Northumbrian Build Thread

[steam4ian]

G'day Pete

Keep trying with the fireboxes. It looks like you are developing the skills to form the firebox out of one piece.

Note Doubletop's advice regarding not annealing before machining. Don't ask me how I know, work things back to hard before machining.

More hot weather coming!

Regards
Ian

[Smifffy]

10 out of 10 Pete.

I'm very impressed, keep at it :-)

Smifffy

[jma1009]

i can only second Smiffy's comments! excellent work! so pleased you havent gone down the commercial boiler route that seems to prevail at the moment. boiler making is really quite straightforward and easy so long as certain fundamentals are observed, and in next to no time you have a major part of the loco completed (usually about 6 weeks spare time in my case).
well done! hope to see further progress over the next few weeks!
cheers,
julian

[philh1]

Excellent Pete, keep going with the copper bashing. I will be joining you soon.

I went a bit light headed when I saw the cost of silver solder so I am just building myself up to looking at it again.

PhilH

[peteh]

Mar 5, 2013 20:38:07 GMT philh1 said:

I went a bit light headed when I saw the cost of silver solder so I am just building myself up to looking at it again.

PhilH

Yep - It's a bit of a shock to the system. I brought some older cadmium bearing stock from CUPalloys around 2 years ago, just as the cadmium free was coming in. Luckily I was over to visit my Mum at the time so didn't need to pay postage to Australia as well . Did not get various temp types though and wondering if this will be a problem later.
On another point - I can no longer get MAPP gas cartridges for my gas torch, so will have to get a bigger burner for my propane torch.

[doubletop]

Mar 6, 2013 2:22:56 GMT peteh said:

On another point - I can no longer get MAPP gas cartridges for my gas torch, so will have to get a bigger burner for my propane torch.

Pete

If you are thinking about new propane burners. I have a sievert torch with the older type burners. It was hopeless doing the inside of the firebox as it kept going out in the enclosed space. I then got hold of two of the Sievert cyclone burners from Reeves in the UK. Even with the shipping they were 1/2 the price of the local BoC outlet. The air intake for the cyclone burners is at the handle end so no issues when using it in an enclosed space. My 86Kw 2944 burner now only comes out when some serious heat is required, like the boiler barrel.

I go back to my previous point whether a MAPP gas cylinder would have enough heat capacity for even a small boiler like this. Others may be able to advise?

Pete

[jma1009]

pete,

when you come to silver solder up the boiler it's a good idea to read as many construction series as possible. don young's RAILMOTOR description in ME 1968 is one of the best IMHO, as is LBSC's JULIET boiler in the mid 1950s.

certain things have changed over the years... very few of us would ever now use coke for packing around, and gone are the days of the 5 gallon paraffin blowlamp which i started my first boiler with.

martin evans always used to say turn down tubes to a press fit in the tubeplates...we now make them 2-4 thou loose with a couple of nicks with a triangular file too.

a great deal of thought needs to be spent in thinking about each stage and where to put the firebricks and how many to contain the heat and still give easy access and get the heat in the right place and without making the throwback of heat so intense that it is difficult to apply the silver solder. i might spend 45 mins arranging and rearranging the firebricks and fluxing everything up...for a heat up that takes 10 mins, and 30 expensive seconds applying the silver solder. the appropriate flux (something that will stay active for a long heat up and be a bit more aggressive than ordinary easyflo flux) is required, and lots of it.

preparation and cleanliness of the joints is essential, and dont let the silver solder melt in the flame...it should be melted by the heat of the copper.

yours is a relatively small boiler so in theory no problems should be encountered and easyflo and later easyflo No.2 should suffice throughout and will make the job a lot easier for a beginner. you must have sufficient heat (a combination of the heat source plus reducing heat loss) to heat the joints up within a reasonably short space of time. as the boiler construction progresses MORE HEAT is required as the increasing mass of copper soaks up the heat.

at some early stage you need to decide how you are going to fix the firebox boiler stays... as this determines quite a bit the sequence of operations on the inner firebox. if they are to be silver soldered then you need to consult some of the later boiler construction descriptions, and alter your method of construction to suit your heating equipment, and level of expertise/confidence. you cannot apply silver solder into an inner firebox of a small boiler with a propane torch raging away as well without leaving the firebox doorplate off... the silver solder will get caught in the flame, and as doubletop has pointed out unless you have a cyclone burner the flame will go out in the confined space. ive never used oxy-acetelyne, and i never intend to, and unless you know how to use it properly on a copper boiler ignore anything said about using it as it is totally irrelevant and could easily lead you to assume a sequence of operations and construction that are totally unsuitable for propane or the gas that you are using.

