johnsmachines

machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment.

Tag: model steam

6″ Vertical Boiler, Triple Expansion Steam Engine and Southworth Pump, all working together. Fairly well.

2 videos of the triple and the vertical boiler and the Southworth boiler feed pump working together for the first time.  Not perfectly yet, but working.

 

Thinking about future exhibitions….

Still recovering from The Royal Geelong Show, where my beam engine and the Trevithick      dredger engine ran for ~8 hours per day for 4 days, and required almost constant supervision. I was very pleased that they did so without a problem.

For future exhibitions I would like to also run the triple expansion steam engine using the vertical boiler, for which I recently made the Southworth boiler feed pump.  And there are occasions where I might run the triple and the beam engine together from the vertical boiler.  That arrangement will occupy a fair bit of bench space, and in this post I am considering options for the arrangement.

But first, I needed a steam outlet manifold to handle multiple engines, simultaneously, and hopefully to avoid a big tangle of pipes.  Here is the manifold.

IMG_8246.JPG

The manifold has 6 x ¼” outlets and one 3/8″  outlet.    

Option one lines up the boiler and engine like this….

IMG_8243IMG_8244

Option two is more compact, but ?less appealing.  Pics following..

IMG_8237IMG_8238

IMG_8239

The lump of wood under the engine is temporary,  just to give an idea of the heights.

OK, this post is just an excuse to show some pics.  I have decided to go with option one.  It is closer to the appearance if the boiler and engine were actually in a boat, and also will make it easier to add the beam engine to the right of the boiler if/when I run the two engines simultaneously.

And I doubt that I will be able to avoid a jumble of pipework.  The triple has 6 pipes attached, the boiler has more, then there is the beam engine.  And, I will need a water container from which to feed the boiler.  That will be located behind the boiler.  Still considering whether it should be a squarish box on a stand like the railway water towers, or a cylinder on a low stand.   Any thoughts?

 

 

 

Royal Geelong Show 2019

The “Show” was held over the last 4 days.  I will not bang on again about my republican leanings.  See posts from previous years if that persuasion is of any interest.  The weather was ordinary.  Quite a few showers and blustery wind.  But we were mostly warm in the Vintage Machinery shed where our Model Machinery cage is located.  Fairly good visitor numbers, but not much real interest in our model engine offerings.

I exhibited my beam engine and Trevithick dredger engines, both running on piped steam.  The vertical boiler and feed pump was on static display, of no interest to anyone.  My Stirling engine got the most attention from kids, who are attracted by the swirling spiral colours, and not much interest in the intriguing method of running.  I am convinced that models must be moving, colourful, and have some relation to what people and kids see on television if they are to have any traction with the public.

But, the model and full size engine exhibitors enjoyed the displays, and an occasional visitor engaged in conversation.  Here are some pics and videos of some of the shed displays.  There dog shows, bird breeding, monster trucks,  horse riding events, cattle and sheep judging, and side show rides but these were not recorded by me.   I did visit the Amateur Astronomy display, and will visit the workshop of one of the exhibitors soon.

50 yrs vintage machinery.JPG

Beam with lagging.JPG

I had applied wooden lagging to the beam engine cylinder

Package boiler and Trevor.JPG

Steam for the engines is provided from this Package Boiler at 25psi.   Enough to turn them over.  Capable of much higher pressures.

Package boiler diag

cage bench north

Cage Bench North includes the Trevithick dredger model, the beam engine and the Stirling engine.

Cage bench south

Cage Bench South.  Swen Pettig’s prize winning flame gulper, and 1″ Minnie under construction.

Stuart swen

Stuart and Swen ?discussing engine repairs.

P1033007.JPG

Model Engineering first prize!

triple.JPG

And the full size triple expansion engine.  The Vintage Machinery boiler is being upgraded, so there was insufficient steam to run the triple.

 

 

Boiler Feed Pump Pumping

Yesterday I reseated the pump valves, reassembled the pump, then tested it on steam.

Most of the following video has the boiler at only 25psi, but I did run it off camera at up to 75psi.

After making the video I redirected the exhaust steam from the pump into the firebox.  It actually seemed to improve the gas flame, maybe by acting as a blower.  Not so sure about this being permanent though, because the exhaust steam contains oil from the displacement oiler, and I dont want that oil to be deposited in the firetubes.

I will make a water tank to supply boiler water.  Maybe the exhaust steam could be passed through a heat exchanger in the tank, so the boiler feed water is preheated.

