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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.

Category: Trevithic Dredger Engine

Back to the Trevithick Dredger Engine Model – the lagging.

The only surviving Trevithick dredger engine, in the London Science Museum, shows no signs of ever having been lagged.  I know this, because I examined it closely, recently, during my UK trip.

No lagging, no marks in the paintwork, which would indicate wooden lagging strips ever having been attached.

But, we know that Trevithick readily adopted ANY improvements to his designs, and lagging was appearing on engines at about the epoch of the dredger engine design. Plus, his engines were in use as late as mid 19th century, and lagging was well established as a normal feature by that time.

And, my model definitely needs some efficiency improvement.  Using a 40kW burner to power an engine of this size is ridiculous.   So I Have added some lagging.

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Equipment for applying lagging, from the left…   scroll saw, super glue (I used 6 tubes), strips of wood (in this case, Australian Jarrah, grinder for shaping, Dremel for shaping, good light, and the engine with some of the strips glued in place.

I used about 48 strips of wood with some spares.  These were cut and sanded in advance.  5mm x12mm x 130mm.

The Super glue is used to hold the wood strips in place temporarily, until the brass boiler bands are installed.

I started at the top, and worked my way down on both sides.  Most effort is made in fitting around  pipes and boiler bosses.  Unsatisfactory strips are levered off and scrapped.

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A rebate was milled on every wood strip, to permit removal or tightening of the boiler end plate nuts.

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I used rubber tree ties to maintain pressure until the glue dried, but in most cases I just applied finger pressure until the wood stuck fast.

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Some pipes and fittings necessitated grooves being made with round files.

Super glue does not provide a permanent bond to copper for some reason.  And it certainly will not survive the heat from steaming.  But it is fine for a quick and temporary bond.

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After making and applying the brass boiler bands (this was covered in the “6”vertical boiler” posts) I used olive oil to seal the wood.  See discussion which follows.

I chose olive oil to seal the grain openings of the jarrah.  I know from previous firings that the temperature of the boiler shell does not exceed 100ºc.  Olive oil will not smoke or flame until the temperature exceeds  200ºc, which is higher than any other common oil.  Also, as a failed olive farmer, I have plenty of old olive oil.   At worst, my engine steamings might smell like a fish and chip shop.  And refreshing the oily surface will be quick, cheap and easy.  And the olive oil will not form a skin which might peel or flake.  Anyway, this is “model and experimental” engineering.  If it does not work, I will make some new lagging, alright!.

And I took some more photos with my Panasonic Lumix 100-2 camera…….

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Still some more painting required to the end plate, and some fittings.

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That domed boiler end with the cylinder protrusion also needs some paint.  But the lagging looks good hey?

Even SWMBO has relented…  “It can go with the other engines”.  It will, when it is finished.  Still requires more painting.

First Steam Locomotive.

In 1802 a Richard Trevithick designed engine was made by the Coalbrookdale company.  Not much is known about it, but is recorded that the steam pressure reached 145psi!  Trevithick had previously operated his road steam locomotive up the Camborne Hill, but this was the first one to run on rails.

The next one was made for the steelworks at Merthyr Tidfil, Wales.  It was a Trevithick engine which ran on rails.  The owner made a 500 guinea bet with a rival (an astronomical figure.  Somewhere I read that it would be equivalent to a million dollars these days), and in Feb 1803 the engine towed 5 wagons, loaded with 10 tons of iron ore (or coal, not sure), and 70 odd bods, a distance of 10 miles.  There was dispute about whether the bet had been won due to some technicalities, and no record of it being paid, but it was a moral victory.  The age of steam had really begun.

The biggest problem was not the locomotive, but the rails.  They were not strong enough, and frequently broke.  It took the genius of George Stephenson to solve that problem, by using forged iron in preference to cast iron.  And his son Robert to increase the efficiency of the engine and boiler in the form of “Rocket”.  But that is another story, for 30 years later.

Unfortunately the original of the Merthyr Tidfil loco has not survived, but several replicas have been made, based on original drawings.  I saw one of them at Swansea, Wales, not far from Merthyr Tidfil.  Not a steaming day.  It does run.

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Not great photos.  The lighting conditions in the National Waterfront Museum were difficult.

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The typical big, skinny Trevithick flywheel, and driver’s wagon.

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Square main shaft.  Hex nuts were not around in 1802.  

