34039 Boscastle WC class

That's the point. With a copper box you are going to need a foundation ring.

 

Please could any of the learned peeps on this subject explain how a thermic syphon works. I have a general idea from its title, but cannot visualise it and have looked everywhere for info but I just cannot find ought.
Thanks in advance,

Chris

 

Not sure I am learned but a thermic siphon is a device which gives additional surface area for heat transfer in the firebox. There were many types tried over the years and even cross flow tubes were proposed (did any of these actually make it in to service?).
The first siphons were a bath tub like shape was let in to the top of the firebox, developments looked interesting then Nicholson proposed feeding the bottom with cooler water from the throatplate area.
The shape is like a slanted Y with the leg being connected to the firebox tubeplate and the open part exiting on the firebox crown.
I had a copy of a paper published in the proceedings of the I.Mech.E but it is probably back on the UK. This was a great summary of efforts to increase boiler efficiency which seemed to lean heavily towards feedwater heating. The date was the 1950's so I guess it was trying to drum up support for what became the 9f project.

 

This is an inside view, below the cladding that hid everything - it's actually from an E10 4-2-2-0 rather than a 4-4-0, but the boiler construction is essentially identical. There were two banks of cross water tubes; those at the front inclined upwards from left to right; those at the back sloped the other way. One of the manhole covers that covered them in service is lying on the ground in front.

I've often wondered about the boiler washout procedure, and in particular whether the cross water tubes were washed out at every washout - if so, that is a lot of extra work to remove the boiler cladding and insulation around the firebox, then the manhole covers, then do the washout, then put it all back again. No wonder Urie reckoned they were more trouble than they were worth and got rid of them as and when fireboxes needed replacement.



Tom

 

Not learned but interested. It helps to consider the Bulleid boilers in the context of loco design outside the UK, where as in much else, the USA tended to lead. Thus wide, steel boxes, were the norm in many countries and it was normal to fit some circulating device (which was easier in steel than copper). I attach a page from Bruce's "The Steam Locomotive in America" (Bruce was director of steam loco engineering at ALCO), and interestingly he refers to these as methods of brick arch support, which may indicate what he thought about their claimed steam raising properties. The top configuration, arch tubes, was the most common, presumably because it was simplest and cheapest. The "inverted T" circulators were used on some large locos including the South African 25s and the Russian P36s. On syphons in particular, I attach one page of an article from the Locomotive Cyclopedia of 1930 describing these. Bear in mind that Locomotive Cyclopedia was written by the advertisers whose job was to sell product, so not surprisingly, all sorts of benefits are claimed for syphons. Note that the main diagram is of a loco with two sets of syphons, the forward ones being in the combustion chamber.

 

It's interesting that there are several advantages to syphons referred to in the latter article, but the one Bulleid explicitly refers to in his comments (your post No. 20) is about keeping the crown covered even if the water level gets low. That factor, and the support to the brick arch and firebox crown would seem to me reasons to keep them on preserved locos; removing them would lead to a host of re-design troubles.

Tom

 

An experienced Bulleid loco fitter, on looking inside Tornado’s firebox said, “what holds the roof up?”

 

That one photo answers a lot of questions, much clearer than diagrams I've seen previously.

 

When I had the same question, I found a good source, but cannot now re-locate it. I did find this which is pretty good.

To add to what others have said, it's a multi-function device; that note lays them out pretty well. Primarily, it takes cold water entering the boiler, runs it through a narrow channel in the hot part of the firebox (thereby improving the heat transfer), and exhausts it onto the firebox crown, which is the area that could most use the extra cooling; the fact that it's heated before it gets there reduces the thermal shock.

Noel

 

Thank you for the information supplied guys, I now have a much better understanding of it all. I did not appreciate the other advantages it has from the little I knew either .

 

The new inner firebox has been trial fitted to the boiler and it has been NDT tested, with approval given from the boiler inspector. The new tender tank (5250 Gal) is on order for delivery "late Summer" ....so good progress.

 

Saw the boiler last weekend. Progress looked to be good.

 

Does anybody know what happened after the Mercchant Navy was tested at Rugby without thermic syphons in the firebox?

The report states that it steamed as well and the the super heat temperature was higher.

When was the modified inner firebox removed: soon or directly afterwards or did the locomotive run with it for some time?

 

SNCF did experiments on some american made 1-4-1Rs with thermic syphons and made the same conclusion that they were not really worth the bother.
The heat extracted in the syphons are not available for the tubes and superheaters , that are miles cheaper and easier to maintain.

 

There has been some shunting in Loughborough shed and Boscastle is in a new location. (Photograph by A. Morgan)

 

I'm a bit late to this but do Bulleid siphons look a bit like this?

Looking at the photo of Boscastle undergoing restoration in the 70's, i'm reminded of 34016 looking much similar at Quainton Road, and what an extraordinary aesthetic difference a pair of smoke deflectors can make

 

Hi Ross
Yes that is the thermic syphon, painted blue, in the firebox. The red painted with white stripes part, is the section through the brick arch, which is between and either side, of the two syphons. Ellerman Lines at the NRM is very useful!

 

Ellerman Lines would be even more useful if the huge brains at the NRM could manage to get the rollers under it working again. Then it could usefully explain how the valve gear works.

Bet it would cost less than the rebrand/logo change did.

 

The rollers were removed a long time ago.