Truck bearings: Solid vs. RB


Richard Hendrickson
 

Several times lately I have noticed members of this group using the
term "friction bearings" to differentiate solid bearings from roller
bearings, despite objections on previous occasions from myself, Tony
Thompson, and others. The correct terminology for solid truck
bearings is "solid." "Plain bearings" is an acceptable alternative.
"Friction bearings" is wrong and misleading. All bearings have
friction, including roller bearings. "Friction bearing" was invented
as an advertising ploy by roller bearing manufacturers to imply,
incorrectly, that roller bearings were frictionless. In fact, though
roller bearings have much less starting resistance than solid
bearings, they have considerable friction which - as with other
bearings - increases as load and speed increase. The term "friction
bearings" was never adopted by railroad mechanical engineers, who
knew better; it does not appear in the dictionary section of any
edition of the Car Builders' Cyclopedia. So please, guys, don't
perpetuate the mistake of calling solid bearings "friction" bearings.

Richard Hendrickson


Pierre <pierre.oliver@...>
 

Thanks Richard, for that clarification. I've never been comfortable with the "friction bearing" phrase myself and I've always wondered what the correct term should be. In part because a solid bearing is closer to a bushing than a bearing in my world of mechanical creations.
Pierre Oliver

--- In STMFC@..., Richard Hendrickson <rhendrickson@...> wrote:

Several times lately I have noticed members of this group using the
term "friction bearings" to differentiate solid bearings from roller
bearings, despite objections on previous occasions from myself, Tony
Thompson, and others. The correct terminology for solid truck
bearings is "solid." "Plain bearings" is an acceptable alternative.
"Friction bearings" is wrong and misleading. All bearings have
friction, including roller bearings. "Friction bearing" was invented
as an advertising ploy by roller bearing manufacturers to imply,
incorrectly, that roller bearings were frictionless. In fact, though
roller bearings have much less starting resistance than solid
bearings, they have considerable friction which - as with other
bearings - increases as load and speed increase. The term "friction
bearings" was never adopted by railroad mechanical engineers, who
knew better; it does not appear in the dictionary section of any
edition of the Car Builders' Cyclopedia. So please, guys, don't
perpetuate the mistake of calling solid bearings "friction" bearings.

Richard Hendrickson



[Non-text portions of this message have been removed]


midrly <midrly@...>
 

Richard--

Thank you, Thank You, THANK YOU!!!!!!!!!!

Most on this list know that plain bearings ride on top of a journal on a film of oil, and friction is not what a railway wants in a journal bearing.

Now if we can only eradicate that equally annoying and also inaccurate phrase "throwing" or "operating a turnout" while we're at it...

Steve Lucas.

--- In STMFC@..., Richard Hendrickson <rhendrickson@...> wrote:

Several times lately I have noticed members of this group using the
term "friction bearings" to differentiate solid bearings from roller
bearings, despite objections on previous occasions from myself, Tony
Thompson, and others. The correct terminology for solid truck
bearings is "solid." "Plain bearings" is an acceptable alternative.
"Friction bearings" is wrong and misleading. All bearings have
friction, including roller bearings. "Friction bearing" was invented
as an advertising ploy by roller bearing manufacturers to imply,
incorrectly, that roller bearings were frictionless. In fact, though
roller bearings have much less starting resistance than solid
bearings, they have considerable friction which - as with other
bearings - increases as load and speed increase. The term "friction
bearings" was never adopted by railroad mechanical engineers, who
knew better; it does not appear in the dictionary section of any
edition of the Car Builders' Cyclopedia. So please, guys, don't
perpetuate the mistake of calling solid bearings "friction" bearings.

Richard Hendrickson



[Non-text portions of this message have been removed]


Bruce Smith
 

Steve,

This is one instance where supposedly prototype savvy modelers forced a term into use that is technically incorrect. I think this happened for 2 reasons, the first being that "switch" was being misused to represent "turnout" ("I bought a #8 switch from Walthers") and the second being that the backlash against that misuse went too far and folks assumes that any use of "switch" was incorrect ("Ooooh, if it is a turnout and not a switch, then I had better say 'throw the turnout'"). Its always fun to watch the real railroaders cringe when somebody does that <G> .

Regards
Bruce
Bruce Smith
Auburn, AL
________________________________________
Steve says:
Now if we can only eradicate that equally annoying and also inaccurate phrase "throwing" or "operating a turnout" while we're at it...


Brian Ehni <behni@...>
 

I always though "throw" was the proper term, since you have to throw the
lever over.


Thanks!
--

Brian P. Ehni

From: "Bruce F. Smith" <smithbf@...>
Reply-To: STMFC List <STMFC@...>
Date: Thursday, April 26, 2012 8:17 AM
To: STMFC List <STMFC@...>
Subject: RE: [STMFC] Re: Truck bearings: Solid vs. RB






Steve,

This is one instance where supposedly prototype savvy modelers forced a term
into use that is technically incorrect. I think this happened for 2
reasons, the first being that "switch" was being misused to represent
"turnout" ("I bought a #8 switch from Walthers") and the second being that
the backlash against that misuse went too far and folks assumes that any use
of "switch" was incorrect ("Ooooh, if it is a turnout and not a switch, then
I had better say 'throw the turnout'"). Its always fun to watch the real
railroaders cringe when somebody does that <G> .

Regards
Bruce
Bruce Smith
Auburn, AL
________________________________________
Steve says:
Now if we can only eradicate that equally annoying and also inaccurate
phrase "throwing" or "operating a turnout" while we're at it...








[Non-text portions of this message have been removed]


Jack Burgess <jack@...>
 

<I always though "throw" was the proper term, since you have to throw the
<lever over.
<
<
<Thanks!
<--
<
<Brian P. Ehni

I think the term is to "line" it...

Jack Burgess


tyesac@...
 

Richard, Pierre,

Right you are! If anybody thinks that solid bearings are obsolete technology, think again. Anything driven by a crankshaft has solid bearings; from a formula 1 race car to diesel locomotive. Properly lubricated, they're a low resistance bearing that's able to tolerate heavy loads. A key issue for the changeover for the railroads was that roller bearings have less finicky lubrication requirements, typically only the roller cage requires greasing at initial installation. Having large percentages of the freight car fleet that doesn't require constant vigilance for oiling helped tip the scales for the more expensive roller bearings.

