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machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment.

Tag: hebel

6″ Vertical Boiler- First silver Brazing

So what is the big deal?

Well for a start, this is a big deal financially.  The materials to be joined are expensive, and some are difficult to obtain.

And the silver solder itself is expensive.  We ended up using 4 sticks of 45% silver solder, and an unknown quantity of oxygen, acetylene and propane.

And the end result will be inspected by an expert boiler inspector, and if it is substandard, it will be rejected.  No argument.

So yeah, it was a big deal.  Look at the pics.   A few friends called in to watch and help.  It was a cold wet winter day, and I had the workshop wood heater working to keep the troops happy.

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I used steel wool to expose the elemental copper.

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Me applying flux.  Note the silver solder rings which were made on the lathe.  Don’t ask where the brush originated.

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The firebox wrapper was placed on the aerated concreted form to keep the tubeplate level, and allow the tubes to penetrate exactly 2mm.  The tube ends were fluxed, and silver solder rings placed into the join.

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The 44 fluxed firetubes with their rings of silver solder are in place.  The top tube plate will not be brazed at this time.  It is there to keep the firetubes in the correct position.  The firebox tubeplate is also fluxed and sitting in position on its Hebel block.

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Me on the left with the propane weed flamer applying gross heat, Stuart with oxyacetylene applying local heat and silver solder, and Swen cheering.  Brendan is the photographer, trying not to get burnt.

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We probably should have reshaped the forge to reflect the heat more efficiently.

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When the brazing seemed to be finished, the work was allowed to cool to 200c, then quenched in water then a 15″ soak in 20% sulphuric acid to remove any remaining flux, then a further water soak to remove any acid.  Yes, the top plate is upside down.  Yes, it will be reversed eventually.

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Inspection from inside the firebox.  Most firetubes have taken the silver solder properly, but a few of the inner circle and the flue require a second application.  The brazing heat looks to have been inadequate near the centre, probably due to the density of the firetubes.

So, not a perfect result, but not bad for a beginner.  Stuart opined that the job would have been better if my silver solder was the older, (more dangerous) but more runny type which contained cadmium.

Turning Concrete on a Metalworker’s Lathe

OK.  The concrete is aerated… Hebel.

But, it does turn easily and cleanly.

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But it is concrete, and probably very abrasive, so I have covered everything in plastic, and used an old carbide cutter.

I needed to refine the dimensions and shape of the supporting block while brazing  my 6″ vertical boiler, so I turned it.  And it worked brilliantly.

 

6″ Vertical Boiler. Ideal soldering set-up block. Concrete!

OK.  My non machinist readers will have no idea what I am talking about.  And I suspect that my machinist readers wont either.

I need some precisely machined and measured blocks to set up the soldering for the boiler.  I want them to not suck up my soldering heat (so no metal), and to not stick to my silver solder (so not steel, copper, etc).

How about concrete?  More specifically, aerated concrete.  Hebel.

Look at the pics……  I need a cylinder, about 100mm high and 110mm diameter, which will not absorb heat and not stick to silver solder.

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This is a 600x400x75mm Hebel block.   Cost $AUD4.60.  It is part of my forge, but will be replaced easily.

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Marked out the bit I want.

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So I cut it on the bandsaw.  It is aerated concrete.  Hebel.

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Cuts quickly and easily.  Probably not good for the blade.  But we will see.

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How accurate is the thickness??   Pretty amazing IMO.  within 0.1mm.  The second measurment is after a quick touch up with emery paper on a flat plate.

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And this is the first setup, ready for soldering.   Watch this space.  soldering in 2 days.

 

6″ Vertical Boiler- the Firehole

The firehole is the opening where coal is shovelled into the firebox.  It is oval shaped, and is exposed to the boiler pressure.  It is made from thick copper tube.  Oval holes must be formed through the boiler wrapper and the firebox wrapper.

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The elliptical hole in the boiler wrapper, and the firehole tube.

The first task is to shape copper tube which is circular, into oval shaped tube.  I decided to make an oval shaped split wooden form and to compress the annealed copper tube with the form.

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The wooden slab is cut into 2 pieces which are then cramped together, and the oval hole is CNC machined.  

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A 1″ 25mm length of 3.2mm thick walled tube is cut off, then annealed.  Note that I have upgraded my forge.  I bought some aerated concrete blocks (Hebel), and enlarged and encased the forge.  The white Hebel blocks reflect the heat and the forge temperature rises quickly.   the outside of the forge remains quite cool, testimony to Hebel’s insulating properties.  Hebel is quite inexpensive.  A 600 x 200 x 100mm blocks costs $AUD4.60.  Heating time is 60 seconds, vs 90 seconds with the previous setup.

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The wooden form and the unshaped thick walled copper tube.

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After squeezing the annealed coper pipe in the form, using a 6″ vice.  Nice elliptical shape.  Note the pencil witness mark.

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Then the elliptical hole is cut into the boiler wrapper.  The vice jaws were replaced by temporary aluminium jaws 4″ high, adequate to hold the 6″ diameter tube.  Cutting the elliptical hole on the CNC mill.  There are wooden plugs in the boiler tube to prevent the boiler tube from distorting

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The finished boiler hole and the elliptical insert.  This was tense machining. 

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The fit is a bit too tight.  I will take off another 0.1mm so it is an easy sliding fit, suitable for silver soldering.    Then to cut the same elliptical hole in the firebox wrapper, but while the main cylinder is set up in this position I can cut openings for the ashpan and safety valve bush.                                                                                                                              

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