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.

Tag: model cannon

More Gearing Up, and more to come.

This was 4 days ago.
Today. Re the gears on the right, bottom row…. one was machined from bar stock, the other was cast, had the outer ring removed, and a new ring soldered on, then the teeth were cut. Can you pick which is which? And all of the round gears have spent 3 hours in the gemstone tumbler to remove sharp edges. The tumbling has reduced the surface oxidation on the large gear castings, but some more time required to totally remove it.
CNC milling the spokes in one of the intermediate gears. Neat job, but the internal corners with fillets are not really kosher. This gear is barely visible in the finished model.

And the gears with ratchets attached need 2 mates. I tried to make them yesterday, but we had a wild day with thunderstorms and high winds, and my machines were playing up. I might get back to them today. (the ratchets can be seen in the header photo).

In country Victoria we are out of level 3 lockdown! Hooray! Still can’t see family from Melbourne, and minor restrictions on visiting local friends, and need to wear masks when out and about. But things are on the improve. I doubt that we have seen the last of the virus however.

Trunnion Mounts -3

I did not expect these mounts to require a third day session, and they are still not finished!

I discovered that two of the drilled holes in each bracket were in the wrong position, by approx 1mm.  That is a really bothersome error, because the correct position includes half of the existing hole.

I managed the problem by threading the errant holes, and Loctite gluing in some threaded rod.  Each rod was trimmed flush with the surfaces.   Then drilling the new hole, partly through the Loctited metal patch.  That fix worked well.

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Threaded rod glued into the errant hole.  Trimmed flush later.  Then redrilled correctly.

 

THE TRUNNION PINS.

The pins hold the trunnion caps in place.  And they took another whole day to make and install.   Ah….  just as well I enjoy all of this.  They are tiny, and I spent at least 50% of the time looking for them on the workshop floor after accidentally dropping them on several occasions.

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Milling the pin handles from 2mm steel.  The handles ended up at 7mm long.  The holes were drilled before the outlines were cut.  Then the tabs were ground off using my newly made belt sander belt.  The belt lasted 15 minutes before the belt itself tore, with the join still intact!

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Then some delicate silver soldering of a ring to attach a securing chain later, then the pin shaft itself.  The wire through the ring is just to hold it in position during soldering.

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And that is one of the 8 pins made.  I will polish them in a gemstone tumbler next session.

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On the model, the pins are jammed into position with a cam action, after some filing-shaping.  On the original cannon there was a small protrusion on the inner end of the pin shaft, which fitted through a slot in the side of the carriage.  I could not figure out a method of making such a tiny slot (1mm wide x 1mm deep) through 4mm of steel plus 2mm of brass, but the cam action seems effective.    I will attach some chain soon, because I do not wish to make any more of these.  And yes, the pins handles are slightly over-scaled, but I think not outlandishly so.

So, apart from polishing riveting and painting, I think that the trunnion mounts are finished.

Now planning to make the gear train for the carriage positioning on the chassis, and the pinion, quadrant gear, and bevel gears for the barrel elevation.  We are currently in level 3 lockdown for Covid containment, with level 4 looking likely any day, so obtaining brass for the biggest gears is difficult.  I am considering workarounds.  Apparently community anxiety and depression, family violence, and even suicides are mounting.  When I am in the workshop I am in a different world, thank goodness.

 

 

 

 

 

 

 

Trunnion Mounts -2

It took a whole day making and fitting  the top caps of the trunnion mounts from brass.

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A 76 x 76mm piece of brass was milled to 10mm thickness.  The trunnion straps will finish at 9.5mm , giving me a 0.5mm machining allowance.

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The 4 straps were cut out using a new 4mm endmill.  Rounded internal corners were milled square, and the bottom tabs were milled to 2mm thickness.

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2mm wide slots were milled into the brackets, and ends of the slots were filed square.  None of my rifling files were small enough, so I ground one to size, leaving the faces and one edge  intact.

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Trunnion mount almost finished.  Pins in the tags to come, and they will pull the strap down tight with a cam action.  The half circle line on the bottom bearing is a painting border to delineate the bottom bracket from the bronze bearing surface which will not be painted.  If you inspect the full size trunnion in the previous post you will see what I mean.

