Matt has posted what I've always thought. The European engines compared to ours is like comparing a watch to Big Ben. I never thought their engines were built for the heavy service that American engines were.
I've often said that some of our tenders were as heavy as some of the trains they hauled.
I'm going to go hide under the desk now.

OK, but how does that relate to the ability of Tross staybolts to reduce staybolt breakage in typical U.S. large locomotive boilers?

I thought Matt covered that pretty well in his post about the design of the boilers vs ours.

To quote Cousin Vinny - " Sooooo have the laws of physics been suspended in your (U.S.) boiler and apply only in a German boiler?" U.S. boilers are much larger and move more - but in the same directions in the same amounts per inch.
Really? What?
Let's try to learn why the Flannery Bolt Company translated all of Mr. Tross' work to English in 1952 and presented it to the Master Boiler Maker's Association.
Come out Don!

European steam locomotive boilers were often worked very hard. But European maximum allowable axle loads were and are much lower than in the USA. 15 to 20 metric tons (about 33,000 to 44,000 lbs) is common for mainline steam power built 1920s-1960s. Comparable engines in the USA ranged from 55,000 to 75,000+ lbs per driving axle. So the largest European steam loco boilers tend to be about the same capacity as medium-sized American ones. For example, the 1,340 2-8-2 locomotives built in 1945-1947 by Baldwin, Alco, Lima, Montreal, & Canadian Locomotive Works to rebuild the war-devastated French national railways (SNCF 141R class) are a compact tight-clearance design based on an updated USRA 2-8-2A (light Mikado), especially the Green Bay & Western 2-8-2s. Driving axle load is 20 long tons (about 44,000 lbs). The later 141R deliveries had roller bearings. They're impressive mainline excursion engines. See http://en.wikipedia.org/wiki/SNCF_Class_141R and http://www.martynbane.co.uk/france/lemistral07/141r.html

- Doug Debs

So there's 17 141R's on the bottom of the ocean off Newfoundland. Hmm. LOL

Steve

Hey, I just said it was my opinion. Your mileage may vary.
German boilers grow in MM. 8!)
I'm back under the desk now.

The amount of deflection in the boiler, like most things, is proportional to its size. So what works in a smaller boiler may not work in a larger one. Therefore when comparing standards between Europe and the US one should consider among many issues is the relative boiler size. Is there some more room under the desk?

Robby Peartree

Robby- I follow your logic. But if a Tross stay is less prone to breakage in a small German boiler, shouldn't it make even more sense to apply them to a U.S. boiler that deflects more?

Let's not lose sight of the forest for the details of the trees. Previous threads have covered the larger design concept differences between common German (balloon boiler)and US practice. The German approach was to accept and absorb deflection as an inherent part of how the overall boiler was considered and built, ours was to control and minimise it, if I am understanding it correctly. So, if we take a US style heavy rigidly mudringed boiler and replace some of the rigid stays with Tross stays instead of flexis in the "breaking zone", are we making a better, more robust rigid boiler or allowing the stresses to just migrate further before being controlled? Sure, the origination of the stresses is the same, but it is the ramifications of the potential differences in the reaction that I'm thinking about.

So, is it right to think of Tross stays as simply another rigid stay design that just handles stresses by dispersion rather than concentration, or by doing so do they allow for greater or differently reactive movement in the steel the stays are staying in the first place?

dave

Dave,

It is right to think of Tross stays as simply another rigid stay design that just handles [bending] stresses by dispersion [across the staybolt shaft] rather than concentration [at the sheet, or fulcrum of the bending.]

The Tross stay does not necessarily make the rear boiler more rigid, but because the staybolts can handle more bending stress before actually permanently bending, the rear boiler tends to return to its original shape when the stresses (fire induced, shrinkage induced) are removed. When the rear boiler can better retain its designed shape, it can better retain its designed pressure.

It was more practical for the Germans to engineer lightly-built boilers to handle higher stresses than rebuild the railroad infrastructure for heavier boilers. As we helped rebuild the French infrastructure, certain districts in France could handle the 141R, which Chapelonized, is a very impressive locomotive indeed, and BTW, has a pretty chunky mudring.

The quality of heating surface and quality of the combustion and drafting systems have a lot to do with boiler capacity. It is interesting to note that German boilers have a lot of superheater surface and put out some very hot steam. Many locomotives are Lentz poppet valve or nifty piston valve, and have some pretty good steam rates per/hp.

There is nothing impressive about a locomotive which is provided so large a boiler it cannot be run out of steam no matter how inefficiently its steam engines are operated.

So is it all boiling down to "Size Matters"?


Any room left under that desk?......mld

I believe that's a reasonably accurate paraphrase of Matt Austin's original post, while a similar paraphrase of Matt Janssen's would be "it's not the size of the ship, it's the motion of the ocean".

:-)

From a practical POV, the majority of museum and tourist operators run power that is comparable in size to European standards, so, if we're thinking practically rather than theoretically, for most of us there's not an issue about size as much as construction comparisons to be made. If I'm replacing a firebox on, say, a 50 ton prairie in the US, retaining the heavy mud ring and thick wrapper sheet, I'd want to know if it would make sense for me to spec and engineer Tross rather than straight rigid stays since it takes the same amount of welding to install either. The deciding factor for me would be lifetime economy and robustness, remembering that the most expensive train you sell is the one you can't run because your locomotive is down. If Tross stays reduce the impact of stress cycles on the entire assembly, I'm interested. If they reduce stay breakage but increase knuckle cracking or tube loosening, maybe not so much.

dave