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.

Boiler stand, gas fire, and firedoor latch/catch.

The boiler will most often be fired on gas, but it is being made so that it can also use coal-wood.

So the base needs to cope with ash from coal or wood, and also have adequate clearance to fit a gas (propane) burner.  And to look OK.  And to be not too heavy to carry.

This is what I have come up with.

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Two plates of 6mm aluminium, separated by brass pillars.  It should polish up nicely.

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This is the first burning test. Fail!  Too much yellow.  Not enough blue.  Back to the drawing board.  Propane – air mix is not correct.

So I increased the jet diameter……

The flame size increased, but the mix did not improve.   A work in progress.  Another jet change, and an adjustable regulator to be tried next.

To do something positive, I made a firedoor latch and catch.  Some CNC and filing.

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Not finished, but going OK.

 

Just how strong is a silver soldered join?

I bought some 6mm x 0.7mm brass strip to hold on wooden lagging on my 6″ vertical boiler.   Trouble was that I could find suppliers who had the strips only in 300mm (12″) lengths.  So I decided to join 2 of the strips to provide the 450mm lengths that I need.

I have made band saw blades with silver solder, quite succesfully, but the ends were scarfed so the join was over a 5mm or so length of the blade.

I wondered whether I could butt join the brass strips with silver solder, and if so, whether the join would be adequately strong.

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So here are the brass strips end to end, fluxed and weighed down so they do not move.

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And here is the silver soldered join.  Not particularly neat, but OK for the purposes of the test.

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The other side.  As I said, not particularly neat. And I did not even bother with an acid soak.

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So I drilled a hole in the end of the joined strips, and wired on a hefty weight.  The top end was held in the vise.   Seemed OK so I increased the weights.

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Looking down the strip from the vise.

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By this stage I was standing back, expecting the soldered join to give way.  But it did not.  Hmm.   Must do a tidy up soon.

 

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21 kg, 46.3lbs.

At this point I stopped adding weights.  I think that the soldered join should hold the wooden strips to my model boiler!

Are you impressed?  I am.

 

 

 

A new skill- riveting stuff

And I don’t mean pop riveting.  I used some solid copper rivets on the vertical boiler today.  I tried to avoid them, hoping to use small bolts and nuts instead, or even soldering,  but ended up doing it properly and using solid copper rivets.

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They do look the part.  No?  This is the ash pan door.

The copper rivets are already annealed.  You need an anvil with a depression which is the same same shape and size as the rivet head, a hammer, holes drilled and a method of cutting the rivets to length.

I secured the anvil in the vise.  The anvil was a bit of steel rod into which I bored a hemispherical depression with a ball nose end mill.  I super glued the boiler parts together, then drilled them.

Then hand held the parts containing the rivet, used side cutters to cut the rivet to length so that about one diameter of rivet was protruding, placet the rivet head onto the anvil, then gave the cut end a few taps with the hammer, to pean it over and secure it.  Easy as!

Those are the first solid rivets I have used.   Ever.

Then I silver soldered the handle in place.

The next job was a bit trickier.  I made some holes in the smoke box lid to let the safety valve and dry steam header poke through.  I tried drilling them initially, holding the lid with my hand, but the inevitable happened….   the drill bit grabbed, spun the work around, threw it and left a row of little dents on the copper surface.  I had been contemplating polishing the copper or painting it.   I guess this little accident means that I will be painting it.

So next I held the lid on the wooden form which I had used to make it, and held the form in the drill vise.  No more grabbing and throwing, but it was a bit tense.  I gradually worked up the drill sizes, and when it became close to the desired measurement, I filed the last bits.

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Those taps are vertical.  They appear to diverge because the iphone has a wide angle lens.  2 penetrations made.  One more to go.

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Redesign Trevithic Model Dredger Engine

Further to my previous post I played around with the drawing of the boiler flat end.  I have come up with some changes, which will bring the design closer to the original Trevithick design, as far as can be ascertained.

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I have already made the cutouts and drilled the holes, so I have compromised somewhat with the changes.

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Not a great photo of a computer screenshot.

On the left is the end plate with the cut outs and drilled holes as at present.  The black holes are the ones which I would have to fill, presumably with copper or bronze thread, silver soldered into place.

On the right are the:

1. modified inspection hatch, covering the rectangular hole.  I would likely change the shape a bit closer to a circular shape than drawn here.

