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. I read every comment and respond to most.

A Chuck in a Chuck

Sometimes, the chuck in your lathe is too big.

I needed to machine some of the aluminium castings which I had made for the cannon chassis.  They were too high by 1-2mm.  But, the flanges were delicate and thin walled, and although the ends were flat and roughly parallel, they were not actually parallel.  I wanted to use my most rigid and precise lathe, which is the Colchester Master 2500.  But the bore on the chuck was greater than the diameter of the part which I was turning.

So this is the setup.  A chuck in a chuck.

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The Colchester 3 jaw is 200mm diameter, and it neatly holds a 80mm chuck off my Boxford TCL125 CNC lathe, which holds the part.  It is a centre column from the scale model Armstrong gun which I am currently assembling/making.   It is a bit irregular, with thin 2mm flanges and fins.  I really did not want to damage it, but it needed 1-2mm trimmed from its height.

So, I held the part in the 80mm 3 jaw, centre drilled it, and supported it in the 3 jaw and the tailstock.  It worked well.  No disasters.

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I machined the three castings which I had made.  And reversed them to machine the bases.   The setup worked well.   I need only 2 of these, and could use any of them.  The machining did reveal some porosity of the castings, but overall I am quite pleased with the end result.

p.s.  You might notice some advertisements in my posts from now on.  Unfortunately I am at my storage limit on my current WordPress plan, despite deleting virtually all embedded videos, and placing the main ones on YouTube.  I am facing the prospect of either deleting old posts, or increasing my WordPress payment plan to a business plan, which is substantially more expensive.  I have decided to see if monetising the site will cover the cost of upgrading to a business plan.  I do hope that the ads will not be too intrusive.  Let me know what you think.

Armstrong Cannon Chassis Wheels

The assembly of my Armstrong cannon is progressing more slowly than I anticipated.  No excuses.  Just lots of holes to drill in precise positions, parts to turn and mill.  And my workshop sessions have become shorter in the winter cold.   Not that I mind the cold.  I just light my workshop wood fire to remove the chill.

Today I have been making the wheels for the chassis.

 

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Not a great photo. It shows a front wheel, 33mm diameter, turned from stainless steel. No axle yet.

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And a rear wheel, 50mm diameter.   Yet to have the track groove turned into the periphery.

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I thought that the wheels would be easy to make.  Just a bit of basic turning to size and form turning for the track groove and decorative relief on the faces.  But as usual, I used whatever material I had on hand in the size.  In this case stainless steel.  It looks great when turned, but does work harden quickly, causing tooling problems.  Parting off, through 50mm of hardened stainless steel is not much fun.  In the end I used the band saw for parting, then tidied up the ends on the lathe.

 

Model Armstrong Gun Cypher

Yesterday I spent some time with 600 grit emery paper on the barrel.  A bit more elbow grease is required, but I took some pics of the progress….

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From the left, the sighting line called the “line of metal”.  There will be a corresponding line on the muzzle.  Next is the weight of the barrel in hundredweight.  81cwt = 4 imperial tons plus one cwt plus 2/4ths of a cwt plus zero pounds.  One hundredweight = 112 lbs, so this barrel weighs 9128lb / 4140kg.   The arrows indicate that the barrel has been “proofed” and accepted for service and also possibly mark the end of bore.  The dot would be where the “vent” would be located (the ignition or touch hole) usually about half way along the powder cartridge.  Then the reigning monarch’s cypher.  In this case, Queen Victoria, with her motto, that of the Order of the Garter.  HONI SOIT QUI MAL Y PENSE.  The translation from French is  “Shame to him who thinks ill of it” (“it” being the Order of the Garter)

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The Royal Gun Factory number of this barrel, and axis lines.  One reference stated that they mark the centre of gravity of the barrel, but according to my assessment, the COG is well behind this point.

The other trunnion marks are yet to be lasered.  Maybe late next week.

I am delighted with the quality of the laser “engraving”.  It is sharp, crisp and finely detailed.  Again, thanks to Stuart Tankard for the use of his laser, and for operating it.

