rebuilding engine trucks and boxes

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rebuilding engine trucks and boxes

Post by DaveLathrop57 on Wed May 29, 2013 1:35 pm

Now that there's a lull in the water treatment conversation and we've found a couple strategies for the tender trucks, time to consider the locomotive's wheels. Recently Strasburg made adapters to mount roller bearings in steam locomotive trucks. Don't know more about what they did or how......or how it may compare to other possible methods. Tennessee Valley has equipped 610 with an oil lubricating system that is working very well, supposedly based on something from SP. Again, I have no details, or alternative methods to bring to the table right now. And, there's no shortage of things like pins and bushings and bearing surfaces to be dealt with on the suspension and linkage on the trucks and spring rigging. Anybody want to offer details, methoods or ideas?

Dave

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Re: rebuilding engine trucks and boxes

Post by Overmod on Thu May 30, 2013 7:51 pm

I confess I would be tempted to look at modern hard coatings and tribology to make 'plain' hydrodynamic bearings work better, perhaps by implementing a preluber to get the film established in the 'brass' before the engine moves.

You'd have to split or otherwise divide the outer races and cages to get the bearings on there without pulling the wheels. If you're going to pull the wheels, you might as well machine up a whole new axle with the inner races optimized, or whatever. And then we get to the lateral compliance in the existing truck frame; probably not enough to work single tapered bearings so either SKF or pairs of opposed tapered bearings as on tender trucks. And then better design for much larger axlebox size in the truck pedestals.

No question life will be easier with the rollers in, particularly if the 'right' grade of superfinished bearing and M-942-compliant GREASE lube (just like what goes in the, ahem, converted tender truck bearings) is used. Even those half-million-mile bearings from the '90s have essentially infinite service life if put into 110. So I'd look into seeing whether a 'replacement' axle that takes an appropriate size of double-roller freight-car bearing 'inboard' can be made up, with the outer end machined or built up or collared as necessary to take the wheels that will be used.

I would NOT use an approach that puts some kind of package bearing in there, but with sufficient guarantees (and perhaps some additional crossmember support in the truck frame) it could probably be made to work. I would tend to trust Strasburg's tech people when they say something is right.

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Re: rebuilding engine trucks and boxes

Post by DaveLathrop57 on Fri May 31, 2013 12:39 am

Our contributor from Tennessee Valley is checking out things there...and I'm going to see if our friend at Strasburg can'rt provide some firm data as well.

I'm in particular thinking about different things I've heard about SKF versus Timken. Both these manufacturers of bearings make a railroad line.....and know how they should be installed. Still, some people swear by one and not the other. It may be some are better suited for specific applications than others? So, let's see if we can't learn more about it.

I'm not opposed to doing axle and wheel work if it creates a bearing application that will be robust and reliable with minimal fuss and bother for a very long time. One aspect of the friction bearings is unintentionally lubing the rails since worn out seals seldom get attention - especially since the seals aren't made any longer for some old sizes. Creating slipping hazards makes little sense.

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Re: rebuilding engine trucks and boxes

Post by Overmod on Fri May 31, 2013 5:20 am

The fundamental difference between SKF and Timken is geometry. The barrel-shaped SKF rollers make the bearing self-centering under end thrust, whereas Timken requires opposing thrust (either by providing opposite taper in a stiff structure or pairs of opposing taper on a common journal area) to give more positive thrust control. Timken is nominally easier to adjust for wear (theoretically a SKF-style bearing could be adjusted by moving to a transversely split outer race, but I have never seen that done).

I see no reason to adopt oil lubrication here when modern grease lubrication (for long-life freight-car axle bearings) is so well developed and the products and systems to accomplish it are so widespread (and relatively costed-down). Imho this applies to seals, even seals on inside bearings (2x what is found on outside freight-car bearings

I am not as highly concerned with lubrication leakage from inside bearings with disc wheels. This may be thrown on the track, but not on the railhead except marginally at switch points. The situation is a bit more involved for spoked drivers and spoked trailing wheel, but I would think that nothing more complicated than lips and perhaps a little reshaping of the lateral spoke surfaces would prevent slinging to the outboard face of the wheel (which is what would be necessary to get lubricant on the wheel tread area). The contribution of rod lubrication to this issue is vastly more significant, but not in the scope of this discussion.