2. The chimney secured to the flat plate with a flange and studs with square nuts

3. The firebox flange a simple disk silver soldered to the end plate, a fire door roughly elptical in shape with older style hinges and latch and catch, and an open ash pan.  Actually, I will check the ashpan situation to ask my expert boiler friends whether these were open as  in the London Science Museum engine, or whether it would have had a grille of some kind.

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Even painted, this just would not look right.

 

Trevithick Dedger Engine -Design Changes?

I imagine that everyone who makes a model reproduction steam engine faces decisions about whether to faithfully stick with the original design, or whether to accept compromises due to accessibility of fasteners, metric dimensions, new materials, safety factors and certification and ease of machining.

The Trevithick dredger engine was a quantum leap in its day.  Trevithick was a brilliant, original, creative, genius.

But his boiler was cast iron, 1.5″ thick, because that is what he had available as the safest method for his revolutionary high pressure boiler.  A 1:8 scale model, if it is to be AMBSC certified, must be made of copper, silver soldered.   And the flat end must be LG2 bronze, not cast iron.  Fair enough.  When painted, the metal type will not look wrong.

And I am working from plans originally drawn in 1985 by Tubal Cain, and redrawn by Julius deWaal in 2016.

Unfortunately, despite manufacturing at least 600 engines of this type, there are NO intact authentic Trevithick high pressure boiler/engines or plans in existence.  The Trevithick dredger engine in the London Science Museum was rebuilt in the late 19th century, in Victorian times, and although it contains some original Trevithick components, some of the components had to be built from scratch, and reflect more of the Victorian style than the 1806 Trevithick style.

There are NO known original Trevithick plans or drawings, except for one concept sketch.

The earliest drawing of the Trevithick dredger engine comes from an encyclopaedia which was published in about 1820.  It is, I consider, the best image for the modeller to work from.  Many of Trevithick’s  engines would have been operating when this image was made.

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Note the straight connecting rods, the straight boiler supports, and the absence of decorative mouldings on the flywheel

 

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This is a drawing of the reconstructed Trevithick dredger engine in the London Science Museum.  Some of the features are more Victorian than 1806.

Knowing that the boiler cylinder and vertical cylinder end were all cast in one piece does explain how that complex shape was made.

This is a photo which I recently found, showing the flat end of the LSM reconstruction.   The location and shape of the penetrations is probably accurate, and are possibly original, even though some other details such as the con rods are not.  I am disappointed that the modern plans (Tubal Cain and deWaal) chose to modernise the shapes of the inspection hatch and firebox door.  Unfortunately my 1:8 construction has progressed beyond the point where I could readily make the older, more authentic shapes.

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The flat end of my model as per Tubal Cain and Julius deWaal. It is quite different from the Science Museum engine.  The end is bolted to the boiler flange, so it would be a straightforward task to totally remake it.  The newer version has a larger fire door opening which would be an advantage if the model is fueled with coal.  The inspection hatch is the feature which I find most disconcerting.  As an interim measure I will remake it with more rounded corners and no central depression.  I am considering whether to remake the firebox opening, door and surround.  Some drilled holes would need to plugged in the flat bronze.  The shape shown in the LSM engine would make it easier to fire it with propane.

Or, I could just finish the model as per the plans.  Any thoughts from my readers?  And does anyone have photographs of the LSM engine?  I have scoured the Internet but the quality of most published photos is awful.

This post is a bit rambly, because my ideas are changing even as I write.  Clarifying my thoughts is one advantage in putting thoughts to paper.

6″ Vertical Boiler. Finishing the firedoor

The doors on this boiler have consumed more time and energy than I expected.

Partly because the firedoor has a vent, has a heat shield, is oval shaped, and is mounted on a curved surface which will get very hot in use.

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It is still not quite finished, needing a catch and a latch.  There is a spring which pushes the vent against the door.  And a heat shield which needed a few shaping processes to make sure that it did not foul the firehole.  The heatshield is supposed to be stainless steel, but the copper cutout left over from when the firehole was cut in the wrapper, seemed ideal for the job.  The central shaft is stainless steel, threaded M4 at back and M3 through the door.

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I intend to use propane as the main fuel for the boiler, but I have constructed the firebox so it could use coal as an alternative.  This is the ash pan opening.  Constructed from 1.4mm brass, and silver soldering the join.  Pretty neat hey!  I have made the door and hinges, and will hang the door next session.  I will replace those cap screws with something more suitable.