How were Trunnions Joined to 1866 Barrels? Correction of a previous post.

The earliest cast cannon barrels were cast in one piece, and the trunnions were included in the casting.

By 1866 however, large barrels were made from 4 or more separate pieces, which were heat shrunk together, and additionally forge welded together.

The following information comes from “Naval Gunnery” by Captain H. Garbett, published in 1897.

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The diagram is of a 64lb Armstrong rifled muzzle loader.  The 80 lb muzzle loader, which I am modelling, was very similar to, and based on the 64lb gun, except that the diameters of the sections were larger, giving greater wall thickness.

The “A” tube, containing the bore,  was made from best quality forged steel, in one piece, although earlier models used the “coil” method described below, and earlier than that it was wrought iron.  It was permanently closed at the breech, but in slightly later models it was open, sealed with a copper disk which was held against the cascabel.  The A tube was bored and rifled after assembly of all of the barrel pieces.

The “B” tube, or tapered chase was heat shrunk onto the “A” tube.  It was a coil construction. (see below).

The “Breech Coil” had 3 components, plus a cascable which screwed into place with a deep, asymmetric thread.  One of the components was the “trunnion ring”, which was welded to, and separated the other 2 components.

“COIL” TUBES.

When steel is forged into a strip, apparently it is strongest along its length due to the orientation of the crystalline structure.   It was discovered that the strongest cannon barrels were made from long strips of forged iron or steel (up to 200 feet long), which were then wound around a mandrel, while red hot, forming a cylinder.  The red hot coil was then hammer welded into a solid cylindrical mass, with most of the steel crystals aligned circumferentially.  It was then machined into its final shape, with allowance for final heat shrinkage onto its mates.

 

The “TRUNNION RING”.

The trunnion ring was forged from a single billet of steel.  Two holes were punched through the red hot billet, expanding the sides.  Further hammering shaped the trunnions from the lateral expansions.  The final shape was then machined.

The three breech pieces were forge welded together, and heat shrunk onto the “A” tube and the “B” tube.  I could not discover the construction sequence of welding/shrinking these components.

This post is to correct an earlier post about the trunnions in the Armstrong cannon  construction, in which I stated that the trunnions were heat shrunk into the barrel.  The incorrect implication was that the trunnions were heat shrunk into holes in the barrel sides.  My recent reading indicated that the “trunnion holes” method, which I used in my model, was NOT the method used in 1866.  I am not losing sleep over this lack of authenticity in construction of my model.  One of many compromises which are made when scale modelling.

 

 

Lasering the Model Armstrong Cannon

This is the Queen Victoria emblem and motto on the original cannon at Port Fairy, Victoria.

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The “Victoria Regina” emblem, and Order of the Garter slogan motto.

And this is what is now lasered onto the model cannon..

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Pretty good, Hey?  On the model, the emblem is 20x12mm.    It was downloaded from the internet, edited with Corel draw, saved as a BMP file, and then lasered onto the steel model barrel.   This is a photo of the emblem on the model cannon.  The rectangular background will disappear with polishing.

It was made with a 30 watt fibre laser, driven by its owner, Stuart Tankard.  It took about 30 minutes, 200 passes.   Shows up my substandard turning.

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Shows the emblem appearing after 100+ passes.

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and this is an enlarged image of part the laser engraving.

I have some videos of the process, and I will make them available after some editing.

This was incredibly exciting.  The model cannon requires more polishing, and colouring with a gun blacking chemical.

We also engraved the cannon weight, sight marks, and year of manufacture on the trunnions.  I will post those photos when available.

 

 

and some Carriage Wheels….

The wheels on the carriage, not the chassis.

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I made 20 of these, 20mm diameter,

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The small cap screw bolts will be replaced with solid rivets.

The wheel axles are yet to be made and pinned.  (the Philips head bolts will replaced with solid pins and washers, and held with taper pins.)

And just to remind you of the appearance I am aiming for…

whole cannon R obl

I do wonder about the original colour of these 1866 cannons.  The rusty iron colour has some attraction, but I would be certain that it is not original.  So far I have had no luck finding out what the original colours were.