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And that is a view that you don’t often see.  The pressure gauge is definitely a modern requirement, as I discovered with my dredger engine.

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Notice the fish belly rails.  Originals were cast iron.  “Fish belly” shape to increase the strength, but alas, not strong enough.  Hex nuts again!  And those gears have modern shaped teeth.  Quite a few compromises in this replica.

And I have now arrived in Camborne, Cornwall, Trevithick’s home, and the site of his famous trial of the steam road loco.

I made a pilgrimage to Fore St (“Camborne hill”), then to his statue, to pay homage.

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Richard Trevithick.  Genius.

 

Trevithick Dredger Engine at The London Science Museum

I landed at Heathrow at 6am, dropped my bags at the BNB, then caught 2 buses to the Science Museum.  Not jet lagged, but on a high, to see the only intact Trevithick Dredger Engine known to exist.

The room which houses the Trevithick, also contains 4 large beam engines, a Parson’s turbine (of “Turbinia” fame), and a very large 2 cylinder compound.

Disconcertingly, the first atmospheric beam engine, with wooden beam, was partly obscured by a souvenir stall and racks of clothes for sale.  WTF!   Don’t they realise the historical importance and rarity of these engines.  And 3 further moans, to get them out of the way.   The descriptive labels on all items had minimal information.  Nothing like dimensions, power, etc.  The attendants knew virtually nothing about the engines.  And often, items were behind glass or perspex which was reflective, and prevented good visualisation or photography.   To be fair entrance was free, but to get past the entrance desk it seemed pretty clear that a “donation” of 5 pounds was expected, (which I was happy to contribute).   Those complaints aside, I have to say that the collections were fabulous.

I could see the Trevithick at the far end of the room, so to curb my mounting excitement, I forced myself to not rush up to it, but to try to look at every exhibit on the way.

Eventually I was there and it was there in front of me.

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It was one of the smallest engines in the room (The “Energy” hall).  The older beam engines were many times larger, but that was a major reason this engine was so successful..  more power, lighter, smaller, and several times more efficient at converting coal to rotative motion.  No one could tell me why there is a huge divot in the cast end of the boiler.

The con rods, stands, standard cross tie, and chimney are not original, but were added when the engine was restored in ~1875.  But that is now part of its history.

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From that side it was apparent that the main shaft was square over its entire length, something not previously known to me.

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The boiler feed pump was relatively tiny.  I do not know if it is original.

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The firebox has been re-sleeved.  The chimney mount is part of the end plate casting.  And I think that I got most of these items pretty close to right on my model.  Does anyone know what the incomplete flange at 5 0’clock would have been for?

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Note the odd bolt pattern around the inspection hatch.  I got that wrong.  My change to the oblique slide rod stay angle brackets was correct.

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safety valve weight is adjustable.

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Water preheater pipe detail.  Aren’t the square nuts great!

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The throttle restraints are curved, and have fixed position holes for pins.

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Boiler feed tank.  Cast iron.

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Engine supports appear to be cast integrally with the boiler.

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Flywheel hub

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Flywheel spoke detail.  Likely original.

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Chimney mount detail

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Finally (although I do have more photos), a nice view from above.  I do like the crosshead shape.  I wonder if it is original.  Remnants of another Trevithick dredger engine  not currently on display, reveal a wooden crosshead beam.

So there you are.  Fascinating to me.  Interesting enough I hope to you.  I could see no evidence of wooden lagging at all, but i still intend to install some on my model to slightly improve its efficiency.

i have heaps more photos of other exhibits which I may post later.

 

 

OZ to UK

Well, I am off to Blighty tomorrow, to check out the originals of some of the models which I have made in recent years, and to pay homage to Richard Trevithick.

First stop London.  And the first stop in London is the Science Museum, where I will head straight for the Trevithick Dredger Engine.  This particular engine was made in 1806, but was designed by Trevithick several years earlier.  It was used to power a dredger on the River Thames.  Later the design was used to make steam engines to power the mills and factories of industrial England.  About 600 were made altogether, but this is the only surviving intact example, having been found in ~1878, and restored, albeit with some non authentic features.

I am due to arrive at Heathrow at 6am, and I cannot book into my accomodation until 2pm, so I will front up at the museum and put my case into storage while I spend some happy hours with the Trevithick, and browsing some of the rest of the museum.  I believe that the museum also houses a model of the road steam vehicle, which was built by a clockmaker for Trevithick as a proof of concept model.

