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.

Trevithick Dredger Engine Guide Bars

I was discussing the guide bars with a very experienced modeller, and he finished with some advice….  “make them either very accurately, or very sloppy, otherwise you will have problems!”

The guide bars and cross-head

Well, I decided to shoot for “very accurately”.

I made the cross-head bar, and silver soldered it together.

All seemed good.  Just the guide bar bushes to be made and Loctited into position.  After a soak in sulphuric acid and tidy up.

So I made the bronze bushes, drilled them in the lathe to 9.5mm, then reamed them to 10mm.  Or so I thought.

But when I fitted them to the 10mm guide rails, they were very, very sloppy.   Checked the guide rail diameter… 9.99mm.  Checked the reamer 10.07mm!!  Chinese reamer.

So I searched my reamers and found 2 more.  Another Chinese one measured 10.04mm.  Another was a Sutton, made in Australia.  It measured 10.00mm.  I reamed a test piece, which fitted the guide posts perfectly.   So which reamer did I use?   Guess.

I made some more bushes and Loctited them to the cross-head.  Then drilled and reamed them, carefully, accurately.  This time the fit on the guide bars was snug, perfect.

Is there a point to be made here?  You better believe it.

Trevithick Dredger Engine Guide Bars and Crosshead



As you can see from the photo, I have made the vertical guides, the curved top bar and the crosshead.



The curved bar was bent in the motorised ring roller which I made years ago.  Bending 3.2mm steel was easy.  I have bent steel bar up to 10mm thick in this machine.




Parts of the guide bar.  2mm thick.  I confess that these were CNC’d.


IMG_7120 2.jpg

A few more parts required for the crosshead, but a test fit was quite good.  It is just pushed together at this stage.






Trevithick Dredger Engine- Valves

No workshop posts for a while because I have been making parts for the internals of the engine, and when installed they are not very photogenic.

Since the last post I have made the piston, piston rod and installed soft packing to seal the piston, made the valves and valve handles..



Stainless steel piston rod, bronze 20mm dia piston, and soft packing inserted into the machined groove.

Also made the throttle valve and steam direction valve.



This was the third attempt at making a steam valve.  I went slightly undersized with the first, totally buggered the O ring groove on the second, but the third one looks OK.



Good one (I hope) on the left, and destroyed one on the right.  The lathe tool bit into the bronze.



From left to right.  The bush, the undersize, the buggered, and the OK I hope.  and the plans.

And after all of that, and also making the throttle valve, I discovered a mistake in the plans.  A 1mm discrepancy, which I suspect was an arithmetic mistake on the part of the plan maker.  I decided to modify the valves, bush and valve block rather than remake the valves.



I machined 1mm off the faces shown in the photo, then spent some time prettying it up.  Then took 1mm off the valve lengths, and the valve bush.



This is what it looks like now.  All fixed.  Waiting for Viton O rings to arrive.  Looks OK IMO.








Home Invasion

We had just finished dinner and I was gathering the dishes for washing, when suddenly, very noisily, the broom cupboard door burst open, and two possums fell into our kitchen-living room area.

Possums are in most Australian roof spaces.  They are protected by law.  Not that that would make any difference to my Dr. Doolittle wife…. she actively feeds them, and they come to the broom cupboard from somewhere in the attic space, when she calls them.

But this is the first time that they have entered our living space while we were present.  I suspect that they were having a fight and fell against the broom cupboard door, then fell onto our kitchen floor.

Once before, when we away on holidays, they found their way into our pantry.  Obviously, they thought that they had gone to possum heaven, because every cardboard package had been ripped open and the nice contents were eaten.  The less nice ones were on the floor!

So why do we encourage them?  Normally they are shy and cute and timid.  They have babies.  And they keep stranger possums out of our attic, which is their territory.  And they are not dangerous.  And they are interesting.  That’s why.

So I took a video for a few minutes.  One eventually ran out of the open back door.  I decided to leave the room, because they are a bit more nervous about me, and I thought that my wife would have a better chance of coaxing them outside.