Model Armstrong Cannon. Assembling the bits. And a riveting improvement.

After 4 -6 weeks of making castings, and remaking them, and remaking  them again, I have finally started drilling holes and bolting pieces together, in preparation for final riveting.

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I ground a 2mm diameter end on my centre punch so I could transfer the cast holes on the brackets to the sides of the carriage for drilling.  (using a toolpost grinder on my lathe to grind the center punch.)

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Center popping

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I could not resist pushing some parts together to visualise how the carriage will appear.  10 wheels per carriage to be made.   This is the “B” carriage, on which I try out the techniques.

More riveting.

Using my new riveting gun, I inserted a lot more rivets on the “A” chassis…and I used a technique suggested by one of my readers…bearing in mind that my first riveting efforts marred the surface of the parent metal, and were generally rather irregular rather than neat.

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Virtually NO surface dents, very regular, a big improvement.   I had intended to polish out the machining swirls, but SWMBO said that they were appealing and interesting.

And the technique was this….

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The rivets are inserted 5-10 at a time, then the heads are covered with tape.  Duct tape in this case.  The work is then turned over, and the rivets do not fall out.

Each rivet head is centered over the anvil, and the pneumatic gun is used with the snap on the other end.   The tape stops the rivets from falling out, and also protects the parent metal from the snaps.  I experienced virtually no parent metal bruising.  And was VERY fast.  A major improvement.  Many thanks Timothy G!

 

 

 

 

 

 

 

Firing a Model Cannon

If you want to watch a video of a model cannon being fired, try YouTube.  Or you could watch the following video, sent to me by one of my readers.  This is a slightly larger scale than my model, and a breech loader.  Superbly built.  Click on the arrow to watch it.

When anyone finds out that I am building a model cannon, the inevitable question arises “are you going to fire it?”

Up until recently my answer was “no”, because,  1. I do not have a shooter’s licence, 2. I did not intend to register the cannon and 3. Australia’s gun laws which I support, are strict and policed.

If a model cannon is capable of being fired, it must be registered.  As an owner built gun, it would have to be “proved”, i.e.  be inspected by a gun expert, and have some proving shots with powder alone, powder doubled alone, powder plus shot, double powder plus shot, and finally double powder plus double shot.  Then the gun is certified for the particular weight of powder plus shot.  I think that I got that sequence right.  It was explained to me by a gun testing expert recently.

For a model cannon not required to be registered it must be incapable of being fired.  For one such such as I am building, a muzzle loading, black powder cannon, that would mean not drilling the touch hole.  In my case I could have the appearance of a touch hole, by making a dot at the site, but no drilling.

To investigate the situation, I have checked the Victorian Government website, spoken to police, and spoken to a firearms safety course instructor.  I also visited a shooting range where a blackpowder gun club was having a target shoot.  Members were shooting black powder guns and rifles at targets 50-100 meters distant.

About 50 years ago I was in the Citizens Military Forces, a university infantry company, and had instruction and practice in using a 7.62mm SLR, an F7 submachine gun, and an M60 machine gun.

My point is that the black powder guns were VERY loud.  Painfully loud in fact, until ear plugs were fitted.  Substantially louder than I remembered SLR’s, F7’s or M60’s.  But maybe I have just forgotten.  And the blackpowder shots were accompanied by a gout of flame, and a large puff of smoke.  Spectacular, in fact.

Then, under the close supervision of a gun owner, I fired a black powder hunting rifle myself.  It was loaded by the owner, using a ram rod for the charge, and a mallet then ram rod for the ball.  2 triggers.  The first was a heavy pull to ready the shot.  The second was a hair trigger to fire it.  And hair trigger it was.  Just a touch and it fired.   Despite the BANG, some fire and smoke, and the instantaneous puff of dirt where I had aimed, the recoil was minimal, more of a firm push against the shoulder.  It was an interesting and exciting experience.  Less smoke and flame than the other blackpowder guns nearby, but maybe being a hunting gun, he had used a more modern powder.  The following short video shows my son in law taking instruction.

