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German Firebox Bulging
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Author:  M Austin [ Mon Aug 29, 2011 2:03 am ]
Post subject:  German Firebox Bulging
Professor Tross was tasked with solving pandemic staybolt breakage problems in the German locomotive fleet starting in 1937. One cause of this problem was the flexibility of the the mudring portion of the boilers.
Germans typically made the mudrings 1" to 1-1/2" high. North American practice was to make the mudrings square up to 4" thick. The formal North American name was the Foundation Ring. This forced all the expansion of the firebox sheets upwards and outwards. The German practice did not provide this rigidity.

Note mudring thickness from German cross sectioned locomotive from Wikipedia:
Image

From the paper "Tross New Knowledge Locomotive Rear Boiler" from Matt Janssen's website:

Image

Image

Ilustration No. 6 clearly indicates this as an example of the bulging of the 44 class locomotives. See information of the German Class 44 from Wikipedia here.

From the translation and the scientific writing style of Tross, the comment "was only 80 mm" is obtuse in it's meaning. In a translated paper by Porta, provided by Matt Janssen, the meaning is clearly defined as a 3" spread (appx. 80 mm) of firebox sides in the German 44 Class 2-10-0 locomotive of which almost 2000 were produced.

Image

My personal question is "what would be the reaction, if on a morning inspection, the firebox of Frisco 1630 or Strasburg 90 showed a 1-1/2" outward bulge along the mudring?"
Author:  Kelly Anderson [ Mon Aug 29, 2011 8:08 am ]
Post subject:  Re: German Firebox Bulging
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Author:  Planeman [ Mon Aug 29, 2011 2:47 pm ]
Post subject:  Re: German Firebox Bulging
Could this be a factor in the problems with the Tornado boiler and it's broken stays?

It this the problem Tross was trying to sl=olve with the Tross staybolts?
Author:  M Austin [ Tue Aug 30, 2011 4:58 pm ]
Post subject:  Re: German Firebox Bulging
Planeman wrote:
Could this be a factor in the problems with the Tornado boiler and it's broken stays?

It this the problem Tross was trying to sl=olve with the Tross staybolts?


Yes. The typical German locomotive boiler was really a metal balloon. There is no doubt Tross was a genius. However, Tross was given an unsolvable geometrical problem. He identified most of the design infirmities integrated into well over 10,000 German locomotive balloon boilers. The elastic staybolts he designed are the best solution to an unsolvable problem.

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Author:  jim templin [ Tue Aug 30, 2011 6:03 pm ]
Post subject:  Re: German Firebox Bulging
M Austin wrote:
Planeman wrote:
Could this be a factor in the problems with the Tornado boiler and it's broken stays?

It this the problem Tross was trying to sl=olve with the Tross staybolts?


Yes. The typical German locomotive boiler was really a metal balloon. There is no doubt Tross was a genius. However, Tross was given an unsolvable geometrical problem. He identified most of the design infirmities integrated into well over 10,000 German locomotive balloon boilers. The elastic staybolts he designed are the best solution to an unsolvable problem.


So, the two dollar question is this...how well would Tross Stabolts work in a boiler with a bonafide foundation ring? Either fillet, screwed in, or full penetration welded?
Author:  Tim Botti [ Tue Aug 30, 2011 9:15 pm ]
Post subject:  Re: German Firebox Bulging
That does seem to be an awful lot of expansion - if any component is visually bulging I'd certainly be uncomfortable. But Matt, for the chronically under-informed among us such as myself, was Tross's tapered staybolt designed to solve the problem on German boilers with thin mudrings and other maladies, or would this applicable to staybolt breakage problems on North-American style boilers as well?

I guess I feel like I'm reading supporting arguments without being sure of what your premise is. Not a knock, I'm probably just out of the loop...
Author:  M Austin [ Tue Aug 30, 2011 10:12 pm ]
Post subject:  Re: German Firebox Bulging
Tim Botti wrote:

I guess I feel like I'm reading supporting arguments without being sure of what your premise is.


Jim, Tim

There are 2 different design philosophies at work here. There are several more aspects that need to be posted to show how they are or are not interrelated.
For example, North American practice recognized the wavy side sheets were unavoidable and used the phenomenon to its advantage reducing stresses by as much as 40%. The Germans just lived with it.