Enjoy the uncut, uncensored videos.


The possums are a bit nervous about me, so I went to bed, leaving my wife to cope with the problem.  I think that she sat there with the outside door open until about 2:30am.  The recalcitrant possum had climbed up the curtains onto a pelmet, and would not come down, despite tempting titbits from my wife.  At 2:30am she came to bed and left the outside door open.

I was the first one out of bed at about 7am.  No sign of any possums, even up on the pelmets.  But he/she/it had been all over the kitchen living room TV area, shitting at every step.   There was a pile of liquid crap on the pelmet.  Poor thing must have been really anxious.  I decided that Dr Doolittle could clean it up.





Trevithick Dredger Engine….progress


Finishing bits on the engine assembly.  The stuffing box, the gland, and a threaded plug in the throttle cylinder.  Throttle valve, stem direction valve,  piston and piston rod next.

Antarctic Weird.

Some of you might remember the Google Earth photos which I posted on Jan 6 2018.  “More Weird Stuff”.   The photo was from 1999 imagery.

Antarctica 6 Jan 2018 #2

This 21x7km black rectangular shape/object in Antarctica.  With the white reflections? white-out?.  And the track(?) leading from the south -east.   The satellite image was taken in 1999.  And I occasionally re-open Google Earth Pro to look at it, and wonder what it was.

Well guess what.  It has disappeared off Google Earth.   Nowhere to be seen.  Replaced with featureless white.

Suspicions aroused, I turned on the feature of Google Earth which allows the viewer to scan back and forth over the years.   I had place-marked the spot so I knew that I was in the correct place.  The “staircase” away to the north is still there.

While scanning the “spot” from December 2006, I noticed some odd lines.  Odd in that they were exactly parallel, exactly 1 km apart (you can measure things in Google Earth), and varying lengths, covering 1000’s of square kilometers.  then I noticed a little black dot on the computer screen.  It would not brush off.  Zooming in, it seemed to have a geometric shape, not at all like a natural feature, even pixellated.

Screen Shot 2018-11-01 at 11.02.40 am.png

I zoomed in and out.  If you look carefully (or better still, check this out on Google Earth yourself), you will see a white rectangular shape about 300m x 150m, irregular outline but quite angular and geometric, a black central shape, and a number of smaller grey shapes.  It is aligned almost exactly north-south.  It is bigger than an aircraft carrier.   Buildings?   Artifact?  Natural feature pixellated?

Buildings?   Well it is there, but whited out in the images Dec 2004 and 2005 but not after Dec 2006.

Artifact?  I thought maybe.  Then I looked around the vicinity.

Screen Shot 2018-11-01 at 11.27.23 am.png

Every one of those placemarks pinned by me, represents a similar but not identical object.  Some are clearer than the first one which I saw, particularly in the group under the “Leopold and Astrid Coast” label.  There are at least as many again, less clear, which I did not mark.

If you zoom into the above photo you will get the Google Earth co-ordinates to check this out for yourself.   Make sure that you bring up the December 2006 images.  The centre of the above cluster is the location my original “More Weird Stuff” object, but it is nowhere to be seen after 1999.

I have scanned around the rest of Antarctica and I cannot find anything else remotely like this.  Nor is there anything like this in other years/dates.

Screen Shot 2018-11-01 at 11.06.04 am.png

So, what do you think?  The images show 50-100 of these objects.  It appears to me that someone might have attempted to disguise the objects in the images by applying the thick parallel lines.

I have my own theory, but I will keep my ideas to myself.  For the moment…

Screen Shot 2018-11-01 at 11.07.48 am.png



Soldering the Trevithick Dedger Engine

That is soldering.  Not soddering.



These are the engine cylinder, valve chest, steam pipe (on the side of the cylinder), and flanges, pushed together.  I took this photo, because never again will these bronze parts look so pristine. 




Firstly, a thorough soak in degreaser, then rinsed in water.



Then the steam transfer tube was wired into position.   All joins were fluxed, then silver soldered.   Then a soak in sulphuric acid and a water rinse.  



