This is a two-part question...
How difficult would it be to change a steam loco from friction bearings to roller bearings? What's involved?

Also, how difficult would it be to convert a loco from an oil burner to a coal burner. Keep in mind that it was built to BE an oil burner.

Any insight would be helpful, thanks.

The roller bearing conversion was tried and ultimately failed at GSMRR. I'd encourage you to look at drawings of the cannon box casting that contained the bearings and the axles and compare that to the friction bearing setup with two disconnected boxes. Now compare the relative difference in pedestal opening dimensions between technologies. It isn't going to fit.

Coal to oil (and back again) has been done frequently and continues to be done today. Biggest differences are in the bottom of the firebox and in the front end, not to mention the fuel container in the tender. No firegrate, instead a firepan below the mud ring, an atomizing burner penetrates the firepan for fuel injection into the combustion space, air is regulated in entering either from below, above, beside and around the burner in some well designed combination as well as through the firedoor usually, and the front end is simpler containing in "normal American" practice a shorter exhaust stand and nozzle, a lift pipe and a petticoat pipe in ascending order. The firebox is lined with firebrick or a similar liner to reduce flame impingement on the steel, and to provide more thermal mass in the firebox.

Canadian practice was to place the burner below the firedoor and use a brick arch. US was under the throat and no brick arch. These are rough guidelines, partway down the pan wasn't unusual and many new designs use a centrally located burner through the floor.

So, I'd look at an oil conversion for the bearings rather than a roller conversion, and redesigning the entire combustion and drafting as a whole rather than just in part.

dave

Thanks for the quick reply Dave, but where would I go to look at cannon box bearings? I have no frame of reference at this time...no loco to look at. Are their any pages you can point me to so I may see what you are referring to?
I am a neophyte at this; trying to learn as much as I can in a relatively short amount of time.
Thanks again!

No problem - I'm lucky enough to have seen the GSMRR conversion and talked to guys who were involved, and to have a lot of old books in my library. I can't find out much about where you are of if you have any affiliations on your profile, but if you are near a larger museum with an archive or library, you could start with the cyclopedias there. If you live in Roanoke you are very fortunate - crawl under 611.

Imagine......both boxes that hold the crown brasses on the drivers axles not being seperate, but joined inside to inside by a hollow heavy tube that holds them in a permanent spatial relationship with each other. Now imagine them being bigger and enclosed on the bottom, with the roller bearings trapped within them. The axles ride in the bearings and fill the hollow tube, with the wheels pressed on outside of the boxes. So, the axle diameter must be larger than the wheel center bore diameter.....hence the large size of the box to hold the largest part of the axle and the bearing that it rides in, and the seals.......that hold the lube in and keep the dirt out. Since they are joined, neither box can rise and fall relative to the other along the center line of the axle which keeps the roller bearings from being damaged by diagonal racking.

Maybe Hugh Odom can refer you to online pictures or drawings that will make it much clearer. He's my go-to guy for modern steam stuff. Check out links from his ULTIMATE STEAM PAGE which you can google.

OK, also want to make clear the oil conversion of the bearing is from old grease block lubrication - like Mark and the TVRR guys are doing - nothing to do with fuel. Sorry.

dave

Unfortunately the only RR Museum I live close to is 2 hrs away in Strasburg. I suppose I could get up there some time in the spring and get a look at the underside of 1187. She has friction bearings right?

So, what I took away from what you said (how I understood it) is is the space in the chassis that holds the axles isn't big enough for the expanse of adding roller bearings, the whole chassis would have to be reworked or rebuilt...am I right? There is only enough room in the bearing 'pocket' (so-to-speak) for the bearings the engine was designed for...
That's my understanding at least...
Thus, if a particular type of engine, lets say, that hasn't run for a number of years, went in for restoration to operational condition and the 'trust company' or 'head honcho' wanted it to run on i.e. NS or CSX for instance, they would have to be satisfied with just tourist lines and secondary lines due to there is no way to add rollers to such a confined space.
Am I right here by saying this?

Yes, you understand the problem: the slot that the bearing box slides into in the locomotive frames would be too small. I don't know if there's anything with rollers at RMPa.......Steamtown maybe? Try googling Hugh's site and you can probably find a drawing or pphoto linked through that somewhere.

