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Friction bearing /Roller bearing adaption
http://www.rypn.org/forums/viewtopic.php?f=1&t=35429
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Author:  VTTom [ Sun Aug 11, 2013 11:23 am ]
Post subject:  Friction bearing /Roller bearing adaption

We run some DLW coaches at less than 20 mph and acquired 6 pairs of roller bearing wheels sets that are adapted to fit in the 5 by 9 journal box pedestals. Does anyone know if there are issues if only one truck is adapted to run with the roller bearings and the other truck is left with the friction bearings, assuming that the wheel diameters and profiles are similiar on both ends of the car? Thanks in advance.
Thomas Gray

Author:  etalcos [ Sun Aug 11, 2013 12:15 pm ]
Post subject:  Re: Friction bearing /Roller bearing adaption

No issues. Most folks, especially the larger the operation, found it desirable to standardize the car, i.e., all friction, or all SKF, or all Hyatt, or all grease bearings, or all oil bearings. On your own operation there is nothing that says you can't change them out one at a time if that's what suits you. Just don't forget to oil the remaining friction sets...

ETA

Author:  LVRR2095 [ Sun Aug 11, 2013 4:22 pm ]
Post subject:  Re: Friction bearing /Roller bearing adaption

I prefer the term "plain bearing" as "friction" and bearing should be mutually exclusive terms.

Keith

Author:  etalcos [ Sun Aug 11, 2013 4:35 pm ]
Post subject:  Re: Friction bearing /Roller bearing adaption

How about "solid bearings". I've heard all three. To me the confusing one is some of the old heads refer to them as journal bearings.

Then there are "motors" vs engines vs locomotives vs......

ETA

Author:  robertmacdowell [ Sun Aug 11, 2013 4:37 pm ]
Post subject:  Re: Friction bearing /Roller bearing adaption

And "friction bearing" is a slander. They roll quite beautifully once they get enough velocity to get the oil layer floating correctly. They are harder to start, which can be an issue for an underpowered museum.

Also they're fixable. You can turn and polish the bearing surface in-house on any lathe large enough. Pouring your own babbit is also perfectly doable. Make your own waste - didn't one group cut up mops or something? Whereas a lot of roller bearings are "unobtanium" - they are more reliable, but when they fail, yer done. You've got one of those knotty engineering kitbash jobs that, in most cases, relegates the car to the back 40 because either nobody knows what to do, they don't finish, or it doesn't work.

Author:  David Johnston [ Sun Aug 11, 2013 9:28 pm ]
Post subject:  Re: Friction bearing /Roller bearing adaption

The railroad industry (AAR) uses the term "plain bearing" so that is probably the way to go. The "journal" is the shaft, in our case the end of the axle. The beariing block is usually refered to as the "brass". Friction bearings were the opposite of anti friction bearings. These terms were used in adds for everything imaginable, but the railroad industry did not fall for it as they knew what the real train resistance attributed to the bearings was. Timken sold the industry on the change to the AP tapered roller bearing based on reduced maintenance cost.

The words locomotive, motor and engine all have different and distinct meanings. It is too bad that slang usage has blurred their true meaning.

As to the original question, the Sacramento Nothern Railway, an ICC regulated railroad, needed to add speed detection equipment to all their passenger cars when they were going to start service over the SF Bay Bridge in 1939. They bought one new roller bearing wheel set for each car, which included the speed detection pick up. The other three were still plain bearing wheel sets. As the passenger cars were retired, the roller bearing wheels sets were the ones with the newest wheels, so they were switched out into cars that were going to be retained. Surviving Sacrament Northern passenger equipment has from one to four of the roller bearing wheel sets. Recently restored Sacramento Northern wooden coach 1005 has three roller bearing wheel sets.

These are interchangeable, but not identical. The plain bearings have about a half inch of free lateral where the roller bearings may have very little to none. This free lateral in the plain bearing gives a better ride and produces less truck wear.

Author:  filmteknik [ Sun Aug 11, 2013 10:59 pm ]
Post subject:  Re: Friction bearing /Roller bearing adaption

Journal bearing is a proper term for plain bearings though probably not commonly used in railroading. Solid bearing is also a term often heard. I cringe when I read "friction" bearing and ascribe the pejorative term to the roller bearing industry. I was shocked when I saw an article where Trains' David P. Morgan used the term. Oh David!