Now if we could only get some model RR manufactures to drop the "friction bearing" term.

Tom Casey


Thanks Richard, for that clarification. I've never been comfortable with the "friction bearing" phrase myself and I've always wondered what the correct term should be. In part because a solid bearing is closer to a bushing than a bearing in my world of mechanical creations.
Pierre Oliver

--- In STMFC@..., Richard Hendrickson <rhendrickson@...> wrote:

Several times lately I have noticed members of this group using the
term "friction bearings" to differentiate solid bearings from roller
bearings, despite objections on previous occasions from myself, Tony
Thompson, and others. The correct terminology for solid truck
bearings is "solid." "Plain bearings" is an acceptable alternative.
"Friction bearings" is wrong and misleading. All bearings have
friction, including roller bearings. "Friction bearing" was invented
as an advertising ploy by roller bearing manufacturers to imply,
incorrectly, that roller bearings were frictionless. In fact, though
roller bearings have much less starting resistance than solid
bearings, they have considerable friction which - as with other
bearings - increases as load and speed increase. The term "friction
bearings" was never adopted by railroad mechanical engineers, who
knew better; it does not appear in the dictionary section of any
edition of the Car Builders' Cyclopedia. So please, guys, don't
perpetuate the mistake of calling solid bearings "friction" bearings.

Richard Hendrickson





-----Original Message-----
From: Pierre <pierre.oliver@...>
To: STMFC <STMFC@...>
Sent: Wed, Apr 25, 2012 7:49 pm
Subject: [STMFC] Re: Truck bearings: Solid vs. RB




Thanks Richard, for that clarification. I've never been comfortable with the "friction bearing" phrase myself and I've always wondered what the correct term should be. In part because a solid bearing is closer to a bushing than a bearing in my world of mechanical creations.
Pierre Oliver

--- In STMFC@..., Richard Hendrickson <rhendrickson@...> wrote:

Several times lately I have noticed members of this group using the
term "friction bearings" to differentiate solid bearings from roller
bearings, despite objections on previous occasions from myself, Tony
Thompson, and others. The correct terminology for solid truck
bearings is "solid." "Plain bearings" is an acceptable alternative.
"Friction bearings" is wrong and misleading. All bearings have
friction, including roller bearings. "Friction bearing" was invented
as an advertising ploy by roller bearing manufacturers to imply,
incorrectly, that roller bearings were frictionless. In fact, though
roller bearings have much less starting resistance than solid
bearings, they have considerable friction which - as with other
bearings - increases as load and speed increase. The term "friction
bearings" was never adopted by railroad mechanical engineers, who
knew better; it does not appear in the dictionary section of any
edition of the Car Builders' Cyclopedia. So please, guys, don't
perpetuate the mistake of calling solid bearings "friction" bearings.

Richard Hendrickson











[Non-text portions of this message have been removed]


devansprr
 

Gentlemen,

If we wish to be precise, then the term solid bearing is incorrect, and in fact does not appear in engineering mechanics texts.

The bearings we are discussing are "journal" bearings, and they are of the Hydrodynamic sub-type.

The term "anti-friction" bearing is applied to roller bearings and other types of bearings where the main relative motion is rolling instead of sliding.

I can understand why marketing types might then label Journal bearings "friction" bearings, even if mechanical engineers never did.

Journal bearings use some form of lubrication between two sliding surfaces. Hydrodynamic journal bearings draw lubricating oil into the bearing gap using fluid mechanics. The lubricant is not under pressure (as it is in auto engines, which use Hydrostatic journal bearings.)

From my engineering book:

"The film pressure is created by the moving surface itself pulling the lubricant into a wedge shaped zone at a velocity sufficiently high to create the pressure necessary to separate the surfaces against the load on the bearing."

This is why the friction of hydrodynamic journal bearings can be so high when they first begin to turn. They may first start with direct metal-to-metal contact but even with a very thin oil film the drag can be much higher than "normal". Since journal bearing friction is a function of film thickness - the thinner the film, the higher the friction (mathematically this friction is a function of one over the film thickness). As speed increases the bearing is designed to induct more oil to create a thicker film.

This is much different than roller bearings, and helps to explain why, during the steam era, if the train got under a few mph and the locomotive lacked the pull to accelerate, the train could just "grind" (figuratively, not literally) to a halt. And it explains why steam era engineers didn't walk out trains at very low speeds - better to keep the moving cars above the speed that could lead to a sure stall as more cars were placed in motion (and hence all of that slack action - a good reason for those buffered draft gear and underframes).

So for steam era journal bearings, until the speed increased to a point where the design film thickness was established, friction could actually drop as speed increased. I do not know the "crossover" speed where drag began to increase as speed increased. Conversely, this crossover speed was also the speed where drag INCREASED as speed dropped. Perhaps it is in an old railroad engineering book.

Makes one wonder if steam may have lasted a little longer if roller bearings had been more widely applied - they are much easier to start and keep rolling at low speeds, which was often a steam locomotive's greatest challenge, and helps explain why steam locomotives pulling modern trains under heavy loads seem to do so well - probably better than when they were built.

This also explains why journal bearing cars appear to come to a sudden stop in the last phase of coasting - they actually do stop quickly (think about the implications for a journal bearing era hump yard.) As they slow, the friction will increase significantly once the film begins to thin (and the slower speed results in an even thinner film - so the friction rapidly builds as the car comes to a stop). I bet hump rider's intuitively understood this, even if they did not know the physics.

Richard is correct that once the steady state film thickness was established (at some unknown, to me, speed) the friction increased with speed - but only linearly, so the total friction per unit distance traveled was nearly constant (no journal bearing fuel penalty for running faster - but there was a fuel penalty for aerodynamic drag at higher speeds.) Note that friction equals heat generation, so the high speed risk was that the heat generated per unit time increased (but not per unit distance traveled), and it could reach a point where the heat could not be rejected fast enough to the atmosphere, and the oil would overheat, potentially resulting in loss of the bearing film - and... Hot box)

And talk about Journal Bearing "hot boxes" - an older colleague at work once told me stories of how when he was a kid, in Portage, PA (on the PRR main), the kids use to take "those oily rags" out of the journal boxes in the winter time to help start camp fires when they were outside playing ice hockey. The innocence of youth....