If CSX would run mainline steam, I think there's a gentleman on this list with something he'd be happy to use for the purpose. You don't need to rebuold an old one for the purpose.

This tech trivia must be boring people...drop me a PM if I can confuse you more.

dave

LOL!! That's funny...I'm not confused anymore. Thanks Dave. I will certainly look up Hugh's site and get more info, but for the moment I believe you covered the gist of it. Thanks again!

The video "The Modern Coal Burning Locomotive" (made by the N&W Railroad) shows some very interesting contruction clips. One of which is installling the housing around the roller bearings on a J. Very short shot but if you look for it you'll notice the size. Also if you watch http://www.youtube.com/watch?v=0j8ERAPo8Z0 at about 8 minutes there is picture of a driver coming out from under the 611 and if you look close you can see the size of the box.

If you look around on this board some where are some of the pictures posted by the Strasburg guys to compair an more standard design of box.

You asked intelligent questions and didn't foam. Those are the ground rules. Follow them and get good information.

dave

Look down this polish loco page, and you will see the a roller bearings jounrnal box housing;

http://www.google.com/imgres?start=123& ... s:123,i:95

The US versions were a lot larger and heavier than this one.

Why is it necessary that roller bearing driving boxes be connected and held in alignment when it does not seem to be necessary on other rolling stock? There must be more to it than just the fact that they are inside bearings. Is it the piston thrust that would damage the bearings otherwise?

Steve

Preecision caused by much tighter tolerances and a diversity of smaller bearing surfaces of higher hardness and overall complexity.

dave.

Roller bearings, tapered roller bearings, do not like to see loadings outside of those imparted on the "X" and "Y" axis of the bearing.....that is, they can readily handle radial and axial loadings (within design limits) but do not handle it well when the center line of the cup tries to twist out of alignment with the cone. Think of the motion between box and axle if a standard plain bearing journal box seized between the shoe and an over tightened wedge as the opposite side moves up and down.
So, the cannonbox acts to prevent above described undesirable loadings AS WELL as putting two bearings into play when handling axial loadings....assuming the more modern 4 bearing design box. Afterall, if the two boxes were not joined together...rigidly...it would be impossible to have both sharing equally the axial loadings.

Now, all of this is in regards to Timken type bearings. SKF is an entirely different animal.

Cheers, Jason

Piston thrust as well as other impressive impact loadings resulted in the design of the bearing rollers, cups and cones as they were by the early 40's.

So why is that not an issue on other rolling stock?

Steve

My question is -- why bother. It's a huge engineering job, a great deal more than just sticking roller bearings in the "right places"... the rollers have to allow for all sorts of dynamic forces that the plain bearings have no trouble with. You can't just stick a roller bearing in slapdash and have it be reliable. How you use it matters. Since your conversion involves digging into metal, a failed attempt at conversion could leave the locomotive crippled, unless you have the capacity and will to fab new parts to unwind what you did - which I rather supremely doubt, as most people are disgusted at that point, and give up.

And then once you're done, 20 years down the road will service and parts for your chosen bearings still be available from a manufacturer? Or will they be "unobtanium"? If the latter, you have cut short the locomotive's serviceable life.

What's the excitement about roller bearings? a) it's a statutory requirement of Class I legal departments -- well, that doesn't matter if you're not running on a Class I.
b) Slightly - and I mean SLIGHTLY - better fuel economy. If you cared even a little about fuel economy, you would not be running a steam locomotive LOL!
c) "they are more reliable", but they fail much more spectacularly and suddenly, and are harder to detect. And we're talking about run of the mill production freight car roller bearing trucks with a billion dollars of engineering and 70 years of fail-learn-modify cycles behind them. Your totally custom, seat of the pants, one-off job? Could actually be LESS reliable than plain bearings.

It's also easier to put sensors in a plain bearing to predict failure. Thermistors will do, with simple analysis by a cheap control computer like a $70 Arduino Mega ADK. On a roller bearing you need to use accelerometers and do very complex signal analysis, notably to exclude external (non-bearing-failure-related) tonals and transients, and then you're deciding to cancel a run based on arcane analysis from a very complex algorithm. "Bearing is 30 degrees hotter than its neighbors" is rather a much simpler reason to stop and shove waste around in there.