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Now I can take some measurements of the model, and start the barrel elevating gear.  There are 4 gears to be cut, including  bevel gears, handle, shafts, gear case, and some complex mounts.

Recovering from Friction Welding

Back to the model Armstrong cannon carriage this afternoon, and fitting 2 internal transoms, which provide rigidity to the carriage.

The transoms had been laser cut some months ago.  I cut the floor from 2.8mm stainless steel.

Each transom is attached to the sides and floor by angle iron, 2mm thick.  In the original cannons the angle iron was mitred at the corners, and for this model “A” carriage I decided to try to replicate the mitres.

The angle iron was again bandsawn from RSS tube and milled to 10x10mm.  I used the following setup to form the 45º angles…

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This is the Eccentric Engineering tool sharpening arm, set up to 45º on my RadiusMaster belt sander, about to form mitre angles on the angle iron resting to the right.

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The Angle iron pieces were glued to their respective transoms, and 2mm holes drilled.  Bolts progressively inserted.  The lengths and cutouts will be trimmed later.

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Then milled and filed the corners until the parts fitted neatly into the carriage.  Rivets will be inserted later.

 

…and for your interest/amusement, depending on your UFO opinion…  Listen to the information, and try to ignore the appearance of the narrator.

 

….and do I think that UFO’s are real?    I would say that my “belief” has risen from 95% to 99% YES.   One of my readers, with whom I have spoken directly, and for whom I have no doubts about personal veracity, has seen one at close quarters.  Do I think that they are of non human origin?  A bit less positive about that one, but it does seem more likely than not.  Waiting to see if and what NYT does publish.

 

Friction Welding

Friction welding is a technique which is used in industry.  It involves rotating 2 metal surfaces against each other, under considerable pressure.  The heat generated from the friction is enough to make the contact surfaces to become red hot, then melt together.   There is a funny and instructive YouTube video on the subject by AVE.

I had a costly and unintended demonstration of friction welding in my workshop yesterday.  I was drilling multiple small holes in the 2mm thick sides of the model Armstrong cannon, when, somehow, I activated the Z axis downward in fast motion.  Probably I miskeyed G0 instead of G1.

The hole was drilled in a fraction of a second and the chuck continued downward.  My reflexes are not TOO bad, but by the time I hit the big red button, the bottom of the drill chuck was grinding into and bending the workpiece.  Which was glowing red hot!

“Oh Dear”! (Or something along those lines.)

I could tell at a glance that the workpiece had been destroyed.  I had a spare piece, so it was going to cost some time to repeat the work already spent on the part, probably at least a day.

But that was only the beginning.

I backed off the quill, and tried to remove the workpiece from the of the chuck.  It would not budge, so I released the 2mm drill bit (actually a carbide end mill) from the chuck.   Well, I tried, but the chuck key would not rotate.  The chuck was frozen solid.  So I went and had a cup of coffee.

On return, it was apparent that the workpiece was welded to the end of the chuck, and the chuck jaws were welded together at the tips.

So, I released the chuck and its arbor from the mill, and broke off the workpiece from the chuck with a hammer.  The weld and the drill bit broke.  But the jaws of the chuck were still welded together.

You might recall that I had accidentally destroyed an expensive Japanese chuck some months back, and this one was its “temporary” replacement.  Obviously I will need to buy a replacement this time, but I am in the middle of my cannon build, and want to get on with it.  What to do?

On close inspection the weld between the jaws stopped about 3mm from the jaw tips.  It involved the surfaces between the jaws and the still present carbide drill shank, and the sides of the jaws.   So I ground about 3mm off the ends the jaws until they started to move.  Then used a tiny grinding wheel in my Dremel to remove most of the weld between the sides of the jaws.   At this stage the chuck is looking very ugly, but it works in a fashion, and I was able to resume my drilling.   Very carefully.

I did straighten the bent workpiece, but it is RS.  I spent the remainder of the day using my spare workpiece, repeating the lost work.    No photos of the damage.  I was not in the mood.

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These are the sides of the second carriage.  For this one I am drilling the holes in both pieces simultaneously, by clamping, and then bolting them together.   Pretty obviously a better method.  Sometimes I am slow learner.  But I do try to not make the same mistake more than 3 times in a row.

