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 – 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.

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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

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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.

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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.

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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.

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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.                                                                                                                              

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.

 

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

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

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The male form

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Prying the copper dome off the male form

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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.

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This is how it will look with the chimney attached.

6″ Vertical Boiler. CNC Drilling Firetube Holes

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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.

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The wooden form is useful as a clamping aid.

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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.

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

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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!

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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.

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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.

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

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Just love that colour

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

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

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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.

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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.

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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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Trevithick Boiler End

The first part to be made for the Trevithick dredger engine is the domed end of the boiler.  It is formed from copper plate which is 3mm thick.  first a circle is marked out, then bandsawn from the copper plate.

I decided to make a wooden form.  Fortunately I have a CNC lathe (see earlier posts about the CNC conversion of a manual lathe), so drawing the profile and generating the G code using Ezilathe was, well, easy.

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CNC’ing the wooden form for the boiler end plate.  The roughing steps.  Carbide tip which has been sharpened to a cutting edge, suitable for wood.

This is the final roughing cut, and starting the finishing cut.

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CNC turning.  Light sanding required to remove the fur.  The wood is European oak.  Central hole for a locating pin.

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The oak form was attached to a red gum block which was held in a 6″ vise.  I have already commenced shaping the copper disk here.  The copper is cramped to the oak form after annealing, and gradually hammered to shape.  Tapped rather than hammering.

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My “forge” is a few fire bricks in a steel shell, and a roof of steel to help retain the heat.  The torch is fuelled with propane.  It was originally a weed flamer, used to burn serrated tussock.

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Red heat was achieved in 90 seconds.  This is 600 degrees centigrade.  copper melts at 1084c, so there is a good safe margin.  I quenched to cool, for speed.

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This welder’s clamp proved to be the most effective method of holding the copper disk to the form.  I fitted  copper and  brass heads to the tapping hammer to minimise the chance of “bruising” the copper.

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Progress

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About 10-12 heating-hammering cycles in 1.5 hours to get to this stage.

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Getting close.  I will finish it tomorrow.  Might wash up before cooking dinner.

Home Made Ring Roller, and first attempts at bronze brazing.

The two projects for which I am currently accumulating materials, will require rolling copper sheet and rod into circular shapes.

A few years back I made a ring roller to make components for steel gates, and it would have been perfect for rolling the copper foundation rings and fireboxes.

It is fairly heavy duty roller, powered by a 1/2 HP motor, geared down 1:40.  I have bent mild steel up to 1/2″ thick 4″ wide, but I founds its limits when I tried to bend some hardened rod.   It left some grooves in the rollers.   And those grooves would imprint marks into the soft copper, which would be totally unacceptable in the two boiler projects.

So yesterday I disassembled the machine, removed the rollers, and turned the rolling surfaces in the lathe until the grooves vanished.  The 31.75mm diameter finished at 30.4mm.  Nice and regular and smooth.  And working smoothly again.

Pretty mundane stuff eh?  But oddly satisfying.

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BRONZE BRAZING

And after that I tried my hand at bronze brazing joins in copper parts.   The boiler inspector requires that certain joins in the boilers use bronze brazing, instead of silver soldering.  I am now reasonably proficient with silver soldering, and had no experience with bronze brazing.  So, do I try to learn a new skill and use it on my expensive copper components of the boilers?   Or do I pay an expert to do the bronze brazing for me?

Well, I decided to buy some bronze rods and flux, and give the bronze brazing a try on some copper scrap.  The AMBSC boiler code requires the use of Tobin bronze.  Local welding suppliers had never heard of it, but I found a supplier on ebay.

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Tobin bronze is another name for Naval Bronze. (according to my quick Internet “research”).  It is relatively resistant to corrosion, and very strong.  Actually much stronger than silver solder and with a much higher melting point.  Silver solder is said to be as strong as the parent metal, so bronze must be awesome.  Bronze will fill gaps, indeed a V gap is desireable, wheras silver solder prefers an even, tiny space which the solder fills by capillary action.