I have put in an application for the firearms safety course which is supervised by the Victorian Police.  Then there is a 2 part multi choice examination, with no incorrect answers permitted on critical questions, and 18/20 (I think) for the rest.  If passed, there is a criminal history check, and references required.  Then a compulsory 4 week wait.

I will get the shooter’s licence, to keep my options open, but have not yet decided about registering the model cannon.  It would be nice to have a video of it being fired, for this blog, but it is very likely that it would be a once only event.  My interest in the cannon is its historical associations, and the technology, plus the challenges of building it.

If the cannon is capable of being fired, it would have to be registered indefinitely, and the owner would need a shooters licence.  After all of the time and effort in its research and construction I  would hope that someone in my family would eventually own it, so I am thinking that I will not make a touch hole, and make it incapable of being fired.  Another possibility which I will explore, is to register the cannon, make a video, then make it incapable of being fired by partly filling the bore and touch hole with molten metal then deregistering it.

Meanwhile it will have no touch hole.

 

 

 

My Daughter Has Caught the MetalCasting Bug

For some reason which I do not really understand, my youngest daughter has become interested in my metal casting activities.

First she watched me do a molten aluminium pour.

Then she rang me a day or two later and asked if she could have a go.  She really wanted to do it in brass or bronze, but as a relative beginner myself, and with only one episode of molten brass, and that one did not go so well, I demurred, and said that her first effort would have to be in aluminium.

So I prepared 3 flasks, printing the plastic parts, and gluing them into a wax tree, then slowly heating the flasks in the potters oven, up to 750ºc over 8 hours.  Then lowered the oven temperature to the pouring temp of 710ºc.  And preparing the aluminium melt at 710ºc.

When Eleanor arrived, we had a couple of practice runs with flasks full of sand, so she could get used to the weights and handling the tongs, and the various movements while wearing the protective gear.

Then the pour.   This is Eleanor’s video of the event.

 

I admit to some substantial reservations about this exercise, but Eleanor listens carefully, asks intelligent penetrating questions, and follows instructions precisely.   Full marks.

And, a very successful pour!

The (non) gripping power of rubber

In order to increase the head pressure of molten aluminium during my casting pours, I increased the height of the casting cylinder to 250mm (previously 100 to 150mm).

That meant that the weight of the casting investment mix increased to 5.25kg. per 250mm cylinder.

This was the result today, when I poured the investment mix, then moved the cylinder with the rubber cap at the bottom.  It would have been OK if I had waited for the mixture to set. (about 20″).

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The rubber end cap slipped off, the investment mixture came out, the 3D printed parts tree fell apart, and an horrendous mess resulted.

After a barrage of unprintable expressions, I hosed the 3D prints down (outside), and washed the cylinder and end cap (outside).

By then the mess on the bench and floor had set, so I was able to scoop most of it up with a BBQ spatula.  Then multiple wipe downs to get the very fine powder off the surfaces.

I still wanted to prepare the moulding cylinder(s), and for some reason I had lost my desire to use the 250mm cylinder, so I made 2 trees with the parts, and split them into two 150mm cylinders.   Without further incident.

While waiting for the investment mixture to set, I did some further work on the previously cast parts.

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Applying some JB Weld  onto one of the cast rear wheel bracket and column assemblies.

Lost PLA Casting – 3rd pour

Today I attempted another aluminium casting session with trees that I had made 2 days ago.  More wheel forks, and barrel trolley brackets.  16 parts altogether.

And this time I installed air release vents, following my previous poor results, and at the suggestion of reader Rob R.

I also made some 50mm extensions of the pouring funnel, to increase the head of melt pressure.  The extensions were “add ons” rather than designed into the system, and the molten aluminium leaked between the extension and the main flask with the tree, so I doubt that they were very effective.

BUT!  Of the 16 parts on the trees, 14 were good to excellent, and only 2 showed any voids, and I assess one of those as repairable.  So, 15/16 is very pleasing.  I feel that I am closer to getting good results every time, if I can make an effective system of increasing the delivery pressure of the molten aluminium.

