Steven,

For what it may be worth, here are a couple photos with some "breadcrumbs" of information regarding the why behind car-type bearing design, with full Babbitt bearing surfaces:






It is interesting to hear Kelly and J. David's comments on the Babbitt pocket type of bearing design, particularly the comments regarding those pockets being 1/8"-ish proud of the rest of the bearing surface when new. I wouldn't think introducing these artificial pressure points would do much good, but, apparently it works as J. David points out.

Last comment for now is to add that - as Kelly has likely mentioned in previous threads - as of 6 years ago we now have all our locomotives at SRC running exclusively on oil lubrication; both axle journals and side rod journals, and we've been thrilled with the results. Operation is much cleaner and cooler than with grease, our operating temperatures being in the lower range that J. David mentions in his post. Personally, I would never have a desire to return to grease lubrication, particularly on the axles/driving boxes. Our side rod and crown brass bearing design is bronze throughout - no Babbitt - and our lubrication is manual; simply replenishing a few ounces of oil per bearing per day in the driving box cellars, even less than that on the side rods.

Erich Armpriester
Strasburg Rail Road Mechanical Services

Interesting - decades ago as a FNG I was taught that any scoring or damage running laterally across a babbitted bearing would lead to overheating due to the oil film being broken at the gap - while and circumferential scoring wasn't a concern. Here we have a design purposely breaking the babbit liners into segments and things run cooler in oil. So, should we no longer worry about laterally scored journal brasses?

Greetings:

Dave: In my experiences moving the Steamtown Collection from Bellows Falls, VT to Scranton, PA, as long as the edges of any defects on axles with plain bearings were polished so there were no sharp edges that might damage the bearing (plain bronze or babbitted), we could get that piece of equipment "over the road", albeit in a special train with folks riding along to inspect and "doctor up" any problem axles along the way, traveling at 25 MPH and stopping periodically to "feel up" axles. Strictly a "home shop for repairs" situation.

All of the axles at Bellows Falls were polished by hand, as needed, with emery cloth of increasingly fine grit, concentrating on the edges of score marks and rusted areas, finishing with crocus cloth. Towards the end, we used an air powered die grinder with flapping wheels on driving axles which were badly rusted. As I recall, CNR #5288 was one of these.

B&M #3713, (prepared for movement at Boston by another crew), was the only one that we had unending problems with. From the first stop we made somewhere about 10 miles from Boston right until it rolled in Scranton, it ran hot, even after we gave up on the Hennesey oil pump type axle lubricators and converted it to grease blocks.

Were these axles all fit for regular service? No possible way (but they all made it to Scranton)!

Be well & stay safe,

J.David

Dragging up a bit of an old thread

We still haven't gotten around to machine work on the side rod bearings as of yet. Other, more pressing issues with the locomotive have reared their ugly head, and kept us in a near-perpetual status of playing whack-a-mole.

I was looking at a status update from the Railway Preservation Society of Ireland on the return of a 4-4-0 to service and noticed that their axle boxes are of the same design Steven started the thread with.
https://www.facebook.com/steamtrainsire ... 1481751116

It seems that the bronze surrounding the white metal is intentionally part of the running surface and that the white metal doesn't sit proud. Seeing as this is in contradiction to what Kelly & J. David mentioned, would it be safe to assume that European practice is just its own animal and that the Chinese practice is very close, but no cigar?

I believe that the Chinese practice of leaving the Babbitt proud is the odd practice. Leaving everything flush seems more standard. If I was responsible for a Chinese engine, I would be concerned about dirt and water getting into the gap between the bearing and the journal. Fly ash when dumping ashes being a prime example.

Greetings:

Kelly, the Chinese thought of that issue. The oil cellars on Chinese steam locomotives have plates welded in about 1/4" from the ends where the axle goes through. Foam rubber is fitted into the slots created up to the bottom of the axle forming dust guards. These have been renewed once on 3025 since the locomotive began running at the Valley in 2011.

In response to stewi10, et al, Kelly is correct: on 3025 the Babbitt in the crown brass pockets sits proud of the bronze. In ca. 2018, a feed on a 4 way divider feeding the crown brass on the left main driver got plugged and the axle ran hot on a Saturday and was reported by the Engineer on the work report. Whoever the Mechanic on Duty was the next day wrote: "Noted" on the report without determining what the problem was. On Sunday the axle got hot enough to melt the Babbitt. They had a dickens of a time digging the melted Babbitt out of the oil hole, but they did, and polished the axle and repaired the 4 way divider. I wanted to drop the wheel and sent the driving box to Strasburg Rail Road to be rebabitted but were in the middle of the operating season, and, and, and. So we didn't. It has been fine ever since running steel on bronze, generally 5+/- degrees warmer than the rest of the driving axles.

However, even though the Babbitt is no longer proud of the bronze, the rest of it is still in there. I wonder if that is enough to keep the axle running cool or is it simply that it is oil lubricated. I was once told that the reason for the Babbitt was because as the axel turns a microscopic amount of Babbitt wears away and is carried with the oil to lubricate the axle. I would be interested to learn the thought process of the Southern Pacific in their decision have Babbitt pockets in the crown brasses of their large road locomotives such as 4449 and what the experience of the 4449 crew has been over the years.

Stay safe & be well,

J.David

Right, but my concern is the 1/8" gap at the top between the bronze part of the crown brass and the journal. Is something in place to block that gap?

Greetings:

Kelly, yes, the foam rubber is secured by fitting snugly into the 1/4 "slot formed between the ends of the oil cellar and the plates inside the cellar which creates the slot: they act as dust guards. The foam rubber extends down into the oil cellar to wick up oil on the lower end, the upper end fits around that portion of the axle not under the crown brass squishing (a technical term) out around the exposed portion of the axle, blocking dust etc. from getting into open area between the "proud" babbitt and the axle.

I have worked on locomotives where the space between the gap in the cover plates between the ends of oil cellar and the crown brass were 1/2" or more with a gap of an inch or more between the journal pad or grease block and the axle the length of the journal. Often times the end at the driving wheel hub had no guard at all.

Dust guards on the wheel side of plain bearing journal boxes seldom do much good after being in service for a year or two. Half the time they are nothing more than plywood. I don't believe that neoprene or rubber ones are made any more. I wish I were wrong about that, but will say that the only time one can be installed is when you the wheels out of the truck and the journal boxes are removed. There are low annual mileage cars at the Valley which never had their journal boxes off in the 37 years I worked there.

J.David