The brazing rods are available in diameters 1.6, 2.4, and 3.2mm.  I had no idea which size would be best, so I bought 1.6 and 2.4mm.  I also bought some 303 flux powder, even though some experts say that flux is not necessary.  OK, lots to learn.  (p.s. flux IS necessary. )

So, onto YouTube, and watching multiple tutorials on bronze brazing copper.  I reckon that YouTube is fantastic for learning new skills.

With silver soldering, the solder goes to the areas which are fluxed.  But, it seems that when bronze brazing, the bronze follows the heat, so the application of heat is critical.  And not just where the heat is applied, but how much.  The thing is, that the parent metal is not melted in either process (unlike welding).   When bronze brazing copper the temperature range between succesful brazing and melting the parent metal (which means disaster) is quite narrow (about 100ºc), and the brazing temperature is about 950ºc, so it is tricky.

And copper is an excellent heat conductor, so the heat spreads rapidly through the parent metal, with result that the bronze filler spreads and it is difficult to get a good appearance.

Here are the results of my first efforts.

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The copper is 3mm thick.  The bronze filler is not pretty, but this is my first ever effort.  I discovered that you cannot actually see the molten puddle until you have moved on a bit, and by then it is easy to have applied too much filler.

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I cut across the join to check the adequacy of the brazed join.  I was quite pleased to see that there were no gaps or voids.  Also, although the bronze filler looks ugly on the surface, it is actually fairly flat, and should be insignificant when painted.   You can see the V which was prepared in the edges of the join.

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Next I tried an angle join.  Looks neater, but not enough bronze filler at one end.  USB for scale.

OK, looking promising, but what about thin copper?  Will that just melt away?  By the way, my heat source is oxy-acetylene.  I tried MAP gas with air, but got nowhere near enough heat.  Oxy-acetylene burns at 3500ºc and copper melts at 1083ºc so it is not difficult to end up with an ugly, expensive blob of copper and bronze.

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This is 1/4″ pipe with a 0.7mm wall.   No problemo.

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and the final test for the day was end joining the 1/4″ pipe.  The hardest aspect was holding them in position.  Quite happy with this.

I tried both 1.6 and 2.4mm bronze filler rod diameters, and for this scale job I preferred the 1.6mm.  The  joins were significantly lumpier with the 2.4mm.

So, with a bit more practice I think that I might be able to bronze braze where necessary on the vertical boiler and the Trevithic dredger engine.

P.S.  Those readers who know about brazing will get a laugh.  I did the brazing without dark glasses!  None of the tutorials mentioned that dark glasses allow you to see what is happening in the molten puddle.  I found out about dark glasses at my model engineering club club meeting last night.  John.

 

 

 

 

 

Bolton 7

For reader Timothy, I hope that these photos answer your query.

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The Bolton7 was my first attempt at engine building.  As you can see, the finish leaves a lot to be desired.

Another Use for Magnets

I purchased some bronze disks for use in the model Trevithick dredger engine.  The disks 204mm diameter had been bandsawn off rod.  I had specified minimum thicknesses of 7mm and 12mm.  One disk was 9.2-9.7mm thick and the other was 12-15mm thick.

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The bandsawn blanks of LG2 bronze.

In preparing the disks for machining I filed off a few protrusions, and using a straight edge, identified the valleys and ridges.

The thicker disk was held in the 3 jaw chuck and both faces were turned flat with no problems except avoiding the needles which were thrown off in a wide arc around my lathe.  Final thickness 12.5mm.  A persisting divot should be able to be avoided in the final part.

The thinner disk needed to be packed out from the jaws of the chuck by 4-5mm in order that the lathe tool  cleared the jaws during machining.  In the past I have used machined packing pieces, but it is always a fiddle to hold the workpiece, the 3 packing pieces and the chuck key in only 2 hands.  Today I had a brainwave.

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I used rare earth magnets!

I tried to measure the thickness of the magnets, but they are so powerful that I was not confident that I was getting accurate readings.  So I just used them and measured the thickness of the finished workpiece.

I am sure that this idea is not original.  But it is to me.

