote:


"Christopher Tidy" wrote in message
...
Hi folks,

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?

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?




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