Friction bearings Vs Roller bearings

[johncolley]

Wow! talk about the good old days! In my senior year (56-57) of High School I was on limited classes because I had a job oiling freight trains and inspecting, changing brake shoes, hoses, etc. at Oakland's desert yard across from the 16th St. station. I remember one old oiler had a real old car that he filled up the engine with 50 weight journal oil every night. It got him home and back to work the next night and he would have to fill it again. Bearings and main seals were all shot, but it still ran! Good memories of the last of the cab forwards, and the beautiful black widows. After them I thought the the geeps were plug ugly.

[Overmod]

Some of this friction-bearing tech stuff is covered in the American Passenger Car book (alas, don't have my copy at hand)

The bearing brasses ARE the upper bearing plate, whether or not they are lined with a different material. The assumption was that a bearing with hard metal in both faces would show rapid wear anywhere surface asperities broke through the oil film which is actually providing the 'hydrodynamic' bearing -- and with steel or other alloys, you'd get point welding wherever these rubbed at high speed under typical load, leading to very rapid galling and... well, hotboxes. So you want a metal that doesn't undergo welding to a steel journal, and that preferably 'wears' in preference to the more expensive polished steel of the axle.

MCB designers didn't think there could be loads UP on a bearing that had a share of a whole railcar's weight bearing (no pun intended) down on it. So they did not include positive location of the brass in the shell. Now, there are a variety of situations that can knock the axle or car in ways that reduce the instantaneous load at the same time as the axle moves -- and this either lets the plate shift a bit around the axle, or ****. Of course, Murphy's and Finagle's laws dictate that when you can detect this problem, full weight will be back on the journal...

Unfortunately too, as on old clocks and watches, it turns out that wherever there is dust or dirt in the lubrication, something quite different happens with wear. Many of the particles in the contaminant materials are very hard -- quartz dust etc. If these particles get into the bearing joint, they preferentially embed in the softer material, and then proceed to 'machine' the harder material. This may have the effect, over time, of increasing the 'wetted' facing areas of the bearing and journal substantially.

Even a little contamination can destroy the oil film in a spot, and cause friction heating sufficient to degrade the lube oil in the film. The use of 'waste' wicks often led to this when little bits of the material came loose and were carried up into the bearing. Consequently some very ingenious pads and other methods of lubricating were devised in the '50s and '60s -- you can find them in appropriate issues of the Car Builders Cyclopedias. Some of these do, indeed, look like pieces of carpet glued to pads -- you want lots of 'fingers' to wick the oil copiously onto the full width of the journal. Flat-surfaced pads or foams tended to have trouble over time, or with less-than-perfect oil (at least, the literature describes this; I don't have first-hand experience).

On the whole, I'll take a sealed 500,000 mile bearing any time!

[Anonymous]

A brass plate? this is between the top of the block and the spring? The bearing itself, a half shell resting on the top side of the axel, hhhmmmmm, how is the shell kept from spining out ? How is lateral movement of the axel limited? Is there a step in the spindle ?

Brass is pretty soft, why is it between the bearing block and the spring ?

[rrnut282]

Another 'problem" that doomed the friction bearing was the problem of the brass top bearing plate shifting. Part of a pre-trip inspection of our older, friction-bearing equipped passendger cars to lift the lid, check the oil level and waste and make sure the brass is still where it's supposed to be. It's a bear to jack up the springs and beat it back into place.

[jchnhtfd]

QUOTE: Originally posted by RudyRockvilleMD

If I remember correctly one of the Northern Pacific's Northerns was equipped with Timken roller bearings.

From an engineering standpoint roller element bearings are superior to friction bearings in that they don't have to be inspected as frequently to ensure an adequate supply of lubricant. Add to that hot boxes rarely occur with rolling element bearings. Rolling element bearings' signatures can be monitored to determine their condition so advance warning of failure is possible.

The ICC has required rolling element bearings on all interchange rolling stock since the mid 1960's.

The Four Aces (road number 1111) as I recall -- she was a standard Northern with Timken supplied roller bearings everywhere, for testing.

The only down side to modern roller bearings that I know of is that when they fail (and they do -- everything does, now and then) they give you less warning and a lot less time than friction bearings. The chaps watching and listening to the 'hot box' detectors have to be a lot more vigilant, as a bearing can go from no problem to 'oops, d__n' in a remarkably short time[xx(].