Dave Evans

Nothing is ever fool proof, because fools are so ingenious ;-)

--- In STMFC@..., tyesac@... wrote:

Richard, Pierre,

Right you are! If anybody thinks that solid bearings are obsolete technology, think again. Anything driven by a crankshaft has solid bearings; from a formula 1 race car to diesel locomotive. Properly lubricated, they're a low resistance bearing that's able to tolerate heavy loads. A key issue for the changeover for the railroads was that roller bearings have less finicky lubrication requirements, typically only the roller cage requires greasing at initial installation. Having large percentages of the freight car fleet that doesn't require constant vigilance for oiling helped tip the scales for the more expensive roller bearings.

Now if we could only get some model RR manufactures to drop the "friction bearing" term.

Tom Casey


Thanks Richard, for that clarification. I've never been comfortable with the "friction bearing" phrase myself and I've always wondered what the correct term should be. In part because a solid bearing is closer to a bushing than a bearing in my world of mechanical creations.
Pierre Oliver

--- In STMFC@..., Richard Hendrickson <rhendrickson@> wrote:

Several times lately I have noticed members of this group using the
term "friction bearings" to differentiate solid bearings from roller
bearings, despite objections on previous occasions from myself, Tony
Thompson, and others. The correct terminology for solid truck
bearings is "solid." "Plain bearings" is an acceptable alternative.
"Friction bearings" is wrong and misleading. All bearings have
friction, including roller bearings. "Friction bearing" was invented
as an advertising ploy by roller bearing manufacturers to imply,
incorrectly, that roller bearings were frictionless. In fact, though
roller bearings have much less starting resistance than solid
bearings, they have considerable friction which - as with other
bearings - increases as load and speed increase. The term "friction
bearings" was never adopted by railroad mechanical engineers, who
knew better; it does not appear in the dictionary section of any
edition of the Car Builders' Cyclopedia. So please, guys, don't
perpetuate the mistake of calling solid bearings "friction" bearings.

Richard Hendrickson





-----Original Message-----
From: Pierre <pierre.oliver@...>
To: STMFC <STMFC@...>
Sent: Wed, Apr 25, 2012 7:49 pm
Subject: [STMFC] Re: Truck bearings: Solid vs. RB




Thanks Richard, for that clarification. I've never been comfortable with the "friction bearing" phrase myself and I've always wondered what the correct term should be. In part because a solid bearing is closer to a bushing than a bearing in my world of mechanical creations.
Pierre Oliver

--- In STMFC@..., Richard Hendrickson <rhendrickson@> wrote:

Several times lately I have noticed members of this group using the
term "friction bearings" to differentiate solid bearings from roller
bearings, despite objections on previous occasions from myself, Tony
Thompson, and others. The correct terminology for solid truck
bearings is "solid." "Plain bearings" is an acceptable alternative.
"Friction bearings" is wrong and misleading. All bearings have
friction, including roller bearings. "Friction bearing" was invented
as an advertising ploy by roller bearing manufacturers to imply,
incorrectly, that roller bearings were frictionless. In fact, though
roller bearings have much less starting resistance than solid
bearings, they have considerable friction which - as with other
bearings - increases as load and speed increase. The term "friction
bearings" was never adopted by railroad mechanical engineers, who
knew better; it does not appear in the dictionary section of any
edition of the Car Builders' Cyclopedia. So please, guys, don't
perpetuate the mistake of calling solid bearings "friction" bearings.

Richard Hendrickson



[Non-text portions of this message have been removed]


Anthony Thompson <thompson@...>
 

Dave Evans wrote:
Gentlemen,
If we wish to be precise, then the term solid bearing is incorrect, and in fact does not appear in engineering mechanics texts.
The bearings we are discussing are "journal" bearings, and they are of the Hydrodynamic sub-type.
Nope. These bearings are journal bearings because they bear on the axle journals. The journal is the part of the axle that the bearings ride on. It does not matter whether they are roller bearings or solid (or plain, if you prefer) bearings, they are all journal bearings.

Richard is correct that once the steady state film thickness was established (at some unknown, to me, speed) the friction increased with speed - but only linearly, so the total friction per unit distance traveled was nearly constant (no journal bearing fuel penalty for running faster - but there was a fuel penalty for aerodynamic drag at higher speeds.)
Tests showed that at speeds like 30 or 40 mph, the difference in rolling resistance between plain and roller bearings was negligible. The big difference, and as Dave say, a very important difference for steam power, was at starting speeds.

Note that friction equals heat generation, so the high speed risk was that the heat generated per unit time increased (but not per unit distance traveled), and it could reach a point where the heat could not be rejected fast enough to the atmosphere, and the oil would overheat, potentially resulting in loss of the bearing film - and... Hot box)
This is probably true, but my impression from reading and from talking to railroaders of that era is that hotboxes occurred because the waste would get snagged or bunched and get into the bearing surface, and presto, much reduced lubrication. This could and did happen at quite modest speeds. Whether really high-speed trains ever had hot boxes from speed alone, I don't know, but if so, one would expect a LOT of the cars in such a train to have the problem.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@...
Publishers of books on railroad history


John Hagen <sprinthag@...>
 

Very enlightening Dave and thanks for posting.



It would seem to me that the speed at which the oil layer would establish
itself would depend on how much weight was riding of the bearings. With the
weight of a loaded car versus that of an empty I think it would take a
higher speed to drag that oil completely around the bearing surface. And the
temperature would also effect it. In sub zero temps that oil is not going to
be easy to drag into that "squish" area.



