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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

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.

Model Trevithick Dredger Engine on Steam. Fail. Well, maybe a bare pass.

Well, I was really not expecting this.

After all, the engine was running well on compressed air at 30psi, and the burner appeared to have a good flame.

And Stuart was coming to be involved with the big event.  So nothing could go wrong!

I set up the iphone on a tripod.  Checked the light.  Oiled the bearings and slides.  Filled the boiler.  It takes 2 litres of water.  And hooked up the propane.  when Stuart arrived I lit up the burner, and sat back to see how long it would take to raise steam.

Some steam leaks were expected, on this first steam run.  Leaks don’t show on compressed air, unless they are severe.  As the water heated up, some leaks appeared.  The water feed clack valve and the sight glass were bad.  The clack valve just needed some goo.  Later I disassembled the sight glass, and cleaned the valve, with some improvement, but more work needed.  Or a new sight glass valve.  A couple of other trivial leaks were easily fixed.

So we watched the clock, and checked the temperatures.  Ot took 20 minutes to start raising steam.  That is a bit slow.  Eventually it reached 20psi, but the pressure refused to go any higher, despite fiddling with the gas and air controls.

At 20psi, I opened the throttle and gave the flywheel a swing.  You can see the result.

After that, we let it cool down and fixed the clack valve leak.  The sight glass valve leak was looked at later, but could not be fixed simply.

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The burner flame.  A bit feeble.  A bit yellow.  And occasionally blown out by the cylinder exhaust gas puffing into the chimney.  Stuart says that I need to angle the cylinder exhaust gas upwards in the chimney.  Apparently Trevithick did not do that on the full size models, but perhaps he should have.

The burner was definitely not up to the job, so in this last video, it got some assistance.

It does go!   Just needs a few tweaks.  Lovely sound.

Drilling is not boring

Firstly the base.  I wanted to drill all of the wooden pieces together, to make sure that they aligned, even if the lengths weren’t absolutely accurate.  Wood is like that.

So, using the bottom piece as a pattern, and squaring each piece as it was placed, I glued them together using PVA glue.

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And squaring each piece as it was placed.

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Those angle blocks made handy glueing weights.  The short bits are intentional.  That allows the flywheel crank room to rotate.

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My workbench.  I needed some room, so I tidied it.

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That is better!

Now some short videos of the drilling.  Sorry the videos are so short.  If my Internet connect was better I would have stitched them into one video, but alas…

I was intending to show making a 5mm drill bit longer, by silver soldering a piece of 5mm drill rod to the bit, end to end.  I have done this before, quite successfully.  Silver solder is very strong.   Almost as strong as the parent metal.  But in this case it was unnecessary, as the videos will show.

 

 

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With the base complete and bolted to the engine, I made the last pipe connection joining the feed pump to the pre-heater.

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Ready for the first run on steam next session!

A Long Drill Bit

I have not been looking forward to attaching the Trevithick Dredger Engine to its base.

I needed to drill through the steel plinth and the wooden plinth, and then through the top part of the base.  Trouble was that the boiler and engine were in the way.

And it was not feasible to tip the whole assembly upside down and drill from underneath.

Ahah! what about a long drill?   I measured it.  The drill would need to be 450mm long!  Even a long drill bit, ferociously expensive, comes at a maximum length of 150mm.

So, I made a long drill bit, 5mm diameter, 600mm long

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That is a new 5mm cobalt drill bit, silver soldered into some 8mm drill rod.  Could have been a bit shorter, but it was long enough.

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Using the long drill bit, I was able to drill through the steel support, and through the top wooden layer of the base.   Then bolted the parts together.   And was then able to place the engine and the wooden layer on their ends, and to drill the remaining holes from below, confident (fairly confident anyway), that nothing could go wrong.   As in the above picture.

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Meanwhile, I had added the valve which controls the boiler feed pump output, and connected it to the boiler feed pump.

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Boiler feed pump valve.  This valve was left over from the vertical boiler project.  Just right, when I have repainted it.

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Next I must drill a 5mm hole through all layers of the base.   150mm!  4 holes, one in each corner.   The long drill made today will not do because the 8mm shank is too thick.   I must make another long drill, with a 5mm diameter shank.  Watch this space!

 

 

Moon

I know that this blog is titled “johnsmachines”, but I do get interested in “other stuff” too.

I came across this video on YouTube yesterday.  It runs for 4 hours.

The footage was shot by an amateur astronomer, through telescopes which anyone can buy.  A 9.5″ Celestron  reflector (Schmitt Cassegrain I think),  and an 80mm Orion refractor.