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Here is the thin workpiece held in the 3 jaw, and packed away from the chuck by rare earth magnets.  Of course the magnets are attracted only to the jaws, and not the bronze workpiece, which helps, but I will try this on steel later.  Should work for magnetic metals also.

After machining both faces I took various measurments of the workpiece thickness.  The measurements in mm were 8.73, 8.68, 8.69, 8.72, 8.70, 8.72.   Not perfect, but not too bad at all.   I wonder if I might have improved the measurements by surface grinding the magnets.  I wonder if the chuck and its jaws are contributing to the variation.  It was certainly an easy method.

If the workpiece had been thinner I could have increased the thickness of the packing by doubling up the magnets.

For those who are following the Trevithick Dedger Engine build, the bronze was not cheap.  The 12-15mm disk was $AUD90 and the 9mm disk was about $AUD80.  From George White P/L, Melbourne.  I will be nervously trying to not muck up the machining.

A New (to me) Tool

One aspect of our weekly GSMEE meetings (Geelong Society of Model and Experimental Engineers) is that I learn something new at every meeeting.  The exposure to new information is not too surprising considering that our group has members who are or were a machinery designer, mechanical engineer, CNC operator, marine engineer, aircraft mechanic, a quarry operator, gun enthusiasts, a fireman and various other areas of expertise.  Even a bee keeper.  And even a retired gynaecologist.

Recently Neil brought in a boiler which was assembled but not yet soldered.  And it was held together with spring loaded clamps the like of which I had never before seen.  Some other members were also very interested in the clamps, which are, apparently, extensively used in aircraft panel assembly and repair, and also in car body work repairs.

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Neil’s boiler end plates, clamped together.

The clamps are called CLEKOS or CLECOS.  They are easily applied and removed and are reusable.  They are used for temporary joining of materials to facilitate marking, drilling, riveting, soldering, welding or gluing.  Exciting to me because I can see many applications in model engineering and wooden toy making.

The Clecos come in a variety of sizes and configurations.

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This Cleco requires a 1/8″ hole, and will join materials up to 1/2″ total thickness.  This type joins 2 or more pieces of material which have a hole drilled as small as 2.5mm up to 5mm.  The range of hole sizes may be larger than I am aware.   Only one face of the materials needs to be accessible, so the Cleco can be used to fasten material to a closed container such as a boiler.   It is spring loaded and requires a tool to apply and remove it.  Application and removal is very quick.  Any materials which will accept a drilled hole can be used-  metal, wood, cardboard.  It would not work with easily compressed material such as foam rubber.  The application pliers are available on Ebay and are inexpensive.

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This spring loaded Cleco looks particularly interesting.  The clamps are small, have clamping thickness of 20mm and a reach of 1/2″ to 1″.  Again, they are not expensive ($AUD7-11), and very quick to apply and remove.  Surprisingly powerful grip would be quite adequate for gluing or riveting or soldering.

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Some Clecos do not require the application pliers but use a wing nut.

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And others use a hex nut.  Anyone know why there is a copper surface coating?

The Clecos are surpisingly inexpensive.  On Ebay I have seen the spring loaded fasteners as cheap as $AUD1 each, and the pliers at $AUD15.    I bought a kit comprising pliers and 20 fasteners for $AUD49.  Ebay UK has the best selection and many have free postage.  The range on US sites is good, but postage costs assigned by Ebay are astronomical.

(A reader has commented……

The Clecos and other skin pins are colour coded, silver 3/32, copper colour 1/8; Black 5/32′ gold 3/16 brown 1/4…..     thankyou “someone”.)

 

 

Trevithick Dredger Engine Flywheel

You must forgive me for rushing this blog.  I do feel rather pleased to have made a start on the Trevithick Dredger Engine.

The first part for the TDE was waterjet cut from 6mm mild steel.  I emailed the DXF drawing Tues, it was cut out Wed and picked up today.  Impressive service from Colin and Sandy at Waterjet Geelong.    340mm diameter.  The finish of the cut is so good that some light filing and rounding the sharp edges is all that will be required.  I will machine the bore hole after the shaft is made.  The magazine article is my workshop copy.  It will not remain this pristine for long.