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These are the extension pieces to the funnels on the investment flasks.  The shape was made with the plastic funnel.  If I had positioned them before the investment plaster had set hard they might have worked better, but as they just sat on top of the already hardened plaster, the join leaked molten aluminium rather badly.  I have a different system in mind for my next pour.

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Previous failures were cut up and thrown into the melt.

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See the tiny silver dots surrounding the central funnel.  That proves that the air vents functioned as intended.

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The aluminium trees.  Not very pretty, but delightful to see.  10 parts on the top one, 6 on the other.  It is odd to see the wax spaghetti turn into aluminium spaghetti.   I will separate the parts tomorrow.

And while the investment burnout and baking was proceeding, I worked on previously cast parts.

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The centre columns have beep painted with etch primer.  A little more filling required, then I will use the best 2 on the models.   The 2 bracket and column assemblies on the right were initially considered unusable due to large voids, but I used some aluminium solder to fill the defects, and they might possibly be OK.  The 2 on the left just need some tidying, machining removal of  melt tubes, and minimal filling.

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I will probably remake this one, but will continue to salvage it and see how well it comes up.  Note the solder fill on the RHS.   That will not be seen on the model.

One more melt and pour, and that should be the last of the castings made for the model Armstrong cannons.  It has been a challenge, and lots to learn, but very interesting and very satisfying.

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Finally for today’s post…  I noticed some black marks on the normally pristine white wall above the casting bench.  They extend about 4 meters above the floor.  Do you know what they are?  The paint has been melted off the wall by bits of flying molten brass, resulting from the steam explosion 2 days ago!

Many thanks to Rob R for his spot on suggestion about the air vents.

Brass Melt. Dangerous!

Today I received by mail 2 new crucibles for my furnace, so I tried a melt of brass.

The source of the brass was machining offcuts, machining failures (quite a few of them), and machining swarf.   The swarf was not very clean, probably containing some aluminium, cutting oil,  dirt and grunge.

It was an interesting experience.

Firstly, the temperature had to increase to 1000ºc.  Later increased to 1050ºc.  It is very hot.  And the impurities came off as smelly fumes, and dross.

But, I poured some ingots.

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And I made another remelt.  And later remembered something which I had read somewhere…..   molten metal and water is dangerous.

After making a few brass ingots, and quenching the moulds so I could remove the ingots, I proceeded to another brass melt.

When I poured the molten brass  into the mould, IT EXPLODED!

IDIOT!!!!

FU**ING IDIOT!!!

I had caused a steam explosion.  Probably the mould was still damp.  And when the molten brass entered the mould, it EXPLODED.   I kid you not.  It went BANG.  Luckily, none hit me, but some of the molten brass had landed up to 2 meters away.

OK.  Lesson learned.  Molten metal must be treated carefully, with respect.  And NEVER put it in a container which is not thoroughly dry.

And after inspecting those brass ingots, I will never try to melt dirty brass, or any other dirty metals.

Meanwhile, preparing for another aluminium pour.

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Here is the next tree.  You might note that there is a spaghetti appearance of wax tubes added to the tree, to allow efflux of air from the cavities, as the melt enter them.

Next aluminium pour on Thursday.  Fingers crossed.  Stay tuned.

Video of Casting Small Complex Cannon Parts

This video was taken and edited by my daughter Eleanor.  I was doing an aluminium pour of some parts for the Armstrong RML cannon, explaining the process to her.  I was hardly aware that she was videoing, so the interaction is conversational.

Although the pour was not a success because none of the parts were good enough to use, it does show the process as seen by someone who previously knew nothing about it.

 

 

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There is also a 20 minute video of the whole process which I will add to this post when it is available.

Reader Rob has suggested that the positions of the defects suggests that air entrapment is the cause of the voids and that the fix is to position some vents at the positions at risk.  I will try that with my next pour.  Thanks Rob.

Here is the 22 minute video.  Just as recorded.  Not planned or edited.