I used to be an amateur astronomer, and still retain an interest.  One of my worst decisions ever was to give away an Orion 10″ reflector about 10 years ago.

Anyway, back to the video.  It shows the surface of the moon, concentrating on some interesting areas.  Following are some screen shots.  It is titled “Live Moon Surface Observation”.  Worth a look.  Suggest jumping to 28minutes and watch maybe 5 minutes, zooming in and out.

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80mm refractor.  Look at the protruberance in the top left crater.  Looks like a clenched fist.  That is really unusual.  Impact craters often have a central spike, and it is thought that the moon has had volcanic activity in previous aeons.  But there is no atmosphere to cause wind erosion, and no surface water.  Just traces of ice in the depths of craters at the poles.  So how could that shape have arisen?   And look at the bottom right crater…. that rectilinear shape.   Circular shapes are meteor impacts, in many case impacts upon impacts.  So how do you explain straight lines like these?

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The same craters through the reflector scope.  Image reversed.   Look closely at the areas surrounding the craters.  Do you see the other rectangular and square shapes?

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Close up of the fist.  Pixellation appearing.

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Enter a caption

Earth’s moon is strange.

It is the largest moon in the solar system relative to the parent planet.

It is much less dense than earth. (why? if it is made of the same rock).  (5.51g/cm vs 3.34g/cm.  Thought to be due to Earth’s metal core.)

It almost exactly blocks the disk of the sun during a lunar eclipse.  Coincidence?

The other side of the moon always faces away from earth.  Until the space program, no human had ever seen the other side of the moon.  The other side, incidentally, is quite different from the side which we see.  Much more cratered, no large flat areas.  Presumably most meteors come from the direction away from the sun (because they are scooped up by the gravitational field of the sun).

One moon day is exactly the same length as a lunar month.  It is the only moon in the solar system where this applies.  That is why the other side of the moon always faces away from earth.  Another coincidence?  (correction.  Pluto – Charon also exhibit this behaviour, so it is not unique, just unusual.  Thought to be due to “tidal locking”- thanks Gene).

OK.  I know.  You came to this site to look at my machines, particularly the Trevithick dredger engine.   I am still fiddling with small details which are not very photogenic, but necessary before I run it on steam.  Currently hooking up the boiler feed pump.

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I was intending to pull apart the pump to show you the components.  It is more complicated than the exterior shows.  Piston, O ring, 2 stainless steel balls, one spring.  I machined that 3 way junction box from a gas fitting, adding the delivery union to the top.   Nothing tested yet.  I hope that it works!

 

 

 

Sight Glass on the Trevithick Boiler

Not real happy about this one, but it is necessary if I am to run the dredger engine in public, at club meetings etc.

The original dredger engine had 3 taps to check on the boiler water levels,  like this.

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An earlier stage of construction, using taps to reveal the boiler water level.

Unfortunately that setup is unacceptable for boiler certification, so I have installed a sight glass using the same penetrations.

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The red colour does not help.  But when I run the engine on steam, this is what will be seen.   Functional, but nothing like the original.  If I use compressed air, or steam from an outside boiler (i.e. my burner not being used), I can reinstall the taps.

The sight glass is a bit short, but it should comply with the regulations.

I have spent another half day experimenting with different spring configurations, so that the safety valve releases at 40-50psi.  Eventually I decreased the coil pitch of the spring, and the valve now releases at 45-50psi.  That will do.

Trevithick Dredger Engine. The Dredger

I have no intention of modelling the dredger, but in making decisions about the engine base have gone back to the sources to find out about the gun ships.  These are referred to as “gun brig”, “bomb-ship”, “hulk of a dismasted ship”, in letters by Trevithick and others.

The first three of these dredgers were recorded by Trevithick as being 80, 120 tons and 300 tons.

Trevithick dredger on Thames - Rees

This diagram is probably of the dredger “Blazer”, with a 6hp Trevithick engine powering the bucket chain and winch. The cylinder diameter was 14.5″ and the stroke was 4′.  Trevithick recorded that his dredger would lift 100 tons of mud per hour.  Rock and gravel 180 tons per 6-8 hour tide.  It must have been impressive enough for him to obtain a contract to lift 500,000 tons per year from the bottom of the Thames at 6 pence per ton.   Other dredgers had Trevithick engines of up to 20hp. (ref. “The Life of Richard Trevithick” by Francis Trevithick 1872)

 

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Magnified view of the engine house on the dredger.  Note the relative sizes of the flywheel and the bucket chain driving gear.