The 20mm bore still accepted a 20mm diameter silver steel rod (i.e. no significant distortion from the heat), so the rod was super glued in place, and used to turn the flanges flat and perpendicular to the bore.



The assembly was heated to release the super glue.






Trevithick Dredger. A start on the Engine.

Some photos of progress on the Trevithick Dredger engine.  I am still making components for the engine, which is a single cylinder, double acting steam engine.  The valves and throttle are cylindrical, which is the method used by Trevithick over 200 years ago.



From the left…  the cylinder, with rectangular steam ports and bottom cap; flanges; steam tube.  The steam tube was bronze rod which was OD turned, then drilled, then split longitudinally, then bevelled so that it fits snugly to the outside of the cylinder.  Tricky machining, done with a steel plug to avoid squashing the part in the milling vise.    Some of the 5mm holes in the large flange should have been threaded.  Error in the plans.  Now considering whether to remake the flange or thread the holes 6mm and make some stainless steel stepped studs.  Probably the studs…




Components pressed together.  Later they will be silver soldered.




The valve chest was made from a chunk of bronze, which was first squared up…



Then marked out..



After preliminary drilling and reaming, the block was sawn to produce the truncated cylindrical hole.  (any better suggestions to describe the shape?)



The steam chest will contain the cylindrical valves for throttle and steam opening-closing and direction.  A complex item.  Quite a few hours of nutting out and machining.  Not quite finished.
















Hydrostatic Trevithick Boiler Test

This is a video showing how I performed the hydrostatic test on the boiler.

The engine is currently being made, but not at the time of the video.

The test is to hold water at double the working pressure of the boiler, for 20-30 minutes, checking for bulging or distortion of any of the components, and any significant leaks.  Any leaks would need to be fixed, but for the boiler certification, as long as the pressure can be maintained for the duration of test, that is OK.

The working pressure of this boiler will be 50psi, but the minimum pressure in the AMBSC code is 60psi, so the hydrostatic test will be done at 120psi.   As you will see in the video, the pressure reached 140psi at times.

In fact, the AMBSC code is formulated in terms of materials and design to cope with 8 times the working pressure, so the safety margin is generous.

The video is taken over 20 minutes.  I ran the actual test for over an hour.

I am afraid that my very messy bench and workshop are evident in the video.  No apologies.  That is just the way that I work.


Model Engines on Steam

It is Geelong Show time again.  It is actually titled the Royal Geelong Show, but having had more than a gutful of royal non-entities visitors being adored by unthinking cringers, flocking around Harry and Meaghan Kardashian, Windsor, and being a committed republican, I refuse to bother with the “Royal” handle.  (they are probably very nice people, I just cannot stomach the hoo-ha).

More importantly, it gives us steam junkies a chance to run our small engines on real hot steam.

For a treat, I am sharing four short clips taken today.

The first is a small beam engine, made by Swen Pettig.

The next two engines you have probably seen before.  My beam engine, and the triple expansion engine.

The small engine to the right is a Stirling engine which is running on the heat from the exhausted steam from the beam engine.

The triple is leaking a bit more than it should, although it is running amazingly smoothly on 25-30 psi.  The valve glands need repacking.

And finally, a model IC engine, the really odd Atkinson.  A 100+ year old design.  2 stroke. Made by Rudi vanderElst


Hydrostatic Boiler Testing

The boiler on the model Trevithick Dredger Engine was ready, I thought, for the next boiler inspection.

So far the boiler inspector has approved:

  1. The plans
  2. The boiler materials
  3. The machined materials
  4. The results of the first bronze brazing session
  5. The results of the first silver soldering session

Next was the hydrostatic test of the assembled boiler components.  This is a test which involves pumping water into the boiler, and holding it there for 20-30 minutes, at double the maximum operating pressure.

I intend to operate the boiler at a maximum of 50psi, but the minimum in the AMBSC code is 60 psi, so the test will be done at 120psi.