 

 

 

 

 

 

 

Second Pour.

One definition of stupidity  is repeating a set of actions and expecting a different outcome.

Well, after my partly successful first molten metal pour, I repeated the same steps, (with some minor corrections), and hoping for a more successful result.

The day was entertaining, with one of my daughters videoing the exercise.  But this was the result…..

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The aluminium melt has not properly filled the cavities at the top (nearest the funnel).  The bottom cavities have filled nicely, with good definition of the printing details.

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The second flask with the same  result.

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My daughter found the exercise very interesting, particularly the pour and the boiling out of the investment material.  But she was a bit disappointed that the end result was not better.

So, I am considering how to change the process.

I believe that I need to increase the filling pressure in the upper half of the flasks.

Possible methods:

  1.  Install a vacuum system for the melt pour
  2. Use a vertical extension for the melt funnel, to increase the height of the column
  3. Increase the diameter of the funnel tube
  4. Increase the number of the funnel tubes
  5. Don’t place tree branches close to the funnel

I had previously considered 1. as recommended on YouTube by several contributors.

The investment powder is a significant cost, so I would prefer to use as much of the volume of the flask as possible, which makes 5. an unattractive proposition.

There are difficulties with instituting 2. but I am thinking about this one.

And possibility 6, is to try bronze or brass, which has a much greater density, and probably less viscosity than aluminium.  I am waiting for some more furnace graphite crucibles to arrive before I can try this one.

Meanwhile I have to 3D print some more PLA parts.

 

Tomorrow’s Pour. And a family member is interested!

My family is vaguely interested in the stuff which I make.  Engines, traction engines, cannons etc.  But I doubt that any of them read these posts.    The grandchildren like the steam engines, particularly the 3″ traction engine.

But, the molten metal casting has struck a chord in the youngest daughter, and tomorrow, when I do my second metal pour, she is coming to watch!  At least I will have someone to hold the video camera.

So I prepared 3 trees, and poured the investment material for 2.  I took some pics but forgot to bring the camera home.

Also, I am conducting an experiment.

I know that my early 3D prints were too porous, and allowed the investment material to penetrate the the moulds.

Tomorrow I am still using the original models which I know are too porous, so I am trying something.

I have covered the porous surfaces with super glue to try and seal them.

So, watch tomorrow to see if this experiment looks promising.

(p.s.  The super glue experiment did not work)

 

A Closer Look at the results of yesterday’s Metal Pour

Yesterday I made some cast aluminium parts for the model 1:10 Armstrong RML cannon. It was the first time I had done lost PLA casting, and seeing the castings emerg from the investment mixture was thrilling.

Today I had a closer look at the parts, band sawed them from the trees, and tidied them up with some belt sanding and filing.

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There were 3 central columns.  In each case the vertical side flanges came out almost perfectly, but the bases contained some voids.

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The undersides of the bases shows that the voids match the internal structure of the original 3D print.  This indicates to me that the fault arises from the 3D print, not from the molten metal pour.  Those columns were among the first 3D printing that I had done, and I remember that the surface layers were only 3 layers thick.  Since then I print substantially thicker surface layers, which I believe are more water tight, and less likely to let the investment material leak into the structure of the print.

Although they look very ordinary, I will fill these voids with JB Weld, then paint them with automotive filler primer, then the final paint coat(s).   If they are still substandard I will start again with new 3D prints,

I also poured 6 wheel forks.  2 were so bad that I have melted them down into ingots for re-use.  The other 4 looked resurrectable.  Unfortunately I had a mishap when bandsawing the parts from the tree.  The tree was flung across the workshop, and one of the forks snapped.  Of course it was the best one.

So 3 of the 6 forks were put into the re-melt, and I did some tidying up on the other 3.

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This lot was remelted into an ingot for future re-use.

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The 3 on the left after some tidying.  Same problem with the voids in one base, but structurally OK and can be fixed.  I scrapped the one on the right.   I might eventually remake them all.

