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.

6″ Vertical Boiler

Today I made a start on the vertical boiler.  I will be working on this as well as the Trevithick dredger engine, trying to coordinate the boiler inspection stages for both projects.  I have most of the materials, including the boiler cylinder copper tube and the copper plate for the boiler ends.  So today I made the top tube plate and the foundation ring.

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The tube plate was a similar process to the Trevithick boiler end which I described in the previous post.  I made another form but this time I used Gippsland blue gum.  The European oak form which I made for the Trevithick did not last the distance with all of the hammering, and it broke.  The blue gum is an incredibly hard tough wood, and it did not even show any marks after making the boiler end today.

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The end is quite flat.  It is an easy sliding fit.  Holes for firetubes and flue yet to be drilled.

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The electronic thermometer is quite handy, making sure that the copper is adequately heated.  I take it up to 600c, and maintain it there for 30 seconds before quenching.  Dull red is 500c, bright red is 600c.

THE FOUNDATION RING

The foundation ring is made from square section copper 9.5×9.5mm.  I rolled the rod to form the circle so it just fits into the boiler tube.

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This is after 3 or 4 passes of the un-annealed square rod, through the home made ring roller.

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The ring is almost closed

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Measuring the external diameter of the ring.  The large calipers are made of aluminium, were  inexpensive, and are surprisingly accurate.

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At this point I needed to bend the very ends of the copper rod, so I annealed the copper, and bent the ends by hammering over a steel form.  The ring roller does not bend the last 30-35mm.  The weed flamer gives out a lot of heat; nice on a cold day.

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The red hot glow of copper is a superb irridescent colour.

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Then the ends were trimmed (after cooling) and bronze brazed.  I would have silver brazed the join, but I misjudged the position and needed to fill a gap, so bronze was required because of its gap filling property.

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Tidied up in the lathe, and cleaned with a brief soak in sulphuric acid.

So, making progress.  A beautiful winter day in the workshop in Victoria, Australia.

Trevithick Boiler End-2

I could not understand why the domed boiler end would not fit into the cylindrical boiler shell.  After all, I had carefully measured the required diameters, and precisely made the wooden form, and I used a heavier hammer to finish the bending the flange.    But the bent over flange still remained too big to fit into the cylinder by about 1mm.

A phone call to my expert friend Stuart provided the answer.  Of course!   When you make a 7″ disk fit into a 6″ space (roughly speaking), the material has to go somewhere.  The material thickens up!

So back to the lathe.

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Skimming the surface until it fits into the boiler cylinder.  Turning copper, I discovered, requires a very sharp cutter, and low rpm’s.  The relief on the cutter was too severe, so I flatttened the cutting edge when sharpening it.   Those chatter marks occurred at 600 rpm but vanished at 300 rpm. 

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And at this point it was an easy sliding fit, perfect for silver soldering later on.  I also polished the surfaces for the photo.  Those hammer marks were more persistent than I expected.  Probably just as well that it will be painted.    The scrathches on the turned face were from test fitting the end in the cylinder.

AND ON A DIFFERENT SUBJECT…..

Reader Tim sent me some photos of this lathe which he has aquired.  Looks like a quality machine.  And I look forward to seeing it after restoration.

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