I never really thought about all this but basically what has to happen the
lubricant must actually lift the weight of the car up off the bearing
surface. That fact that it even happens without an oil pump is somewhat
amazing to me. Here is a lesson for drivers. Even though your vehicles
engine has an oil pressures pump it takes a bit of time. Measured in
seconds, to get that pressure to the bearings. The colder the longer. That
is why all manufacturers recommend letting you engine idle for a bit before
moving off and not revving it even when not in gear.



If you have a relatively small car that can be easily pushed try pushing it
when it is fully warmed up. Then try it on a warm morning but before
driving. Lastly, wait for COLD weather and try pushing that now virtually
immobile block of icy metal. This will demonstrate just how resistant to
movement oil can become in frigid temps. Twenty-five years in the automotive
service business and I know the answers. It's a great thing to tell a
customer when he/she complains that the car gets poorer fuel mileage in cold
weather.



John Hagen



From: STMFC@... [mailto:STMFC@...] On Behalf Of Dave
Evans
Sent: Thursday, April 26, 2012 17:25
To: STMFC@...
Subject: [STMFC] Re: Truck bearings: Solid vs. RB





Gentlemen,

If we wish to be precise, then the term solid bearing is incorrect, and in
fact does not appear in engineering mechanics texts.

The bearings we are discussing are "journal" bearings, and they are of the
Hydrodynamic sub-type.

The term "anti-friction" bearing is applied to roller bearings and other
types of bearings where the main relative motion is rolling instead of
sliding.

I can understand why marketing types might then label Journal bearings
"friction" bearings, even if mechanical engineers never did.

Journal bearings use some form of lubrication between two sliding surfaces.
Hydrodynamic journal bearings draw lubricating oil into the bearing gap
using fluid mechanics. The lubricant is not under pressure (as it is in auto
engines, which use Hydrostatic journal bearings.)

From my engineering book:

"The film pressure is created by the moving surface itself pulling the
lubricant into a wedge shaped zone at a velocity sufficiently high to create
the pressure necessary to separate the surfaces against the load on the
bearing."

This is why the friction of hydrodynamic journal bearings can be so high
when they first begin to turn. They may first start with direct
metal-to-metal contact but even with a very thin oil film the drag can be
much higher than "normal". Since journal bearing friction is a function of
film thickness - the thinner the film, the higher the friction
(mathematically this friction is a function of one over the film thickness).
As speed increases the bearing is designed to induct more oil to create a
thicker film.

This is much different than roller bearings, and helps to explain why,
during the steam era, if the train got under a few mph and the locomotive
lacked the pull to accelerate, the train could just "grind" (figuratively,
not literally) to a halt. And it explains why steam era engineers didn't
walk out trains at very low speeds - better to keep the moving cars above
the speed that could lead to a sure stall as more cars were placed in motion
(and hence all of that slack action - a good reason for those buffered draft
gear and underframes).

So for steam era journal bearings, until the speed increased to a point
where the design film thickness was established, friction could actually
drop as speed increased. I do not know the "crossover" speed where drag
began to increase as speed increased. Conversely, this crossover speed was
also the speed where drag INCREASED as speed dropped. Perhaps it is in an
old railroad engineering book.

Makes one wonder if steam may have lasted a little longer if roller bearings
had been more widely applied - they are much easier to start and keep
rolling at low speeds, which was often a steam locomotive's greatest
challenge, and helps explain why steam locomotives pulling modern trains
under heavy loads seem to do so well - probably better than when they were
built.

This also explains why journal bearing cars appear to come to a sudden stop
in the last phase of coasting - they actually do stop quickly (think about
the implications for a journal bearing era hump yard.) As they slow, the
friction will increase significantly once the film begins to thin (and the
slower speed results in an even thinner film - so the friction rapidly
builds as the car comes to a stop). I bet hump rider's intuitively
understood this, even if they did not know the physics.

Richard is correct that once the steady state film thickness was established
(at some unknown, to me, speed) the friction increased with speed - but only
linearly, so the total friction per unit distance traveled was nearly
constant (no journal bearing fuel penalty for running faster - but there was
a fuel penalty for aerodynamic drag at higher speeds.) Note that friction
equals heat generation, so the high speed risk was that the heat generated
per unit time increased (but not per unit distance traveled), and it could
reach a point where the heat could not be rejected fast enough to the
atmosphere, and the oil would overheat, potentially resulting in loss of the
bearing film - and... Hot box)

And talk about Journal Bearing "hot boxes" - an older colleague at work once
told me stories of how when he was a kid, in Portage, PA (on the PRR main),
the kids use to take "those oily rags" out of the journal boxes in the
winter time to help start camp fires when they were outside playing ice
hockey. The innocence of youth....

Dave Evans

Nothing is ever fool proof, because fools are so ingenious ;-)

--- In STMFC@... <mailto:STMFC%40yahoogroups.com> , tyesac@...
wrote:

Richard, Pierre,

Right you are! If anybody thinks that solid bearings are obsolete
technology, think again. Anything driven by a crankshaft has solid bearings;
from a formula 1 race car to diesel locomotive. Properly lubricated, they're
a low resistance bearing that's able to tolerate heavy loads. A key issue
for the changeover for the railroads was that roller bearings have less
finicky lubrication requirements, typically only the roller cage requires
greasing at initial installation. Having large percentages of the freight
car fleet that doesn't require constant vigilance for oiling helped tip the
scales for the more expensive roller bearings.

Now if we could only get some model RR manufactures to drop the "friction
bearing" term.

Tom Casey


Thanks Richard, for that clarification. I've never been comfortable with
the "friction bearing" phrase myself and I've always wondered what the
correct term should be. In part because a solid bearing is closer to a
bushing than a bearing in my world of mechanical creations.
Pierre Oliver

--- In STMFC@... <mailto:STMFC%40yahoogroups.com> , Richard
Hendrickson <rhendrickson@> wrote:

Several times lately I have noticed members of this group using the
term "friction bearings" to differentiate solid bearings from roller
bearings, despite objections on previous occasions from myself, Tony
Thompson, and others. The correct terminology for solid truck
bearings is "solid." "Plain bearings" is an acceptable alternative.
"Friction bearings" is wrong and misleading. All bearings have
friction, including roller bearings. "Friction bearing" was invented
as an advertising ploy by roller bearing manufacturers to imply,
incorrectly, that roller bearings were frictionless. In fact, though
roller bearings have much less starting resistance than solid
bearings, they have considerable friction which - as with other
bearings - increases as load and speed increase. The term "friction
bearings" was never adopted by railroad mechanical engineers, who
knew better; it does not appear in the dictionary section of any
edition of the Car Builders' Cyclopedia. So please, guys, don't
perpetuate the mistake of calling solid bearings "friction" bearings.

