Soldering/brazing a boiler.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian John on 25/12/2014 04:04:50:

… Finding the exact centre is easy when you know how. First make a dot in the centre by eye using a fine tip marking pen. Then check it by putting it in a drill : look at it end on while you turn on the drill. If the dot wobbles about then you are not in the centre. < etc. >

.

Well done, Brian … you are in the process of re-inventing the lathe.

No, I am not being sarcastic: This voyage of discovery is an excellent way of learning.

In time; you may need to revise your personal interpretation of 'exact' … but what you have done is to make something fit for the present purpose, with minimal tooling.

Keep it up.

MichaelG.

[JasonBModerator @jasonb]

Brian, if you can hole your drill securely try offering up the pen while the rod is rotating it takes out quite a bit of teh trial and error. If you have a sharpie then start a bit off centre and it will draw a ring which you can gradually make smaller so you end up with just a small bare area in teh middle which is where to put teh punch mark. I use this quiet a bit when woodturning but just use a pencil.

The "Kaowool" or Kaolin wool blanket is some by the model trade here and often used on boilers

[Brian JohnParticipant @brianjohn93961]

I have got the little wobbler engine running nicely on air. It is a nice tight fit of the piston in the cylinder (it makes a pop sound when you pull it out by hand) and the cylinder spacer sits closely against the main frame. But when I run it on steam it only runs for about 45 seconds and then it runs out of steam….literally ! I am not sure what else can be done here other than to increase the heat source and hence produce more steam.

The 3BIM and 7BIM engines from PM Research run quite nicely on this Midwest boiler which was always the main point of building this kit but it would be nice to get the wobbler engine running like it should. The initial design of this boiler calls for Sterno fuel (and a soft soldered boiler) to be used but this would produce less heat so that should not be the problem.

Do the solid fuel tablets produce more heat than a spirit burner ?

Edited By Brian John on 27/12/2014 03:30:48

[JasonBModerator @jasonb]

The tablets produce a flame over a wider area so the bottom of the boiler will get heated, your small dia burner probably looses a lot up the flue.

Try restricting the amount of steam that can get to the wobbler, pinching the silicon tube will do for a try, it will act like a regulator as not let all the steam rush through the engine so it should run for longer but at a slower speed. If that works you can think about adding a valve to regulate the flow.

J

[Brian JohnParticipant @brianjohn93961]

I have made some adjustments and the engine runs successfully on one complete burn of the spirit burner. This only uses about 1/4 of the water in the boiler so I still need a bigger burner with a longer run time :

First I changed the the angle plates that the boiler was sitting on and used 20mm M5 screws instead as I did not think the heat was getting to the bottom of the boiler efficiently. Photo 1 shows what I used initially and photo 2 shows what I replaced it with.

I did try putting a clamp over the silicone tubing but that did not make much difference. I noticed that there was quite a bit of water forming around the top of the cylinder spacer where it meets the main frame so I tightened it up by adding an extra washer as per photo 3.

This did the trick and it runs like the clappers as in photo 4. I am building a small plinth for the engine to sit on but it still requires a few coats of clear polyurethane. I may also raise the boiler a bit higher to the next set of holes as I think it may be sitting too low and too close to the flame.

I do not like the way the top of the boiler ''ripples'' as it cools. The copper is only.38mm thick and was designed to be soft soldered. I hard soldered it and the extra heat may have made it soft…too soft ? I do not know but I wear full face protection when I am running it. I will build another boiler of the same design but the copper will be 1.8mm thick and should be much safer. I am also not sure about using wooden lagging. It looks great but it does char a bit around the bottom edges and may be more trouble than it is worth. Those boiler bands have to be very tight !

Edited By Brian John on 28/12/2014 04:05:43

Edited By Brian John on 28/12/2014 04:06:24

Edited By Brian John on 28/12/2014 04:12:11

[JasonBModerator @jasonb]

Brian if your wood is charing then you are probably loosing a lot of the flame and therefore heat around the outside of teh boiler. With the original tubular base the heat would have nowhere else to go but the base of teh boiler then up the flue which are all heating area.