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The hinges are quite small.  3mm wide, and when trimmed will be about 18mm long.  To make them I drilled a 1.5mm hole in a piece of brass rod, silver soldered the rod to some 1.3mm sheet brass, then bandsawed- cut the piece into separate hinges.  Since that pic was taken I have milled the width to 3mm, and trimmed the lengths.  I dropped one hinge, and spent a fruitless hour trying to find it.  Fortunately I had made a spare, but I cannot aford to lose another.  The hinges will be riveted to the door and the ashpan surround.

Hanging a door on a boiler.

After yesterday’s disaster, I realised that I could not fix the door and vent that I had spent so many hours making.  The vent holes and the vent itself were too big for the opening into the boiler.  So I had to totally redesign and remake them.

But you know what?  When you make something a second time, you have done it before. And the second making is MUCH faster.

So I remade the firebox door and the vent control grill.  Then I made another hinge.  And I attached them to the boiler.  And you know what else….   I broke another f*****g 1.5mm drill bit in the hinge…. again.  But it is OK.   I have made that mistake only twice on this job, so I have got two more goes before I slit my wrists.

As for the suggestion that I use EDM to remove the broken drill piece, I really doubt that would work on a 1.5mm drill.  But maybe…..

But the broken drill bit was in both the door and the hinge.  So I just left it there, and it can become half of the hinge pin, permanently.

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The top hinge pin is the broken drill bit.  The bottom half is the 2mm cap screw which I managed to thread in place.  The photo is upsidedown.  This is not yet finished.  I still need to make and install a baffle for the door.  And the ugly soldering splodge will disappear under the paint or the wooden slat lagging….  haven’t decided yet. 

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The door is eliptical.  And it will be painted so I have not fussed too much about finish.  This photo needs to rotate 90º.

 

Two steps forward one step back again!

I had a whole day to myself, in the workshop.  SWMBO was happy painting or something, and the kids did not need us to baby sit the grandchildren.  So, let’s make the 6″ boiler fire door and ash pan door.

But first, I silver soldered the 4 joins on the super heater, and all went well.

The firehole is oval shaped, and the plans call for a rectangular door.  So I spent some time planning the machining for the rectangular door boxed section.  Then I thought … hang on…. this oval is really nice… why am I hiding it behind a rectangle ?

So back to the computer, and I worked out a method to make an oval door.  A bit like a hobbit door, with an adjustable vent.

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And here I am, machining it with a 2mm cutter.  In 1mm deep bites.  That brass is 4mm thick.

And I made a bracket to complete the hinge….

Drilled the holes for the 1.5mm pin…..

And the f*****g drill bit broke!!!!

I could not get it out.  It was a cobalt bit, and all of my methods for digging out broken bits were tried, taking a couple of hours, and failed.

So I reshaped the hinge end of the door..

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and I will silver solder a hinge end on tomorrow.

6″ Vertical Boiler.Spearhead Superheater

Some more progress on the 6″ vertical boiler.  Not much to show, but here it is.

Actually, I have been wondering whether to continue with this blog as a “what I have done today” type diary, or whether to post less often, but when a significant milestone has been passed.  Your feedback would be welcome on this decision.

The superheater is a copper item, which steam passes through, and is located in or just above the furnace.  As a result the steam becomes hotter and drier and more energetic before it is passed through the engine or whatever it is being used for.

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This is a lump of copper, 10mm thick which I have cut off a bar which I had in stock.  It will be machined into the superheater spearhead.

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The copper spearheads machines into shape.  Copper is soft, but it grabs the cutters.  Not nice to machine.  Expert Stuart said that I should have used lubricant.  Next time. 

The sperheads are bronze brazed to copper pipes, but the difficult bit was bending the 1/4″ copper pipe to fit.

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The spearhead is bronze brazed to the copper pipe.  Tricky, but seemed to go OK.  Don’t know yet whether the bronze join is steam tight.

The tricky bit is the 2 x 90º bends, really close to each other.   Does anyone have any good method for doing this?  I ended up with this result, but it is not pretty, and I am sure there must be a better method for creating the bends.

The silver soldered joins are yet to be done into the brass fittings shown.  I ran out of time in the workshop.

This is getting exciting!  I am not too far off firing up this boiler!

Then a visit to the boiler inspector.

Trevithick Dredger Engine-2 steps forward, 1 step back.

A few posts back I reported how I very cleverly silver soldered together some “sliced bread” bits of brass and bronze, because I did not have big enough material.