So my next post here will hopefully include some photos of the above.    It is planned that this will all follow a 22 hour flight from Oz, via Singapore.  Not sure what shape I will be in, but hopefully I will have something to show you.

The next few days in London are planned to include The London Water and Steam Museum at Kewbridge, the pumping station at Kempton, The Crossness Engine at Abbey Wood, HMS Belfast, and maybe a return visit to pay my respects to the Harrison Clocks at Greenwich.  Busy busy!

Then a 4+ hour drive to York.  If I leave early enough I should reach York with enough time to visit the viking museum, and maybe even fit in a visit to the glorious minster.

The next day is scheduled for the National Railway Museum, which I have never seen before, and has been recommended by many bloggers.  And I will be meeting a reader of this blog, who will be showing me around the rail museum, and other interesting sites around York.

And so on.

I hope to be able to post some photos as I progress, but that will depend on Internet connections at my booked accomodations.  All Air BNB.

Later stops will include Manchester, Coventry, Leicester, Swansea, Merthyr Tydfil, Camborne, Dartmouth, Portsmouth.  Each place has been chosen so I can see outstanding museums, engines, mines, historic ships and places significant for Richard Trevithick.

The final stop at Portsmouth was mainly to visit the Fort Nelson Museum so I can see the Dardanelles Cannon close up.  But I will not miss the opportunity to see the Henry 8’s Mary Rose, HMS Victory, HMS Warrior, the submarine museum  etc etc.    Ben L, I will be in Portsmouth Tues 28 May pm until Fri 31 am if you are able to meet, perhaps one evening?

If you are getting the impression that I am very excited about this trip, you are absolutely correct!     John.

 

A Fraternal Photo

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Me and my brother Peter.  No doubting the genes.

My brother also makes steam engines, but he prefers the ones which move on steel rails. Unfortunately he lives a long way away, in the deep north of Australia, so we see him and his wife only once a year or so.

Trevithick Engine by Lumix, and an Ottoman cannon.

Some more photos with the Panasonic Lumix LX100M2.

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The Trevithick dredger engine, still lacking lagging and paint.  The chimney has a chimney extension connector, sitting a bit crooked.

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I am very impressed by the quality of these photos.

And some shots of the 1:10 model Ottoman Dardanelles cannon, which I made a few years ago.  It was intended as a practice run in wood, before making it in bronze.  The wooden model is 600mm (2′) long, and since finishing it I have not felt the need to make a bronze example.  I plan to visit the original at Fort Nelson, Portsmouth, in a few weeks. Watch out for a video/photographs on johnsmachines.com

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I think that you will agree that the quality of these photos is excellent.  The photographer is still learning.

Sir Ding Dong.

Not much happening in the workshop.  Visited by my middle daughter and family this weekend.

The boys are now 3, and responsive enough to not touch hot or moving parts and to watch out for wriggly pets.  I have seen 3 so far this season.

So we decided to give the boys some exposure to live steam.  They were intrigued by lighting the fire in the boiler, then adding wood and coal, and building up steam.  Nervously then enthusiastically operating the whistle.

Then the fun bit.

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Sir Ding Dong is a 3″ scale 2 cylinder compound steam traction engine.  It will tow this load easily.

We have had virtually no autumn rain yet, and the ground cover is very dry.  But it was a sunny and windless day, so it seemed safe enough to operate the steam engine.  No problems.  The kids, aged 3 to 69, loved it.

Oh, and by the way, the Trevithick dredger engine boiler passed its final inspection!  WooHoo!

 

Video of the gas burner which works

The first 6 minutes of the video  is getting up to 40psi.  Then a couple of minutes of the engine working.   Big file, so be patient.

At Last, a burner which does the job!

You are probably fed up with my burner trials.  I certainly was.

Fundamentally, I was trying to get enough heat into the Trevithick model dredger engine boiler, and just not managing it.  My boiler is a scaled down version of the original, in copper.  It takes a lot more heat than the 6″ vertical boiler which I made last year and I think that the reasons are…

  1.  The Trevithick design, although revolutionary for 1800 was and is a very simple, primitive, relatively inefficient design by later standards.   No water tubes and only one fire tube (the flue).
  2. The linear dimension is scaled down 1:8.  The surface areas (heat exchange surfaces) are scaled down 1:64.  The volumes, representing power output, are scaled down 1:512.  So the scale is a major factor.
  3. The firebox is 60mm diameter.  I had no success burning coal or wood, although I gave up on that one quickly after one attempt.
  4. Absence of lagging.  Reproductions of Trevithick’s engines have wooden lagging, but there was no indication of lagging on the LSM engine, or in the 1819 drawing.  I do intend to install wooden lagging, in fact I have cut and prepared the strips ready to install.