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The “B” carriage on the left, and work to date on the “A” carriage on the right.  The bolts will eventually be replaced with rivets.

BTW,  I have de-monetised this blog.  You should not see any more advertisements.  I noted that the income from the ads from the one post on which they appeared, was one cent.  Yep.  One cent.  If I had monetised the site from its beginning, 6 years ago, I would have earned approximately $AUD6 dollars.  Nuf said.

Meanwhile, I discovered some more videos from posts 5-6 years ago.  I have deleted the videos.    A pity about that, but it has created some more storage space and allows me to continue to post on the current plan.

Carriage Assembly, and Gun Spiking.

If you have been following the build of the model Armstrong cannon, you might remember that most of the steel panels for the carriage were laser cut a few months ago. In the past few days I have been drilling dozens of 2mm holes, ready for final riveting.  Meanwhile the parts are held together with 2mm bolts and nuts.  I expect that the rivets will not be installed until I can see that everything fits and works as it should.

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Only a few fasteners so far, but it is surprisingly rigid.

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The angle iron is cut from the corners of rectangular section tube with 2mm wall thickness.  It does require some more finishing and rounding off, but the scale is accurate.  The big hole is to allow the hydraulic recoil tube to be inserted.  The recoil cylinder will be 18mm diameter.

SWMBO’s comment….  “It looks like it is made from Meccano”.  I guess that there are a lot of holes.

Meanwhile I have discovered an excellent reference source, published in 1879.  It is a free book, available online at Google Books.  “Treatise on the Construction and Manufacture of Ordnance in the British Service”.  517 pages.  Original price 9 shillings.  It is full of gems for the cannon modeller.  As an example, this is a drawing of the sights on the 64 pounder RML converted to 80 pounder.  You will see that the barrel shape is different from the one which I am modelling, which is a mark 3.  But it is probable that the sights remained the same as those pictured.  A great find, with enough detail for me to scale down and model.

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Note that the sight on the right is not vertical, but sloped at approximately 2º.  That is to compensate for the slight deflection of the projectile to the right, caused by the rifling.

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From the same book, a detailed description of the Vent / touch hole / ignition hole.  It was NOT just a simple hole drilled into the barrel, but a copper cylinder which was threaded into the barrel.  The touch hole was drilled through the copper.  The reason for this was that the touch hole gradually became bigger with use, and needed replacement after a certain number of firings.  It also allowed repair of the touch hole if the gun was “spiked” by the opposition, but that was a major exercise which required specialist knowledge and tools, and a return to the factory.

 

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.

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.

 

 

 

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.

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.

 

 

 

 

 

 

 

TURKISH BOMBARD – a-post-script. And metal casting setup ready.

I made this 1:10 scale model of the Turkish Bombard which currently resides in the Royal Armories Museum, Portsmouth, in 2016.  I specify “currently” because I originally saw this cannon in 1979 at The Tower of London.  And long before that it was used in Turkey, guarding the Dardanelles.  Quite likely used in anger in 1805 against a British fleet, approximately 340 years after it was made for Sultan Mehmet “the conquerer”. 

And I re-visited the original in May 2019. It seems like half a lifetime ago. Mainly I visited the UK to see the Trevithick dredger engine in the London Science Museum, but the Turkish bombard was the second reason. I could not find a photograph of the touch-hole in the bombard anywhere. And my requests to the museum went unanswered.

The original bombard in the Royal Armories Museum, Portsmouth, UK.

So, here is my photograph of the touch hole, in case anyone else is inclined to make a model. I guarantee that this is the only photo of the touch hole which you will find, with my hand anyway.

The Turkish bombard touch hole
My 1:10 scale model of the bombard. I still have not added the touch hole.
The Arabic script around the muzzle. Not as good as in the original. But as good as I could manage in 2016.
and the large thread between the barrel segments


So, I made this model, in wood, as a practice run, intending to make a bronze model eventually.

The reason for this post script is that I had a question from a reader about a remark which I had made in 2016. And I could not find my original photographs. So I took some more, as you have seen.

And……… very excited to announce that I now have a foundry setup, and could possibly make a bronze example of the bombard. But first I intend to obtain some casting skills, by making parts for my 1:10 Armstrong cannon.