So I assembled the boiler, with a gasket under the big flat flanged end, and tested it in my workshop.  It pumped up OK to 120-140psi, but there were several leaks.  Most of the leaks were fixed fairly easily with teflon tape, but there was a persistent ooze of water from the big flat end gasket.  It was not holding pressure.

Next step, a thicker gasket.  Some improvement, but not enough.  I was still noting a drop of water every 3-4 seconds.

Next step, gasket goo on the gasket.  Maybe some further improvement, but still not enough.

OK, what next?  Maybe the big flange, or the big flat end plate was not  perfectly flat?  So an hour or so, rubbing the flange on 600 grit wet and dry on a flat plate.  There did appear to be some distortion.  The plate had been carefully lathe turned, but maybe the heat from the brazing caused some distortion.   A further reassembly then a test still showed more oozing than I was happy about.

Finally the penny dropped!

The flange was held in place by 24 stainless steel threaded rods with square nuts holding the flat plate in place.  Some of the holes in the flat plate had evidence of the threaded rod in the form of threading marks made by the threaded rod.  These were acting like threaded holes rather than relief holes.   So I drilled them all by a further 0.5mm.   Problem solved!

Pressure held to 140-160psi, with very slow pressure drop.  The drop was caused by slight ooze from the pressure pump taped joins.  See the videos.  The occasional drip which appears in the video is coming from the leak in the pump delivery hose.

So now back to the boiler inspector….


Why I Don’t Sweep Up Swarf.

Yesterday I spent some time spreading metal swarf around my workshop floor.


The weather is warming up as we enter spring in Australia.

My workshop is on a farm, and we have tiger snakes.  The authorities have warned us to expect more snakes than usual, due to the particular weather conditions this year.  I saw 2 snakes on the road leading to the farm.  And my neighbour visited me to inform me that he had spotted a 2 meter long, fat tiger disappearing into the freestone wall at the front of my property.   That is a very big tiger, even allowing for a bit of exaggeration!  Even baby tigers can kill.

And in recent years I have encountered tigers twice – IN my workshop.  Both times were after I had swept the floor.

So now, I spread the sharpest, nastiest swarf that I can find, all over the workshop floor.  To make the snakes feel unwelcome.  So far, so good this season.

Dredger Engine Bling

Getting ready for an exhibition tomorrow.  The organisers want “works in progress” so I am taking the dredger engine.  In its present state it is more a dredger boiler than an engine, but I doubt that anyone will mind.

IMG_7934.JPGSo I spent the day inserting a lot of square nuts on stainless steel studs, and bolting on some valves.   Looks quite interesting?   The stainless nuts came from China and were inexpensive.  A pity to paint them black.


The boiler is almost ready for pressure testing.  All of the parts are made, but sealant needs to be applied to the threads and joins, and possibly some gaskets.  I will do a hydrostatic test to 120psi, fix any leaks, then take it to the boiler inspector.  I am aiming to have it certified for 60psi, but will probably run it at maximum 50psi.

I have made the engine cylinder and the bronze cap which seals the vertical tube.  Looking forward to getting stuck into the engine.

Trevithick Dredger Engine. Finishing the flat end plate.

Today I brazed the inspection hatch to the flat end plate.  I did have some qualms about using the shape which I hade made, because it is quite round, whereas the example in The London Science Museum is more elliptical with one edge shaved off, and bolts which are irregularly placed around the perimeter.  But it is done now.  I admit that I was influenced by reactions from club members who were complimentary about the hatch which I had made, picking it out for special mention when I took it to yesterdays meeting.  And if I do not like it later on, I can remove the surface and make another one, more wonky like the original.


IMG_3426 2

The inspection hatch is ready to be brazed into position, and I have made a ring to attach the firebox door and surround.  The blowdown valve is very close and I had to grind a recess.

Before brazing I made a firebox door and surround, and bolted it to the end plate.



The surround bolts to the end plate, through the ring.  Here setting them up for drilling and tapping the M2 bolts.  That is an adjustable parallel, making sure that the door surround is horizontal.  Being glued to hold the position for drilling and tapping.