Regarding the rippling of the boiler. when the remaining water/steam cools it will create a vacuum within the boiler, try and have somewhere open so the vacuum won't form

[Ian S CParticipant @iansc]

You would retain heat within the boiler by having a fire box around the burner. For a horizontal boiler I have about the same size, it requires three wicks about the same size each, as your one, this is barely enough to run the motor at full power to propel a small boat. the Mamod boiler that I have has a trough that is filled with meths, and has a large flame area.

A cylindrical fire box would keep the fire from singeing the lagging, and direct the heat up the chimney. You need a air inlet at the bottom, preferably bellow the flame level.

Just had a look on Google, the kit has a firebox, you should use it.

Ian S C

Edited By Ian S C on 28/12/2014 10:07:51

[Brian JohnParticipant @brianjohn93961]

I have some thin brass sheet on order which should arrive this week. I will construct something then. It will also help to protect it from the wind.

[FMESParticipant @fmes]

Posted by JasonB on 28/12/2014 07:34:52:

Regarding the rippling of the boiler. when the remaining water/steam cools it will create a vacuum within the boiler, try and have somewhere open so the vacuum won't form

Brian, just pull the cylinder away from the stand and put a pin or similar in the gap, this will let air enter the boiler as it cools and prevent a vacuum build up.

[Brian JohnParticipant @brianjohn93961]

I had cut away the bottom of the brass sheet which would have formed the firebox because it was so hard to work with and it looked unstable. I had another go today but the thin brass sheet (0.12mm or .005'&#39 is very tricky stuff …and sharp !

I have had a rethink and the easiest way to build a firebox is using some 50mm diameter copper pipe cut to a suitable length. I think 45mm should do. I will only have to cut a hole in the side for the burner to enter it and perhaps drill some 6mm air holes around the sides. I am not sure why I did not think of it before !

[Ian S CParticipant @iansc]

Shim brass is far too thin, it would need to be something like 18swg to 20swg, or a bit of stainless steel tube would look nice, although it will soon go blue.

Ian S C

[Brian JohnParticipant @brianjohn93961]

I have constructed a firebox out of 50mm copper tube…scrap yards are wonderful places ! I was going to just sit the boiler on top of the firebox as per the photos. Should I silver solder the firebox to the base of the boiler ? The aim is to prevent heat escaping around the base of the boiler and singeing the wooden lagging.

I

Edited By Brian John on 14/01/2015 05:26:32

Edited By Brian John on 14/01/2015 05:28:46

Edited By Brian John on 14/01/2015 05:29:34

[FMESParticipant @fmes]

I reckon you've made a really good job there BJ, but I think the support brackets make it a bit clumsy looking, Are they permanent or do you have some cunning plans in mind.?

Mind you, once you have the boiler attached to the firebox you shouldn't need those brackets.

I would have thought that the firebox could literally be soft soldered to the boiler, it will be easier than trying to get the whole thing hot enough again and risk running an already made joint, and as the soft solder would be in contact with a 'water cooled' surface its unlikely to come apart with just a spirit burner flame.

Lofty

Edited By Lofty76 on 14/01/2015 11:43:34

[Brian JohnParticipant @brianjohn93961]

1. Before the addition of the firebox the boiler was to sit on bolts passing through the brackets. The holes at various heights on the brackets allowed me to raise and lower the boiler above the flame. The brackets are probably not needed now. Yes, I think they are ugly too but they do prevent the boiler from toppling over.

2. I do not have much luck with soft soldering ; I do not know what I am doing wrong. I find silver soldering much easier !

Edited By Brian John on 14/01/2015 12:47:31

[Brian JohnParticipant @brianjohn93961]

Here it is running with the firebox which improves efficiency greatly. I will have to solder it to the boiler but I am still deciding whether to hard or soft solder it. The brackets had to be removed as they were not holding things as intended. I put a lot of work into those brackets !

I had to shift the brass handles as they interfered with the placement of the spirit burner….something to remember next time. The wooden mounting block for the engine should also be about 10mm lower.

I do not have any power tools for cutting timber. I was thinking of buying a jig saw and using a 100mm blade to cut this piece of 70mm X 70mm pine but some people have suggested that the blade will flex and I will not get a straight cut. What is the best way to remove 10mm from this mounting block ?