 

And this is the diagram of a cross section of a bomb-vessel from a century before Trevithick.  It is mounting a 13″ bore mortar.  Note the massive supporting beams.  You can see why Trevithick chose this type of vessel to mount his steam engine and dredging machinery.  IMG_7452 2.JPG

A Tour of the Model Dredger Engine

Now that I have a tripod for my video camera (an iPhone), I have become a bit more enthusiastic about making videos.  Terrible standard of video compared with Joe Pieszczynski, and This Old Tony, and Stefan Gotteswinter, but maybe better than just text and photos.  I will be interested in your responses.

The Dredger Engine is still not quite fully made, but while I had the video set up for the spring making exercise yesterday, I added the following.   It is totally unscripted, and unedited, so there are errors.  “pressure valve” instead of “pressure gauge” for example.  Have fun counting the errors.   The final 30 seconds is me having difficulty turning off the camera!

 

Making Springs and Other Stuff

Other stuff first.

MOVING STEPS

SWMBO has always considered that having a winch on a vehicle is a bit of a wank, but I have used it many times getting out of bogs, getting other people out of bogs more often, moving machinery, pulling down/moving trees, straining fences etc etc.   SWMBO was intending to replace these concrete steps, because they were crooked with respect to the house which she is fixing up.  I said that I could straighten them.

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This is after straightening.  I jackhammered the path slab, lifted the floor slab with the 4WD high lift jack, and pulled the steps with the Landcruiser winch.  Easy as.  Took 30 minutes.  SWMBO was delighted!   

MAKING SPRINGS

And I used my new spring tool.  Brilliant!  Recorded on videos.  Again, apologies for my lousy video technique.  I had forgotten to bring the spring making instructions, so it was all trial and error.

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This was my first effort.  Aluminium wire, just to try the tool.  As you can see, there were multiple errors.   Feed rate too slow for the RPM, forgot to enter a stop command at the end, feed rate much too slow at the beginning on the left.

So I started with aluminium, making many mistakes, sometimes repeatedly, but eventually learning.  Progressed to soft iron wire, and eventually to stainless steel spring wire.

Following is a series of pics and videos.

 

 

The mandrel was 4mm diameter, and there was a bit of spring back, with the final ID of 4.4-5.0 mm.

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Initially I secured the end of the wire by catching it in the collet, but quickly replaced that method, and drilled a 1.5mm hole in the mandrel.  Again, I forgot to issue a stop command in time.   The starting coils were hand wound by manually turning the spindle and jogging the feed.  If I was making multiples of the same size spring that would be simple to program on the CNC.

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Ah!  Getting the hang of this!  That one looks good!

In the next video, a good spring is made.  The mandrel wobble is occurring because I had bent the mandrel, when the steady was not hard enough against it.  Bend straightened afterwards.

 

 

 

 

 

 

And the safety valve with its new spring…

 

 

But screwing in the safety valve was a bit of a struggle…

 

 

And re-installing the safety valve lever was almost comic..

 

 

So, that’s it for this post.

How did you like the videos?  I suppose that I should have stitched them together into one long video.  Maybe I will do that later for YouTube.   And to edit out all of the errors.

Later today I will post another video, this time a longer one, a tour of the Trevithick engine.

Well, what a nice day!

Wednesday is always a good day.  That is when our model engineering group has its weekly meetings.  Mostly a 2-3 hour informal gathering around a large table, chatting about current projects, new tools, the weather, rarely politics or religion.  Coffee.   And once each month a more formal evening meeting, involving discussion of club business, “models on the table” and usually a guest speaker.   Today was the informal 2-3 hour chat variety.

I used the opportunity to ask about methods of making a rectangularish water tank for the Trevithick dredger engine, riveting, folding brass, caulking with solder, etc etc.    And Stuart T, knowing that I had to make a stainless steel compression spring for the safety valve of the Trevithick, brought in his tools for making springs.

This is one of the tools.  It was designed by Dwight Giles, and made by Stuart.

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Published in Model Engine Builder 2007.

The tool is mounted in the lathe tool post.  The V supports the chuck mounted mandrel, and the brass washers apply drag to the spring wire.  The lathe threading gears supply the pitch to the spring.  Looks excellent, and I was hoping that Stuart was intending to lend it to me.  Otherwise I would make one of these tools.   But why were there two of the tools?   “Oh, one is for you!  I was making one for myself, and it was just as easy to make two.”

Not the first time have I been the recipient of Stuart’s generosity.  When I make the spring (soon) I will take some pics, and post them here.