I replaced the analogue controller with a digital type in the potter’s oven which I had recently purchased, and today my wiring was checked by an expert before we ran a test run. (thanks Stuart!) All good, up to 750ºC, which is enough for preparing the investment molds.

Here is a shot of the oven, and the metal melting furnace.

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from the right, the melting furnace which should be adequate for 3kg of brass/bronze,  and the investment oven. The oven might also be useful for metal tempering. Note the Hebel bricks behind the oven.

Hopefully, the first attempt at a casting session in a couple of days.

 

Armstrong Cannon Wheel Assemblies -2

rear wheel and support

There are 3 major components of each wheel assembly, plus the wheel, axle, and king pin.

The wheels, axles and king pins are straight forward metal turning, but the other 3, the wheel bracket, the king pin post, and the chassis bracket, are castings in the original.

For my 1:10 model I am planning to cast the king pin column, and the wheel bracket.  But I will fabricate the chassis brackets.

There is one chassis bracket for each of the 4 chassis wheels, and they are all different.  Front different from rear, left and right hand versions.  And each one has angles of 90º, 30º, 20º, 6º, 2º so the machining was quite a mental exercise.  No major stuff ups though.

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Here is the main component of the left hand rear chassis bracket, being held in position.  It will be bolted on later, and have several flanges silver soldered to it.   Those M2 cap screws will be replaced by rivets eventually.

Meanwhile, having decided to cast the king pin casing, and the wheel bracket, I spent many pleasant hours (or was it days?), drawing them.  Then yesterday, I 3D printed an example of the king pin casings.

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2.5 hours to print PLA examples of rear (left) and front king pin casings.  I need to see the original cannon to check some details before committing to cast these in bronze.  The PLA parts will disappear during during the casting process.  (A pity.  They are quite attractive No?)  You can see why I chose not to machine them out of bar stock.   3 pin holes in the left hand print ? the result of not storing the PLA spool in a dehumidified container.

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So, it might not look like several days of computer and workshop time, but that is how long it has taken.

In Australia we have had some easing of Covid-19 restrictions, but not opening of museums or historic collections of cannons.  So I still cannot go to Warnambool (a 2.5 hour drive) to check details on their Armstrong 80 pounder rifled muzzle loader.  Flagstaff Hill Maritime Museum does not answer their phone.  Hmmm.  Maybe I could climb the fence and sneak in……    but maybe not.

Armstrong Cannon Chassis Wheel Assemblies

The steel chassis is virtually finished, although I am delaying inserting the final rivets which join the girders together, in case I need access to the individual girders for more machining or drilling.

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The 2 chassis’ are not identical.  Can you spot the differences?  And still waiting for more rivets to arrive.  The copper colour on the front one resulted from dipping it in well used sulphuric acid after some silver soldering.

 

Considering how to model these wheel assemblies…..

front wheel and mounts

The front wheel assemblies

rear wheel and support

The rear wheel assemblies

The rear wheels and supports are larger than the front ones.  But the top views are essentially the same.  The wheels themselves present no difficulties.  They will be turned from 50mm diameter steel rod.  And the axles will be all identical.

But, those supports are complex, and will need to be silver soldered parts, or possibly cast from 3D printed lost PLA bronze or brass.  Just drawing them was challenging.

This is a complex project, and the parts are complex.

Considering that the original cannon barrel was made in 1866, and the steel/iron chassis made approximately 20 years later (the original barrels were mounted in a wooden carriage),  the standard of the workmanship in the originals is simply superb.   Even at 1:10 scale, and using modern equipment including CNC machinery, I am struggling to match the standard of fitting steel pieces together so neatly.  I am in awe of the original engineers.

(and by the way.  Neil M, who very kindly loaned me the rivet gun which died, has loaned me a replacement gun.  The replacement gun is a bit bigger, and more fierce.  It requires more care in not overdoing the hammering, and bending the steel parts or producing “two-bobs” in the work piece.  “Two-bobs” will be understood only by older Aussies?  They are unintended dents in the workpiece produced by hammering.)

A Transom on a cannon. And a lost hearing aid.

