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

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.

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.

img_7463.jpg

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.

img_7461.jpg

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.

 

Trevithick Boiler Feed Pump, and a base.

Quite a few potential workshop days are being foregone because we in southern Oz are experiencing a very hot summer.  And the few more moderate temperature days are “lost” to essential jobs for SWMBO, and around the house.   Shouldn’t complain about the weather.   Townsville, Queensland, where my brother and family lives, has been declared a disaster area due to torrential floods…  1000mm (39″) rain in the last few days, with more on the way.  And the next ice age has apparently started in USA.

But,  back to the workshop for a few hours here and there, I have made the boiler water feed pump for the Trevithick dredger engine.   As usual, I grossly underestimated the time these few simple components would take to make.

IMG_7413.JPG

The pump is driven off the crossbar where the stroke is 100mm (4″).  At the pump, the stroke is ~17mm (~5/8″).  The suction side has an 8mm (stainless steel) non return ball valve and the delivery has a 6mm non return SS ball valve.  The plans specified a dummy pump, for appearance only, but I have made it functional.

IMG_7417.JPG

The 2mm ss cap screw is to limit the ball movement to 0.8mm travel.  Something less conspicuous will replace the cap screw.  Probably a ss grub screw.

The rod driving the pump piston is a piece of bronze brazing filler rod.  Just happened to be the correct diameter.

I will need to add a further pump, hidden somewhere, for boiler approval.  It will probably be a hand pump.

The next step is to design and make the stand for the engine.  The plans specify a large, and in my opinion –  ugly, wooden box.  So that is not on my option list.

Most of these “dredger” engines were used in factories and mills.  Some were used to drive mine pumps, and a few were used on dredgers.  In the factories and mills they would have sat on masonry or wooden bases, and on the dredgers they would have sat on the very solid decks.  (the dredgers in some cases were converted gun ships, designed to mount large black powder cannons,  mortars or seige guns, so they were very solid!)

Now, some pictures of other dredger engine models, and the reconstructed full size one, and their bases.  I have numbered the pictures, and I would be interested in my readers opinion about which would best suit my model.  Please leave a comment.

 

B002617|10280908

1. The engine as mounted in The London Science Museum, on large wooden blocks.

Dredger1.jpg

2. A Model Dredger Engine on a masonry base.  I could do something similar, but I would used aerated concrete.

images-6

3. A very simple wooden base.

Screen Shot 2019-02-01 at 10.39.21 am.png

4. A beautifully crafted model on a cabinet maker’s base.  Acknowledgement to fredyfredy42.                                              I like the colour scheme too!

Screen Shot 2019-01-30 at 5.30.56 am.png

5. Another simple wood block base, reminiscent of the gun boat decking and frame.

odellen 2 137 (69).JPG

6. An elegant wooden base

fullsizeoutput_f29.jpeg

7. And finally, the modern, aluminium base for the beam engine which I made a few years ago.  I like it on the beam engine, but I doubt that it would look OK under the Trevithick.  The dredger engine is shorter, taller, and narrower.

 

 

Timing the Trevithick Dredger engine-4

Success!!

After the debacle of the valve sleeve rotating because I had not secured it, I secured it with a grub screw, and had another attempt at running the engine today.

But before that I shortened the valve lever blocks by 2-3mm.  I had noticed that air was entering the cylinder well before top and bottom dead centre.  Shortening the bars delayed the entry a bit.   Still a little bit before TDC and BDC, but watch the videos to see the result.

 

So, it is still not finished, and the timing will need some fine tuning.  But it works!   Phew..

It works in forward and reverse, depending on piston position when it starts, or if the flywheel is given a initial swing.

In the above videos the engine is not bolted to the box, and some of the noise is the cranks hitting the box.  The valve arm being hit by the striker is also contributing to the noise.

I will work on the gas burner next.

 

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

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

Drilling the 2 holes took most of the day.

Figuring the setup was the biggest challenge.

IMG_7329.JPG

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

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

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

IMG_7331.JPG

The Dremel chuck and the shop made spindle.

IMG_7330.JPG

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

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

IMG_7333.JPG

And here is the gear crank pinned to the mainshaft.

IMG_7334.JPG

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

IMG_7328.JPG

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

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

Making a Lead Ball for the safety valve

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

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

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

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

IMG_7302.JPG

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

IMG_7305.JPG

Then milled them pretty close to square and identical.

IMG_7308.JPG

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

IMG_7309.JPG

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

IMG_7312.JPG

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

IMG_7313.JPG

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

IMG_7315.JPG

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

IMG_7319.JPG

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

IMG_7325.JPG

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

IMG_7326.JPG

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

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

 

 

 

How Many One Off Parts Can You Make Per Day?

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

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

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

IMG_7299.JPG

The pressure valve arm, stand and restrainer in place.

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

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

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

Trevithick Dredger Engine.. the steam valve operator.

IMG_7268.JPG

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

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

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

Another day in the workshop.

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

So, I used a heat sink.

IMG_7260.JPG

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

IMG_7261.JPG

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

IMG_7262.JPG

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

IMG_7263.JPG

And the finished door.  Looks OK IMO.

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

IMG_7265.JPG

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

IMG_7266.JPG

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

IMG_7267.JPG

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

%d bloggers like this: