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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.

Tag: model steam

Trevithick Dredger.. attaching the flywheel and driving gear to the mainshaft.

The flywheel and driving gear both are attached to cranks which join the connecting rods to the mainshaft.  It is important that both cranks are attached with the same angularity.   Seems simple.  The cranks are identical.  But small taper holes, through brass and silver steel.

Drilling the 2 holes took most of the day.

Figuring the setup was the biggest challenge.

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This is the setup on the milling machine.  The mainshaft is cramped on parallels, and ends of the cranks are resting on smaller parallels.   The square sections of the cranks have been centered.

First problem was that the 2.5mm drill bits were not long enough for the chuck to clear the gear.   I did not have adequately small ER collets (would have required ER8’s), but I did have a Dremel chuck which was small enough.  But no spindle for the Dremel chuck.  The Dremel chuck has a really odd thread.  I measured it at 40tpi, and 7.05mm diameter.

So I made a spindle.   Thank goodness for CNC threading.

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The Dremel chuck and the shop made spindle.

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Dremel chucks are convenient, but they are not very accurate.  Fortunately, once the hole was centred, the drill bits and reamer seemed to follow the centred start.   Here I am about to ream the hole which has 3 steps   2.5mm, 2,8mm, and 3mm.   The shop made spindle is held in the milling machine drilling chuck.

I took the reaming very gently, not wanting any broken bits of high speed steel stuck in the workpiece…. and all was well.

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And here is the gear crank pinned to the mainshaft.

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And this is the setup for the flywheel end.   Fortunately, by good management or good luck, I was able to remove the flywheel, leaving half of the crank insitu, for drilling reaming and pinning.

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I spent some time assembling the cranks and testing the rotation movements.  It does rotate, but there is still some sticking on the guides, the cause of which I have not identified/isolated.

So I sat back and enjoyed one of my Xmas presents.   Ah!   Bliss!

Making a Lead Ball for the safety valve

The deWaal plans for the Trevithick Dredger Engine call for a 30mm diameter lead ball for the safety valve.

I considered substituting steel or brass, and turning the ball, but lead is almost 50% more dense than the other metals, and that could be detrimental to the functioning of the safety valve, so I worked out how to make the ball in lead.

I have previously cast lead balls 14mm diameter, but this is significantly bigger.  I did briefly consider making a plaster of Paris mould, but I could find no balls of the correct diameter for the POP mould, so I decided to mill the mould.

On rummaging through my big milling cutters, I discovered that I have a ball nose cutter, 31.75mm diameter.  It was part of a package of cutters which I had purchased years ago, and almost forgotten.  I had bought the cutters BY WEIGHT.  I think that I paid $US5 per pound, and I bought 20lb.  Mostly the cutters were resharpened end mills, but one of them was an unused 31.75mm ball nose.  Pretty close to perfect for this job!

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First I cut off two 25mm lengths of 40mm square solid alu bar.

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Then milled them pretty close to square and identical.

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Then used the 31.75mm end mill to make a hemisphere in each alu blank and drilled and tapped for a 5mm cap screw in each corner. 

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On the left is the mould, screwed together, with a hole drilled into the spherical cavity.  Here I am heating it in a frypan, ready to accept the molten lead, which is being prepared in the cast iron saucepan on the right.  I hasten to add that SWMBO knows nothing about this.  Those utensils are part of my workshop gear, and will never be used for human consumption.  SWMBO does not read this blog, so I am safe.  I hope.

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From my previous experience with lead castings, I have decided that the mould should be 250-300ºc so the lead will not solidify in the small entry hole, and also to minimise the formation of voids in the casting.

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Here is the molten lead after pouring.  It is still liquid.

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And after cooling and splitting the mould.  The hemispheres were not exactly aligned.

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And there was a big void.  I could have filled it.  But I decided that if I made the mould even hotter, it might work better, so I made another lead sphere.

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The next one, on the left, worked perfectly.  I heated the mould to 300ºc, and no voids at all.   I also reversed the bolting positions which removed the hemispherical misalignment. Drilled and tapped for the supporting ring.

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And here is the weight in its final position.   I dropped it, resulting in a Death Star indentation, which I kind of like.  A little bit of polishing will remove the latitude lines.

Only one part for the day’s work again.  But it was a LOT OF FUN!