So my colleague Stuart suggested that I try his Sievert burner…

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This is a Sievert 2954.  Stuart tells me that at full blast it puts out over 40kW!   The ring is steel, machined to fit the firebox, and a close fit to prevent cold air being sucked around the edges.

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Fitted into the firebox.  It coped reasonably well with the back pressure at about 1/2 strength. 

This unit raised steam from 2500cc of cold water in 10 minutes, and got to 20psi in 14 minutes.  The target of 40psi was reached in 18 minutes.

At 40psi the safety valve operated, and despite continuing to pour in the heat, the pressure did not rise above 40psi.  So I am expecting that the boiler inspector will be happy with the safety valve.

I then ran the engine for 45 minutes, turning the boiler feed pump on and off to keep the boiler water level up.  All went well.  I have made a video of the event, but the upload failed last night, so I will try again later.

Next, to contact the boiler inspector for the final (I hope) inspection.

 

More Gas Burner Experimenting

First I tried the Sievert 2943.  I tried different gas settings, and different positions of the burner in the fire box.  I quickly discovered that an opening had to be present next to the supporting flange.  Despite that, steam was produced in 10 minutes, and 20psi was achieved in 15 minutes.  My aim is to obtain 40psi, and maintain 40psi during engine operation.

Unfortunately this burner does not work if there is any significant back pressure in the system.  Stuart has advised me to try the Sievert 2954 which he says will cope better with back pressure.  The Sievert 2954 has a similar appearance to the 2943, so I have not photographed it.

I have borrowed a Sievert 2954, but it needs some setting up, so I thought that meanwhile I would try a burner style which had been mentioned earlier.  It is a tube with multiple transverse slots.  Despite being constructed rather roughly and quickly, it produced a good hot flame.  Perhaps a bit small, but promising.

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If the next Sievert is not satisfactory I will come back to this style, and experiment with different slot numbers and sizes.

If you are becoming a bit bored with all of these gas burner experiments, I understand.  When the burner is finally sorted I will be delighted and relieved.

I have machined some wood to be used for lagging.  It is West Australian Jarrah.  A dark coloured wood which is often used for exterior flooring.  I will apply it to the boiler soon.

 

Experiment Failure

Sometimes information derived from a failed experiment is just as useful as a successful experiment.  Several readers predicted that burning coal would not not work in my dredger engine boiler, but I had to be convinced.

So, I removed the gas burner.

I have 3 types of coal.  One is Welsh steaming coal in 25-30mm lumps.  It has an attractive shiny appearance.  The other is coal lumps which were picked up next to a local railway line and are probably from Newcastle NSW.  I also have some brown coal, but it is in the form of briquettes, and I did not attempt to use them.

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Welsh steaming coal top, railway line droppings bottom.  All too big. 

Both black coal types were too big for the ~60x40mm diameter firebox in the dredger engine.  How to make them smaller?

Smash them up with a hammer and pass them through a sieve?  That would leave a lot of unusable tiny fragments as well as bigger bits.  And be very messy.  And require making a sieve.   If my experiment was successful that is what I would do in future.  Did not happen.

Meanwhile, I tried a hammer with a splitter edge.  The Welsh coal had definite layers, and split fairly predictably, with not too much dust or tiny fragments.   The Australian coal crumbled unpredictably into many fragments with a much lower usability fraction.

I started the fire with newspaper, then pine and hardwood kindling.  I should have paid more attention to the wood sizing, because it was problematic getting the wood alight.  Also, I had not set up a blower for the chimney.  I was relying on a really long chimney extension to provide enough draught.

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Chimney extension.  worked well.  Now what is that black circular patch on the ceiling?

Got the fire going with the assistance of a gas torch.  When the fire got going the draught seemed adequate.

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The wood fire at its best

Tried to add coal lumps, but they would not fit the firebox while the wood lengths were in place.  Firebox is just too small.  So I persisted with wood.  Soaked some in mineral turps.