Then I spent a day machining the outlines, drilling the holes and finishing the parts.

Today I silver soldered the parts to the Trevithick boiler.  The joins in the material were so good they were invisible, and the fact that the joins were there did not enter my brain.

And this was the outcome.

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Before

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After

The beautiful silver soldered join melted as I attempted to silver solder the part to the boiler.  It has made the part unusable.

I will go through the exercise again, but next time I will bronze braze the join.  Bronze will not melt or let go with silver soldering temperatures.

I will try to not make this mistake again.  I try to not make the same mistake more than 3 or 4 times.

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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How to make small bits of brass (or bronze) into big bits of brass (or bronze).

I needed some brass plate 6mm thick, 50mm wide and 150mm long for the Trevithick boiler-engine..

Prices on Ebay were horrendous for thicker material, and I could find no local supplier.

Silver solder, when properly used, is said to be as strong as the parent metal.

And I had some 75 x 75mm brass square section about a meter long.  I bought it years ago for a project and most of it was unused.

So, I cut some slices off the end, sliced bread fashion, and silver soldered pieces together.

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2 Bread slices of brass (centre) and machined joined pieces on the sides.

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The square section brass log (I can barely lift it), 2 slices at the back, and 2 pieces edge silver soldered and surface machined.

I also needed a large thick piece of LG2 bronze for the Trevithick dredger engine.  The middle round piece needed to be bronze because it is exposed to boiler pressure.  The outside pieces could be bronze or brass so I used brass.

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So I silver soldered brass edge pieces to the central piece of bronze.  The soldering was done on the very flat Hebel aerated concrete block,  and the final piece was very flat, requiring minimal machining.

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This is the non machined underside of the brass-bronze-brass piece.  It has been rubbed on a surface plate covered with emery paper, just to demonstrate the flatness of the soldered piece.

 

Trevithick Dredger Engine. Making and brazing the boiler cylinder tube.

The boiler cylinder tube is the vertical cylinder which penetrates the boiler shell, and boiler end plate, and eventually houses the cylinder and piston within the boiler.

In the previous post I described cutting the hole which encloses the cylinder.

Today I made the cylinder, and brazed it in place.

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Reference lines accurately marked using machinists blue.

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It is 51mm diameter, and wall thickness 3.2mm.

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Bronze brazed into position.

And now that the brazing is completed I can cut the boiler tube to its final length.  This was left until all the brazing had been completed, in case there was a major stuff up and it had to be repeated.  That should be the last bronze brazing join on this engine.  I can return to the easier, and lower temperature silver brazed joins from on.  I must mention that working close to a workpiece which is close to 1000ºc, for 5-10 minutes at a stretch is fairly uncomfortable.  Now I know why the bronze brazing torch is a minimum of 450mm long.  Even so, I got skin burns from the metal buttons of my jacket when I touched them after a session.   A leather apron from now on.

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Measure twice, cut once.  Actually, I measured this 3 times.

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Cutting with the drop bandsaw.  Very slow feed rate so the blade does not grab this very soft copper.  This removed 3 of the remaining 4 unwanted holes.  Just one remains to be filled.

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Final length of the boiler.  All nicely square.

 

Adjusting Pressure Gauges

In a recent post about 2 pressure gauges which I bought at a club auction, a reader (Daredesign) asked whether pressure gauges are able to be adjusted if the calibration is out.

 

 

One of our GSMEE members used to manufacture pressure gauges, so I asked him.

Frank and an artist made about one gauge per day.  They were precision instruments, reading within 1:200 of the gauge reading.  And priced accordingly.  The face marks were painted by hand onto each gauge face by the artist, in positions marked by the instrument maker in a temperature controlled room.

Pressure gauges CAN be adjusted.  And the better the quality of the instrument, the more readily it can be adjusted.  The means of adjustment depends on the nature of the error.

If the error is a constant number throughout the pressure range, the pointer is removed from its tapered spindle and replaced in the new position.

If the error varies throughout the pressure range, the adjustment is of the inside mechanism.  Two arms named the link and the quadrant are joined together and the join position and angle between the parts can be adjusted.  The length of the link can also be adjusted.  Frank gave me a detailed explanation of the types of errors and the adjustments, and I do not remember the details.  I imagine that these procedures should be left to experts like Frank.