 

 

 

How Many One Off Parts Can You Make Per Day?

Obviously it depends how many machining operations are required per part, but these days I find that one or two parts per day is about all that I can manage.  That includes deciding on then finding the material,  drawing up the part in CAD, mounting the material and the cutter(s), then machining and finishing time.

Take today for example.  My aim was make a steam pressure valve for the Trevithick Dredger Engine.   It consists of a lead ball weight 30mm diameter, a lever arm with a hook, a simple stand with a M6 male thread, a movement restrainer, and the seat and valve.  6 fairly simple parts.  I thought that I might get it all done in one day.

But at the end of the day, all that I had made was the arm, stand and restrainer.  3 simple parts.

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The pressure valve arm, stand and restrainer in place.

Admittedly the arm is stainless steel of unknown grade.  I broke 2  (4mm) cutters before I had slowed the milling feed rate to a snail’s pace 40mm/minute.  Machining time for that part was over an hour!  Then at least another hour of hand filing and finishing.

It is just as well that the worst day in the workshop is better than the best day of working!

And next will the interesting job of making the 30mm diameter lead ball weight.  Still thinking about that one.

Trevithick Dredger Engine.. the steam valve operator.

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I did not know what to name this assembly.  It attaches to the cross head, and pushes the handle of the steam valve up and down each revolution to admit and release steam from each end of the cylinder.

It uses the U shaped metal strip which I cut out and bent yesterday.   It is 230mm long, and I made it from brass, including the filler strips which actually contact with the valve lever.  I made the filler strips a few mm longer than necessary, so I can file them as necessary when the engine is timed.

Trevithick Dredger Engine.. the firedoor fittings. Or silver soldering tiny pieces.

Another day in the workshop.

Yesterday I  bolted the latch to the door.  But how to attach the catch to the surround, and the restraint to the door.  The plans call for tiny screws, but that method did not appeal.  I decided to silver solder them in place.  Silver solder is immensely strong, and does not require tapping and threading minute screws into position.  The problem with silver solder is that some parts of the firedoor are already silver soldered, and I did not want to risk undoing that previous solder.

So, I used a heat sink.

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The catch is held in position by pressure from the latch.  I did NOT want to melt the solder of the hinge, so I rested a sizeable block of brass on the hinge.  Pure copper would have been even better.  Then, as I was soldering the catch, any heat travelling toward the hinge would have been absorbed into the brass heat sink.

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A staged shot, after soldering the catch was finished.  I was careful to keep the flux just in the joint which was to be soldered, to avoid the solder running into other areas.

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A close up of the soldered catch.  The iphone camera is pretty good hey?  That catch is only 3mm wide.   A bit of filing and finishing needed.

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And the finished door.  Looks OK IMO.

The next job for today was to machine a strip of metal 6mm wide, 2mm thick and 600mm long.  I decided to make it from brass because I have a sheet of brass the correct thickness, and I was already thinking about the tight bend which was going to be required.

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So, I bandsawed a strip of brass from the sheet, about 50mm wide.  Then removed the milling vice and universal divider from the milling machine.  I am amazed at how those items are becoming heavier with age!    Then cramped the brass strip to the table and machined the sawn edge with a 6mm end mill which protruded into the milling table slot.  Fortunately I managed to not enlarge the T slot during this procedure.

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Then moved the brass strip, and indicated it parallel.  Then used the 6mm endmill to cut off the 6.5mm strip.  Probably not very efficient, but it worked, and the strip was correctly sized and dimensioned.

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Finally, annealed the middle of the strip, and bent it around a 5mm thick piece of steel, with a rounded edge.   This will become the fitting which operates the steam inlet/outlet valve.

Trevithick Dredger Engine ….Con Rods

I had previously bent the brass U pieces which hold the split bronze bearings to the wooden connecting rods.  I had also made the con rods and the bearings.  Today’s job was to fit them all together.

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Bending the U pieces on my shop made bender.

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And the Jarrah con rods.  The U pieces need to be shortened.

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With the bearing in place, measuring the amount of shortening required (approximately).

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Using an end mill to shorten the U piece arms.  Note the paper between the workpiece and the vice jaws.  That reduces the chance of the work moving.  How do I know?  Dont ask.