Hand tapping the 2mm bolt holes.  I drilled them after glueing the surround to the end plate with SuperGlue in the previous picture.   Then heated it to release the glue.  Did not break the tap, but I was careful to avoid touching the copper, and used tapping lubricant.



The door is cut out, but yet to make the hinge, catch and latch.


And just to remind you what I initially made, according to the Cain/deWaal plans…



These parts are now in the “failures” drawer.  Or should it be the “I changed my mind” drawer.


Trevithick Dredger Engine- soldering the big boiler flange.

Today I soldered the large flange which holds the flat end plate, to the boiler shell.  The flange is a large piece of LG2 bronze, but it is quite delicate because the centre is removed, leaving only the rim.

Here is a photo of the flange in position, fluxed, and ready to apply heat and silver.


But before this step I made a special tool.  Can you guess its purpose?



It is a disk of 12mm thick steel with a steel bar bolted to the surface.   A hint….  the disk diameter is slightly less than the internal diameter of the boiler shell.



Here is the tool in use.  With all of the heat from yesterday’s brazing, the boiler shell had distorted slightly, and the flange to be soldered was a bit tight in places.  So I identified the tight spots, placed the tool against the tight spot, and gave the bar a whack with a hammer, slightly expanding the tight spots.   After this, the flange dropped into position easily and nicely.



After soldering the flange.  No video I’m afraid.  Not enough hands.   To minimise the risk of the flange distorting with the soldering heat, I rested it on a plate of flat steel during the soldering.   Note the different shape of the forge for this braze.   



And after the brazing, the end plate was nice and square.



Square in both directions.






Trevithick dredger engine – second silver soldering session.

Soldered the bushes, the boiler supports, and the engine support.  Did not quite have time to tackle the boiler main end flange.



The LG2 bronze bushes were made yesterday, and the holes were prepared.  Today I fluxed them and silver soldered.  45% silver, cadmium free.



After soldering, and before the sulphuric acid soak.  The Hebel blocks are ideal for setting up the forge area to a particular size and shape.



The boiler is upside down in this photo.  I have just soldered the engine support.  Looks messy doesn’t it.  But it looks much neater after the acid soak.  And the splodges will vanish after eventual painting.   I used the bolt in the bush to get the support level and straight, while soldering.



Then the boiler supports were soldered, and the unit was dipped in 20% sulphuric acid for 15 minutes, after slow cooling.  Note the Plimsoll line, which was the depth of the acid.  I was unsatisfied with the alignment of that boiler support, so I reheated it and tapped it into a better position.  If it leaks steam, I might need to touch it up, but at least it is properly positioned.



At the end of this session.  The big flange is just sitting there, waiting for soldering in the next session.



Actually, this was not the first brazing session.  It was the third.  I had previously silver soldered the firetube.  And if you have been watching this build you might recall that I bronze brazed the domed boiler end and the boiler wrapper, and the vertical cylinder into the domed boiler end.  Despite the copper reaching red heat during today’s session of silver soldering, the bronze joins remained intact.  Bronze has a higher melting temperature than silver solder.  Which was one reason I did the bronze brazing first.




Trevithick Dredger Engine Boiler Bushes



Drilled previously, with wooden plug to prevent boiler deformation





Bushes made, but one is a bit tight, so using the Dremel to make it a loose fit, in preparation for silver brazing.





That is about right.  Roughly 3-5 thou gap.





The middle bush and the right hand one are additions to the Trevithick concept.  The middle one is a banjo fitting which will eventually connect to a modern pressure gauge… a boiler inspector requirement.   The big one is a water filler point.





All plugged up, ready for silver brazing then a boiler inspector hydrostatic test.  The thread which is visible is blind.  It does not communicate with the boiler cavity.

Ready for silver brazing in a day or two.


Trevithick Dredger Engine Progress

Made the cylinder, boiler bushes, and engine supports today.



The cylinder is LG2 bronze.  Drilled and reamed the 20mm bore, turned the outside diameter between centres, then milled the rectangular steam inlets at the ends.  The inlets were actually milled then the square corners were filed.