dont expect the job to look like a professionally made boiler... silver solder will run everywhere on occasions and you will use far more than you might expect. however dont forget that silver solder cant form a proper joint on a tight joint where it cant flow, or a dirty joint or where there is no flux. on the otherhand silver solder isnt a 'filler' and gaps should be avoided, and the sequence of heating considered to avoid any gaps forming over parts that may move with different rates of expansion during the heat up process. any rivets should have a ring of solder round them and shouldnt be closed up so tight that the silver solder and flux cant penetrate the joint. i also use a long thin length of stellite rod with a pointed end to run round joints whilst they are still liquid to break up any flux bubbles and ensure the silver solder is doing its stuff.

i never turn the ends of barrels or tubes. dont see the point. dunno why anyone would want to turn the end of a barrel when it's hidden in the joint with the smokebox!

anyway that's my 2 pennyworth at this stage!

cheers,
julian

[jma1009]

it wont be too long till you get something like this!

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[peteh]

Cheers Julian, I'm not the quickest worker - usually only getting part of Sundays at the moment for ME stuff.

Having cut down a lot of the surplus I think I have 2 good firebox ends. One of our boiler inspectors is nearby on Saturday*, helping run the Sausage sizzle for one of our local machinery firms sales day, we put on a display and cook the free snags and get a nice donation for our club and year long discounts I'm going to run these past him before getting onto the other plates.

* Just realised that is the NEXT weekend - 16th.

[peteh]

Image didn't come out on the previous post - trying again

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[philh1]

Julian,

Many of the articles that I have read indicate the use ot at least 2 stage silver soldering i.e., a higher temp alloy 1st and CuP alloys from the UK even supply alloys for three stage soldering. Would you not recommend this for a boiler like Northumbrian?

PhilH

[jma1009]

hi phil,

that is a very important point you have raised and one with which im sure many will have lots of different opinions. the lower melting point silver solders are the most expensive but are easiest to work with so far as flow characteristics etc are concerned for a beginner. silver soldering a boiler can be very daunting and sometimes nerve wracking and anything that makes the job easier in my book is a benefit, especially for a beginner. we all probably have a different interpretation of what amounts to 'easier'.

the cost of silver solder is pretty immaterial in my book when you compare to the price of the alternative ie a commercially made boiler.

therefore my personal preference is to use the most expensive silver solder and the easiest to use.

the above pic of the last boiler i made was made initially with the non- cadmium Johnson Matthey silverflo 55 (CupAlloys provide a suitable grade of this type) the equivalent of the old easyflo. final stages and the tubes were done with easyflo No. 2. i always use Thessco F flux for boiler work as recommended to me by alec farmer of Reeves many years ago (again CupAlloys provide a suitable alternative). only 4 rivets were used in the whole of the boiler... to attach the crown girder stays to the top of the inner firebox. i could quite easily have used a different higher melting point grade of silverflo for the throatplate joint and some of the sub-assemblies. each to their own and there isnt a right or wrong way in many cases.

i do have a few personal quirks when making my own boilers, again as recommended by alec farmer, which i think makes things easier for me and suits my idea of how to put the thing together in the easiest way. one of the most difficult stages is fitting the foundation ring, and i fit the front part of the foundation ring to the bottom of the throatplate with sifbronze before fitting the throatplate to the boiler. i also fabricate the crown stays with sifbronze, and attach the firehole ring to the inner firebox doorplate with sifbronze, again all recommended by alec farmer. all these joints get run over with silver solder in any event later on. i also like to braze the dome bush to the barrel early on and adopt alec farmer's advice of only turning a small register on the dome bush.

the standard LBSC/martin evans type throatplate joint is a simple butt joint in effect and great care must be taken over this part of the boiler early on if this type of joint is adopted, and to ensure it doesnt shift if you are careless later on when getting nearby jobs up to heat for subsequent stages. very careful placing of firebricks (i use thermalite blocks) can help enormously. the slower less localised heating using propane i think also assists preventing problems occuring with previously finished joints.

once you get into the swing of it, it isnt really that bad and it's one of those things where once you start making the thing you wonder why you had been putting it off or not done it before!

cheers,
julian

[philh1]

Thanks Julian,

I hope Im not hijaking Petes thread too much but would you mind adding just a couple of words of clarification please?

Is Thresco F the equivalent of Tenacity Flux?

Why do you believe the foundation ring is a bit tricky - is it difficult to get a good fit, or more heat is required or even simply difficult to hold in position?