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The holes are carefully drilled M4 through the U piece and the wood.  Stainless steel square nuts on SS threaded rod.   Then the bearing was reamed again to the finish dimension.  I have yet to make the wedges which hold the pieces in position.

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The (almost) finished connecting rods.

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And a test installation on the engine.  A bit of workshop clutter to add to the atmosphere.

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And I had a bit of daylight on this beautiful summer day, so I made and installed the firedoor latch.

I am hopeful that I will have this engine running before I say goodbye as my subscription to WordPress finishes.  Not exactly sure when that will happen, so if I suddenly disappear, do a search on YouTube for the video of it running on steam.    Still a fair bit to do before that happens, but things are progressing!

 

More Trevithick, and Xmas

The last 20% of the build takes 80% of the time.  Someones law.  But SO true.

I should be Xmas shopping.  But frankly, buying stuff which costs money, is not wanted or appreciated, takes time, and should be donated to people who really need it….  irritates me.

At least the adults in my family have taken a sensible decision to randomly allocate one person to buy a present, for one person only, to a maximum amount.

But it does mean that the one present should be meaningful.

I decided on something that my allocated recipient might like.  A bit unusual.  Something they (he or she) would never normally buy, and should make an impression.  But there was a catch….  I had to drive to the shopping centre, park, find the shop, and buy.

So I looked up the shop on the computer, noted the address, drove there, parked, paid parking, walked several hundred meters, and could not find the shop.  Walked for about an hour.   The shop no longer exists.  It has closed and they have not changed the Internet info.  Bummer.

But at least I actually own one of the items.   It is a bit old.  Actually about 40 years.  But it is in good condition.  so I will wrap it and give it.  And hope that its aged condition is not  detrimental.

My allocated recipient is the au pair, from Italy, aged 19, who lives with and looks after some of my grandchildren.  She is a lovely girl, and I believe that she is really enjoying her stay in Australia, with my youngest daughter and her family.

The present is an Australian flag.  I hang it on out front gate every Australia Day.  I hope that she sees it as a compliment, and a memory of her stay in in Oz.

I will buy a replacement for myself.  It will probably be made in China, but so what?

So today I had a few hours in the workshop after wasting a half day in the shopping mall.

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And made and installed the water feed tube from the pre-heater to the boiler.  I had made the clack valve in my previous session.

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I find that it is actually quite tricky to make the bends in exactly the correct place, with exactly the correct angular bends, and to silver solder the flanges at the correct angles.   This one worked out well.   I usually bend a piece of aluminium wire to roughly the correct dimensions, on which to base my copper tube bends.

Finally, normally, I detest Christmas (actually it is Saturnalia, a pagan roman festival).  The commercialism, the waste on presents, the killing of turkeys, pigs, sea life.   It is all gross, and I hate it. Yes, I am a grinch.  Once, I just refused to take part in it, but the fall out was immense, and I am not strong enough to repeat that protest.  But this year, my adult children have made a decision which makes me immensely proud.  They have decided to limit adult presents to one per person, (the grandchildren still get heaps), and the meal will be vegetarian.  A step in an wonderful direction.

 

Trevithick Dredger Engine- the stays

 

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The stays appear simple but they took several hours to make and adjust.

When I arrived at my workshop today I discovered that someone had attempted to steal the Toyota Landcruiser tray which I leave parked there.   A window had been smashed, the doors were unlocked, and the cowling over the steering column had been removed and broken. (presumably in an attempt to access wires to start it.)  The driver’s door lock showed signs of being jemmied.   The ignition lock also showed signs of being forced.  The thief must have been an amateur, unable to get the vehicle started.

The police arrived soon after being telephoned.

Fortunately the vehicle is drivable, but repairs are required.  I am relieved that it was not actually stolen.  The police told me that these vehicles are in demand by thieves.  They are built like tanks, and useful in ram raid thefts.

So the dredger engine will be put aside while I install video cameras at my workshop.

(I have deleted a paragraph here.  It was written with exaggeration caused by anger.)

After the police left, I made and installed the stays which are visible in the photos.

 

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The lower end of the stays attach to the boiler flat plate end.

 

 

 

Trevithick Dredger Engine Progress

First day of summer in southern Australia today.  And it was very warm and windy.  Keeping my eyes open for snakes, but none seen.

