P2 Locomotive Company and related matters

In the States, while the cups are welded to the boiler, the caps are screwed into the cups, potentially allowing stay renewal without changing the cup.

https://www.midcontinent.org/staybolts-help-1385s-boiler-keep-in-shape/

 

I'm glad that I'm not the only one to be confused by @W.Williams statement. U shaped foundation rings are forged to that profile and certainly don't have square corners.

It's usual practice with flexible stays for a cup to be welded into the outer wrapper, whether the firebox end is riveted or welded. The stay itself has a spherical end to fit into the cup and there is a screw top fitted after the stay is installed.

 

Meiningen don't appear to use screw caps; they appear to be welded. In fact, they must be welded as there is no way of turning them.

 

I wonder what that does to their supposed flexibility?

 

Mid Continent aren't a good source for steam expertise unfortunately, very much a diesel operation, but to their credit they survive without a large population nearby and the competition of the various attractions of Wisconsin Dells of course.

 

Exactly. That was my interpretation of the pictures that I’ve seen. To be honest I’ve not seen the assembly process, but those covers have to be welded.

 

But that's the way they do flexibles in the States. The Big Boy has the same.

 

It should be OK as long as the weld is well away from the stay. It won't leak but the cup won't be re-useable. If you had to do any amount of work on either sheet, with this amount of flexibles, the easiest way would probably be to replace both inner and outer sheets. That might explain why 60163's throatplate fouled the rear drivers after overhaul? With the American method, you only have to drill out the inner end to remove the stay.

 

This is becoming a pretty hilarous discussion on geometry!

Saying in which plane the U resides is probably the way to avoid all this churn.

Tornado has internal forged U's, but the underside of the Found, that is the bit you can see is flat. Like other gresley boilers.

The Bullied one is interesteing, id never seen that and hadnt realised it was effectively more rolled plate, a fairly elegant solution to the problem, and quite flexible too!

WRC Video #18 - Flexible Staybolts

How similar are the Flexible stays in the above to Tornado's?

 

You need to be slightly careful saying “Bulleid” foundation ring as they differ between Merchant Navies and Light Pacifics.

On an MN, the foundation ring is essentially a conventional forged “bar” type, with the inner and outer firebox sides riveted in position.

By contrast, on a light Pacific, there is a u-shaped channel that runs round the bottom of the firebox, and the inner and outer sides are welded to that channel, essentially forming a single piece of metal that runs down the outside of the firebox, doubles back at the foundation channel and runs back up the inner firebox.

You can see that foundation channel clearly on the photo on this page with just the inner firebox and foundation channel.

https://www.bulleidsociety.org/21C123/21C123_Firebox_Appeal.html

The light Pacifics were designed later and the design saves weight, possibly confidence in welding techniques had improved as well. Obviously, it can only work if the inner firebox is steel - with a copper inner firebox, you have to have a conventional forged foundation ring and riveted construction.

Tom

 

The WC "channel" foundation ring was the subject of some of Burrows and Wallace paper to the ILocoE in 1958 on experience with the steel fireboxes. The foundation ring was fabricated from pressings (sides and corners). Initially there were problems with stay breakage, attributed to the greater flexibility, which was cured by controlled cooling down and substitution of monel for some of the steel stays "in the more highly stressed areas". There were also problems with the corners, which were not as flexible as the straight portions but this was eliminated by water treatment.

Prima facie, the flexible stays on the P2 boiler look like a Flannery two piece design. See attached images from the Flannery catalogue. Bulleid used thinner stays to avoid these save for around the diaphragms at the lower end of the syphons.

 

The 2 piece stays are pretty much what the 'New' boilers have, but with some differences, Flannery's diagram shows the cup simply seam welded to the wrapper, but in order to comply with British standards the welds need to be 'prepped' and full penetration. Similarly the firebox end is shown threaded, presumably screwed through the plate and nutted inside, in the German design the stay fits into a plain hole in the inner box, and is seam welded, in to comply with British practice the inner hole has to be prepped and full penetration welded. The inner end of the stay has a 'tell tale' hole drilled 'up the middle' which will pass water should the stay break.

In German practice stays are regarded as consumable, so any authorised worker can grind the seal welds off and replace a stay when needed, British practice regards stays as an integral part of the boiler which can only be worked on by an authorised person and a coded welder with all the associated paperwork involved. As has been pointed out elsewhere due to the grate area required within the boiler shell dimensions (dictated by loading gauge) the stays are shorter, and coupled with the full penetration welds considerably less flexible, so what works in one circumstance may not work in the other.