So, although I ended up with 6 use-able parts out of 9 made, and most of those require filling, I am still reasonably happy with this first attempt.  I think that the 3D prints were the weak link in the chain, and with that assessment I will try another casting run in a few days.

Meanwhile, back home I printed a Tyrannosaurus Rex.  I think that it is my best 3D print so far.  It is 250mm long, and the level of detail is excellent, even the vestigial arms are intact.

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About the colour.  No one has any idea what the original T Rex skin colour was.  So even this red is possible (but unlikely).   Nor do the scientists know what noises the T Rex made.  Could have been a reptilian hiss, or a roar, or a porcine grunt.   Whatever, I am glad to never hear it.

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The print took over 24 hours.

Metal Pour

50% preparation of the PLA originals, 45% preparation of the investment, and 5% management of the pour.   You have seen making the trees with the PLA originals.  Today I melted metal, poured, and held my breath.   First metal pour.   I also made some videos, but the autofocus on the Panasonic LX100-2 is so crap (or maybe it was the operator who was more focussed on the metal pour), that I have scrapped the videos. But some stills are OK, as you will see.

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I purchased an ingot of casting aluminium, and bandsawed some pieces to fit into my melting crucible.  Then I washed and wirebrushed the pieces in hot detergent.  There was minimal dross in the melt, so this step was worthwhile, and the ingots must have been fairly free of contaminants.

Next, was measuring the investment powder and water, using kitchen electronic scales.  After mixing there is a 10 minute window for thorough mixing, removal of air bubbles in the vacuum chamber, and pouring into the investment moulds, which had been prepared beforehand.  (see last post).

10 minutes sounded like lots of time, but this was a real time and motion study, having everything ready, with no delays.   But when I saw the clouds of silica dust I remembered that I should be wearing a mask.  So, quick dash, pull on mask, find hearing aids dislodged by the mask, and back to mixing the investment mixture.

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Then, 1.5 hours for the moulds to set hard, and remove the rubber caps with the pouring funnels built in.   That exposes the bottom of the wax trees.  The hose clamps were to assist security of handling the steel cylinders with flask forceps.  Next time I will position them closer to the funnel end.

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The moulds, after removal of the rubber ends, are placed in the investment oven, for 4 hours at 250ºc, 2 hours at 400c, and 2+hours at 750ºc.  The wax and PLA plastic is burnt out and the investment powder sets really hard.   The steel cylinder is red hot.  The wax and PLA comes out as smoke, with no other remnants seen.

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The aluminium ingots are melted at 710ºC, and any dross is scooped off the surface.

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Meanwhile, I have placed a sheet of cement sheet on the floor, a tray of dry sand, and moulds for any excess aluminium melt.  There is a bucket of cold water ready.

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when the mould has been at 750ºc for at least an hour, and the aluminium has melted at 710ºc, the mloten metal is poured into the moulds, which have been removed from the investment oven.  Made a video, but not showing because very poor quality.  After about 30 minutes, the still very hot mould is plunged into cold water, which blows out much of the investment.

And here is the result……

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These are the rear wheel forks.  I need 4.    2 were unusable, and will be remelted.  4 are good to OK, and after some filling with JB Weld, and painting, will be fine.  The 2 failed forks were those closest to the funnel.  Not sure why.

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These are the centre columns.  I need 2.   All 3 are repairable.  One is very good.   Again, the top one, closest to the funnel, (RHS) will be remelted. I did not vacuum the melt into the moulds, and the weight of melt is lowest at that level.  (maybe the cause for the poor result there?)

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so, when I had a closer look at home, none of the pieces are perfect, but they are not too bad.  For a first run, I am really pleased.

With many thanks to Stuart Tankard for his advice and encouragement.

 

 

Making a Tree

The adequately sized vacuum chamber arrived today, much more quickly than I expected.   Initially it would not seal and I could see no holes or leaks.  But when I removed the silicon gasket I found a small silicon flake which was the problem.  Thorough cleaning, and all was well.

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The 1/4hp vacuum pump on the left.  The new 5 gallon chamber hooked up.  And the too small 3 gallon chamber on the right.  I have an idea for using the smaller one, so will hang onto it.