Can you clarify a little bit regarding the 'small register' on the dome bush. Do you mean you use a shorter length of spigot on the bush that enters the barrel or do you make some form of adjustment to its diameter?

Do you ever use the equivalent of asbestos sheeting to protect previously finished joints like the tubes? My main concern is the fixing of the rivet style side stays because a lot of joints have been completed before this stage. I would imagine that it is easy to accidently remelt the solder round the ends of the tubes inside the firebox whilst you are concentrating on the stays.

PhilH

[jma1009]

hi phil,

i believe Tenacity 4A flux is the equivalent of Thessco F flux.

most people add the foundation ring as the last braze up together with the backhead etc. IMHO there is no reason why this job shouldnt be simplified by doing the front section of the foundation ring early on. one less problem to worry about when doing the final braze up. having inspected many boilers with dodgy foundation rings it has always appeared to me that this is one of the most difficult bits... both heat wise and fit wise. if the front part of the foundation ring is done earlier on it also aids lining up and fitting the inner firebox and crown stays, and the front part of the foundation ring can be shaped in such a way to provide a simple butt joint with the sides of the foundation ring later on (ie the front part of the foundation ring is full width with shaped ends to fit in the flanged joint between the outer firebox wrapper and throatplate.

dome bushes...usually these are shown with a deep rebate with a lot of metal being turned off. alec farmer's advice was to turn only a shallow rebate... just enough to locate the dome bush. a larger hole in the copper is required, but the bush acts as a useful heat sink when silver soldering, and the holes for the dome studs or bolts can be made blind. all don young's later designs follow this practice.

ive never used asbestos to sheild joints already done from the flame... just plenty of thermalite blocks cut up to size and shape.

for the silversoldering of the firebox stays i use the method used by the late bill carter. it is somewhat labourious but well worth it IMHO. i do one side of the firebox at a time. the holes are drilled and then deburred all sides, and countersunk inside the firebox and on the outside of the outer firebox. i then silver solder one side of the firebox at a time as follows... using a jig i make up rings of silver solder 2 for each stay. the stay is inserted from the inside (leaving plenty sticking outside to act as a heat sink) and 2 rings added to each in the water space. i work along furthest from the back with the inner firebox doorplate left off. takes ages! then the whole side is fluxed inside and out all sides. a few phosphor bronze threaded 'rivets' are made up and put near the foundation ring sides which are also added at this stage, and a few on the last column of stays nearest where the inner firebox doorplate will go to ensure the gaps remain the same. the inner firebox is then heated up with the side im not doing and the tubes sheilded by thermalite packing. the boiler has the bottom of the firebox facing up, and thermalite blocks underneath and on the side im not doing and blanking off the smokebox end and a block on top of the barrel. in next to no time the copper heats up and the silver solder can be seen to flash through from the water space around the rivet heads inside the firebox. no need to get a stick of solder anywhere near the flame. then the outside of the wrapper has similar treatment and a flash around the end of each rivet will be seen. finally, and this is where tenacity 4A or thessco F helps coz it's a relatively long heat up, i add a bit more flux to that side of the foundation ring at the top and silver solder that in position using silver solder rod applied to the hot copper.

getting the inner firebox doorplate to fit after doing both sides of the above isnt too difficult. the stays and firehole ring between that and the backhead are already brazed on. the tricky bit is getting the holes for those stays and the firehole ring to line up on the backhead....but it doesnt take too long... about as long as it takes to drill tap and fit cylinder cover bolts to one end of a cylinder.

i am sure others might be able to suggest improvements on the above method. making the rings of silver solder a tight fit on the stays so they dont move and stay hard up against the plates takes ages as does getting them in position, but as the silver solder isnt 'in the flame' you can heat the plates up direct from the opposite side of where the silver solder rings have been applied.

in actual fact i find deburring the stay holes after drilling takes the most time!

i hope the above explanation isnt too tortuous!

cheers,
julian

[peteh]

Phil,
You are not hijacking, just increasing the knowledge on this thread for fledgling boiler makers like me and thee. Please continue to ask here, and many thanks to Julian and all the other who have contributed their knowledge.
Got a larger burner for my propane torch today but very hot and muggy so not sure if I'm going to brave the workshop today

[philh1]

Julian,

Brilliant. That description is excellent. I had noted the '2 ring' technique for side stays before but for me, yours is the clearest description that I have read so far. I hope you don't mind answering a couple more?