Richard Hendrickson





-----Original Message-----
From: Pierre <pierre.oliver@...>
To: STMFC <STMFC@... <mailto:STMFC%40yahoogroups.com> >
Sent: Wed, Apr 25, 2012 7:49 pm
Subject: [STMFC] Re: Truck bearings: Solid vs. RB




Thanks Richard, for that clarification. I've never been comfortable with
the "friction bearing" phrase myself and I've always wondered what the
correct term should be. In part because a solid bearing is closer to a
bushing than a bearing in my world of mechanical creations.
Pierre Oliver

--- In STMFC@... <mailto:STMFC%40yahoogroups.com> , Richard
Hendrickson <rhendrickson@> wrote:

Several times lately I have noticed members of this group using the
term "friction bearings" to differentiate solid bearings from roller
bearings, despite objections on previous occasions from myself, Tony
Thompson, and others. The correct terminology for solid truck
bearings is "solid." "Plain bearings" is an acceptable alternative.
"Friction bearings" is wrong and misleading. All bearings have
friction, including roller bearings. "Friction bearing" was invented
as an advertising ploy by roller bearing manufacturers to imply,
incorrectly, that roller bearings were frictionless. In fact, though
roller bearings have much less starting resistance than solid
bearings, they have considerable friction which - as with other
bearings - increases as load and speed increase. The term "friction
bearings" was never adopted by railroad mechanical engineers, who
knew better; it does not appear in the dictionary section of any
edition of the Car Builders' Cyclopedia. So please, guys, don't
perpetuate the mistake of calling solid bearings "friction" bearings.

Richard Hendrickson





devansprr
 

Sorry Tony,

The Mechanical Engineer's definition of "journal" is that portion of the shaft that rotates within a bearing, AND the relative motion between the two is sliding. There is NO sliding motion in a roller bearing, so a roller bearing does not have a "journal".

Some in the railroad industry may have retained the term "journal" to refer to the entire assembly, or the portion of the truck that is fastened to the outer portion of the bearing, or even to the portion of the shaft that the roller bearing is pressed onto (a legacy use, but incorrect), but roller bearings are not journal bearings.

Today, roller bearings are often included with the axle assembly - it is not something installed in the field. The tapered rollers roll between a "cone", typically press fit onto the axle, and the cup, which is the outer, stationary assembly that is mechanically fixed to the truck. Roller bearings are actually pairs of tapered roller bearings at each truck side frame (So two pairs per axle) so they can also react the thrust loads that result from curves (rated at about about 25% of the radial load). It is the need to react thrust loads, without creating excessive surface loads on the rollers, that contributes to the fine tolerances required for railroad roller bearings, and hence why they are an integral assembly that is pressed onto a portion of the axle with a very high precision outer diameter. Perhaps some still call this region of the shaft a journal, but technically that is incorrect.

Nowhere in Timken's railroad literature does the term "journal bearing" appear. There is, in one of their maintenance guides, two instances where they interchange the word axle and journal, but ONLY when they discuss machining the axle to the proper diameter. But as soon as they discuss installing the bearing, it is installed on the axle, not a journal. The only other appearance of journal refers to publications.

So roller bearing and journal bearing are the proper engineering terms to distinguish between the two bearing types.

The term "Plain" bearing does not appear in any of my engineering books.

Dave Evans
BSME
MSME
Lehigh University

--- In STMFC@..., Anthony Thompson <thompson@...> wrote:

Dave Evans wrote:
Gentlemen,
If we wish to be precise, then the term solid bearing is incorrect,
and in fact does not appear in engineering mechanics texts.
The bearings we are discussing are "journal" bearings, and they are
of the Hydrodynamic sub-type.
Nope. These bearings are journal bearings because they bear on
the axle journals. The journal is the part of the axle that the
bearings ride on. It does not matter whether they are roller bearings
or solid (or plain, if you prefer) bearings, they are all journal
bearings.


Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@...
Publishers of books on railroad history


Anthony Thompson <thompson@...>
 

Dave Evans wrote:
The Mechanical Engineer's definition of "journal" is that portion of the shaft that rotates within a bearing, AND the relative motion between the two is sliding. There is NO sliding motion in a roller bearing, so a roller bearing does not have a "journal".
I urge you to check any Car Builders Cyc in the period of this list. The definitions for railroad use are quite clear.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@...
Publishers of books on railroad history


devansprr
 

-- In STMFC@..., Anthony Thompson <thompson@...> wrote:

Dave Evans wrote:
The Mechanical Engineer's definition of "journal" is that portion of
the shaft that rotates within a bearing, AND the relative motion
between the two is sliding. There is NO sliding motion in a roller
bearing, so a roller bearing does not have a "journal".
I urge you to check any Car Builders Cyc in the period of this
list. The definitions for railroad use are quite clear.

Tony Thompson Editor, Signature Press, Berkeley, CA

Tony,

A fair point. My 1940 Car builders cyc is actually rather schizophrenic on this - if we want to adopt a clear naming convention based on the prototype of our era - I believe the term is "We're hosed"

In the cyc's definition of terms, there are two entries - one for Journal Bearings, and one for Roller bearings. There are also a WHOLE bunch of entries for "Journal xxx", but no "journal roller bearing", or "roller journal bearing". The definition of journal is the part of an axle or shaft on which the journal bearing rests.

The confusion is that the definition of Journal bearing includes rollers and balls (and then a reference to see roller bearings), along with the "traditional" journal bearing components.

Looking through the vendor documents, you can sense the source of the confusion. All of the roller bearing vendors used the term journal in their adds, but generally in reference to the "journal" not the bearing itself.