[Brian JohnParticipant @brianjohn93961]

1. What is the difference between 2%, 5% and 15% silver solder. I thought that they had different melting points but the manufacturer says they do not. What is the purpose of having different percentages of silver ?

2. If I try to soft solder this firebox to the boiler which flux should I use ? I did try soft soldering some pipework last week with Bakers flux but it was a terrible mess. Can I use the same flux as I use with 45% silver solder : CIG 602 ?

I may just have to try hard soldering it with the 45% silver solder and hope I do not wreck the rest of it !

Edited By Brian John on 16/01/2015 05:31:46

[Ian S CParticipant @iansc]

Brian, no you can't use the same flux as for silver solder. Are you using a soldering iron, or the torch for heating, if an iron it will need to be quite substantial to put enough heat into the work, a little iron for electrical work just won't do it. I have a large electric iron(175W), but for this sort of work I have a collection of old copper irons that require heating, these irons weigh about 1kg. The important thing with soldering is that the metal must be clean, your Bakers flux should be OK.

Dad taught me to solder when I was 9yrs old, using his little electric iron that he used building radios, a 65W Solon, I'v still got, and use it, I think it was bought just before WW2.

Ian S C

[Brian JohnParticipant @brianjohn93961]

No, I do not have any large irons. I am using the torch. I think I will try to silver solder it with the big burner and hope the rest of it does not fall apart.

Why are there different percentages of silver in solder : 2%, 5%, 15% and 45% ? What purpose does it serve ?

[Ian S CParticipant @iansc]

Brian, look up Cup Alloys, and find out about silver solder alloys, and all you ever need to know about silver soldering.

Ian S C

[Brian JohnParticipant @brianjohn93961]

1. Is it worth putting a turbulator (helix strip of copper or brass) in the chimney ? A friend suggested it. I am surprised that it is not mentioned at all on this site ; I have done numerous searches and turn up nothing.

2. I was wondering if there was a formula for the optimum number of twists in the helix given the diameter and the length ?

3. Why have a chimney at all on the vertical boiler unless you are burning coal or wood ? Surely you are only losing heat this way ?

4. If a chimney is necessary then it should be much narrower to minimise heat loss. I think this particular diameter was only chosen for aesthetic reasons.

[JasonBModerator @jasonb]

1. On such a small boiler it won't do a lot. One full turn would be about the max before it restricst flow. A couple of cross tubes would have been far more efficiennt, maybe on your next one.

2. I'm sure there is

3. Where will the combustion gasses go without a chimney – they will just smother the flame and put it out through lack of oxygen. Try lighting your blowlamp and then sticking it in an old bean tin as see how quickly it goes out.

4. Again there are formulas for chimney area, too small and the fire won't draw air and the gasses will smother the flame.

[Brian JohnParticipant @brianjohn93961]

Silver soldering 19mm pipe into 65mm end caps (all copper) : how much ; ''gap'' is permitted before it compromises the join ? On the bottom 65mm end cap I have drilled a 19mm hole through which the pipe fits very snugly ie. it will sit there by itself. But on the top end cap the pipe passes right through without making much contact with the sides of the hole. Is this too much play to make a good join ?

[JasonBModerator @jasonb]

As its not under any pressure it should be OK provided its not such a large gap that the solder can't bridge between the two, assume this is for a burner?

[Brian JohnParticipant @brianjohn93961]

No, this is the new boiler I am building myself. It will be under pressure so I will buy two more end caps and drill the holes smaller to make sure I get a snug fit with the flue/chimney. I think I took too much off when I was deburring the sides of the holes.

Edited By Brian John on 21/01/2015 08:24:48

[Jesse Hancock 1Participant @jessehancock1]

I would recommend you buy MODEL BOILER &BOILER MAKING by Ken Harris. This is a darn good read stuffed full of information pertaining to Boiler making.

Latest reprint 2000. Available from good bookshops or online by TEE Publishing.

Not sure but I think it was under MAP once.?

I could wade in using the book but it's handy to keep for personal reference.

I highly recommend it. *****

Jesse.

 

Edited By Jesse Hancock 1 on 21/01/2015 09:35:14

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