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The thinness of the flywheel is a Trevithick characteristic.

Buying Copper Pipe for Model Boilers

My next 2 projects require 150mm (6′) copper pipe for the boilers.  The Trevithick dredger engine will operate at only 30psi so the wall thickness needs to be only 2mm thick to comply with the AMBSC regulations.  But the other project, the vertical test boiler will operate at 100psi and the copper needs to be a minimum of 2.5mm thick, or preferably 3.0mm or 3.2mm.

I had purchased a 350mm long x 2.8mm wall thickness piece of 6″ copper pipe at an engineering club swapmeet, so I thought that would be OK for the test boiler, but when I examined it closely I noted some scribed lines from the previous owner’s intended project.  There were also some drilled holes, but they can  be used or filled.  The scribed lines were unacceptable, so thinking that they were not very deep I carefully skimmed the cylinder surface on the lathe.

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The headstock end is held lightly in the 3 jaw chuck.  The tailstock is centered in a piece of fitted Delrin.

Taking off 0.05mm per pass, and using a sharp Diamond lathe tool (from Eccentric Engineering), when the marks finally were removed, the wall thickness was down to 2.45mm, just below the minimum thickness for the test boiler.  Bummer!  I can use that piece for the lower pressure Trevithic engine, but what to use for the test boiler?

So I contacted every Australian copper pipe supplier that I could see on the Internet, every model engineering vendor, and visited every plumbing supplies vendor in my region.  2mm thick pipe is available but nothing thicker.  Then to overseas suppliers.  Eventually I located some at MaccModels Engineering Supplies in the UK.  £7.67 per inch for the 3.2mm x 6″.  So my 12″ piece will be almost £95 ($AUD190) plus postage.  I took the opportunity to stock up a few other sizes which I will need for the 2 projects.  Postage came to $AUD170.   A bit painful.

So, to end this expensive story, my 3.2mm thick copper pipe is on its way.  I do feel a bit guilty about the Avgas being burnt to get it here, the kilogram x kilometers of air pollution and CO2.  And the annoyance that it is quite possible that the copper ore was mined in Australia, but I had to go to the other side of the world to buy a bit of the manufactured product.  Or is copper still mined in the UK?

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Gradually accumulating the materials.  The copper sheets and disks are 3mm thick.  The square section rod is for the boiler foundation ring.  I don’t want to start cutting until I have all of the materials.

The OTHER NEXT PROJECT

In the previous post I showed the boiler which I am intending to build.

In this post I will show you the steam engine which I also intend to build when I have AMBSC approval and I have accumulated the materials.  I have discussed the plans with the boiler inspector, and am in the process of redrawing the plans taking into account the required modifications so it can be run at public exhibitions.

It is the TREVITHICK DREDGER ENGINE, at 1 in 8 scale.

This was designed by Richard Trevithick, and made in 1806,   It was the first high pressure steam engine.  It also employed a steam blower, cylindrical boiler, safety valve, and many other innovations.  Incredibly, the engine worked in its first iteration.   Richard Trevithick was indeed a genius, although relatively unrecognised in his own lifetime, and for almost 2 centuries since.

Here is the earliest drawing which I could locate of the dredger engine.

It is from an encyclopedia which was published in 1818.

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This is a drawing of a Trevithick dredger engine which was reconstructed in 1885, with some errors, including the bent connecting rods..   Of particular interest is the piston-cylinder assembly which is partly encased by the boiler to minimise heat loss. The large, thin, flywheel is a characteristically Trevithick feature.

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The Trevithick engine as reconstructed, and as it is displayed in the London Science Museum today.  The blacksmiths who formed the domed boiler end, pentrated by the cylinder assembly must have been incredibly skilled.

The Trevithick Dredger Engine was drawn at 1:16 scale by Tubal Cain in 1987, and modelled by him. His plans were published in “Model Engineer” magazine.