The boiler bushes are also LG2 bronze.  Straightforward turning.  Not quite finished.



The cylinder support looks simple but it is more complex than it looks.  The middle is LG2 bronze, but I did not have a large enough piece of bronze, so the wings are brass.  The join is bronze brazed, so it will not come apart when it is silver brazed to the boiler.  The angled supports are a tight press fit into the wings.



Next I will silver solder all of the joins.  They are just sitting in place in this photo.




Trevithick Dredger Engine – what was the original design? -2

Further reading and exploring web sites, email to London Science Museum (LSM), asking opinions of boiler experts.  Even considering a quick trip to London. (from Oz).

What I have learned is interesting.

Richard Trevithick did not manufacture any of the several hundred of his high-pressure engines.  The ideas and designs were his, but the engines were manufactured in different sites and by different makers.  The designs changed with time and as new ideas presented themselves to the brilliant mind of Trevithick.  And each manufacturer put their own stamp on the designs.

For example, look at the following pictures of the boiler flat end plate.  One is in two pieces, riveted together.  The other is a casting, and the flanges for the inspection hatch and the chimney, and probably the blowdown valve orifice, are almost certainly part of the end plate casting.  The firebox looks newish, slipped inside the original end plate casting.  I guess that the original firebox had burnt out, but was probably similarly held in place.   If any Brit readers can pop into the LSM and check this out I would be very grateful.

Trevithick boiler shell

B002617 hi res

The model which I am making, and dithering over the end plate design, is based on the reconstructed engine in the London Science Museum.  I intend to remove the aspects which are obviously Victorian in origin, and replace those with parts that I think will be closer to the Trevithick era designs.

Unfortunately, I have already made some of those parts, so my redesign is a bit compromised, unless I scrap them.  Which I do not intend to do.

So this is my redesign of the end plate.  Not quite LSM.  And not quite Tubal Cain/deWaal Not quite, but will have to be close enough.  The red lines are already machined so I am stuck with them.  14 drilled and tapped holes have been filled.  The bronze inspection hatch/plug has been made, but with less standout than shown in the lateral view.

end plate

As an aside, while pondering the end plate, I have made a start on the engine itself.  The cylinder has been roughed out, and will be finished in my next workshop session.  Cain specified brass, deWaal specified bronze.  So I have compromised, and have used an unknown brass/bronze/copperish lump of workshop metal.  It is certainly hard, as assessed by filing.  Photo next post.

New Spindle Motor for the Boxford 125TCL CNC lathe.

Reader Ben asked about the spindle motor replacement on the Boxford.   This is a small CNC lathe, and was often used for teaching in secondary schools in Australia.  Mine was made in 1985, and I replaced the electronics a few years back because they were obsolete and not functioning.  The mechanicals of the lathe were beautifully made and in excellent condition.  I did replace the ball screws, but in retrospect, that was probably unnecessary.   I also installed new and bigger axis stepper motors.

I was still getting some unreliable results, despite the the upgrades, and wondered whether the spindle motor was lacking power.  I was taking lighter cuts to try and cope but clearly a new spindle motor was required.

The space that the motor occupies is fairly tight, and initial searches for a suitable replacement were fruitless.  The new  ClearPath motors looked promising, but enquiries to the manufacturer indicated that the required power and rpm’s were not available.  Then my expert friend (or should that be “friend who is an expert”?), spotted the Ebay ad below, and bought and succesfully installed the servo motor in his 125TCL, so I did likewise.  I am afraid that the electronic aspects remain a mystery to me, so I cannot help with those.  It is a 0.75kW motor, substantially more powerful than the original, but very compact.


Servo Motor.jpeg

Do an Ebay search on the code on the controller.  I paid $AUD339 but it is now plus postage and GST, so close to $AUD400



The new spindle motor and servo controller



A new motor pulley was required.  There is still a high and low belt ratio available, but with the extra power and torque I never use the low ratio.  RPM range is 300-3200.


This has been a very successful modification.

Many thanks to Stuart Tankard for his generosity in time, expertise and advice in getting it going.