There's nothing quite like high humidity for awesome steam watching! Thanks for posting.

Great stack talk in those videos. Seems like a heavy train.

Jeff's videos show the continued rod clank - seems more pronounced on the engineers side. I spent a lot of time around the locomotive last week and didn't notice the clank as bad as I have in the videos from more recently. I hope it's not something that's going to get worse. Though I'm sure the crews are aware of what's going on. Still a little strange.

The crosshead may be fitted with a brass bearing than rollers. Perhaps they didnt replace its bearings. Whether its rods or crosshead, if the bearing is worn a bit, it will start clanking, not a lot, but enough to "clank" because of looseness. The bearing is still secure, it'll just get noisy.

There's recording of O Winston Link of a Y6B switching and you had clankings galore.

Its one reason brass is used as the bearing, its a softer metal, it will wear, not your steel siderods. EZ replaceable.

The "little end" of the main rod at the crosshead on 611 definitely rides in roller bearings. The noise could be clearance/wear in the crosshead shoes, but I'd think that would sound different.

Definitely sounds like it's getting more noticeable. Also some blow-by on the right cylinder and a sticking cylinder cock on the fireman's side (minor issues). That banging sounds like GTW 4070 in the last couple of years before it had to quit running. But it was a solid bearing engine.

BTW- there are low-resolution versions of the drawings for the J class engines, including details of the rods and roller bearings, available for viewing on-line on the N&W Historical Society's website.

A stab at the clank from a non-mechanic here (please don't kill me - I'm very agreeable to correction :) ). Consider what is going on with locomotive running gear. The mechanism converts the lateral push pull of the piston to circular motion at the wheel. Because there is a change in direction at the piston wear will occur at any one of the bearings of the running gear. As stated the bearing is designed to have a hard and soft surface so that as wear occurs, the softer bearing surface (bronze/brass) will wear out at a far less cost and trouble than the harder surface (steel). The clank is the audible result of a worn soft metal bearing as it absorbs a change in direction. In the case of the J rollers don’t quite like this wear stuff and if they decide to fail will do so at a higher cost and trouble – no shimming a roller to get home. A roller bearing assembly costs far more than a standard brass bushing style bearing – thus all the interest in the board in this clank.

Here's another way of experiencing 611 - in a train simulator!

https://youtu.be/kfmi290hzGQ

Here's a link to the arrangement drawing for the main crank pin for J's with a single intermediate rod like 611:

http://www.nwhs.org/archivesdb/detail.php?ID=26487

The drawing shows a sectional view of the main rod, main crank pin, front rod, and intermediate rod. The rod ends actually contain bronze bushings that ride on the outer surface of the Timken roller bearings. I imagine there could be wear in those bushing that would cause the noise.

Here's the crosshead pin and bearings:

http://www.nwhs.org/archivesdb/detail.php?ID=22964

I just went back and watched several videos from the test run on 5/23/15, and while I can't say there's no rod knock, there's clearly a lot less.

Hugh,

Yes, I would agree. Seeing the small wall thickness of these bushings at such a large diameter, you wonder if they were machined after the bushings were pressed into the side rods.

Assuming the roller bearing outer races are one piece but the inner races are split. Due the tight tolerances of these bearings, the split mating joint sets up the running clearance (or possibly preload) of the bearing rollers. Likely no excess clearance for pounding!

However the bushing clearance must allow for relative lateral and vertical motion from one axle to the next and account for quartering differences......so clearances cannot be too tight! They may not last long in hard service.

All the same, I still regard roller bearing side rods as the pinnacle of the art in heavy machine work. Extremely impressive!

Regards,

Randy

Quite thin. Here is pic link to one of 2926 rods where you can clearly see the thin bushing. Lot of good pics of the rods n roller assembly on the NMSLRHS site.

http://www.nmslrhs.org/Photos/2014/02-15/DSCN9128.html
and
http://www.nmslrhs.org/Photos/2014/09-06/DSCN2746.html
and a little machining of the bushing
http://www.nmslrhs.org/Photos/2013/03-16/DSCN1675.html
and
http://www.nmslrhs.org/Photos/2013/03-16/DSCN1662.html
and lots here
http://www.nmslrhs.org/Photos/2012/09-22/index.html

The clank is the change of exerting pressure. The rollers have to take a lot of force by design. I don't think they are going to shatter too easy. The crossheads are not spinning like the drivers. What I hope is they keep them very lubricated.

Looking at the drawings the roller arrangement is rather differrent than what I would have expected, angled.

IIRC, when the folks in Albuquerque disassembled their rod bearings they found some with enough corrosion and pitting to make them unserviceable. They sent these rod bearings back to Timken for service. And Timken also provided some replacement bearings. So, if there is a problem with these bearings on the 611, there should be a fix available. Whether there is enough of a problem to force the locomotive out of service while new bearings are manufactured is another question.

No worries about them shattering, but impact loads can dimple the races and/ or rollers which leads to quick failure of the bearings.

The "angled" arrangement is a tapered roller bearing as devised by Timken. The taper allows the bearing to be adjusted by moving the races.