With this arrival I am almost fully equipped to start casting.   So today I built 2 trees.

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The first tree has no branches, so it is more like a tree trunk.  The red items are plastic models of the central pivot column on the Armstrong model gun.  Glued together with wax which I melted with a soldering iron.  (soddering iron for American readers).  And attached to a wax stick which inserts into the rubber flask end at the bottom.  The actual steel flask is behind.

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And here is the “tree” trunk in position inside the flask, ready for the investment plaster to be poured around it.  After pouring it sits and sets for a couple of hours.  Then after removal of the rubber end, about 8 hours in the kiln to melt out the plastic and wax.   Then the molten metal pour. 

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This is the second “tree”.  Wheel forks for the cannon chassis.  Wax glued to the central wax tree trunk.  The 4″ steel cylinder behind. 

Preparing the moulds, and the metal pour will probably occupy about 10 hours, so I will need a totally free day.  Maybe Thursday.

Riveting the Armstrong Cannon Chassis Model

I am waiting for delivery of the 5 l vacuum chamber so I can commence casting parts for my 1:10 Armstrong cannon.  So today, I spent some workshop time riveting the chassis of the 1:10 Armstrong 80lb muzzle loading rifled cannon model.

I am a total novice as far as solid riveting goes.  The following photos will prove that fact.

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I am holding a new Taiwanese riveting gun.  The girder into which I have just inserted almost 100 copper 2mm rivets is resting on the vice.  The anvil is clamped into the vice.  The snap (home made) is in the gun.

I have marked the surface of the girder with the anvil and snap.  Doesn’t look good, but I am hoping that it will be acceptable after painting.

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I painted the inside of one girder with layout paint just to see if the crappy riveting will be acceptable.  Still considering that question.

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A staged photo of rivet insertion.

And just to lighten this post, yesterday I had a visit from my grandchildren, 2/3 daughters, sons in law, and SWMBO at my workshop.

So I fired up the Fowler 3″ traction engine and gave the kids a demo of filling the boiler with water, lighting the furnace, a discussion about the nature of coal, and a ride.

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Despite the wintery weather, it was a very happy afternoon.   Audrey 4, Edward 4, Charlie 4, and John 7.   And John 70.  We have had an unusually wet autumn, hence the green grass.  No tigers seen.

 

Getting Ready for Casting

Setting up for casting molten metals into shapes for my model Armstrong cannon.  Still getting ready.

Today I made some moulds for dealing with any left over metal melt.  Not a big deal, but it does have to be done before the first melt.  No point realising that there is nowhere to put the left over aluminium or bronze during the pour.  It has to go somewhere.

So today I made some ingot moulds, in readiness.

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The ends of the moulds are sloped to allow easy ejection of solidified aluminium or bronze.

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4 ingot moulds.  Made from 40mm ID thick wall pipe, with long handles.  The diameter of my crucible is 48mm ID, so any ingots made should fit into my crucible later for remelting.

It seems a long time since I have done any welding, and the welding of these items was pretty ordinary.  But the joins seem water tight, so hopefully they will be OK.

Today I fired up the casting oven, to 850ºC, and the load was some ordinary food tins.  They are the correct diameter for investment moulds.  I wanted to see if the tins would cope with these temperatures. (after removing labels of course).

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3 ordinary food tins, at 850ºC.

It became apparent, that the tin joins were welded not soldered.  And the inside and outsides of the tins were covered with some sort of paint or plastic, because it flaked off.  But the metal cans remained intact.  Admittedly, when hot they were VERY soft, but when cooled they retained their shape, and were quite stiff.   I would be prepared to try these for single use moulding projects.

I have realised that my investment plaster mixing bowl is too big for the vacuum chamber which I had bought.  So I have ordered another vacuum chamber, and waiting for it to arrive before starting a mix.  I am using the delay to gather items like the ingot moulds above.

It will probably be another couple of weeks before I am ready to cast.   Meanwhile my 2mm rivets have arrived at last, so I will get back to the riveting.