 

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After a fruitless 3-4 hours searching for my lost hearing aid, I decided to make a bit of progress on the Armstrong cannon chassis.  At least I got the workshop floor swept clean for the first time since last winter.  The tigers should be hibernating in this cold weather.

In the above photo you can see that the rear cross member, which I have named the “transom”, is now bolted into place, with 14 M2 bolts and nuts.  Later these will be replaced with solid rivets.   I reckon that I had about a 70% success rate of inserting the tiny M2 nuts.  The other 30% are somewhere on my workshop floor… probably keeping the hearing aid company, wherever it is.

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When those connections were made, ensuring that the upper girder surfaces were parallel, I filed the angle brackets flush with the girder surfaces.  To ensure that the file did not scratch the girders, I rested the end of the file on a sheet of paper.

The next job is to make the front joining piece of the chassis.  It is a box construction, so will be more complicated, but should make the chassis  quite rigid.

It is a bummer having only one hearing aid.  About $2000 to replace the lost one.  I would have preferred to spend that sort of money on a tool.   Or a good drone.  But SWMBO is adamant.” get that hearing aid replaced!! ” (at least that is what I think that she said.)

 

Armstrong RML. A Little More Progress!

Only a half day in the workshop today.  Wednesday is my Model Engineering Society weekly “Zoom” meeting, and I would not miss that for quids.

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But, I did get into my workshop after that.  And this is what I made….

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I am trying to make a bracket to join the side girders of the Armstrong RML cannon to what I will name the “transom”.  The transom is the lump of steel joining the side girders at the back of the chassis.

“No big deal” you say?  Well, that bracket has angles of 90º, 4º, 6º,  and some indeterminate ones.   And must sit flat with 2 pieces.  And is a single piece of steel.

First I tried to bend a piece of 2mm steel.

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Even though the bender is rated only for 1mm, it managed 2mm thick plate.

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Plus some hammering in the vice…

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…but machining all of those angles and distances was just too difficult….   This steel effort was just not up to scratch.   Look at the gap under the bracket.  Yuck!

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I cut out some brass pieces, and used a vertical belt sander (the Radius Master), to get them to fit snugly…..

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then cut some separate pieces to complete the brackets and secure the transom…..

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checking the fit of the right angle piece…

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then silver soldered the pieces together.  The bits of steel are to keep the brass pieces in position during the soldering.

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That is the angle bracket being held to the transom by my rather dirty fingers.  But, it is all nice and tight, and will do the job. Rivet holes yet to be drilled.   Soldered joint? I hear you ask?  “As strong as the parent metal” I answer.   One made.   A bit of filing required.  And 3 more to go.  They will be painted the same colour as the girders eventually, so who will know that they are not steel.  Just you.  don’t tell, or else….

 

Armstrong RML Model cannon. Assembly -1

Not much happens in each workshop session.  I am still a bit unsure whether I should only post when some significant progress has occurred, or whether the minute daily progress is enough.  Whichever occurs depends on my mood.  At the moment I am posting daily progress.  If it is just too trivial and boring, well, hang in there.  No doubt there will be big significant gaps in the future.

Today I thought about how I would assemble the chassis for the Armstrong cannon.  And I decided to do some woodworking.

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So, I machined a block of wood, exactly the size to separate the chassis girders.

Wood has an advantage over aluminium or steel.  Apart from being cheap, it is slightly compressible.   Here, I have accurately machined a block of wood, and by adjusting the tension in the G-cramps, I can adjust the distance between the girders to exactly what I want.   And using the granite setup block to keep the upper girder surfaces exactly parallel.

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Getting those girder surfaces exactly parallel, on a granite setup block.

 

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Then I marked out one of the end pieces, filed out the girder flange recesses, and fitted it into place.

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The end piece will eventually be riveted into place, using an angle bracket.  The dented girder corner top right, occurred when I dropped the girder onto the workshop floor!  Or maybe it was a Russian shell hit.

So, not much to show for a 6 hour workshop session, but actually, some decisions made.  And more small steps.

And a BIG discovery!  Another  Internet search has shown some more of this exact cannon at Warnambool, Victoria.  And from the few photos on the net, those Warnambool cannons are more complete than the ones which I measured at Port Fairy!

Ah.  Fuck this virus.  I want to go to Warnambool.