[graham.d (OP)]

This object was discovered during building work being undertaken at my neighbour's house. I don't know what it is. It is very heavy and seems to be made of steel. Well engineered and surprising not very rusty. The structure is hollow - maybe some sort of water jacket - and seems to have guides to allow accurate butting to another structure. The steel is at least 5mm thick and no obvious signs of welding - it looks well machined. It may also abutt so as to form a hollow asymmetric tube, but I can't be sure.

Houses here were built around the mid 1920s. We are close enough to London and Biggin Hill Airfield that bombs fell and aircraft were shot down in this area during WWII but it doesn't fit with any bit of a bomb or aeroplane that I know.
 
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[graham.d (OP)]

Hmm, could have posted bigger pics. My computer told be they were 126kb but they seem compressed better than that.

[Geezer]

Hmm, could have posted bigger pics. My computer told be they were 126kb but they seem compressed better than that.

You forgot to "insert image into message". I fixed it for you  []

[Geezer]

Looks like one half of some sort of manifold. But there is no obvious means of attaching it to another half.

Was there ever a gasworks near there?

[graham.d (OP)]

Thanks Geezer. I've never posted a pic before.

No gasworks around here as far as I know.

[Geezer]

It may be a casting that was never completed in terms of fixing holes etc., perhaps because there is some flaw in it, although it does look as if some of the "ports" were drilled and tapped to connect with a flanged pipe.

[graham.d (OP)]

It can't be a casting. It's hollow and it looks like there are inlets and outlets for fluid (water?) to flow around the inside of the casing. If it was solid I would not be able to move it. As it is I'm guessing it weighs well over 150lbs. I can see in these inlets and poke a screwdriver in. The inside of the casing seems to be fairly free from earth. The inlet and outlet are theaded. I don't know what the "access" plates would be for - cleaning/servicing perhaps. There are also other bolts on the thing but I can't see what they are for.

If you look at one end - as though seeing the horseshoe shape - there are raised strips (about 4mm high and 3mm wide). I think they may be designed to locate (in slots) with some other device. I can't think what else they are there for. It must be expensively machined (at least) to make these.

[Geezer]

Why do you think it's not a casting Graham? I think it's pretty unlikely something like that would have been machined out of a solid chunk of steel. If it's not made of cast iron, it could be a steel or semi-steel sand casting that has been machined, although I don't know why it would be necessary to machine it all over.

Mind you, none of that really helps much in determining what it actually is!

I would have thought there would be tapped holes around the ends and the straight faces at the ends of the U, but it does not seem that there are any. It's hard to imagine how it could sustain any pressure otherwise. That's why I was speculating that it may never have been finished.

[graham.d (OP)]

I was thinking it would have been made from plate steel bent into shape then welded. Then subsequently machined to get the adjoining surfaces smooth. I am no expert in the mechanics of this though. How can it be cast if it is hollow inside the curved casing?

I did wonder whether it could be a part of a coal or wood burning stove which heats water in an outer jacket. It seems a complicated construction for such a device but there were things like this in the 1920s (from the internet) though they seem to be cylindrical. If it was designed to be against a wall on one side it may explain its shape.

[Geezer]

Ironworkers have all sorts of tricks that they use to cast hollow objects. They would make "negatives" of the inside and outside in sand from a wooden pattern. The two would be held in the correct relative positions in the mould box and the molten steel would be poured into the void.

The sand negatives are destroyed when the casting is removed, but that makes it possible to cast some very complicated shapes.

[Geezer]

I did wonder whether it could be a part of a coal or wood burning stove which heats water in an outer jacket. It seems a complicated construction for such a device but there were things like this in the 1920s (from the internet) though they seem to be cylindrical. If it was designed to be against a wall on one side it may explain its shape.

You know, you could be right. It might well be some sort of back boiler that sits around the fire in a fireplace to heat water. I was assuming the "ports" went right through to the inside of the "U", but it does not look as if they do. If it is a back boiler, the whole thing is actually hollow and probably cast as a single piece in iron.