It was redrawn by Julius Dewaal at 1:8 scale and published on the Internet in 2016.  The plans are currently freely available on Google Images, as 9 pages of A3 plans.  The plans are beautifully drawn, but require some modification to comply with current AMBSC regulations.  I am currently redrawing the Dewaal plans with the necessary modifications.  When they are approved I will detail the modifications.  A 1:8 scale the flywheel is 340mm diameter (13.4″).

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A schematic drawing of the engine, as it was reconstructed.

So, watch this space.  Getting the plans finalised and the boiler approved will take some time, as well as gathering the materials.  From my preliminary discussions with the boiler inspector I will need to learn how to braze in bronze, and I will document that process.  Finding a supplier of phosphor bronze in the required sizes is proving difficult, and I might have to settle for the nicer to machine, but weaker, LG2 bronze.  If any reader knows of a supplier of cold rolled phosphor bronze sheet 200mm wide and 6-8mm thick, I would be delighted to hear about it.

Triple retrospective

This post is for reader Roy, who asked how the triple expansion engine columns and base and cylinder blocks were aligned, and also about joint sealants.

To be honest, I did not really remember the details, but the posts on or close to Feb 2015 include the following photos.  The aluminium plates were precisely machined keep the column faces exactly separated by the final width.  The plates were bolted to the columns, then to each other.   I lined up the join in the plates with the center of the main bearing housings in the base plate.

The longitudinal alignment with the cylinder bores was determined by the precise drilling in the tops of the columns, and the cylinder base covers.  And a little longitudinal movement in the crankshaft allowed for a few thou discepancy.

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And this is what I used to steam proof the joins.  I used no gaskets.  The Loctite 567.  It was recommended by an expert friend who uses it on full size steam engines (thanks Tom!).  The Loxeal 58.11 is also excellent but it sets very hard, and is very difficult to separate later.

 

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BOILER FOR MODEL STEAM ENGINES

Now that the model triple expansion engine is working on steam, I feel able to put it aside, again, and move onto the next project.  The triple is not quite finished.  It needs cylinder lagging, control rods for the cylinder drain cocks, drain tubes for the cylinder drains, and an extra pump for the condenser cooling, and some paint, possibly.

It also needs a boiler.  I would like to exhibit the triple at club demonstrations and public exhibitions, but for that I need a boiler which is certified by our boiler safety authority.  So I intend to make a boiler to AMBSC code, and big enough for the triple or any other engines which I might make in the foreseeable future.

This is what I have in mind….

boiler assembly

This is a copper boiler with a 152mm (6″) diameter barrel, a superheater, gas or coal fueled, and firetubes (most not shown).  The plans call for a 5″ barrel, but I have been unable to find any suitable copper tube, and I have some 6″, so that is what will be used.  I am currently drawing up the plans.

The certification process here in Australia requires the following steps:

  1. Preliminary discussion with the boiler inspector (done)
  2. Submission of 2 sets of plans to the boiler inspector.  If acceptable, one set is signed off and stamped and returned.  The other set is held by the inspector.
  3. Inspection of the prepared components by the inspector prior to soldering/brazing/welding.
  4. Inspection of the firebox and tube assembly after soldering/brazing/welding.
  5. Inspection of the barrel and outer wrapper after soldering/brazing/welding.
  6. Testing the boiler after completion.  This involves a hydrostatic test, at double working pressure for 20 minutes, then a steam test at 10% above working pressure.

If it passes, the boiler is certified for 12 months, after which it must be retested.  If it passes the retest it is certified for 3 years.

The certification process is performed by volunteer inspectors attached to model engineering clubs, and is done at no cost.

However the materials for a boiler like this are quite costly.  I managed to obtain some  copper tube for the wrapper, and bought some copper plate for the firebox and boiler ends on Ebay.  Bronze for the bushes from a local bearing supplier (LG2), and firetube copper tube from local plumbing supplies.  All up, so far, is approaching $AUD1000.  And yet to be factored is the safety valve, various cocks, sight gauge, hand pump silver solder.  And I intend to make and fit a steam driven feeder pump, and possibly a steam injector.

If there is any interest in this project I will post progress notes and photos.  Let me know.