I was not impressed with the appearance of the fire, but surprisingly, eventually, steam was produced, but never enough pressure to run the engine.  And the fire did require constant attention.  The front of the boiler was quite dirty after all of this.  I am glad that I have not yet painted it.

I will give the wood + coal fire another attempt, but size the pieces better (smaller).  The Sievert type burner is looking more likely.

Later in the day…..

…after a further discussion with Stuart I have decided to try the Sievert burner.   Made some steel rings which are a press fit on the burner, and an easy sliding fit inside the firebox.

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This is the new burner inside the firebox.  Not exactly @Trevithick, but I bet that he would have used it if it had been an option.

I still need to make a fitting to hook up a valve and the propane hose.  And try it out maybe tomorrow.  Another experiment.  I hope to not see flames shooting out of the chimney.

 

 

A Coal Grate. And Monster Emperors of Rome.

Firstly, the book review.  It is short, because I did not enjoy it.  Not that it is badly written, or poorly researched.  But it is really shocking.

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EMPERORS OF ROME.  THE MONSTERS.  by PAUL CHRYSTAL

From Tiberius to Theodora.  AD 145-548

This book is one of the series published by Pen & Sword on the architects of terror. Other volumes include Al-Qaeda, The Armenian Genocide, Bloody Mary, Einsatzgruppen, to give you an idea of the scope of the series.

Now that I have finished with the book, I am examining my own motives in choosing it.  I have read many books about ancient Rome, and find the era fascinating; the personalities, the reasons for the rise and fall of the empire, why the military was so spectacularly successful etc etc.

But to be truthful, I did not actually finish the book.  I had a similar reaction when I read about the Nazis and the concentration camps.  Just too horrible to contemplate.  And I closed it after reading about half.  And will not reopen it.

Paul Chrystal is a well-respected author who has written many books about ancient Rome. He states an aim to use primary sources, and to balance the horror with the mitigating aspects of the monsters. The book is 127 pages long, and it covers 10 emperors, so there is not a lot of space to give a balanced view. Mostly, despite its aims, the book is about rape, murder, treachery, nasty and insane men and women with absolute power doing whatever they felt like doing.

And to be realistic, even the “good” emperors started wars, executed rivals, instigated massacres and mass maimings.  That was the way things happened in ancient Rome. And twentieth century Germany, China, Cambodia etc etc.

So, if you enjoy seemingly endless descriptions of sadistic torture, rape and mass murders, with many illustrations, this book might be for you.

Not for this this reviewer though.

John V.

Now, back to getting enough heat into the 1:8 Trevithick Dredger Engine.

I have made a grate to place into the firebox, and which will replace the gas burner, which has proved to be inadequate, despite many, many experiments with improving it.  So here is the grate.

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Putting a rather unpleasant book to good use.

The holes in the grate are tapered, with the smallest part of the holes uppermost.  The fold at the back is to prevent coal being pushed off.  The taper is to prevent clogging the holes with clinker, and possibly to improve the velocity of air flow through the fire.

And how did I drill so many small holes so neatly?

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CNC of course.  Took about 45 minutes.

But after that I had a conversation with Stuart Tankard.  He reckons that I will do no better with coal than I have with propane to date.   Hmmm.   Might give it a go anyway.

Stuart’s suggestion is to try one of these….

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It is 50mm diameter, has a large jet (0.81mm diameter) and has a fearsome flame.  Looks more like a silver soldering torch.  If I use it I might get a flame coming out of the chimney.  Hope that it does not melt the silver solder.

 

 

Trevithick Dredger Engine. Gas or Coal?

Despite my best efforts, and good advice from experienced modellers, I have not been successful with using propane as fuel.  The engine runs, but I cannot get the boiler pressure over 20-22 psi, and that is not adequate.  Partly the problem is that the Trevithick boiler is the FIRST high pressure boiler ever, and is rather simple and primitive.  I do have alternative propane solutions, but they involve redesigning and remaking the burner.  I might end up doing just that, but meanwhile I am going to try coal.

I use coal to fire my 3″ scale traction engine.  It is messy, dirty, and a bit of a pain to get fired up.   But once going it is HOT.  And smells good.  But needs constant attention, observation, and skill.  Not just a matter of adjusting a gas knob.

But, the original Trevithick dredger engines used coal.  Or wood.  Or dried alpaca dung.