(if the video is not showing, click on the https link below)

 

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.

P1032772.JPG

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.

P1032773.JPG

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

P1032774.JPG

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.

P1032775.JPG

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.

P1032776.JPG

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…….

P1032781.JPG

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

P1032808.JPG

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.

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…

IMG_7794.JPG

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.

IMG_7785.JPG

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.

IMG_7775.JPG

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.

 

Next Project

The Trevithick dredger engine model is almost finished.  Currently applying some paint.  And getting it ready for the final boiler inspection.  I am guessing about 2 weeks.

I have chosen a spot in the house where it will sit, and will post a photo in due course.

A few people have been asking if I have decided what to make next.  In terms of a major build, the answer is no, I have not decided.  I have considered a few possibilities.  Those possibilities include a model of Stephenson’s “Rocket”, Trevithick’s “Catch Me Who Can” or “Pen-y-darren engine”, a Shand-Mason fire engine, or even another cannon.

What I will do, is to complete several unfinished projects, and if a major project becomes obvious, imperative, then anything is possible.

The unfinished projects include…

  1.  An Arduino controlled rotary table.  The mechanicals are made.  Just need to dive into the electronics.
  2. The Southworth steam powered boiler feed pump for the vertical boiler.
  3. The CNC controlled tool post milling attachment for the Boxford CNC lathe.
  4. Paint the Bolton beam engine.  Lag the cylinder.  Install a cylinder oiler.
  5. Finish the triple expansion model marine engine.  The lagging, the piston rings, the gaskets, the oiler and oil pipework, and painting.

Looking at that list, I really do not need to start another major project.

And sometimes it is nice to sit back, and enjoy the glow and satisfaction of previous projects.  It does sound rather self satisfied, no?  So here is a selection of videos, mostly first runs of newly completed projects.  Most are YouTube links, but one or two will run directly.

This was the first model steam engine which I made about 5-6 years ago.  It is a Bolton 7 single cylinder mill engine, and this was the first occasion I had run it on steam.  It was a very exciting moment, seeing it actually running on steam.

Next came the Bolton 12 Beam Engine.  Still a crowd favourite.  The beard was ordered off by SWMBO not long after this.

Then a couple of Stirling engines.  How they work is still a mystery to me.

 

Then the problematic, difficult triple expansion engine, which took 3 years and several extended breaks to get to the working stage.  Still not finished completely.  Stuart Tankard’s boiler.  Since then I made a vertical boiler.

And somewhere in there I made this little reversing engine for the club competition.  Alas, it failed in action.

And 3 cannons came out of left field.  They started as a CNC project, but then took on a consuming interest of their own.  About this time I saw the necessity of learning how to put together a video.  Still learning.

IMG_6859

The 6″ vertical boiler.

And finally the Trevithick dredger engine.  The historical aspects of this engine, the genius of Trevithick, the fact that the engine works…. has been marvellous.  The engine is looking quite different with some paint applied.  And the propane burner is significantly better than appears in this video.

So, if you are still with me after all of those videos, congratulations on your stamina.  It is  therapeutic to take stock sometimes, and to wonder about where making all of these engines is going.  It was not to any plan.  Still no plan.  Just enjoying the moments, the days.

Trevithick Dredger Engine. Almost There.

Firstly some pictures.

 

IMG_7660.JPG

IMG_7661.JPG

IMG_7662.JPG

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.

IMG_7651

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.

IMG_7652

 

IMG_7653.JPG

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

IMG_7655.jpg

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

IMG_7654.JPG

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.

IMG_7657.JPG

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.

IMG_7650.jpg

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.

IMG_7636.JPG

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.

IMG_7600

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.

IMG_7600.JPG

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.

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.

Screen Shot 2019-02-20 at 6.53.00 am.png

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?

Screen Shot 2019-02-20 at 6.39.51 am.png

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?

Screen Shot 2019-02-19 at 7.35.54 am.png

Close up of the fist.  Pixellation appearing.

Screen Shot 2019-02-19 at 7.42.50 am.png

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.

IMG_7560

IMG_7561.JPG

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.

IMG_7162

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.

IMG_7556.JPG

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)

 

Screen Shot 2019-02-16 at 6.06.32 pm.png

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!

 

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.

IMG_7476.JPG

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.

IMG_7478.JPG

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.

IMG_7477.JPG

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.

%d bloggers like this: