Hush tones:Tomorrows 31st. Canterbury Tornado anyone?

Yes, the tell tale would be "LEAKING STAY" I would have thought.
The stay may/may not be broken. However, during normal inspections during it's layover/water stop at Canterbury West it seems that the 'seal' to either the inner or outer firebox is no longer watertight, apparently, causing rather hot water to become visible to the support crew inspections.
Coming back just Loco+Support Coach requires boiler pressure much lower than maximum. This results in much reduced stresses on the boiler and, therefore, on the leaking stay. [To haul the whole train would require full boiler pressure, of course, with consequent stresses of main line speeds/work.] The leak was probably not 'pouring' with water I guess so, at reduced pressure with two fully working injectors, there is a major margin of safety to reach it's London base at DBS's Hither Green Depot.
Well done to the person(s) that spotted it and took the decision to call for replacement diesel. Hopefully this problem can be repaired quickly so that 60163 is back gracing the main line.

 

Not only that, but hopefully the Class 66 could arrive in good enough time so that passengers going all the way back to Newport etc. don't have too late a finish.

Regards,

Dan

 

I do hope it's not serious and can be fixed with minimal effort

 

Yesterday's tour was still good,despite the problems. Well done to all at Pathfinder,DB and NR for coming up with a solution and also for providing us a clear run right through the London suburbs in both directions. Tornado was in fine form on the outward with some great sound effects and acceleration.

We left Canterbury about 7:15 and were in Didcot for 22:15 (home for 01:30 so 6 hours Canterbury-Wakefield isn't too bad!) so that was just 45 minutes late,hats off to all for such a good pull back,mainly by missing Victoria out. Thanks to the signaller who got us fast line from Acton,i think we nearly kept up to HST timings :O

Tornado made it back to HG under its own power,so hopefully its not major.

Cheers,
Mark

 

A bit of "official" info here.
http://www.a1steam.com/index.php?op...for-inspection&catid=1:latest-news&Itemid=123

 

Showing my ignorance here (or my young age).. what function does a stay perform ?

 

For goodness sake man - basic engineering

Fireboxes are generally square, whereas a vessel under pressure will naturally seek to adopt a spherical or cylindrical shape - accordingly to maintain the straight-ish sides of the interior and exterior of the firebox the walls and roofs are structurally supported and connected by hundreds of stays arranged in close set rows over the entire structure that prevent the natural distortion and retain a flat plate surface.

They accordingly have not only to withstand the boiler pressure itself, but also the physical forces attempting to deflect the steel and copper from their design square-ish shape to the spherical that the pressure seeks to adopt

 

But not basic engineering to someone who's not a steam engineer. I'm sure there are subjects about which you're far from "au fait."
Just out of interest, is the spacing of the stays in a round topped firebox markedly different from those in a flat topped one?

 

If you have any interest in steam preservation - and over 1,700 posts on here and an international career in project management etc, implies more than a casual interest; I am amazed that something as basic as this is not innate knowledge.

I am no engineer myself, but the basic structure of a loco firespace is the origin of how the thing works prima facie - fail to understand that and you aren't at first base. There again, I fear that many posters on here know more about a keyboard than a fooplate or how a loco is actually constructed and operated.

As to a round top firebox - you are still trying to create rigidity and uniformity of dimensions and clearance between inner and outer wrappers - so there is little visual diference to the staying adopted.

Now take a look at an LNWR firebox with its topside girders with screwed in stays holding the inner and outer wrappers separately - there's a structural nightmare for you. I don't think the coal tank's stays had been removed in generations when looking at the remains of what was extracted a couple of years ago. They are all new now!

 

Which is exactly why us older and supposedly more knowledgable types should answer honest questions without giving people a slap !

 

There is a simple drawing of a boiler/firebox and location of some firebox stays here:

http://wapedia.mobi/en/File:Fire_tube_boiler.gif

So, for those who also wanted the answer to ADB968088's question - now you know ! Enjoy

 

Does Tornado have screwed stays or welded stays?

I thought it was the latter?

Jim S

 

Being pedantic, the tops of the firebox in a round topped and a Belpaire firebox are both flat or, at the most, slightly curved. It is the outer wrapper that differs. With a round topped boiler, the outer wrapper, being round is naturally self supporting so doesn't need staying. The Belpaire wrapper, with its flat(tish) top needs supporting in a similar way to the firebox and this is generally achieved by crown stays, connecting the two surfaces of the firebox crown and wrapper. This is one of the big advantages of a Belpaire firebox. With a round topped wrapper, the crown stays have to be attached to the wrapper at varying angles, which is a complex fixing. As an alternative to this, some boilers have sling stays or girder stays to support the firebox crown.
The attached thumbnail shows the staying of a round topped wide firebox boiler quite well and gives an indication of the angle at which the crown stays meet the outer wrapper

As regards stay spacing. This is generally the same and more dependent on boiler pressure/plate thickness than anything else and applies equally, whatever the type of boiler. Usually about 4" centres for 160-180 psi closing to about 3" centres for 225-250psi for flat plates of 1/2" thickness. If you want an empirical formula, plate stress = ( Pressure x pitch of stays2) / (4 x plate thickness2) Pressure is in psi, pitch & thickness in inches.

 

Just because its obvious to you and I what a stay is, doesn't mean its a prerequirement before you dare post on this board, lest someone bite your head off.

 

Right, we have had quite a discussion on stays and different types of firebox and thanks to all who have taken the time and effort to explain such.

Please feel free to continue the discussion on this, perhaps in the locomotive MIC section here:-

http://railways.national-preservation.com/forumdisplay.php/43-Mutual-Improvement-Classes

or the progress on Tornado here:-

http://railways.national-preservation.com/showthread.php/10750-Tornado

Thanks, Neil.