johnsmachines

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. I read every comment and respond to most.

Tag: model steam boiler

Trevithick Dredger Engine- First silver soldering session

Today I fitted the chimney right angle piece, drilled and soldered on its flange, and drilled the end plate to accept the flange.  Then I CNC drilled the big bronze end plate to accept the flange.

 

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The angle piece is a commercially available plumbing part.  The stainless steel square nuts came from China.  Joins are silver soldered.  In a departure from the Tubal Cain/Julius deWaal plans, I decided to attach the chimney flange directly to the flat end plate.  I reckon that’s what would have been done in 1806, and it is what shows in the 1820 Rees Encyclopaedia drawing.   Note the unwanted threaded holes, now filled with stainless steel threaded rod.

Then I carefully positioned the bronze end plate, the firebox and the firetube, and silver soldered them together.

 

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The parts are fluxed and pushed together, ready to apply some serious heat and expensive silver.

 

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Not pretty, but I am happy with the silver joins.  Minimal retouching required.

Next, the inspection hatch will be soldered to fill the rectangular hole.

Then the main bronze flange will be permanently attached to the boiler shell.  I intend to silver solder it, but considering bronze brazing.

 

 

 

Almost ready for the boiler inspector.

Almost ready for the boiler inspector!

It feels like the countdown to the finals medical exams!

So today, I drilled the gas jet from 0.22mm to 0.3mm.   A drill bit to drill 0.3mm, is, at least to my eyes, barely visible.  It is finer than the finest sewing needle.  If I pick up a 0.3mm drill bit I can not feel it.  It has no discernable weight.

So this is how I increased the jet size from 0.22 to 0.3mm.

Oops!  I forgot to take a photo.  I bought a set of micro drills from Jaycar, and the smallest bit was 0.3mm.  So I mounted it in the Dremel, and ran it at 10,000 rpm.   for a vise I used my fingers.  The drill went straight through the millimeter or so of brass with no detectable resistance.   Managed to miss my fingers.

0.22mm to 0.3mm diameter is almost a doubling in area of the jet orifice, so I tested the flame.  It was (not surprisingly) much bigger!   And still a good blue colour, with minimal yellow.  So I stopped there.   I also installed an adjustable propane regulator Huib.

Then I made an angle piece to secure the boiler to its baseplate.

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I needed a non rusting disk, 165mm diameter, with a 152mm hole.  The disk was 2mm thick.  So I roughly bandsawed it out in 2mm brass sheet, then set it up in the lathe as shown above.  Turned the outside diameter.  The brass sheet is held just with pressure between the headstock and the tailstock, and the disks of wood.

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Then I held the disk in the 3 jaw chuck and used a parting tool to cut out a disk to form the middle.  The waste middle came out with a bang.  I was careful to stand to the side, anticipating the decapitating scythe.   And I was not disappointed.  I did have to check that my head was still attached.

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Again, I was so involved with the machining that I forgot to take pics.  The vertical part of the angle piece is a slice of copper tube which I had reserved.  It was silver soldered to the brass  disk, then screwed to the boiler wrapper.   Some further fitting, and it ended up like this.

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The hand pump has been mounted.  yet to be connected.  A steam driven water pump will eventually occupy the spare space.  And just to make quite sure that there is enough water pumping capacity I will also be installing an injector.

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And another nice bit of bling (John).  This globe valve was made by Stuart Tankard.  I have borrowed it, pending me making one of my own.

Trevithick Dredger Engine- Supports

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These are the boiler supports for th Trevithick Dredger Engine, which need a little more finishing.

As you can see my CNC mill is working nicely.  The slow feed rate is because the brass is just super glued to the mounting base and I did not want to risk it coming adrift.

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The CNC milled parts.  The brass is 7.5mm thick.

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And this was cut out from the edge silver soldered brass bread slices.

And I have also been working on the 6″ vertical boiler.  The brazing with silver solder is almost finished.  I have been redoing some of the joins, and can now get the pressure up to 200psi.  There are 101 soldered joins in the construction (so far), so I am not too upset that a few of them were not perfect and required a redo.  SWMBO was wondering about the bills from the industrial gas supplier.  I have used several fills of oxygen.  Totally abandoned acetylene and using propane now.  It delivers more heat (at a slightly lower temperature), and much less costly.

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