ASF promoted a roller bearing on the interior of the wheel that was supported by a fixed axle (good in curves since it will allow the wheels to rotate at different speeds.) Only the term roller bearing is used here - no journals.

Hyatt refers to the bearings as roller bearings only, although they were contained in a "journal box" and the "journal" part of the axle was where the bearing was pressed on. But their roller bearings are not referred to as journal bearings.

Timken uses the term roller bearing, or Timken bearing, but not journal bearing. They do stress the importance of a good journal box - mainly to maintain the oil supply - a feature no longer used today (just thin grease today, and only in select areas) (More on this later)

SKF seems to be the most confused - spherical bearings, spherical journal bearings, and even spherical roller journal bearing. Ughh..

Based on how the definitions and the ads are written, I would surmise that the industry knew it was confronting at least 50 years of long established journal bearing practice, and was caught between trying to promote a new and hopefully better technology while at the same time avoiding the perception that roller bearings were a major change that would obsolete equipment and the maintenance workforce (or require significant re-training).

Hence the conundrum.

But I would note that the terms "friction bearing", "plain" bearing and "solid" bearing do not appear in the cyclopedia. Anti-friction bearing does appear in some of the ads to describe roller bearings.

So while the prototype in the era may have been confused with the new technology and its terminology, we will either need to remain similarly confused, or adopt some form of standard convention.

As a mechanical engineer, I will stick with journal bearings (not to be confused with Journals, journal boxes, etc), and roller bearings. Plain, solid and friction are out for me. YMMV.

Dave Evans


atsfnut <michaelEGross@...>
 

Much appreciate the clarification, Richard. I confess to being one of those who has used the term incorrectly, most likely because of its general usage. Proof again that if you tell an untruth often enough, it soon passes for the truth.

Cheers!

Michael Gross
La CaƱada, CA

--- In STMFC@..., Richard Hendrickson <rhendrickson@...> wrote:

Several times lately I have noticed members of this group using the
term "friction bearings" to differentiate solid bearings from roller
bearings, despite objections on previous occasions from myself, Tony
Thompson, and others. The correct terminology for solid truck
bearings is "solid." "Plain bearings" is an acceptable alternative.
"Friction bearings" is wrong and misleading. All bearings have
friction, including roller bearings. "Friction bearing" was invented
as an advertising ploy by roller bearing manufacturers to imply,
incorrectly, that roller bearings were frictionless. In fact, though
roller bearings have much less starting resistance than solid
bearings, they have considerable friction which - as with other
bearings - increases as load and speed increase. The term "friction
bearings" was never adopted by railroad mechanical engineers, who
knew better; it does not appear in the dictionary section of any
edition of the Car Builders' Cyclopedia. So please, guys, don't
perpetuate the mistake of calling solid bearings "friction" bearings.

Richard Hendrickson



[Non-text portions of this message have been removed]


Anthony Thompson <thompson@...>
 

Dave Evans wrote:
In the cyc's definition of terms, there are two entries - one for Journal Bearings, and one for Roller bearings. There are also a WHOLE bunch of entries for "Journal xxx", but no "journal roller bearing", or "roller journal bearing". The definition of journal is the part of an axle or shaft on which the journal bearing rests.
The 1953 Cyc has this definition for Roller Bearing: "The general term applied to a group of journal bearings which depend on the rolling action of a set of rollers in order to reduce rotational friction."
To me this is pretty clear evidence of calling all these bearings "journal bearings" whether or not roller bearings were involved. That's why I would object to terming a solid bearing as merely a "journal bearing," because in railroad definition that is not separated from a roller bearing.

But I would note that the terms "friction bearing", "plain" bearing and "solid" bearing do not appear in the cyclopedia. Anti-friction bearing does appear in some of the ads to describe roller bearings.

In the same Cyc, you will find that Magnus refers to their bearings as solid bearings. Railway Age ads and editorial material use both "solid" and "plain" as adjectives for conventional journal bearings.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@...
Publishers of books on railroad history


rwitt_2000
 

Thanks Tony,

I believe I will adopt the term "plain bearings" or "plain journal
bearings" when discussing the conventional journal bearings used on
freight car trucks. After reviewing this discussion, for me at least,
the term "solid" has become less descriptive.

Regards,

Bob Witt

--- In STMFC@..., Anthony Thompson <thompson@...> wrote:

Dave Evans wrote:
In the cyc's definition of terms, there are two entries - one for
Journal Bearings, and one for Roller bearings. There are also a
WHOLE bunch of entries for "Journal xxx", but no "journal roller
bearing", or "roller journal bearing". The definition of journal is
the part of an axle or shaft on which the journal bearing rests.
The 1953 Cyc has this definition for Roller Bearing: "The
general term applied to a group of journal bearings which depend on
the rolling action of a set of rollers in order to reduce rotational
friction."
To me this is pretty clear evidence of calling all these
bearings "journal bearings" whether or not roller bearings were
involved. That's why I would object to terming a solid bearing as
merely a "journal bearing," because in railroad definition that is not
separated from a roller bearing.

But I would note that the terms "friction bearing", "plain" bearing
and "solid" bearing do not appear in the cyclopedia. Anti-friction
bearing does appear in some of the ads to describe roller bearings.

In the same Cyc, you will find that Magnus refers to their
bearings as solid bearings. Railway Age ads and editorial material use
both "solid" and "plain" as adjectives for conventional journal
bearings.


devansprr
 

Tony,

As I also wrote, I think the Cyclopedia's are schizophrenic on this and do not provide clear guidance. They needed a better editor ;-)

The root cause for this is that journal bearing assemblies had internal components that were individually called the journal and the bearing.

But you are confusing the vendor discussions of "plain" and "solid" bearings. The vendors are NOT advocating use of the term "plain bearing" or "solid bearing" as a description of the overall bearing assembly. They always describe the overall assembly as a "journal bearing". The term plain or solid refers to the internal bearing component - the single machined part of the bearing that included the Babbitt surface. The Babbitt surface was the surface, typically finely honed, and often coated with a softer material than the main bearing casting, that was in direct contact with the oil film - the axle journal being on the other side of that oil film. And it was the oil film that transmitted the load of the car from the babbitt surface to the axle journal.