So I intend to build a coal grate.  The firebox is only 65mm diameter, so the coal lumps will need to be small, about 1cm diameter I guess.  I will make some sort of crusher to reduce the size of the traction engine coal.

I have made a start on the grate.    Again, it is all experimental.  And I will need a blower of some sort.  Maybe a small computer fan on the chimney.   All fun.   Wait and see.

No book review today!   And Antarctica and moon not mentioned!  I do have  a review in the wings about the Roman emperors who were monsters.  But another day for that one.

A Visit to The Boiler Inspector

My colleague and friend Swen is building a 1″ scale traction engine, and he is about to commence the boiler.  He wanted to discuss some issues regarding the plans with the club boiler inspector.  I had some questions regarding the Trevithick Dredger Engine final inspection, so I tagged along.

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Swen (purple T shirt) and Adrian discussing the traction engine boiler plans.

The boiler inspector is a marine engineer, currently working on tug boats, but with a lifetime of experience in ocean going ships.  His personal interest is mainly with steam and other trains.  But he is very happy to watch the progress of older, more historic models, like the Trevithick.  But always the emphasis is on safety.   Safety over historicity, authenticity, etc.   As it should be.

I was interested to note that Australia’s model steam regulations are widely used as the bench mark in other countries.

My current obstacles to final boiler certification are

  1.  The boiler feed pump is not working.  When I described the situation to Adrian he diagnosed the problem as the suction ball valve.  So afterwards I was working on that.  I have attached a sacrificial ball to a brass rod, and given it a firm whack to the seat.
  2. The difficulty getting the boiler pressure up to the pressure to demonstrate that the safety valve is working. Using propane, I can get the pressure up to 22psi, which is adequate to run the engine, but not high enough to make the safety valve release.  Adrian suggested that I reduce the mass of the lead weight, so it releases at 35psi rather than the current 40-45psi.  And to consider lagging the boiler.   The picture from 1819 shows the dredger engine boiler unlagged.  But the Pen-y-darren engine and the “Catch-Me-Who-Can”  and the Cambourne Road loco are all lagged.   So I suspect that Trevithick would have approved if the dredger engines were lagged.   So guess what?   I am going to lag my dredger engine, and I hope that if Richard Trevithick is watching that he will approve.   I will use Australian hardwood, and paint or stain it black.  Or maybe some English oak, if I can find some in my workshop.   The lead ball in my model is much bigger than shown in the 1819 drawings, so I will have no hesitation in making a smaller one.
  3. What is the water volume of the boiler?  I knew that I had to use 2000ml to get the water half way up the water gauge, but I did not know the actual volume of the boiler.  So today I measured it.   Surprisingly, it was 2750ml.   Almost 3 litres!   No wonder it takes 20 minutes to get it steaming!

So, very close to the final inspection.

Meanwhile, there is very little of pictorial interest for this blog.   So I decided to show some of my workshop(s).

Next, in response to reader Tim, I will show my silver soldering and brazing setup.   Then maybe some of my lathes.  Please note that I am not claiming any expertise.  Just interested amateur stuff.  Might be a change from Antarctica hey?

 

Painting the Dredger Engine

OMG!

You are not painting?

You know that…

1. You always get runs

2.  You always get hairs in the paint

3.  You have NO artistic sense of colours

All of the above is true.

So I have relied heavily  on opinions from my readers about how to put some paint on the Trevithick dredger engine and the colours.

Firstly, yes, I got some runs, and sandpapered them out between coats.

Secondly, yes, some brush hairs ended up in the paint on the engine, but I was on the lookout for them, and removed most of them.  The few remaining were sandpapered out.

Thirdly, yes, I have no artistic sense of colour, but neither did Trevithick so I am in good company.  Most of my readers said to paint it black, so that is what I am doing.  Matt black.  (SWMBO says that matt hides a multitude of painting sins.)

But, I am leaving most of the brass unpainted, so that I can polish it up for special occasions.   I will paint the boiler.

 

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So here I am painting the chimney.  Note that I have found a good use for the 4 jaw chuck.  Apart from holding the Xmas tree steady. 

I am brushing on the paint.  I have an air brush, but there are a lot of surfaces which I do not want to get paint on, so I am brushing.

I am using matt black epoxy enamel for most surfaces, and pot belly stove black for the hot surfaces.  No primer (except on the base).  2-3 coats.