Steve

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Author:  VTTom [ Mon Aug 12, 2013 12:16 am ]
Post subject:  Re: Friction bearing /Roller bearing adaption

Thank-you, these roller bearing wheelsets have too good of wheels to pass up.
David's comments makes sense: "These are interchangeable, but not identical. The plain bearings have about a half inch of free lateral where the roller bearings may have very little to none. This free lateral in the plain bearing gives a better ride and produces less truck wear."

Author:  LVRR2095 [ Mon Aug 12, 2013 3:49 pm ]
Post subject:  Re: Friction bearing /Roller bearing adaption

etalcos wrote:
Then there are "motors" vs engines vs locomotives vs......

ETA


On the PRR a "motor" was an electric locomotive. You would see signs where the overhead ended that said..."A.C. Motor Stop." And boy did they mean it!

Keith

Author:  filmteknik [ Mon Aug 12, 2013 4:51 pm ]
Post subject:  Re: Friction bearing /Roller bearing adaption

If the play in solid bearings is advantageous, why isn't this designed into the roller bearing trucks? Not in the bearings themselves which require tight tolerances, but in how the bearing interfaces into the truck frame.

Steve

Author:  David Johnston [ Mon Aug 12, 2013 6:39 pm ]
Post subject:  Re: Friction bearing /Roller bearing adaption

In about 1980 the AAR changed their standard design for the three piece freight car truck to add about 3/8" clearance between the bolster gibs and the side frame column to help address the problem. But this is not a perfect solution since the wheel sets have to push the side frames around more that with plain bearings. AAR does not currently have standard designs for other truck types, so manufactures were on their own to address problem if there was one.

Author:  David Johnston [ Mon Aug 12, 2013 6:44 pm ]
Post subject:  Re: Friction bearing /Roller bearing adaption

The bearing interface into the three piece trucks with a bearing adaptor. The bearing adaptor is crowned and is allowed to roll under the side frame to avoid loading the outer ends of the bearings as the track cross level changes. There is no lateral movement at this location by design.

Author:  Overmod [ Mon Aug 12, 2013 9:48 pm ]
Post subject:  Re: Friction bearing /Roller bearing adaption

> If the play in solid bearings is advantageous, why isn't this
> designed into the roller bearing trucks? Not in the bearings
> themselves which require tight tolerances, but in how the bearing
> interfaces into the truck frame.

Note that several of the early designs of four-wheel 'Delta' trailing trucks featured this. Because the pivot pin could not be located in the ideal place, some lateral motion of the first truck axle relative to the frame was necessary (the rear axle of course took the booster and had to be both orthogonal and without lateral play). The lateral was provided with two hardened rollers per side (and there is, somewhere, a discussion of the metallurgy of these rollers and how they were heat-treated). The Timken book describing locomotive 1111 shows this device clearly in section.

Note that this approach is only for rigid truck frames, not 'three-piece' freight trucks. Those, as noted, get by happily with camber on the bearing adaptors.

You do not want lateral play of the journal and inner race relative to the outer race (i.e. with cylindrical rollers) due to sealing problems. Timken made a good point about the tapered roller bearings being relatively easily adjusted for wear (which of course a cylindrical-roller bearing would NOT be).

You also do not want lateral play between the axle and the inner race of the bearing, although technically you might do this with splining or keys of some sort. More trouble than it's worth, especially if the axle seizes in the race when not centered, or if the ... well, spun bearings are no fun wherever you find them.

Author:  Kelly Anderson [ Tue Aug 13, 2013 9:01 am ]
Post subject:  Re: Friction bearing /Roller bearing adaption

This thread inspired me to look in the AAR manuals regarding lateral fits of the various parts of a freight car truck. New bearing adaptors have 1/8” to 3/16” lateral slop on their bearings, and between 1/32” and 3/8”(!) lateral slop to the truck frame. Of course these are dry metal to dry metal, which would take a lot of force to slide back and forth, especially compared to the lateral slop in a lubricated, rolling plain bearing, which could slide back and forth with very little force.

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