[Anonymous]

Chet Huntley wrote a book eons ago where he described a locomotive in Montana that was used to demonstrate how well roller bearings worked. As I recall, the ladies of his hometown were all invited down to the station, issued gloves, and asked to pu***he locomotive. It moved... I kinda doubt we would be able to do the same with locomotives today, gloves or not...

Erik

[dknelson]

I believe the famous photograph of Charles Atlas pulling the Broadway Limited train using a rope over his shoulder was meant to advertise the roller bearings on the trucks.
I have seen advertisements in 1960s era issues of Railway Age magazine for an oiled waste substitute for friction bearing trucks that looked like a chunk of shag carpeting.
Dave Nelson

[Anonymous]

I do believe that friction bearings can also no longer go through interchange with other railroads.

[eastside]

I submitted a similar question here on roller bearings, see "Roller Bearings" 6 Apr 2004, but didn't get an exact answer. There's a magazine citation there also. It was different in that I wondered how much more efficient the locomotives became once they were pulling roller bearing freight and passenger cars. I guess it took something like the government to mandate roller bearing for rolling stock, much like air brakes were, because ownership was diffuse.

[Anonymous]

QUOTE: Originally posted by Overmod

Interesting that in the late '20s it was recognized that *running* resistance of roller vs. plain bearings was not that different. The reliability and 'sealed maintenance' characteristics of roller bearings imho are more significant than starting antifriction in many cases. I remember (I think) that the limiting lifetime of Timken freight-car bearings was limited by wheel wear, rather than anything about bearing metallurgy or tribology, as early as the 1970s.

With respect to steam roller bearings, the situation is a bit complex. The NP engine is, of course, the famous "Four Aces", built for Timken as a demonstrator; a successful as well as good-looking locomotive. Many roads did not use roller bearings in the trailing truck, due to firebox heat and ash problems, if I remember rightly.

Rollers on the driving axles could get interesting. N&W, and perhaps other roads, had early versions that were incorporated in the hubs (Louis Newton has a rather good picture of one in his Rails Remembered volume 3). Something like this was my solution to the inside cranks on a Withuhn conjugated duplex locomotive, where the inner race diameter of the 'main' drivers is very large, greater than the crank circle; the hollow axles are of very great diameter, and external bridges between the bearings, outside the throw of the conjugating inside rods, provide the necessary lateral stiffness. Main drivers are not ideally provided with lateral motion, so there is less problem with designing suspension, frame, etc.

Later modern steam power used very substantial axlebox structure (IIRC called a 'cannon box' or something similar; I don't have references nearby) to keep the bearings "perfectly" aligned; this lessened the requirement for tight and near-perfect adjustment of axle alignment in the frame (e.g. via Franklin self-adjusting wedges). Timken used tapered rollers, while SKF used a barrel-shaped roller (which had some of the lateral self-aligning and thrust geometry of a ball bearing while preserving line contact, or at least that's the description I was given)

There are roller bearings on some axles in the Baldwin 60000 demonstrator (of 1926) preserved at the Franklin Institute in Philadelphia. I remember this because the bearings took a 'set' while the engine sat on display for so many years ("egg-shaped" was the term they used at the time to describe it) and needed to be rebuilt a few years ago.

My opinion is that the 'datum' or reference axle on a 4-8-4 should be the main driver axle. Since the locomotive is almost certainly double-acting, it doesn't 'matter' from a thrust standpoint whether the self-adjusting wedges are at the front or rear of the axlebox -- my preference is to put them at the rear because that 'unloads' the wedge a bit more, permitting easier self-alignment action, during acceleration. All the axles need to have the wedges at the same side, with the non-wedge side being precisely machined, built up if worn, etc. -- it is the precision and accuracy of this machining that controls the clearances mentioned above, including the rod clearances.

An interesting case involves the geometry of side-rod bearings on lateral-motion axleboxes. There is no particular difficulty with the wheel bearings here, because of the substantial axlebox construction. But the rod bearings -- that's another story! One solution is to provide a spherical bearing (like a ball-and-socket joint) outboard of the actual antifriction roller bearing outer race, lubricating it appropriately. UP 844, I believe, is an excellent 'poster child' for observing exactly how this sort of lateral motion is best implemented...