Later in the meeting, Swen Pettig, recently returned from a fabulous trip to Scandinavia and UK, called for shoosh, and stood up to make a presentation.  Some people knew what was coming.  I didn’t.  But in “recognition for writing about his model making” (now my ears pricked up), Swen had picked up an item in the UK which he thought I might find interesting.  Knowing of my current interest, some might say obsession, with Richard Trevithick, he had looked for and found the following item.

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A Two pound coin.  I did not get the significance, until I looked more closely.  Holy Shit!  That is a Trevithick engine on the coin.  The Pen-y-Darren railway engine if I am not mistaken.  Made in 1804.  And using many recognisable features which are in my slightly later dredger engine.  The coin was minted in 2004, 200 years later.  Wow!!

I did not even know about the coin until today.  But I am honoured and very grateful for this lovely gift and thought, Swen.

One wag suggested that I should make another gas knob for the engine, and mount the coin in the knob. (thankyou for the suggestion, President Brendan.  I will do no such thing).  It will be a  valued possession.

Incidentally, the reverse of the coin has an image of the Head of State of Australia.

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Gas control on an historic model?

Well, no likes and no comments on this morning’s post… no picture the problem????   hmmm???

So, this afternoon, the weather was windy and wet, and unsuitable for winching concrete steps, so I retreated to the workshop.  Much to SWMBO’s disapproval.

And did a bit more with the gas supply and control.

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And that is what it looked like.

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OK, except that Primus knob does not appeal.  And the wooden base is looking decidedly wonky.  More about the base later.  I have some improvements in mind.

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This wheel was a reject from my triple expansion steam engine model.  I wondered if it would look OK on the Trevithick.  It certainly looks better than the Primus knob Yes/No?

Possibly not historically accurate, but maybe yes for 1850-60?

 

Historic Model Compromised?

I was attempting to model the Trevithick Dredger Engine as true as possible to the original.  But, I also wanted it to run, so the flywheel would spin and the crosshead move up and down and the unusual valve control lever flick up and down.

There are several problems with this approach.

  1. The 1 in 8 scale.  This is the biggest problem with making a model.  Since the scale applies only to linear dimensions (e.g. the boiler is 6″ diameter compared to 48″ for the original), surface areas are at a scale of 1 in 8×8 (1:64) and volumes and weights are at a scale of 1 in 8x8x8 (1:512).  So my little model weighs a few kilograms (not actually weighed it yet) compared to 4 -6 tons for the original.   It does mean that there is a safety advantage in scaling down, in terms of boiler explosion risk, despite the fact that the model will be run at roughly the same boiler pressure as the original (50 psi).
  2. Some components do not scale well.  For example, the square nuts.  To my eye, they look too big.  If I was to make another of this model, I would make the fasteners smaller.
  3. The requirement of the model actually running.  The original was fired with coal, or in some situations wood, and even dried animal dung (in Peru, look it up.  There was no coal and no trees in the silver mines area).  I have made my model so that it could run on coal, but to be honest, that is unlikely to happen.  So I have made a gas burner.  And that involves gas pipes and regulator valve, which are impossible to conceal, and detract, IMO, from the appearance.
  4. Boiler regulations.  I want to run the model at club exhibitions, which means that the boiler must be certified.  The boiler certification regulations make no special allowance for historic models, so several compromises have been made.  For example a pressure gauge has been installed, and the water level taps must be replaced by a glass sight tube.  Not a biggie I guess, but it all adds up.  I will keep a separate set of parts which can be used when it is displayed as a static model, which will be most of the time.
  5.  Is this a model dredger engine or a model factory or mine engine?  I still have not decided.  Hence the rather ambiguous base.  I do not intend to build a dredger or section of a dredger, or a factory or mine or parts thereof.  But I have to admit that the base which is appearing in the photos so far does not look “right”.  Still pondering that one.
  6. And finally the colours.  Although Trevithick was a brilliant engineer, he was no artist.  I doubt that beauty, or attractiveness of line, ever entered his thoughts when he was designing.  If his engines were painted, the colour was probably utilitarian black.  Not that we know.  I can find no reference to colour in any of the works about Trevithick and his engines.  And there is not a skerrick  of original paint on the original engine in the London Science Museum, as far as I know.  Later engines, in the Victorian era, were painted in gorgeous colours, and I am tempted to paint my model as if it were a Trevithick engine which was being used in the Victorian era.  That is not so silly.  It is known that Watt engines, and even Newcomen engines were still being made in the 19th century, and Francis Trevithick records that many of his father’s engines were in use in the mid 19th century.  That little subterfuge could also explain why my model has a pressure gauge and sight glass!

