A recent picture of 1361 has led some to claim it had thermic syphons. True? That sounds too 'progressive' to me for the K4 design, but I don't mind being proven wrong.

FWIW, PRR loco diagrams don't show any syphons for the K4.

At this point, if it's going to get a new boiler, and the improvement doesn't change it's overall appearance, but does improve it's operating efficiency, then I wouldn't have a problem if they did add thermic syphons to it. They should also probably turn it into a liquid biofuel-burner, but I know the flame war that suggestion will start.

It is not getting a new boiler. New firebox only.

Sorry. But syphons would be in the firebox, so putting them in a new firebox would be appropriate.

To be true to the definition of preservation and restoration, the original firebox design should not be altered with the addition of thermic syphons.

I suspect the initial reporter saw the arch tubes and assumed they were the syphons.

"To be true to the definition of preservation and restoration, the original firebox design should not be altered with the addition of thermic syphons."

Please confirm this statement is a joke. You realize the locomotive will NEVER run if put back to PRR blueprints, right? There are a couple of other PRR locomotives in the same pickle.

"Please confirm this statement is a joke. You realize the locomotive will NEVER run if put back to PRR blueprints, right? There are a couple of other PRR locomotives in the same pickle."

*Please confirm that this statement is a joke*. In staying true to historical preservation you make ONLY what modifications are NECESSARY to accomplish your mission. Increasing firebox sheet thickness, making adjustments to staybolt specs to meet Federal standards are just that. Adding an appliance that the engine historically didn't have, nor would have ever had, and furthermore never needed, without reasonable justification, doesn't make sense. If they, down the round decide that the extra fraction of a percentage of efficiency on a 3% efficient locomotive will make that much of a difference, well...

Like the coalboards on 765, PTC, 26L Brake systems, these are changes made to the historical nature of these machines because the benefits outweighed the cost of altering them. Of course, it all depends on what your mission is to begin with, if operation is the main goal over to historical appearance, then it's not something to be as worried about as say, a group specifically wanting to preserve their artifact as it was in "19xx".

Saying "add it just because..." as people have suggested with no more insight or informstion on the locomotives restoration is slope to approach cautiously. Modifications need to be justified in some way, and a syphon wouldn't make that much of a difference while substantially increasing costs, matainance, and engineering problems to have the boiler alteration approved.

Again I ask "Is it *necessary*?" And from my perspective, way back in the audience, with no affiliation or insight to the restoration, and thus just my humble opinion: No.

-Sam

So is the consensus that what appeared are for arch tubes and not thermic syphons?
This stems from a photo from a Trains online article, that shows 4 parallel circular holes in the throat sheet. As a layperson, I would think that if these holes were for thermic syphons, they would not be circular.
https://www.trains.com/trn/news-reviews/news-wire/firebox-replacement-plans-advance-for-prr-k4a-restoration-project/?fbclid=IwAR3b-soe0hWIbK-l7Hu5j1GZun1M7mJ-N-0j9ZUgadVqwiIa53or3kkVzT4

I just Googled 'locomotive thermic syphon' and got a quick hit, taking me to a Wiki page, which confirmed my recollection of what a thermic syphon is. Imagine a letter Y, with one leg bent. That bent leg would go into the throat sheet, just like in the picture linked above. But the top of the Y is open, a long slot that mates with a slot in the crown sheet. Or, another way to look it is to think of an arch tube , oval shaped at the crown sheet end.

I'm pretty sure the K4 onlyhad arch tubes, but it would be possible, with the new firebox to add syphons. And that new firebox apparently will not have any differences in appearance outside, just different stays and heavier material, from what I've read.

I'm not saying adding syphons is or is not desirable, but what do I know? I just rewire Alcos, and I don't use the historically correct 'cloth and asbestos' insulated wire. Exane!

Hi folks,

I reached out to FMW Solutions with this question. Here is their answer (which I greatly appreciate):

"Thanks for reaching out. Those four holes are where the arch tubes intersect with the inner throat sheet.

Interestingly, we have found records indicating that the PRR experimented with installing duplex arch tubes in the K4 Class. This arrangement consisted of two sets of four arch tubes, with the front four extending between the crown sheet and throat sheet and the rear four extending between the door sheet and throat sheet. These tubes supported two partially-overlapping brick arches, a back arch and a front arch. That said, I would not be surprised if PRR experimented with thermic syphons in the K4 class at some point.".

1361 didn't have syphons at the '85 rebuild, just 4 arch-tubes; 3" I believe; the large plugs on the back-head and throat are for the insertion of rolling tools.

The other engine I worked on afterward was the B&LE 643 which did have syphons; 4 in fact being such a huge engine; I was amazed at the number of additional stays required on the "Y" portions.

Do the syphons really work well enough to justify their installation and maintenance? Is the boiler "Freer Steaming"? Is fuel/water consumption reduced?

An old boiler maker told me to think of a percolator coffee pot but, in the coffee pot, you have a heat source at the bottom and a funnel shaped fitting collecting the bubbles as they form rising to create the circulation thus making the coffee.

In a Steam Locomotive, you have the heat source again at the bottom but the similarity stops there since the syphon is inverted compared to the percolator; most of the boiling takes place around the flues and above the crown sheet; if you neglect the weight of the water, everything is at an equilibrium. It must work but I draw a mental blank when trying to visualize "circulation" over the crown sheet and around the firebox from the syphon effect. Is it the greater heat on the "Y" portion pulls that water up from the mud ring area as it expands relative to the higher density water?

An injector works in a similar equilibrium but uses the energy created by the high velocity steam and the inverting of the second cone to build pressure; maybe I just answered my own question!

Happy New Year and Thank You for staying with me as I stray from the original topic!

Heck! I'm going to make some coffee!

It's real simple. The complete restoration to service at full boiler pressure is in the very capable hands of professionals with proven track records. They know what they're doing as do the industry leaders providing the finances to get the job done.

Any sidewalk superintendents should feel free to direct your detailed boiler questions to FMWsolutions.com and I'm confident you will receive a complete answer.

Happy New Year, Ross Rowland

Chattahoochie Valley 201 was retrofitted with syphons - now the welds joining the syphons to the crown and throat have cracked, but she hasn't run in decades..... anyhow, verbal history from some now dead people was that they couldn't keep her cold when the syphons had been installed. no matter how lightly they tried to fire her. Probably a cumbustion system originally designed and built with syphons would have worked even better and more efficiently. Somebody probably did some quantified testing at some point back in the day, if it could only be found.

I stand by what I wrote about the '85 rebuild as the FMW folks have verified.

Restoration/Preservation: re-install the Hydrostatic Lubricator!!