Review of the "wavy side sheet" thread would be helpful for the time being. More to follow.

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Author:  Tim Botti [ Tue Aug 30, 2011 10:16 pm ]
Post subject:  Re: German Firebox Bulging
Thanks Matt. The nuts and bolts stuff is what we need more of here.
Author:  M Austin [ Wed Aug 31, 2011 2:18 am ]
Post subject:  Re: German Firebox Bulging
On the French 141 R 1199, note the single row of mudring rivets, indicating a thin mudring. Even though American built, the boilers were modified at European request.

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Author:  Robby Peartree [ Wed Aug 31, 2011 11:47 pm ]
Post subject:  Re: German Firebox Bulging
Hi Matt

Given the flexibility of the trough ring on this locomotive I have to wonder about the Flex bolt pattern I see in these pictures. With that type of trough design it seems to me you would want to have flex bolts in a different pattern than in the US? Or am I missing something?

Thanks

Robby Peartree
Author:  Dave [ Thu Sep 01, 2011 4:38 pm ]
Post subject:  Re: German Firebox Bulging
I suppose I'd like to understand more about the difference between how Tross staybolts react to various real life stresses relative to the rigid stays we are most familiar with over here, and how that impacts on their usefulness in different styles of boiler construction. I can envision how too much staybolt flexibility might be a bad thing in a boiler with a very rigid foundation ring.

dave
Author:  Mike Tillger [ Thu Sep 01, 2011 7:30 pm ]
Post subject:  Re: German Firebox Bulging
What material specification were Tross style staybolts to be made from, and what material were the sheets they went into??? Would the results be the same with the materials that are readily accessible to most restoration groups in this day and age, as it seems to be getting harder and harder to find PVQ steels with the tensiles equal to what the original construction called for??

Mike Tillger
Author:  M Austin [ Fri Sep 02, 2011 1:41 am ]
Post subject:  Re: German Firebox Bulging
Robby Peartree wrote:
Hi Matt

....it seems to me you would want to have flex bolts in a different pattern than in the US? Or am I missing something?

Thanks

Robby Peartree


Tross did not like ball and socket flexible bolts or flexible bolts in particular for that reason.

Dave wrote:
I can envision how too much staybolt flexibility might be a bad thing in a boiler with a very rigid foundation ring.

dave


If the philosophy is to control stress by restraining expansion.... Yes.

Mike Tillger wrote:
What material specification were Tross style staybolts to be made from, and what material were the sheets they went into??? Would the results be the same with the materials that are readily accessible to most restoration groups in this day and age, as it seems to be getting harder and harder to find PVQ steels with the tensiles equal to what the original construction called for??

Mike Tillger


Tross elaborated on materials in German specs which I have no access to. His major problem was dealing with the geometry which is independent of the tensiles.
Author:  Mike Tillger [ Fri Sep 02, 2011 7:58 am ]
Post subject:  Re: German Firebox Bulging
Matt,
If I may edit my prior post:
What material specification were Tross style staybolts to be made from, and what material were the sheets they went into??? Would the results be the same with the materials that are readily accessible to most restoration groups in this day and age, as it seems to be getting harder and harder to find PVQ steels with the tensiles and elongation results equal to what the original construction called for?? Since he allowed for more "flexibility" in his design would he have required a material with more ductility?

Mike Tillger
Author:  Bruce Mowbray [ Sat Sep 03, 2011 8:09 am ]
Post subject:  Re: German Firebox Bulging
From a practical point of view,

It looks like Tross came up with a more flexable (less cross section) staybolt in order to provide more flexibility in the bolt itself and not bending the sheets instead. He may have used a high alloy steel (heat treated 4340?) that put up with bending cycles as well as heat and returned to it's original form once bent. The welding on the ends would not affect the thinner center portion where the flexing would take place. One thing to notice is the practicality of easy bolt replacement when they did break. Cut broken bolt with a torch though the enlarged telltale holes. Grind weld flush to sheet and punch out bolt. Move to inside and repeat. (You probably wouldn't have to burn the inner bolt half) Slide in new bolt and weld both sides and your done. No threads to mess with and with the larger hole, less chance of nicking the sheet.

Bruce Mowbray.
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