Frank also explained the workings of the Bourdon tube which is the main component of most pressure gauges.  The Bourdon tube is a thin walled, oval section, copper-beryllium  alloy tube, bent into an arc, and closed at one end.  With pressure increase the tube tends to straighten, and the movement is translated into movement of the dial needle.  The copper alloy is chosen because of a property called hysteresis, which I understand means that it returns exactly to its original shape when the pressure in the tube returns to its resting level.Bourdon tube pressure gauge. 

In this diagram, the quadrant is named “sector”.  The angle between the segment lever (or “quadrant”) and adjustable link should be 90 degrees when the pressure is halfway in its range.

So, I hope, Daredesign that this answers your question, and that I am reproducing the information accurately.

 

Steam Driven Water Pump for Vertical Boiler

Unfortunately I did not make this pump.  It was made by Stuart Tankard.  I have the castings and plans, and intend to make one for my 6″ vertical boiler but I have too much on the go at present and will finish the vertical boiler and the Trevithick engine first.

Enjoy the pics.  Stuart sets the machining standard for the rest of us to aspire to.

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We did not see it running today, but it does work.

It is a 6” Duplex pump from Southworth Engines.

Trevithick Dredger Engine. Cutting through the domed end plate.

This was a part of the build which I was dreading.

I needed to cut a 50mm diameter hole through the boiler wrapper and the domed end plate, and the bronze join in order to insert the vertical cylinder which houses the cylinder, piston etc..

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In this reconstructed Trevithick boiler, the vertical cylinder is visible.  

A series of photos is probably the best method of explaining the process…

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The boiler is held in a vise with extended jaws.  A wooden plug fills the cylinder so the vise does not squash the softened copper.  The 50mm hole saw is fine toothed, and run very slowly (250rpm), using hand feed also very slowly.  The copper is 3mm thick, doubled to 6mm at this stage, and with a middle layer of hard bronze.

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When the full depth of the hole saw was reached I cut a horizontal slit with an angle grinder and snapped the piece out.  Then resumed the hole saw cut.  The middle of the domed end was the least supported, and it flapped about a bit, despite its 3mm thickness.

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The wooden plug is visible.  2 more cuts to go.

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Some extra length of the shaft was required, so I switched to ER40 and ER25 collets to hold the hole saw.  Cut completed.

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The domed end was slightly distorted by the cutting, since the copper was annealed by the previous bronze brazing heat.  So I inserted the original wooden form, and hammered it into place to reshape the domed end.  Worked quite well.  The edges are a bit chewed rough, but since this join will also be bronze brazed, and therefore gap filled with bronze, it should not matter.  In fact I intend to chamfer the edges to create a V to fill with bronze.

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And with the 50mm cylinder in place it all looked nice and square.  The removed copper pieces sitting on the vise.

And….  thanks to Stuart T, my CNC mill is again in action.  Stuart identified the probable culprit component (a chip on a board for the encoder for the Z axis servo motor), made a new board for the new chip and installed it.  He was not confident that it would fix the problem, with the likelihood that a complete electronic rebuild of all electronic components would be needed.  But it worked!   Hooray!!   I feel like my right hand has been repaired.   Thanks Stuart.

Trevithick Dredger Engine- bronze brazing and some milled parts.

 

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The copper tube which I am using for boiler shell has 6 holes, intended for another project by the previous owner.  Here I am trimming the length, so 2 of the holes will eventually be removed.  Using a drop bandsaw, with a wooden plug so the tube is not bent by vise pressure.

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Bronze brazing the domed boiler end to the boiler wrapper.  The assembly absorbs a huge amount of heat before it reaches brazing temperature.  Showing the temporary forge, and the torch head for the oxy-propane fuel.  The join has been completed in this photo.

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The join in progress.  Note the positioning copper rivets, and the tacking points.  At this point I ran out of oxygen and had to finish the braze on the following day.

And today I made some parts for the boiler’s removable flat end.  My CNC mill is out of action, so GSMEE President Brendan kindly allowed me to use his machine.

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CNC spotting 3.2mm brass plate.

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The almost completed firebox door base.  Spotting did not allow for the removed material in the rebate, and the drill ran out in one hole- some repair required.  I will plug and redrill that hole.

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The manhole cover.  It will eventually be painted.

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Sitting in intended positions.  Fastener holes spotted, yet to be drilled and threaded.

Oxy-acetylene or Oxy-propane for silver soldering (and bronze brazing)?

