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: dredger engine

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.

 

 

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.

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.

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.

 

A Gas Burner for the Trevithick Dredger Engine

Last post I asked if anyone could guess what the redgum pieces were going to be used for.

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Today I turned up another piece of the puzzle, which might be helpful..

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And look where it fits..with a 1mm gap.

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Just to bend a piece of annealed brass in the press.   Hmm.. I wonder where this will fit..

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Ah… now I see…

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Silver soldered.  Ceramic burner needs to be cut.  Diamond saw?  Maybe I will try the bandsaw..

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Well, that is surprising.  I expected that the ceramic material would laugh at the bandsaw blade.  But no problem at all.  Like a hot knife through butter.

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After sawing the burner roughly to size, the edges were given the curved contour with a belt sander.  Again, easy as.  It is sitting in position, but needs the edges sealed with some heat resistant goo.   Any suggestions?

The gas burner will be easy to remove if I ever run the Trevithick engine on coal.  I am still fiddling with gas jets, hoses and connections.

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.

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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.

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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.

 

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

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

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3. A very simple wooden base.

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

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

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6. An elegant wooden base

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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 – 1. theory.

The plan is this…

  1. Finish constructing and installing all of the components, including gaskets, seals.
  2. Install a pressure gauge, in a temporary position.  Trevithick did not have pressure gauges available, but the current model boiler regulations insist on one.  So my plan is to have one installed eventually on the base, out of the viewing public sight, but where the operator (me) can see it.  For the purposes of the timing, which requires some pressure in the boiler, the gauge location will be on top of the boiler, but moved to its final position later.
  3. Install a fitting to admit compressed air to the boiler.  And a valve to adjust the flow and turn the air on and off.

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The lever with the hole controls the entry and exhaust of steam into each end of the cylinder. (The other handle is the throttle.)

The timing is adjusted by removing material from the blocks above and below the lever.  The blocks were made, deliberately, a few millimeters too long.

I will put some compressed air into the boiler, at about 20psi, and slowly move the lever until I hear air entering the cylinder at each end.  The lever position at which  air enters each end of the cylinder will be marked and measured.  Then the blocks will be machined or filed to the correct length.  I will assume that if the entry point is correct, then the exhaust will automatically be correct.

That’s the theory.

I have started making fittings for the pressure gauge and air couplings, and hope to get to the timing in the next day or so.   I will also be checking the pressure at which the safety valve lifts.  I will be aiming for 55-60psi.

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

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

Drilling the 2 holes took most of the day.

Figuring the setup was the biggest challenge.

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

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

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

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The Dremel chuck and the shop made spindle.

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

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

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And here is the gear crank pinned to the mainshaft.

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

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

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

Making a Lead Ball for the safety valve

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

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

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

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

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

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Then milled them pretty close to square and identical.

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

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

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

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

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

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

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

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

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

 

 

 

How Many One Off Parts Can You Make Per Day?

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

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

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

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The pressure valve arm, stand and restrainer in place.

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

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

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

Boxing Day in Oz

So, Xmas day was great.  Perfect weather, middle daughter’s home and vegetarian cooking thanks to her husband and all guests, and limitation rules for presents so that aspect was not gross.  And SWMBO agreed to be designated driver home.   So I could freely partake the lovely Aussie big reds.   And whiskeys.   And best of all… cigars.

Don’t remember much about the trip home.   But apparently we made it because I woke up with a dry throat but no headache. Must have been good reds and single malts.

Then best of all…. Boxing day!   Means that it is all over for another year.

A slow start to the day, then a half day in the workshop.

I spent several hours measuring various dimensions of the build to date.  Although I had been careful to keep the dimensions correct, the cross head was sticking and jamming on the slides.   Some dimensions were out by up to a millimetre…   mainly due, I suspect, to movements during the big silver soldering sessions.

So I tried various permutations and commutations to minimise the aberrations.  And started introducing brass shim strips to remove the aberrations.

And It gradually started to improve the situation.

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Shims under the base, and between the base pieces and the boiler.

Then I installed the valve timing mechanism.

But…..  it fouls the domed end of the boiler.

What to do?     After a lot of messing around, trial and error, swapping components around, I have decided to remake a couple of components AND to ease the fit between a couple of the others.    At least the cross head has stopped jamming so I am winning.

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Close up shot of the valve switching mechanism.

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The photo shows a vertical mark where the mechanism is scraping along the domed boiler end.

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where I left it for the day.  Will give it a miss tomorrow…   very hot day predicted.

 

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