I was pondering how to attach the crankwebs to the flywheel.  I had decided that I would not silver solder them together, because the heat would likely distort the thin flywheel.  And pressing them was not feasible because I had machined them to a sliding fit.  Whatever method was used, I wanted it to be reversible i.e. future disassembly possible.  So, in the end, I used small brass screws which will not be visible when the engine is painted.

 

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countersunk brass screws holding the assembly together.

 

I made 2 more U shaped bearing retainers to fit on the ends of the connecting rods (same as shown in last post).

Then made 2 shafts which will be attached to the cross head bar, to join to the con rods.  These are made from silver steel.

 

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The concave end had a radius of 10mm.  Fortunately, I had a 20mm end mill which worked well to produce the curve.  A bit of finishing required for these parts.  I will probably run them for a while in my gemstone tumbler to knock off the sharp edges and polish them.

 

 

 

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They will be pinned in place at the ends of the cross head bar.

 

Trevithick Dredger Engine Guide Bars

I was discussing the guide bars with a very experienced modeller, and he finished with some advice….  “make them either very accurately, or very sloppy, otherwise you will have problems!”

The guide bars and cross-head

Well, I decided to shoot for “very accurately”.

I made the cross-head bar, and silver soldered it together.

All seemed good.  Just the guide bar bushes to be made and Loctited into position.  After a soak in sulphuric acid and tidy up.

So I made the bronze bushes, drilled them in the lathe to 9.5mm, then reamed them to 10mm.  Or so I thought.

But when I fitted them to the 10mm guide rails, they were very, very sloppy.   Checked the guide rail diameter… 9.99mm.  Checked the reamer 10.07mm!!  Chinese reamer.

So I searched my reamers and found 2 more.  Another Chinese one measured 10.04mm.  Another was a Sutton, made in Australia.  It measured 10.00mm.  I reamed a test piece, which fitted the guide posts perfectly.   So which reamer did I use?   Guess.

I made some more bushes and Loctited them to the cross-head.  Then drilled and reamed them, carefully, accurately.  This time the fit on the guide bars was snug, perfect.

Is there a point to be made here?  You better believe it.

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.

 

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- the flat end

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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.

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204mm diameter.

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

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The disk which will become the flange is tapped.

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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.

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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.

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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. 

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The end plate and the flange mated together

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

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

 

6″ Vertical Boiler- Steam Outlet & Safety Valve Standard

Some more progress over the last 2 days.

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

 

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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.

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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.)

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.

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.

TRIPLE EXPANSION MODEL ENGINE- FIRST RUN (air)

This is a short video of the first run of the Bolton9 Model Triple Expansion Steam Engine, which I have been building on and off over the past 3 years.

The video is a bit shakey, because it is taken on my hand held phone while I am using he other hand to operate the controls.  I really did not expect the engine to work!

It runs a bit roughly, and is still quite tight, but settles down in the final few seconds.

It is not running very smoothly, because it is on air rather than steam, and because it is probably only powered on the high pressure cylinder, and maybe a bit on the intermediate, and not at all on the low pressure cylinder.

The next day it would not run.  Very frustrating.  I suspect that one of the eccentrics slipped on the crankshaft, and threw the timing out.  Not the easily accessible low or high pressure valve, but the intermediate one, which needs another teardown to get to it.

But Hey!  It will work.  I can see the light at the end of the tunnel.

One of my readers has requested a description of the triple engine timing procedure, so that will appear on this blog soon.  Unless you have a particular need for the timing info I suggest that you give that post a miss.

A Turntable for the Triple Expansion Engine.

I have not weighed the Bolton 9 triple expansion steam engine, but I would guess that it is 20-25lb.  (weighed it.  25.5lb)

Access to the various bolt on bits and pieces has become increasingly difficult and tricky, and involves frequent repositioning of the engine.

I removed the bolt on base and that has improved the situation a bit.

Then I had a brainwave, thought bubble, inspiration  whatever, and I tried a ball bearing turntable….   you know….. one of those Chinese restaurant middle of the table gadjets.

It is incredibly useful!

Here are some pics and a video showing it in place;  just a demo of the engine at its current (unfinished) stage.  I think that the turntable might  become a frequently used tool for heavier models.

triple apr7.JPG

The Bolton 9 on the turntable

triple water pump valve.JPG

And the latest additional bits…   non return valves on the water pumps.

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