There has been a big learning curve for me in making the 6″ vertical boiler and the Trevithick dredger engine.  I have used silver solder for previous projects, and I thought that I had the method under control.

I have always used oxyacetylene for my earlier, smaller projects, presuming that the higher flame temperature would produce results more easily.  That is what I tried to do with the 6″ boiler project.  But I struggled.  In order to produce a broad flame, and not burn the copper, I used a big, number 26 nozzle.  Initially it produced a lovely big hot flame, but within minutes it started popping, and blowing out.  Faulty acetylene gauge?  Gun not up to the job?  Acetylene cylinder running low?  So I replaced the acetylene cylinder. Cost $AUD100.   Seemed to fix the problem temporarily, but then the popping resumed.   Faulty gauge?  A borrowed replacement gauge produced the same result.

So back to the welding and gas supplier.

“You cannot run a nozzle bigger than No 15 when using acetylene.  The acetylene does not come out of solution in the cylinder quickly enough”.

OK.  So what do I do?  “Use propane”.  “but you need different hoses, different gauge, different mixer and nozzle”.  OK, give me those….  cost $AUD 260.   And it worked!!!

Propane and oxygen burns at a lower temperature (~2820ºc) than acetylene and oxygen (~3420ºc) , but the gas volume delivery of the propane is MUCH greater than the acetylene.  So the delivery of the heat is much greater.

For me, I will be returning the acetylene cylinder and permanently switching to propane.  Much cheaper and much more heat.  But, that heat can lead to unintended consequences…So, here we are on the Trevithick dredger engine.  I needed to bronze braze the join between the firebox and the firetube. (a boiler inspector requirement).  Bronze melts at 836-1030ºc which is not far off the melting point of copper.  And my first attempt ended in disaster!  I melted the copper firetube!!!  An expensive blob of copper and bronze!!! (no photos.  I was too cross with myself).

The next effort was an improvement, but not pretty.

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Using a holesaw to cut a 38mm hole in the 64mm copper tube.

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The angle was not quite right, but fixed with some careful filing.

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Setup, ready for bronze brazing.  The firebricks are holding the pieces in position.

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After bronze brazing.  It is not pretty, but I am a beginner at this.

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The end plate was used as a jig.

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And then I accidentally dropped it. (#$#%&**#)  Restored to proper shape with some careful blacksmithing.

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My great great grandfather was a blacksmith.  

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OK.  It is not pretty.  But not bad for a gynaecologist.

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And to show you what Trevithick’s blacksmiths made to his design.  I count at least 19 individual iron pieces, riveted together.  This was the firebox and firetube of the first high pressure boiler.  Incredible!

 

 

 

 

 

6″ Vertical Boiler. Calibrating the pressure gauge

I bought 2 pressure gauges at a recent Model Engineering Club auction night.  I paid $AUD40 for the pair, although I was really only interested in the smaller one.

It was a bit of a gamble.  Would they work?  Accurate?

Stuart mentioned that he had an instrument for calibrating gauges, and he checked my gauges.

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This gauge was item 51 at the auction.  It is about 4″ diameter and has some style!   Brass of course.   The cream painted instrument with the shiny brass weights is the calibration gauge.  It confirmed that my gauge was spot on at pressures of 50, 100, 150, 200 qnd 250psi.

The smaller gauge, 38mm  1.5″ diameter which I will use on the Trevithick dredger engine, was not quite as accurate, being 2.5psi out, but is adequate for use.  It is also British made, brass, and nice appearance.

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6″ Vertical boiler. 2nd Braze

Today was cold, wet and windy. so the wood heater was started when I arrived at the workshop.

Then a couple of hours using emery paper and steel wool to get shiny copper surfaces ready for silver soldering on the vertical boiler.  Then copious application of flux to the surfaces.  Loose bits held with iron wire.

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A slight re-shaping of my forge to accomodate the shape, and allow access to the top front and sides.

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Not so pretty after applcation of heat from the oxyacetylene torch and the weed flamer at the same time.  Both hands were fully occupied, so no action photos.

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And after the usual sulphuric acid bath and rinse.  A couple of joins need to be redone, and then a test for leaks.

Reader and GSMEE member Ian asked about the cam lock clamps which I used in a recent post.

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They are “KNU-VISE” clamps, used in aircraft manufacture I believe.  I bought a box full of them in Ebay’s early days, when bargains were still to be found and US postage was not prohibitative.  Very useful for powerful clamping up to about 50mm.

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