The first question relates to the throatplate. The throatplate itself should have a reasonably generous radius between the flat surface of the plate and the side flanges (to minimise stress). The cuts in the boiler barrel are typically carried out with a hacksaw with sharp corners. This means that when you fit the throatplate - in theory - you will see daylight between the plate flange radius and the corner of the boiler barrel. On some drawings, a generous fillet is drawn which might suggest a lot of solder is fed until the daylight disappears. Is this daylight not as bad as I think it will be or does it take some careful 'adjustment' with a mallet to close the gap?

You also hint at my next question in your previous answer for the foundation ring. The boiler construction manuals always suggest a piece of square copper for the ring but surely the front and back sections of the foundation ring will need a wider section to accomodate the shape between the firebox wrapper and the radius on the firebox plate flanges? I have visions of an expensive silver solder rod disappearing into the possible void but a small hole remaining.

Pete - I am going to get one of those fangled cyclone neck/ nozzles for my torch. It sounds like I might need one for those peskey side stays.

PhilH

[jma1009]

hi phil,

you are quite correct about that gap at the top of the throatplate each side where it is supposed to join the outer firebox wrapper. i have never seen it commented upon before in print. i machined out of copper 2 pieces with a quarter of a circle and a slight rebate to add to this gap on my last boiler which had this method of construction that i'd not used before. otherwise it is a potential source of weakness and difficulty. i made a few dummy ones out of brass that ive still got somewhere so if i find them in the junk on the bench i'll take a pic. (previous boilers ive made have had a double flanged throatplate and a separate outer wrapper to the barrel avoiding this problem).

the slightest error in hacksawing the split between barrel and outer wrapper of course makes that gap greater.

i managed to obtain a slab of C106 copper which i make the front and back pieces of the foundation ring out of. think there's just enough left for another boiler. in fact the square rod you mention is now extremely difficult to get in the correct size anyway.

although the double flanged throatplate entails more copper bashing and making of formers it has certain advantages. you avoid the butt joint between throatplate and barrel so beloved of LBSC and martin evans, and the water space between front of the firebox and barrel can be given a generous curve which aids water circulation. certain boilers with this butt joint are known to come apart even in the most skilful of hands at this point in the course of latter silver soldering stages... LBSC's BRITANNIA being perhaps the best known culprit.

cheers,
julian

[philh1]

Julian,

Once again, you have helped enormously. I guess one way to overcome the throatplate issue is to very carefully file the underside of the barrel to match the throatplate shape or use a shaped strip of copper that wraps round the underside of the barrel?

I will try to get some copper section for the foundation ring and file it to shape.

I think the come apart bit of the throatplate pushes me towards using a higher temp alloy for this first joint and maybe use a couple of rivets to ensure it stays put.

PhilH

[doubletop]

Just to chip in on the flux. I had a devil of a job getting anything to work on my early simple boilers. I only built the Northumbrian because I wanted to try my hand at a proper boiler. The advice I was given was to use Tenacity 5, its a flux for stainless. I couldn't get hold of it in NZ but my supplier offered Harris Stay-Silv® Black Flux. Its also a flux for stainless. I've haven't looked back and never had a failed heat up. I've tried silver soldering stainless and had no problems at all.

The one problem I did have was chasing leaks. Each time I dealt with one another joint gave a problem in the leak test. The problem areas were the corners of the cuts to the barrel and the joint to the throat plate. and the foundation ring. Attention has to be paid to getting joints tight and don't expect the silver solder to bridge any gaps. It won't.

Now this bit may be contentious, and I didn't do it. One of our club members with a scientific background suggested that if you have any small gaps sprinkle copper dust or fine copper turnings. If I remember correctly the silver solder forms a chemical bond with the copper at the interface and the combined copper dust and silver solder has a far higher melting point than raw silver solder so is less like to re-flow on a subsequent heat up. I guess the copper and silver solder just holds hands and helps to bridge the gap. First up though don't have any gaps to start with.

Pete

[philh1]

Thanks Pete,

I am currently looking at the CuP alloys pages and they seem to have the equivalent fluxes.

I am very surprised that these issues (boiler barrel/ throatplate and foundation ring joints) are not described in much more detail because they look to me like the tricky bits as regards accurate fitting. And as I said previously, the descriptions tend to say use bits of square copper which don't look to me as if they will always work for the front and back.

Just so you understand where I am coming from, I have done silver soldering before - many years ago as an apprentice. I spent 4 months in one department where the silver soldering of small bore 1/2" to 3/4" copper tube assemblies was a daily job - all done with oxy-acetylene. A boiler is much more of a challenge but I have previously experienced running out of solder and nearly burning my fingers because the solder has disappeared down a hole that was never ever going to 'bridge'.

I will definitely pay attention to these areas as I fabricate them.

PhilH