Porta's HAWP, more specifically the drip-groove feature, could be easily adopted (for little more than a purpose-built jigged set of cutters, or a template, for routine wheel turning. Some thought can be given to how periodic wheel maintenance would be implemented -- but is wheel wear on this locomotive expected to be a regular maintenance item (as it would be on a formal excursion engine)?

I see the design as being more a tradeoff between lower cost and ease of maintenance/repair for plain bearings vs. very long unmaintained life for AAR-grade grease-lubricated bearings (derived from freight parts and practice). I also see no reason why methods cannot be mixed (e.g. plain bearings on trailing truck with rollers elsewhere) just as they were in historical locomotive practice.

As I noted elsewhere, the plain bearings would not be the usual style; they will encircle a greater proportion of the journal, and will have some crowning or other features to permit effective pressure prelubing as well as running supply. I suspect that AAR seals and materials, used here, would have long enough life.

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Re: rebuilding engine trucks and boxes

Post by DaveLathrop57 on Fri May 31, 2013 9:58 am

Oil for main boxes, not rollers.

Please sketch out your proposed journal - I'm not quite envisioning what you mean.

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Re: rebuilding engine trucks and boxes

Post by Overmod on Fri May 31, 2013 10:12 am

No access to making a sketch here on the road, but will see what I can do.

Bearing brass is made slightly crowned, so that the bearing area is slightly relieved just at the top. Oil is fed there, and the hydrodynamic film forms upon prelubrication pressure.

Brass is made sectional, further 'around' in the areas that see fore-and-aft thrust forces at the rods. Think of this as two curved sections, ahead of and behind the axle journal,laid in at the time the box is laid over the journal. Not sure what arrangement needs to be made to align these pieces or shim them to the box for clearance, but Franklin-like sprung wedges might be one approach that would be reasonably self-aligning (this is in addition to wedges or other alignment at the pedestals)

This provides some of the circumferential action of a roller bearing. Some additional lubrication may need to be provided there, but I would not expect this to be more than a usual 'cellar' kind of arrangement... or flow from the top ... would provide.

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Re: rebuilding engine trucks and boxes

Post by DaveLathrop57 on Fri May 31, 2013 11:26 am

Difficulties have arisen (assuming I understand your idea) with any disruption in the curved contact area between the brass and journal. Using the standard cellar configuration, any gap running longitudinally across the contact surface prevents lubrication and results in overheating and failure. Not so for circumfrentially aligned scoring in the brass......so unlesss we were to find a way to introduce lubrication wherever there's a gap.....probably not a good idea. Which becomes a maintenance situation, not an idiot-resistant reliable situation. Kludging friction bearings into reacting like rollers? I don't know if that's any better than just using rollers.

Perhaps I'm missing the point. No hurry, we can wait until you are in a position to sketch something out on the back of an old envelope and scan it in.

Dave

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Re: rebuilding engine trucks and boxes

Post by Overmod on Fri May 31, 2013 11:53 am

This is only different from a 'crowned' bearing in that the top "space" is only a fraction of an inch long and just enough relieved to contain the oil needed for the hydrodynamic film over the bearing area from which standing presses out the lubricant. There is plenty of circumferential area in contact, just not at the very top. I do also think that something other than brass or white metal be considered for the bearing liners, and that some form of chemical superfinishing be considered for bearings and/or journals whether or not hard coatings will be used.

There is also the general principle of the Isothermos bearing to consider -- these didn't do so well in high-speed ATSF service, but might be fine on 110 with some care...


Last edited by Overmod on Fri May 31, 2013 11:56 am; edited 1 time in total (Reason for editing : Phone misspelled 'superfinishing')

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practical advice from TVRR

Post by DaveLathrop57 on Sun Jun 02, 2013 3:46 pm

John Bohon was involved with NHVRR and now works for TVRR. He's got a lot of great practical experience and we miss his involvement. Here's information about their conversions from an email he send me privately - he's been very busy and hasn't registered here yet.