 

Trevithick Blower

I am sure that my readers will have gathered by now that I am not an expert.  At least in matters of metalworking, model engineering etc.  I am, or was, an expert in my profession, some years ago.  But this blog is about how a non expert copes with  problems in model engineering.  It aims to be entertaining, occasionally helpful, and a diary of my workshop doings.

When Trevithick designed his revolutionary engine, (“revolutionary” in all senses), he arranged for the exhausted steam to be funnelled into the chimney, after pre-heating the boiler feed water.

It was a matter of convenience apparently.   Rather than ejecting the spent steam directly  into the air, it would go up the chimney, away from the operator.

But almost immediately it was noticed that the fire in the firebox was more vigorous, hotter, more efficient  Thus was born, the steam engine blower.

So I made the junction between the exhaust and the chimney as per the plans, at an angle of 90 degrees.

But, I noted that on the exhaust stroke, the fire in the firebox spluttered, and occasionally went out altogether.

In more modern steam engines, the exhausted steam is inserted into the chimney, but parallel with the chimney, not at a right angle.

So, I thought, do I stay with the Trevithick design, or the more logical more modern design.  I was having problems with my fire, so the decision was easy.  I would pretend that Trevithick would adopted this design.  Maybe he did.

But that meant breaking the silver soldered join, inserting a new angled copper tube, and rejoining it all.

 

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As Trevithick designed it on the left and on the right as I remade it today

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Right is the exhaust piece between the preheater and the chimney.   Left is the new blower tube, which must be joined end to end, and then poked up the chimney.

This was going to be tricky.  And end to end join of 2 pieces of 9.5mm copper tube, and the join being right where the tube enters the chimney.  But then I remembered a tool which had sat unused for several years…

OK,  This is probably very old hat to most of you.  But it was exciting to me.  First I had to assemble the tool.   Sorry I missed the camera.

 

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I decided to solder the pipe join first.  Rested the end with the flange on a lump of scrap brass, to act as a heat sink, and protect the flange join.

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That worked well.

Then I soldered the assembly into the chimney, after bolting all of the parts into their positions.  Sorry.    Forgot to take a photo.    But it all worked well.   I like the tube expander, but it needs some extra fittings so it works on smaller tubes.

 

 

Trevithick Dredger Engine. Almost There.

Firstly some pictures.

 

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So, I have reassembled the engine and the burner and the base.

Did you notice the base?

No?   Excellent.  That is the idea.  A nondescript matt black base which is barely noticed.

Yes?  OK,  well it must be OK.

Then a trial of the burner inside the firebox, using the changes which have evolved over the past few days.

During the video I am constantly changing the propane flow, and there is a clear “sweet spot” point where it looks really good, and feels very hot.  I have not yet tried to steam with it.

Oh Shit!

PART 1

I was drilling a hole in the end of the Trevithick burner today.  The burner was securely held in the vice, but the heat annealed brass was not as strong as the torque in the 6mm drill bit.

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After the initial self hatred at misjudging the situation, I thought …oh well, I will have to make another one.    Then I thought, …I wonder if I can repair it…..

I still have the wooden forms which I used to make the burner originally, so, roughly twisted the part back into shape.  It was pretty malleable still.  Then forced it into the wooden form.  And beat it into shape with the copper hammer.   This was looking promising.

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Then forced in the other part of the form, and applied the 20 ton hydraulic press.

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The curved shape was pretty good, but there was still some twist.

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I still had to drill an 11.5mm hole, so this time I used the form, successfully.   Then removed the twist by hand after knocking out the form.

Tapped a 1/2″ x 26tpi thread, and assembled the burner.

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All beautiful again.  And now the burner tube is properly secured.   The bulge under my thumb was pushed straight.

 

PART 2

My reader/advisor Huib, suggested filling the tube with stainless steel scouring wool, in order to improve the flame.

I asked SWMBO, and was directed to the appropriate supplier.. the local supermarket.

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Bought 3 types of stainless steel scouring pads.  The finest grade was available only impregnated with soap.  I am not sure how soap burns, probably pretty well, but I do not need that added complication.  Fortunately it mostly came out when tapped.   All very inexpensive.

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Then I experimented with all 3 grades, various degrees of packing it in, and using various lengths.  I even tried mixing the different types of steel wool.  It cuts easily.  Eventually I decided the best way was to have a loose wad of the fine mesh in the first 1-2 cm of tube, then a very light piece of the fine mesh in the distal 10cm.

