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.

A Nice Day!

First was a trip to the boiler inspector, to inspect the first silver braze on the 6″ vertical boiler.  Passed!  And quite complimentary about the quality of the build so far.

And….  he has OK’d my plans for the Trevithick Dredger engine boiler.   Which is nice because I have already started it, and was going to build it in any case.  Only requirement is that I have to add a pressure gauge.  As far as I know, none of Trevithick’s engines used pressure gauges, just weight based safety valves.  So a pressure gauge will not exactly be in keeping with the historicity of the model, but it seems a small price to pay to get the boiler certified.   Now I am trying to work out where to place the pressure gauge so the operator can see it, but not the viewing public.

Then a late entrance to our GSMEE day meeting.  (Geelong Society of Model and Experimental Engineers).   I showed my progress on the 6″ vertical boiler.  And took some pics of some of the other items brought in by members.


A very nice lagged boiler and engine by Neil


and that firebox door is titanium!  And check out the screws in the base….  no-one is going to be able to unscrew this model!


The steam control valve for Neil’s engine.  He used a solder with which I was unfamiliar…. “StayBrite” which is said to have a melting point above soft solder, but not as high as silver solder.   Bought at JayCar.   The cap screws have BA threads… unusual!


And finally, a small steam driven pump brought in by our senior member Laurie, made decades ago by a friend.  Laurie is a club treasure, being a great raconteur, especially about his WW2 experiences in the Australian army, and having made superb models when younger which are still regularly run and exhibited.   The coin for scale is an Australian 50 cent piece; large, heavy, and it takes about 10 of them to buy a cup of coffee; much disliked.


Trevithick Dredger Engine- the flat end


The 6″ vertical boiler has had its first brazing session, and has been put aside while I wait for the boiler inspector to give the “go ahead” so I can proceed to the next brazing session.  I am told that the first braze is the most difficult.   The next braze is bigger, but the components are all on or near to the surface, and it is consequently more straightforward.

So, while waiting, I pulled out the Trevithick Dredger Engine, and decided to make the flat end plate and flange.  These are machined from LG2 bronze disks 13mm and 8.5mm thick.

bronze blanks

204mm diameter.


An aluminium sacrificial plate was made and held in the milling vise.  The bronze disks were CNC drilled.


The disk which will become the flange is tapped.


The holes in the end plate were CNC’d on the mill, which died during the procedure.  The Z axis went crazy.  Fortunately I managed to hit the panic button and the end plate was not destroyed.   Currently Stuart & I are trying to determine the cause of the robot madness, but that looks like being a lengthy process.   The rebate being completed on the lathe in the pic would have been an easy CNC mill process, but the workpiece was quite thin to be held in the lathe chuck.


Showing how the end plate was held in the lathe chuck, with double rare earth magnets holding the plate away from the chuck jaws permitting the tin workpiece to be turned.  A bit tricky, but went well.


The flange on the left will eventually be brazed to the boiler shell.  The end plate on the right will be bolted to the flange. 


The end plate and the flange mated together


The big tube 65mm diameter will become the firebox,  the smaller one 38mm dia will be the firetube exhausting to the chimney.


None of the tubes are yet cut to length, but starting to take form. 


Timing a Stuart Triple Expansion Steam Engine

Reader Steve kindly sent me these notes which detail how to time a Stuart model Triple Expansion Steam Engine.   The notes are quite clearly written, and I recall that a few readers had an interest in the subject.  Thanks Steve.

Easier to read if you enlarge the picture of the text.

Triple Timing

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.


I used steel wool to expose the elemental copper.


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


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.


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.


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.


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


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.


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.


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.


Gaskets with CNC, and progress on the Trevithick Dredger Engine.

Tomorrow I start silver brazing the 6″ vertical boiler.

But today I started machining the bronze end plate of the Trevithick Dredger Engine.

First I prepared a 100x25x200mm sacrificial aluminium block to hold the expensive bronze disks which will become the end plate and flange of the Trevithick boiler.


CNC drilling the 8mm thick bronze end plate and the sacrificial mounting block.


This thicker bronze disk (13mm thick) will become the flange which is brazed to the boiler shell.  The holes were also CNC drilled, then threaded using a battery drill, held vertically in my shop made threading jig.  The flange and the end plate require more holes and shoulders.  The mounting block will assist with repositioning.

Earlier I had called on GSMEE president Brendan, who happens to possess a CNC laser cutter.  I had discussed the possibility of CNC cutting some gaskets for the steam pump which will be made for the 6″ vertical boiler.  “No Problem”, said Brendan.


Taping the gasket material to the CNC laser cutter table.


Starting the cut.


The 15 gaskets accurately cut out.  Cut out by hand would have been a half day job.  The laser finished it in about 3 minutes, perfectly (plus maybe an hour drawing the pattern using a CAD program).  It is a 40 watt laser, and will cut through 3mm plywood.  No problem with this 0.4mm gasket material running the laser at 25% power.