Dave,

Actually it is 630 that has been converted to oil. We are using a product manufactured on original machines in the UK. It is almost the same system SP used on many of their engines including 4449 which they called a spring pad lubricator. Doyle McCormic of the 4449 crew was very helpful in providing information for the 630 conversion. Basically there is a thin pad on top of a spring loaded plate that has a wick going into the oil sump. Also included is an oil line from the lubricator coming down into the crown brass. I am currently involved, off and on, with the manufacture of the aluminum oil cellers on 4501 for this device. I question the boxes due to reactions you can get mixing metals but so far I suppose there have been no problems with 630. As a part of the box we make felt seals to go on the tops of the boxes and fit against the axle. The oil we use is called Pin Bearing, and Journal or PB&J for short. Other than the habit of most oil bearing boxes catching water we have had little problem with this device. My experience is that is true with all oil boxes. Once we get the lubricator properly adjusted heating problems seem to go away. On a couple of the axles on 630 heating started to occur after initial installation but cranking the lubricator seemed to purge out an air bubble which solved the problem. We have no clue how an air bubble could be in the line after the lubricator had been pumped and run for a distance before the problem occurred.

In addition to the new boxes and lubricator system a good bit of extra machining is involved in this conversion. SP ran their spring pad lubricator engines on babbited crown brasses. To accomplish this the crown brass must first be milled to an oversize and then slotted to allow a bonding area for the babbit. Then the babbit must be machined to fit the axle and an oil groove cut across the brass at the point of entry for the lubricator line. The driver box must also be drilled for the oil line. We had the equipment to do the machining in house but it takes a lot of time. Had we contracted it out I am sure the expense woutd have been considerable. I am still not sure how necessary the babbit is since most other railroads ran oil bath bearings on plan brass instead of babbit but our guys seem convinced it was worth the effort.

Moving on to 110, I am not to sure how necessary it is for Bonsal to spend the money on this conversion. As far as I know we have not burned up a brass at a speed below 35 mph on 630. It seems the grease flows and then suddenly crusts over and stops flowing at higher speeds. We do not really know why. At slower speeds the grease is no issue. For the speeds 110 is going to be running conversion to journal pads similar to the ones 17 is running on could be the cheapest way for the group to go. I doubt they will have any more trouble with 110 than they do 17 and get the same results the spring pad lubricators give.

Moving on to the trucks, the lead truck for 4501 is going to be an easy conversion. Basically all we have to do is rebuild the worn out truck and install the new liners and bearings. From what I am told 630 was not nearly so easy. The pedistals were too narrow for the new roller bearings requiring the old bolt holes to be welded up and new ones drilled. From what I am told this was much more difficult than it sounds and was a pain in the ass to do. So far the hardest part of the 4501 conversion is getting the supplier to order the wheelset. Apparently he forgot and we now face another 2 months before we get the wheelset. We need to get 4501 back on her wheels so it looks like we are going to put the old wheels in to put her back together and change them when the new ones come in.

The trailing truck is a different matter. The truck under 4501 had a very large brass and I am told included a lot of lateral in its swing. There was no practical way to install a new roller bearing wheelset in the original truck we could find. Since the truck was terribly worn out and not original to 4501, it came off another 4500, the decision was made to manufacture a new one. That is being done now and is a huge amount of work. The new truck will be almost entirely welded. I am not sure if 110 could be easily converted or not but building a new truck would be very expensive and time consuming just as it is for us.

Again for the service 110 is going to be in I am not sure how much advantage roller bearings in the trucks are going to be. If the axles and wheels are good it would be far cheaper to rebuild the trucks and reuse the old wheelsets just as they are. That would be especially true if the conversions turned out to be as difficult as the 630 lead truck and 4501 trailing truck. If I remember correctly the wheelsets alone for 4501 cost something like $20,000.00. I may be wrong but that number is sticking in my head from what I overheard at some point. If something ever happens to the solid bearing wheelsets they can be fixed much cheaper than rollers can I would imagine.

I hope this information helps. If you have any questions I will try to answer them.