If something here is wrong, I invite correction (e.g., I had not recognized that two Allegheny locomotives had actually survived!)

RME

So, the machined face of the bearing journal block guides in the frame on the opposite side of the wedge blocks is what actually determines CL distance between axels. (whew!)

That should mean then that the tapered blocks are used only in maintaining a tight fit between the guides as they wear.

What about freight and passenger trucks, do they use tapered rollers?

[Modelcar]

Adrian, you mention "the oil isn't in there very long"...., isn't this caboose static in location....What happens to the oil...? And another question...I've thought of using synthetic oil in my John Deere lawn tractor, have you had good luck using it in your mowing equipment...?

[adrianspeeder]

The oil isnt in there very long, and is diluted with other oil. By the way i am also runnin full synthetic for max cooling for the time i run these little air cooled motors.

Adrianspeeder

[Overmod]

Interesting that in the late '20s it was recognized that *running* resistance of roller vs. plain bearings was not that different. The reliability and 'sealed maintenance' characteristics of roller bearings imho are more significant than starting antifriction in many cases. I remember (I think) that the limiting lifetime of Timken freight-car bearings was limited by wheel wear, rather than anything about bearing metallurgy or tribology, as early as the 1970s.

With respect to steam roller bearings, the situation is a bit complex. The NP engine is, of course, the famous "Four Aces", built for Timken as a demonstrator; a successful as well as good-looking locomotive. Many roads did not use roller bearings in the trailing truck, due to firebox heat and ash problems, if I remember rightly.

Rollers on the driving axles could get interesting. N&W, and perhaps other roads, had early versions that were incorporated in the hubs (Louis Newton has a rather good picture of one in his Rails Remembered volume 3). Something like this was my solution to the inside cranks on a Withuhn conjugated duplex locomotive, where the inner race diameter of the 'main' drivers is very large, greater than the crank circle; the hollow axles are of very great diameter, and external bridges between the bearings, outside the throw of the conjugating inside rods, provide the necessary lateral stiffness. Main drivers are not ideally provided with lateral motion, so there is less problem with designing suspension, frame, etc.

Later modern steam power used very substantial axlebox structure (IIRC called a 'cannon box' or something similar; I don't have references nearby) to keep the bearings "perfectly" aligned; this lessened the requirement for tight and near-perfect adjustment of axle alignment in the frame (e.g. via Franklin self-adjusting wedges). Timken used tapered rollers, while SKF used a barrel-shaped roller (which had some of the lateral self-aligning and thrust geometry of a ball bearing while preserving line contact, or at least that's the description I was given)

There are roller bearings on some axles in the Baldwin 60000 demonstrator (of 1926) preserved at the Franklin Institute in Philadelphia. I remember this because the bearings took a 'set' while the engine sat on display for so many years ("egg-shaped" was the term they used at the time to describe it) and needed to be rebuilt a few years ago.

My opinion is that the 'datum' or reference axle on a 4-8-4 should be the main driver axle. Since the locomotive is almost certainly double-acting, it doesn't 'matter' from a thrust standpoint whether the self-adjusting wedges are at the front or rear of the axlebox -- my preference is to put them at the rear because that 'unloads' the wedge a bit more, permitting easier self-alignment action, during acceleration. All the axles need to have the wedges at the same side, with the non-wedge side being precisely machined, built up if worn, etc. -- it is the precision and accuracy of this machining that controls the clearances mentioned above, including the rod clearances.

An interesting case involves the geometry of side-rod bearings on lateral-motion axleboxes. There is no particular difficulty with the wheel bearings here, because of the substantial axlebox construction. But the rod bearings -- that's another story! One solution is to provide a spherical bearing (like a ball-and-socket joint) outboard of the actual antifriction roller bearing outer race, lubricating it appropriately. UP 844, I believe, is an excellent 'poster child' for observing exactly how this sort of lateral motion is best implemented...

If something here is wrong, I invite correction (e.g., I had not recognized that two Allegheny locomotives had actually survived!)