[graham.d (OP)]

Perhaps it is cast then. I'm rather ignorant of casting techniques; how is sand used? It must have to retain a shape (the negative of the inside) whilst the molten iron is poured but then "flow" like sand to get it out of the holes. Could that be why there are extra "ports" which are blanked off with bolted plates: so as to get the sand out after moulding?

The other feature is the fine ridges that look like they are for aligning to another structure. Could they be part of a casting too? I tend to think of castings as not being able to produce such detail, but I would suppose it maybe more likely than this whole thing being machined. Is there anything definitive that I could look for?

It is quite big for a domestic back boiler but being part of a wall mounted stove is possible. It seems unlikely that this was ever part of my neighbour's house (or mine) because of its size. It may be that it was on the site (dumped) when the properties were built. There were much older and larger properties not far away, since demolished.

[Geezer]

Perhaps it is cast then. I'm rather ignorant of casting techniques; how is sand used? It must have to retain a shape (the negative of the inside) whilst the molten iron is poured but then "flow" like sand to get it out of the holes. Could that be why there are extra "ports" which are blanked off with bolted plates: so as to get the sand out after moulding?

I have no practical experience of casting - only know a bit from what I've read - the "sand" is a fairly complex mixture of ingredients and it does retain its shape and can reproduce some remarkably fine detail.

Casting is quite an art. Those cast iron central heating radiators that used to be common in the UK are constructed from sections that are cast. They must have had a clever technique to cast them complete with the internal spaces for the water.

Here's a wiki link that has far more information than you probably want to know  []

http://en.wikipedia.org/wiki/Sand_casting

[graham.d (OP)]

Thanks, Geezer. I will have a look. In the meantime I reckon you maybe right about it being a back boiler. If you look at the first picture, I think that is just how it's supposed to be used. The three little widgets at the bottom are probably to support the grate. I think the whole thing was fitted, like that, into the fireplace and was an open coal fire. When that way up it also permits a cold feed and hot outlet to allow convection feed to a hot water cylinder's heat exchanger. I'm fairly convinced.

I would love to be able to identify the maker but I can't find many pictures of old fireplaces on the web and there is no maker's name plate on the boiler.

Looks like their builders can dump it in the skip now. Shame, but can't do much with it. It must have been buried around 50 years and is in quite good condition considering that.

[imatfaal]

I have seen a lot of original fireplaces - but never one with a nifty gadget like that.  seems a little extreme and I would hate to be close when it got airlocked or blocked.  perhaps they never really caught on - or perhaps designed for bigger houses than I have ever owned/rented/visited

[Geezer]

Graham, I doubt if there even was a heat exchanger in the tank. I think the water would circulate between the tank and the back boiler. My folks had a Rayburn stove with a back boiler, and I'm pretty sure it worked that way. When my dad got a bit too ambitious with the anthracite, you could hear the tank rumbling as the steam from the back boiler got to it. It ran for at least fifty years without any problems.

[CliffordK]

Can you find any text on it?

I like the idea of a heat exchanger or hot water heater as part of a stove or furnace.

[imatfaal]

agas in the uk will heat water as well as the room they are in

[graham.d (OP)]

Graham, I doubt if there even was a heat exchanger in the tank. I think the water would circulate between the tank and the back boiler. My folks had a Rayburn stove with a back boiler, and I'm pretty sure it worked that way. When my dad got a bit too ambitious with the anthracite, you could hear the tank rumbling as the steam from the back boiler got to it. It ran for at least fifty years without any problems.

Yes, you may be right here. The house I was brought up in also had a coal fire with a back boiler which occasionally caused boiling. We did have a leak once which caused staining on the wall at the side of the chimney breast. The back boiler was a rectangular box at the back of the fire. There was a flap that could be operated which allowed more heat/combustion-gases to go under the box rather than straight up the chimney. It also worked at least 50 years.

[SeanB]

Don't dump it, rather use it as a feature around the garden. Old metal lasts pretty much forever outside.