Plain or solid babbitts lacked any holes that might be used to control the flow of oil that was in the gap between the babbitt and the axle journal. I believe (but have not researched further) that this was the early and traditional configuration of railroad journal bearings (those of you who have disassembled car engines have observed flow control channels in crankshaft journal bearings.)

At the same time Roller Bearings were being developed, companies like Magnus were developing "Security Bond Oil Control" babbitts that had babbitt surface oil flow "control features" that were supposed to reduce the likelihood of hot box events. They contrasted their babbitts to the traditional solid babbitts by referring to them as "plain" or "solid" babbitts (or bearings, since the babbitt was the load BEARING surface of a journal bearing assembly.)

But to my knowledge, no one on this list is modeling the internal babbitts of journal bearings, so the use of "plain" or "solid" as a GENERAL description of a journal bearing assembly is incorrect.

TO Recap:

A "Plain" Journal bearing would be a Journal bearing with a solid babbitt.

A "Solid" Journal bearing would be a Journal bearing with a solid babbitt.

A Magnus SSOC Journal bearing would be a Journal bearing with a babbitt that included a Magnus SSOC oil flow control channels. From the outside it could not be distinguished from a journal bearing with a plain or solid babbitt.

The overall bearing assembly visible to anyone along the ROW, would not be called a "plain" or "solid" bearing.

Another way to view this is that I think everyone on this list is modeling "bearing assemblies", but we are dropping the word assembly (just as the prototype did).

As for roller bearings, it is important for everyone to remember that a wheel bearing transmitted two principle forces/loads - the weight of the car, and lateral loads from the car moving through curves, which resulted in forces applied by the truck side frame, to the axle, and from there to the wheel flange and to the inside surface of the rail head. Journal bearings transmitted these loads through vertical surfaces on the axle and bearing, hopefully with an oil film present.

Those same forces must be reacted in a roller bearing, and it is possible that how this requirement was satisfied could lead some, or even many, to call roller bearings - roller journal bearings.

Closer examination of the SKF "spherical roller journal bearing" helps explain the 1940 cyclopedia editor's conundrum. Unlike Hyatt (cylindrical rollers) and Timken (taper rollers) whose rollers were in pure rolling contact, in 1940 the SKF bearing's spherical profile really resulted in a hybrid roller and journal bearing. While part of the contact surface was rolling, other parts of the roller's contact surface involved a sliding component (although with much lower relative velocities than a traditional journal bearing). So things are getting murkier.

The downside of the 1940 Hyatt bearing, being cylindrical rollers parallel to the shaft, was that the main rollers could not react the lateral loads - and in fact the Hyatt bearing appears to rely on an oil film journal bearing (sliding surfaces) to transmit the thrust loads.

So as of 1940, it appears that the "Timken Bearing", with its opposing tapers within each bearing assembly used to react lateral car loads, was the only bearing that did not have a sliding contact surface for the principle forces transmitted through the bearing.

Because of their sliding surfaces, the Hyatt and SKF bearings still required oil immersion, and while the Timken bearings also had journal boxes with an oil reservoir, their primary use for oil was to maintain a seal at the axle, and to lubricate secondary sliding surfaces (surfaces that were NOT transmitting the principle bearing loads.)

Bottom line is that Timken and Hyatt did not call their bearings roller journal bearings, and the SKF design was doomed because it WAS a hybrid of roller and journal bearing concepts.

In a modern roller bearing (I believe they are all tapered today - it is the superior design) only a light amount of grease is required. A modern tapered roller bearing really has a whole set of steel on steel rolling surfaces similar to the rail-head/wheel-tread interface, except the contact surface finish and tolerances inside the the bearing are much higher than any rail head to wheel interface, and in fact, within the bearing, no sliding should EVER occur. As a result, lubrication of the roller surfaces is not really required. Greases are used at the bearing to axle seal to lubricate the sliding seal surfaces, and to help keep dirt and water out of the bearing internals, and the grease no doubt aids in preventing corrosion. But modern, tapered wheel bearings now come pre-lubricated for their entire lifetime, and in fact forcing a lot of grease into them can lead to bearing failure.

Again, YMMV, but I think the least confusing "generic" bearing assembly terminology to use is "journal bearing" and "roller bearing". Certainly usage of the era was not pure - just as a few rogue PRR documents include hyphens in car classes.

But outside of the STMFC era railroad hobby, calling a roller bearing a journal bearing will get you very strange looks - EVERYWHERE.

Dave Evans

--- In STMFC@..., Anthony Thompson <thompson@...> wrote:

Dave Evans wrote:
In the cyc's definition of terms, there are two entries - one for
Journal Bearings, and one for Roller bearings. There are also a
WHOLE bunch of entries for "Journal xxx", but no "journal roller
bearing", or "roller journal bearing". The definition of journal is
the part of an axle or shaft on which the journal bearing rests.
The 1953 Cyc has this definition for Roller Bearing: "The
general term applied to a group of journal bearings which depend on
the rolling action of a set of rollers in order to reduce rotational
friction."
To me this is pretty clear evidence of calling all these
bearings "journal bearings" whether or not roller bearings were
involved. That's why I would object to terming a solid bearing as
merely a "journal bearing," because in railroad definition that is not
separated from a roller bearing.

But I would note that the terms "friction bearing", "plain" bearing
and "solid" bearing do not appear in the cyclopedia. Anti-friction
bearing does appear in some of the ads to describe roller bearings.

In the same Cyc, you will find that Magnus refers to their
bearings as solid bearings. Railway Age ads and editorial material use
both "solid" and "plain" as adjectives for conventional journal
bearings.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@...
Publishers of books on railroad history


devansprr
 

Tony, et al,

Three corrections/additions to my previous post. Unfortunately they are not going to clarify the issue.

1) While Magnus did manufacture bearing components with holes in the babbitt, it was National Bearing that sold the SBOC bearing babbitt.