One last thought I had is that when we do rebuild 610 which has some pretty heavy wear on the running gear we may not convert it to oil lubrication on the drivers. The reason is we do not see much opportunity for 610 to run on the mainline and it has never given any heating troubles even when it was on the mainline. We are not sure why that is but it could be lighter axle loadings. Of course since it was a good while ago it may have been the fact that better grease was available or the certain fact 610 was in better shape than 4501 at that time. 4501 was one very worn out locomotive and I am constantly amazed through this overhaul it ran as well as it did for as long as it did.

John

Learned two things: conversions aren't necessarily workable for all sorts of service, and italicizing text on this forum with a 12 year old laptop isn't prectical either.

110 looks (based on visual inspection before tearing down and surveying) to have good axles and wheel centers. If this holds true, I think based on what John says - and the extremely unlikely situation of 110 ever purposely exceeding 30 MPH on anybody's railroad - that improving lubrication rather than converting might be the most useful way to proceed. Must research the PB&J oil and we can consider injecting it into the center of the brass above the axles in controlled quantities along with trying to build in some water diversion over the cellars. This could allow for some sort of crowned bearing such as Robert has written about - but I still need to see a picture to get his idea. Also, the babbit lining VS no lining or another product....and babbit comes in more than one flavor. Thrust bearings in trucks and on mains another place to think about material choices.

I'm going to ask John for more on the oil and why his shop people love babbit.

Dave

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Re: rebuilding engine trucks and boxes

Post by Overmod on Sun Jun 02, 2013 6:19 pm

Babbitt bearings are optimal because they provide a soft conformal layer that (1) any small ridges and asperities in the journal adjust to, and (2) provides a soft bed for any short-term cutting or abrasion that occurs when establishing the hydrodynamic film at startup, or if the film 'crashes' briefly due to overload or supply problems.

They are also useful in case there are any asperities or grit in the lubricant. These preferentially embed in softer brass and then cut into the harder steel in the journals. In babbitt, they embed completely and just rotate rather than cutting.

It's somewhat easier to cast, bed, and machine babbitt bearings, and less work to machine and polish the journals is required. On the other hand, ANY heat checking will eat up a babbitt bearing much more quickly than a brass one, and interruption in lube film causes more prompt bearing damage (including transfer of babbitt to the journal, not a happy thing if it occurs)

I have to wonder whether the Hennessy principle (pumping oil to the brass using lateral motion) is applicable to 110. That might be better than relying on a passive wick up to a proper pad against the journal, especially if the oil in question tends to thicken in colder weather.

Is the grease that was causing problems also a Green Velvet product, or was it M-942 compliant? Did it contain EP additives, and if so, which ones? Were samples of the 'failed' grease taken, inspected, and analyzed?

Extensive hubliner discussions on RyPN.

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Re: rebuilding engine trucks and boxes

Post by rconner on Mon Jun 24, 2013 6:13 pm

The lube system 17 is using now is drip feed for all axles with a common lubricator in the cab. We've been using PB&J for as long as I've been around the engine and have yet to have a bearing run hotter than 100 degrees unless there's water in the cellars. I do not know off hand if the brasses had babitting embedded in them, but the engine has typically been a free roller.

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Re: rebuilding engine trucks and boxes

Post by DaveLathrop57 on Tue Jun 25, 2013 6:02 pm

Thanks Robert - when I was involved, we used straight mineral oil for journals, and had some minor difficulty - sounds like PB&J is the answer.

Unless there's been some heavy wheel work done when I wasn't looking, the steel journals run in the brass crown bearings with  no babbitt lining.  I can't remember about the hub liners.

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Re: rebuilding engine trucks and boxes

Post by rconner on Tue Jun 25, 2013 8:17 pm

The hub liners have babbitt on 17. I know this because I can see it through the spokes, and I find telltales of hub liner wear on the back of the wheels, i.e. where they babbitt is starting to flake off from where the lateral clearance is getting larger. The brasses are starting to mushroom out where the edge of the brass meets the top of the axle so its a good indication that we have a taper developing, most likely due to the way 17 distributes weight without baffles inside the tank. In the future I'd say we need to go the babbitt route for the brasses.

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