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.


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


Marked out the bit I want.


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


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


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.


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


6″ Vertical Boiler- Steam Outlet & Safety Valve Standard

Some more progress over the last 2 days.


The chimney flare sitting in its intended position.  The attachments at the smokebox are completed.



The smokebox tube plate, waiting for its firetubes.  The bronze fittings are the safety valve and its standard on the left, and the main steam outlet standard on the right, sitting in position.


My workbench becomes increasingly cluttered as a job progresses.

Silver brazing is the next step.  There will be 2 major soldering sessions, with boiler inspections after each one.  I will enlist some extra hands and expertise for the soldering.  (Stuart, I hope that you are reading this.)

6″ Vertical Boiler Chimney Flare

I was relieved from duty with the ankle biters for a few hours today, when my wife took them to the local animal sanctuary.  They petted a Tree Python (OMG!), and a Koala, and were entertained by the talking Sulphur Crested Cockatoos, one of which is aged 91 years!

Making the most of my temporary freedom I visited the workshop.  Soldered the chimney support to the smoke box roof, and made a chimney flare.  It probably has a more technical name, but when you see it, you will realise where it goes.


6″ Vertical Boiler- Chimney flange

I was not required for childminding for a few hours yesterday, so a quick visit to the workshop.  Not much to show, but I did make 2 circular flanges to attach the chimney to the smoke box lid, and soldered them in place.

Getting a flange to be exactly perpendicular to its tube was tricky.  I set it up in place, and soldered it, only to find that it had moved significantly out of position.  To fix the problem I turned a steel collar to fit around the chimney, re-heated the soldered pieces with oxyacetylene, trying not to overdo the heat so I did not melt the brass flange, but enough to melt the silver solder, but not allowing the solder to join the steel collar to the brass or the copper.   Then I lightly tapped the flange onto the turned collar, hopefully into the correct position this time.  Sounds simple?  But applying the heat, and tapping the flange required one or two more hands than I possess.

But it turned out OK.

I had drilled and tapped the holes prior to soldering, and they all matched well.


The chimney is about 300mm long.  The bottom part has been dipped in suphuric acid, hence the clean appearance.  Still considering options for the chimney flared section.  It needs some form of decorative flare.



The bottom flange is soldered to the “Heldon” labelled tube, which will be soldered later to the smoke box lid.  The fasteners are M3 stainless cap screws, which will be reversed on the boiler with nuts showing above the flange.

6″ Vertical Boiler- Penetrations

Another few hours in the workshop today.

Continuing preparing the parts for the boiler.  Drilled and reamed 9 holes and the bronze bushes which will be brazed into them.  The bushes provide the screw in points for water inlets and wet steam outlets, pressure gauge, water gauge.


All of these components are just sitting in place, but giving an idea of size and form.

There will be no progress on the boiler for a week, due to forced absence from the workshop.  Child minding the grandchildren.   Hmmm… I wonder if a 2 year old could help in the workshop?   Possibly not a good idea.   Yet.

6″ Vertical Boiler. The final flange on the smoke box.


This is the smoke box lid.  The chimney comes out of the middle but it requires another flange.


So this is the cover, with the extra flange.  How did I make it?  Read on…

First a video.  Click on the arrow.  Listen to my dulcet tones.



The setup on the hydraulic press.   The copper cap has been annealed, and a 19mm hole drilled to just admit the steel taper pin.


After pushing the steel pin with 20 tonnes pressure.  Re-annealing required. 


After the next 20 tonne push.  Re- annealing again required.


After the third annealing and a final push with the press.   A bigger press might have done this in one step, but at the risk of the copper splitting. 


and a 10 minute soak in 10% sulphuric acid…


—and a tidy up of the edges in the lathe.  The intermediate piece is pushed into place, ready for silver soldering.   A couple of circular flanges to be soldered in place to hold the chimney.

Considering the force exerted on the wooden forms, I would not have been surprised if the wood had split on the hydraulic press.  But it held up.  Even so, another time I would be tempted to make the forms in steel.

6″ Vertical Boiler – drilling for bushes

I swapped vehicles to drive to my workshop today because the automatic park brake on my BMW X5 would not release.   And  in swapping vehicles I forgot to take the plans for the projects, so I could not do very much.

But I did set up for the remaining boiler wrapper perforations.


The boiler is ready for drilling the multiple holes.  It is parallel with the mill bed, in 2 dimensions.  But without the plans I could do no more.  Ready for progress tomorrow.

Note the rectangular cut out for the ash pan.

I had previously cut the 44 firetubes from 3/8″ copper pipe.  Today I spent some time squaring the ends and deburring them.  No photo.

It is cold and wet here in southern Victoria, Australia.  I had my wood burner going in the workshop, and spent some time hooking up an industrial gas blower heater, for an extra bit of warmth.

Trevithic Dredger Engine – New End Plate


This was my first effort at making a boiler end plate.  It was OK, but a lot of my hammer blows left dents which looked pretty ordinary.