2) Reading through more of the 1940 CBC, I did find a few instances of "plain bearing" to describe an oil lubricated journal bearing. One was in the SKF ad (they called the entire assembly a plain bearing - not a plain journal bearing.) Curiously, within the Commonwealth truck ad (for passenger trucks), they write:

"The pedestals can be designed to accommodate either the A.A.R. plain bearing journal box or any type of anti-friction journal box."

Because of that line, I looked through a BUNCH of truck ads in the 1940 CBC, and what emerged was that the roller bearing really "messed up" the definition and use of the word journal in railroading.

Previously the journal had been the part of the axle that carried the load - transmitted by an oil film to the stationary parts of the truck. The truck used either an integral "journal box", or it included a pedestal feature that would hold an individual journal box, and both boxes held the various bearing components, to include the actual bearing casting with the babbitt. AAR defined this individual component as a standard journal bearing. Journal bearing wedges could be used to adjust the journal bearing's location relative to the journal box.

It appears that in addition to standard AAR journal sizes, there were standard journal box sizes.

So while Commonwealth described the "AAR plain bearing journal box", the AAR excerpt in the CBC did not include the word "plain".

The roller bearing manufacturers were eager to sell roller bearings for already existing trucks - so they promoted roller bearings that would fit inside standard journal boxes or fit standard freight truck journal pedestals.

3) And this is where Timken called the old style journal bearings "friction bearings".

So I think that leaves us in a bit of a quandary.

Timken clearly wanted to call oil film journal bearings "friction" bearings, since they, and likely others, called roller bearings "anti-friction" bearings. How many others adopted the term "friction bearing"? Who knows. The impact of marketing documents is always hard to determine.

Both Commonwealth and SKF were using the term "plain", but I am not sure if it was for the same use. Commonwealth was describing a plain journal box cast into truck side frames. But was it "plain" because it was generic and did not include any other parts? (I'll take my ice cream plain..." - as in nothing else on it)

SKF may have been using the word plain a little differently (I will take plain water - as opposed to bottled or carbonated water - got to love English.)

I do think "Solid" bearing is out - unless referring to an actual bearing block that lacks any oil flow control holes.

Journal bearing was clearly a common use for any bearing that used the oil film to permit two surfaces under load to move past each other without contact. When discussing the overall assembly, I would say the term journal bearing is used exclusively in AAR and CBC writings.

Roller bearing was also a common use to describe roller bearings, and with the exception of SKF's nomenclature, it seems to be dominant (I would say well over 95% of the usage in the 1940 CBC.)

The CBC's definition of journal bearing includes roller bearings, but that definition, outside of SKF's ad, is almost a singular use in the 1940 CBC.

I do not have much AAR documentation to review - perhaps that can shed light on the use of journal bearings to describe roller bearings.

Several equipment manufacturers used the term plain bearing and friction bearing to refer to the oil film journal bearings. How widespread this use was requires further investigation.

In modern railroading use, the term journal bearing is not used to describe roller bearings. But the portion of the shaft interfaced to the bearing is still called the journal, and the overall structure of that portion of the truck may still be called "The journal".

In engineering texts, the term "journal bearing" explicitly involves only bearings that use oil films for load transfer (no contact of moving surfaces), while "anti-friction" bearings is the term used to characterize roller bearings.

This may be one area where standardization of terms may not be viable (sorry Richard), and beauty is in the eyes of the beholder.

Personally I previously used the term friction bearing for hobby purposes, but I think I will drop that for fear of making professional mis-statements. As an engineer I do not want a colleague to question my skills by my calling an oil film bearing a friction bearing or a plain or solid bearing for that matter (unless we are discussing journal bearing babbitts ;-)

I think I have documented as much of this as I can - for everyone in the group - YMMV.

Dave Evans


Richard Hendrickson
 

After many paragraphs of discussion about bearings and bearing
lubrication, most of it irrelevant for modeling purposes, Dave Evans
concludes:
Again, YMMV, but I think the least confusing "generic" bearing
assembly terminology to use is "journal bearing" and "roller
bearing". Certainly usage of the era was not pure - just as a few
rogue PRR documents include hyphens in car classes.


But outside of the STMFC era railroad hobby, calling a roller
bearing a journal bearing will get you very strange looks -
EVERYWHERE.
Dave seems incapable of comprehending Tony's point that both plain
and roller bearings are journal bearings, and to call one of them
"journal bearings" but not the other invites confusion. This is,
after all, the STMFC list, and most of us aren't physicists or
mechanical engineers, we're modelers. As modelers our chief concern
is to differentiate plain bearing trucks from roller bearing trucks.
It remains true, as I pointed out at the beginning of this
discussion, that "friction bearing" vs. "roller bearing" is a
misleading and misinformed way to do this, and that "friction
bearing" does not appear anywhere in the railway engineering
literature of the steam era. "Plain bearing" and "solid bearing," on
the other hand, are both extensively in the railway engineering
literature, and their meaning is perfectly clear. In fact, "solid
bearing" is what the bearing manufacturers themselves commonly called
their products (e.g. see the Magnus Metal Corp. ad in the 1953 Car
Builders Cyclopedia, p. 1040 ff., where "solid bearing" or "solid
journal bearing" occur repeatedly). Dave and others may, of course,
use whatever terminology they choose, but in the context of STMFC
discussions they risk being though wrong, perhaps even ignorant,
regardless of how many engineering degrees they may have.

Richard Hendrickson


Anthony Thompson <thompson@...>
 

Dave Evans wrote:
I do think "Solid" bearing is out - unless referring to an actual bearing block that lacks any oil flow control holes.
This may be one area where standardization of terms may not be viable (sorry Richard), and beauty is in the eyes of the beholder.
I agree that there may not be a clear usage we can call "standard," but particularly in reading _Railway Age_ (and I have read a lot of their pieces in the 1930 to 1960 era, to understand trucks more fully), I can assure you that the terms "solid bearing" and "plain bearing" are BOTH frequent, and are used in ways which appear to be interchangeable. Whether this accords with your perspective as a mechanical engineer, 60 or 70 years after the time cited, does not seem to me relevant to the terminology which those on this list should prefer.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@...
Publishers of books on railroad history