I had a full day in the workshop yesterday, so I had better front up and straighten those steps for SWMBO.   Actually, it will an interesting job.  I will use a 4WD high lift jack(s) under the house to free the steps, then use the Landcruiser winch with a snatch block to pull the concrete steps into position.  Might be worth a photo.  How the steps ended up out of position is a mystery.

 

 

Fitting the Boiler Feed Pump to the Trevithick Dredger Engine.

The feed pump is attached to the base, and since I had not decided on the final form of the base I had to leave the pump sitting all alone on my messy bench.

But I have now decided to proceed with a wooden base, made of 32x32mm hardwood beams, and a solid wooden top to which the engine and the feed pump are attached.

So today I attached the feed pump.  The engine itself is still just sitting, not attached.  And the bits of the base are still a loose pile of beams of wood, not bolted glued or screwed together.

One minor problem was that there were incomplete dimensions on the plans for the feed pump and its supporting column.   Fair enough.  I assumed that the dimensions would be measured on the job.

First I had to make the steel beam which attaches to the cross head, and the column at the other end, and the pump… 3 attachment points.  I had cut out the beam last week, but it needed a couple of bends.   It was 4mm thick steel, so I did the bending in the workshop press.

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Bending the feed pump beam.

Of course one of the bends was too angular, so a bit of cold blacksmithing to flatten it.

And fitted everything to the engine sitting on the base.

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The holes which were drilled in the top of the base were a bit of a guess, because the distance between them was not on the plans.  I drilled them 28mm apart, but it was clear after assembly that they were too close together.

Then the penny dropped.  The holes in the base should be the same as the corresponding holes in the steel beam… 32mm.  so I filled one of the holes with epoxy filler, redrilled it, re-tapped it and reassembled everything.

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The re-drilled hole and filler are hidden beneath the feed pump.  The space in front of the boiler face is now occupied by gas piping and a gas control knob.  Not quite finished so no pics yet.  Notice the boiler pressure gauge on top of the boiler.  Not as per R Trevithick, because the Bourdon tube type pressure gauge was not invented until 1849, but it is required for boiler certification.   Maybe I will label this as a model of a Trevithick engine which was updated in 1850.

Next to make the pipe between the feed pump and the boiler feed pre-heater, and a bypass tube with valve.   I have not decided on the size or form of the water supply tank. A riveted squarish tank, or even a riveted cylinder would be nice.   Probably make do with a plastic bottle for the time being.

I also need to fasten together those base beams.  Have still not decided how to do that.

There are 4 types of wood in the base.  I might have mentioned one or two of them.  One is the top, one is the beam under the front of the boiler, the base beams is another, and there is a sizeable block underneath everything.  I doubt that anyone will be able to identify all of the wood types.  2 are Australian, one is European, and one is Asian (I cut up a breadboard for that one).

And thinking about a colour scheme.  Flat black is the favoured colour in most other models, but I want to include some Georgian reds blues greens or yellows.  And leave a bit of brass and copper for polishing.

Oh, and I made a ring for the top of the chimney.  Seen in the second pic.

Trevithick Dredger Engine Burner

Reader Huib suggested that I would need to modify the gas burner for my model steam engine even before I had tried it.

He was absolutely correct.  The burner was difficult to light and keep going, unless I blocked off at least half of it. (see previous post).

So, today, I modified the burner along the lines suggested by Huib.

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I added this stainless steel tube with drilled holes to the bottom of the burner, underneath the fire clay burner.  It is wedged into position.

And this was the result.  The burner li up easily when gas was admitted.

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From above you can see that the fireclay burner is red hot over most of its surface.  And hottest at the end which is deep inside the boiler.

I measured the temperature of the burner, and it was 790ºc.  I think that it will do nicely. After that, I sealed the fire clay burner into the brass container with a high temperature boiler sealant.

Yesterday I received in the mail a tiny pressure gauge.  3/4″ diameter, 0-80psi.  from EJ Winter, Sydney.  Order was placed Wed, arrived Thurs.  Great service.  Thanks Ben deGabriel.

Trevithick would not have had a pressure gauge in 1803, but modern boiler regs insist on one, so I have bowed to the inevitable, and will install this gauge on top of the boiler.  Photos to follow.   I expect to be running the engine on steam next time I am in the workshop.   WooHoo!   Not tomorrow though.  Baby sitting.

 

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