I tried to improve the appearance by polishing, but that just accentuated the dents.

The boiler inspector passed it, but I coud see that he was not too impressed.  And neither was I, so I made another one.  This time I made male and female wooden forms, annealed the copper disk and pressed the domed shape.  Then re-annealed and hammered out the flanges.


It was worth the extra effort No?

I will keep the reject part.  Might be useful for something, and will remind me to be more careful.

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.

IMG_6521 2

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.


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


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.


The wooden form and the unshaped thick walled copper tube.


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


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

IMG_6521 2.JPG

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

IMG_6520 2.JPG

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.                                                                                                                              

6″ Vertical Boiler Smoke Box Cover

Today I made the smoke box cover for the vertical boiler.

I decided to try a different method for making the 20 degree conical shape.  Previously I have beaten or tapped or hammered the shape.  This time I decided to press the annealed 3mm thick copper into the desired shape.  It worked!

I needed a 20 degree conical shape.  For various reasons I decided to use 3mm thick copper.

So firstly I turned a male and female form in hardwood.

Then I cut out a circle of 3mm thick copper plate.

Then I pressed the shape between the forms in my 20 tonne hydraulic press.

It worked perfectly! In one go. But the flange still needed beating with a hammer, after multiple annealings.



This is a staged shot of the pressed copper between the male and female hardwood forms.


The female form on the left, and the copper, already flanged over the male form.


The male form


Prying the copper dome off the male form


This is the smoke box lid, shaped and turned, ready to be attached to the boiler cylinder.  It looked a lot nicer after a soak in sulphuric acid.


This is how it will look with the chimney attached.

6″ Vertical Boiler. CNC Drilling Firetube Holes

Boiler6 transparent

After all of the careful flange forming I was careful to not screw up the firetube perforations in the boiler end plates.  At times like this it is great to have a CNC mill/drill.


The wooden form is useful as a clamping aid.


No major stuff ups (or should it be “stuffs up”?).   And I am not pointing out the small ones.  I was unsure in the firebox plate which side to chamfer.  Will I silver solder the top side or the bottom side?  Eventually I decided that I would solder between the firetubes rather than the underside.  Still unsure whether that was the best decision.

The “ligaments” (the metal between the holes) must not be less than 3mm.  The minimum in these plates is 3.5mm.  The holes are chamfered to make the silver soldering process easier.  The extra hole in the top plate is to install the bronze bush for the attachment of the wet header.

6″ Vertical Boiler, Using Clekos, and dropping the Traction Engine into a hole.

Tha firefox wrapper is made, and today I fitted a butt strap.  The butt strap will be riveted to the wrapper, and brazed later.  In order to drill the rivet holes, the parts needed to be held together, Clekos proved perfect for the job.


Using the external clamping Clekos to keep parts in place while I drill the first hole.


Then as each hole was drilled an internal Cleko was inserted.  Worked very well.

Then, a Bit of fun on the TRACTION ENGINE

Oh Bother.  Where did that hole come from?  And why isn’t this traction engine a 4 wheel drive?  Had to uncouple the trailer, and two men to push it out of the hole.

The redesigned steam regulator worked very well, as did the steam driven suction pump.  The new oiler filled up with steam, so I need to fix the non return valve.  Probably a bit of grit in it.


Vertical Boiler Firebox Wrapper

Next part to make on the 6″ vertical boiler is the firebox wrapper.  I had ordered some 3mm thick 5″ diameter tube from the UK, but when it arrived, at vast expense, it was only 2.5mm thick, and would not pass the boiler inspection.

The vendor agreed to replace the item, but still no word when that will happen, so I decided to make the tube myself, by rolling 3mm plate copper sheet.

I calculated that I would require 399mm to make a 5″ tube, and bandsawed a piece off my 300x400mm sheet.

My hand roller is only rated for 1mm thick material,  and my powered shop roller would not fit the 105mm width.  So I tried the hand roller.  It would not look at the copper strip in an un-annealed state.  So I annealed it.   Photo opportunity!


Too big for my “kiln” so it took longer, and lots of spilt heat.  But it was a cold winter day again, so the heat in my workshop was welcome.


The 3mm thickness was a bit of a problem.  The gears in the roller are really not designed to mesh at this thickness.  But with a bit of gear jumping, and a lot of elbow grease, the roll started to take shape.


Re-annealing was required at this stage.  Looking a bit rough.


Just love that colour


The wooden form gives exactly the final shape and size.  Determining the longitudinal cut was tricky.


I determined the squarest end, rested it on the table, and bandsawed the mark.  Then a bit of hand hammering. over the wooden form.


The foundation ring was machined to the final size yesterday.  The outside of the ring fits nicely inside the boiler wrapper. And the firebox wrapper fits neatly inside .  It needs to be OK’d by the boiler inspector before I silver braze it.


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.


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.


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


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 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.


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


The ring is almost closed


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


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.


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


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.


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.