RME

[Anonymous]

I had a thought since this last post. If a steam engine's driven axels were allowed to move freely lateraly through the the bearing's center, a roller type bearing would only be loaded in the vertical plane. Limiting the axels' lateral motion would still be a problem though.

I read somewhere that it was attempted in recent times to convert an older steam loco to roller bearings unsuccesfully.

I could be wrong, but car trucks actually use tapered roller bearings? The axels are fixed lateraly in relation to the truck frame, or is it necessary to have end play in car truck axels?

I have read that steam locos have tapered blocks to locate the bearing journal blocks, the tapered blocks adjusting for wear. Are the blocks at either end of an axel used in conjunction to keep an axel square to the frame? How does this affect center to center distance between two driven axels? In a 4-8-4 for example, which axel is the "reference" for the other axels' center to center distance?

Maybe these are obscure questions, If nobody knows, maybe point me in a direction, I have a genuine interest in this question.

[Anonymous]

I could be wrong, but steam locomotives have a lot of lateral play and loading in their driven axels, which could be less than ideal for roller type bearings, unless somehow tapered bearings were used to handle axial loads.

[Anonymous]

QUOTE: Originally posted by adrianspeeder

my buddys got friction bearings on his caboose he restored. I give him my waste oil from all my mowers (thats a lot, trust me). Without him, i would pay a million to "dispose" it.

Adrianspeeder

Used motor oil has corrosive combustion byproducts, it my not be a good idea to use that for a bearing.

[RudyRockvilleMD]

If I remember correctly one of the Northern Pacific's Northerns was equipped with Timken roller bearings.

From an engineering standpoint roller element bearings are superior to friction bearings in that they don't have to be inspected as frequently to ensure an adequate supply of lubricant. Add to that hot boxes rarely occur with rolling element bearings. Rolling element bearings' signatures can be monitored to determine their condition so advance warning of failure is possible.

The ICC has required rolling element bearings on all interchange rolling stock since the mid 1960's.

[kenneo]

One of the problems with roller bearings and steam locomotives is that, as Mark said, there was a metalurgy problem. The thrust of the piston would create such dynamic forces that would change quickly that the bearings would fail rather quickly when used in the side rods. So, most of their use in steam was on axel bearings, but even there, steamers had dynamic force problems.

In later years, since wool waste was a bit flamable, an improvement was made called a lubricator pad that would lay in the bottom of the bearing box and act like wool waste. Much improved over waste.

As to how effecient rollers are, we had a rule of thumb on the SP for several years while the conversion was taking place to rollers, that - on a car equivelent basis, two roller equipped cars equaled one friction bearing car.

[adrianspeeder]

my buddys got friction bearings on his caboose he restored. I give him my waste oil from all my mowers (thats a lot, trust me). Without him, i would pay a million to "dispose" it.

Adrianspeeder

[UPTRAIN]

Thank you Mark, you beat me to the chase.

[Anonymous]

Thanks fellas!

Larry

[AltonFan]

In its waning years, the Chicago, North Shore & Milwaukee was plagued by "hot boxes", which result from friction bearing failure. An employee suggested to management that they replace the friction bearings on the cars with roller bearings, a couple of units at a time, to solve the problem. However, the CNS&M's management was not interested in improving the line, so the plague continued.

Roller bearings also offered at least a partial solution to the problem of dynamic augment on steam locomotives.

IIRC, roller bearings are now required by Federal law on all rolling stock in interchange service.

[Hugh Jampton]

Friction bearings are like plain bearings. Think crankshaft bearings in your car's engine.

Roller bearings are like the bearings in your car's wheel hubs.

Roller bearings are far superior because they are smaller, lighter and can be lubricated with grease. plain bearings require oil lubrication. The wool waste works like a wick to bring lubricating oil from a small reservoir beneath the bearing up to the bearing surface. Plain bearings require more frequent inspection, mostly to ensure that the lubricating oil has not leaked out.

[Anonymous]

While reviewing some old photos in a book of SP steam in the 50's, they talked about Friction bearings and Roller bearings on their rolling stock. Which of the two are better? The captions under some of the photos stated that Roller bearings were better but Friction bearings were cheaper. If you keep keep them greased, shouldn't either one do the job? Could someone also explain what "wool waste" on Friction bearings is? Thanks

Larry