Small Tube Bender

 

I have recently been busy installing a steam powered water injector on the 3″ Fowler traction engine.  Involved quite a few bends in 1/4″ copper pipe.

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Some of the new pipework on the traction engine.  Since this photo, I have also made the winch functional.  (pics of that in future post)

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Hand pipe benders.

I was not totally satisfied with the regularity in the bends, or the straightness of the runs in the pipe.  That provoked some discussion at our model engineering group, and one member (Stuart T) showed us the pipe bender which he had made some years ago.

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Pipe bender designed and made by Stuart Tankard.

 

As you can see it has a  heavy duty frame,  shoulder bolts holding the rolls with machined slots for various sized pipe, and a 19mm hex connector for the driving battery drill.  A demonstration of pipe bending on this machine convinced me of its superiority to the hand held benders

Fortunately for me Stuart still had the plans which he had drawn up, so I made my own bender.  I made a couple of changes to Stuart’s design.  I made a 1/4″ hex on the driving screw, to accept the commonly used connector for battery drills.  And I did not have any suitable bronze for the main bush, so I made a brass bush, which incororated  a thrust ball bearing which engages during the bending procedure.  Probably unecessary but it was there in my junk drawer so I used it.

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The radius of the bend in the tube is determined by the radius of the roll.  1″, 3/4″ and 1.5″.  Each radius has grooves for 1/8″ 3/16″ 1/4″ 5/16″ 3/8″ and 1/2″ tube.  Since then I have also made 2″ rolls.

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Aluminium rod for the rolls.  

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Using a bearing to centralise the tailstock end before center drilling.

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The lathe tools used to make the grooves.

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3 rolls turned from each length, with an allowance for parting.  Then drilled and reamed, and parted in a lathe big enough for the 2″ bar to be securely held.

 

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Completed bender.  The wooden box keeps the components organised.  Not a tribute to the craft of wood working but it will do.   The vacant pegs are for 2″ rolls which are yet to be made.

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The raw materials for the tool.  1″ X 3″ and 1″ square mild steel, and 1/2″ silver steel.

The bender is held in a bench vice.  The bending process is quick and controllable using a variable speed battery drill.

The symmetry of the rolls (as opposed to the asymmetry of the hand held tools) means that the centre and the mid point of the bend is totally predictable.

Since then, I have made some further changes in the design of the pipe bender.

  1. I have added some feet so it sits squarely on the bench and does not require a vice for support, although it can be held in a vice if preferred.  The tool is quite heavy, so small jobs can be managed without a vise.
  2. I drilled and threaded some extra holes, to accept 2 rows of 3 rolls.  See the photo below.  That pipe bender has now become a pipe straightener.  I made some extra rolls, so now there are 6 rolls of the 2″ size.  As long as the 3 rolls in each row are identical, the rolls in the 2 rows can be different for the straightening process, but ideally there should be 6 rolls for each pipe diameter.  Straightening copper pipe is easy, as long as there are no kinks or very sharp bends, and the copper must be annealed.  The pipe should be approximately hand straightened, cut to length plus about 2″, then pulled through the rolls which have been adjusted so the rows  are almost touching.  3 or 4 passes, with some rotation of the pipe each time results in a near perfect straight pipe.   Any slight residual bend can be eliminated by rolling the pipe on a flat surface.
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Some extra threaded holes added pipe straightening to the tools functionality.

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Two rows of rolls are needed to straighten bent pipe.  So I made 3 extra wheels in 1/4″ and 3/16″ sizes.  Later I realised that the extra three rolls do not have to be identical diameter to the first three, as long as each triple are identical.  The tool straightened this bend quite nicely, although with some experience, I would now probably hand straighten it a bit before putting in the tool. 

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After 2 or 3 passages.

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And some rotation with each pull through

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The copper does have to be annealed to get a good result.

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And to put a bend in that nice straight tube…  some shuffling of the roll positions….attach the drill (slow speed setting)

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And a quick and easy bend. 

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Pretty good

 

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The underside.  Substituted cap screws for grubscrews, so the tool sits flat on the benchtop.  quite adequate for light bending jobs, but straightening needs a vise.