It has improved the flame;   there is no back lighting of the jet itself, and there is a more even flame along the length of the tube.   I think that I will be able to improve the flame further, but will wait until I can test it inside the boiler itself.  In the video the roaring of the flame drowns out my voice somewhat.  You will not miss much.    I am varying the gas control.

So, sorry about the voice track.  The stainless steel stuff is interesting.  It is like swarf, but not sharp.  I wonder how they make it.  I imagine that it works in the gas-air tube by creating swirls and eddies, and better mixing the gas and air, without impeding the flow much.

Back in the workshop tomorrow.  A few connectors to make, check the feed pump, then make an appointment with The Boiler Inspector.

By the way.  The parcel opening post was apparently not very interesting, so I wont bother with that format again.  I am aware that my video technique was pretty ordinary, but I am not inspired to try that one again.  Pity.  I enjoyed making that one.

 

 

Experiments With Propane and Paint

The gas burner on the modelTrevithick dredger engine has been more problematic than anticipated.  In the absence of published information about gas jet sizes, air hole sizes and numbers, the effect of a ceramic cover, and firebox size and shape, I have resorted to trial and error.  Having read many of the comments on the subject in Model Engineering web sites, I can see that most other builders adopt the same approach.

I have lost count of the number of changes which I have tried.  These are the ones which I can remember.

  1. Burner surround made from brass, as per the blog on Feb 5,6 8.   Ceramic top.  Burner difficult to light, and only the end distal from the jet would light.
  2. Fitted a tube with about 40 2mm holes beneath the ceramic plate, to better distribute the gas-air mixture.  The entire ceramic plate lit up, but the heat output was poor, and the the time to boiler steaming was very slow at 25″.  Also the flame contained lots of yellow, indicating inadequate air.
  3. Drilled holes in the end of the burner surround, to increase the air flow.  Some improvement.
  4. Tried 3-4 different gas jets.  Problems with obtaining jets.  Lack of published info.  Different threads and jet body sizes.  Used the CNC lathe to recut some threads to fit the Primus jet enclosure.  (0.5mm pitch, 4.5mm diameter).  This was all trial and error.  Air is admitted through the 4 holes next to the jet, using a venturi effect, which relies on the velocity of the propane coming out of the jet.  Important factors are the diameter of the air holes, the number of the air holes, the velocity of the propane, and probably the diameter of the propane cone of gas.
  5. In order to further increase the supply of air, I drilled the air holes progressively from 4mm to 6.5mm.   6.5mm was the limit due to available metal.  In the video which follows, you will see the effect of reducing and increasing the number of air holes.
  6. Drilled an extra 20 holes in the distributor tube, but the flames from the initial 2mm holes were too big.  Then made another distributor tube, with 60 holes, about 1.5mm diameter.  Better size flames.  See the video.
  7. Each variation has been tried with and without the ceramic plate.  I have decided to not use the ceramic.  It seems to restrict the flow of gas-air mixture, and causes flames to shoot out backwards through the burner surround air holes, sometimes setting the jet alight.

Concurrently while experimenting with the burner, I have been applying some paint.  SWMBO insists that I am a hopeless painter, but I think that it is going on OK.

 

Trevithick Engine. Tweaking the gas burner. Winning?

Looking at yesterday’s photo, the yellow flame indicates inadequate air for the amount of gas going in.  The air holes at the gas jet level were already at maximum size, so I drilled some holes in the burner base itself.

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Yesterday’s photo.  Feeble flame.  Not enough air.   So I drilled holes in the burner end, next to the gas inlet.  (thanks for the suggestion Huib!).  Unfortunately, the improvement was minimal.  And gas flames shot out backwards towards the operator and gas jet.  A bit disconcerting.  And, I wondered, could the ceramic burner itself be restricting the flow?

So the next step was to remove the ceramic burner, and make changes to the spreader tube beneath.

The ceramic burner broke in pieces during the removal.  Possibly still useable.

But I thought, maybe I will see what the flame is like without the ceramic burner altogether.

And this is what the flame looked like…

Now, that is more like it!  (you can see the holes which I drilled in the end of the burner to increase air intake)

Admittedly, the flame will change when the burner is back inside the boiler, but this is the most encouraging flame yet.  Minimal yellow.  The gas flow will need to be reduced.

Next session, I intend to experiment with the hole sizes and number and angles.  I do not expect to be using the ceramic insert in the final version.

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