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.

Category: model cannon

Bronze Tyrannosaurus Rex

Actually, I had some spare space on the tree which I used to make some more small gears, and I had some PLA T. Rex’s, so I added one.

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And this was the cast result, in bronze.  Yet to be cleaned up, tree bits ground off, and polished..

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 Again, the gears are close to perfect.  I like bronze.

And the gears have a short length of shaft, printed in PLA and cast in bronze, which I will be able to hold in a chuck for tidying and turning.  Lesson learned.   Think ahead, how the cast part will be machined….

And at our society Zoom meeting, Frank M  asked about the colour of burning Borax.   I could not remember, so took a shot today…

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I would describe the colour as white-gold, with a touch of green.  Like a volcano.   Maybe I overdid the Borax?

Oh.  And I had a brainwave.  When degassing the investment mix with negative pressure, add some vibration.  I tried applying my sanding machine once, and filled the room with old fine sawdust.  But for this session, I placed the vacuum pump on the vacuum chamber, and could hardly believe the volume of air which came out of the mix.  The best degassing to date.

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and it takes less bench space.   A no-brainer.  Try it!

 

Soft Jaws

The bronze gears which I cast yesterday were cut off the tree with small bolt cutters, band saw and hack saw.   Then a belt sander to reduce the daggy bits.

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The gears, and the tree trunk and branches which will be remelted.

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The faces needed to be flattened in the lathe, but how to hold the rather thin, delicate, irregular gears?

Soft jaws.

Soft jaws made of aluminium, and exactly machined to match the external diameter of gear teeth, so there are multiple contact points, and minimal chance of damaging the teeth.  I made these soft jaws ages ago, for just this sort of job.

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The soft jaws are machined to exactly fit the workpiece.

The soft jaws may be used multiple times, machined to shape each time.  Very handy in this situation.

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The larger gears are good.  I silver soldered some extra material on one of them for the shaft, then turned the shaft to size .  But, holding the small pinion gear is more problematic.  I will need to machine a soft jaw with a taper to hold the teeth.  Next session.  I should have anticipated this situation and designed the gear with a shaft to be PLA printed as one piece.

 

 

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.

Trunnion Mounts -1

On the Armstrong 80 lb RML model cannon, the trunnions are secured to the carriage with  steel brackets riveted to the carriage sides, and the trunnions rotate in a bronze bearing.

3404 trunnion L

The original trunnion on the Port Fairy cannon

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These are the component parts.

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The RSS ready for cutting out the brackets.  And my working drawing, with alterations.

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First the 2mm rivet holes were drilled, then the outlines were CNC milled.  The steel is 2mm thick.

P1074246Tidied the parts with a file and belt sander.

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The brackets sitting on a photo of the original Warrnambool cannon.

The bronze bearing involved some basic lathe work.

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Then the components were silver soldered together.  Delicate work.  I did not want the solder running into some areas, and the join needed to retain a degree of precision.

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After cooling, sulphuric acid soak, and washing, the top half of the bearing was milled off.

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Some filing to make it fit the carriage, then rivet holes drilled with a Dremel while the bracket was clamped in position.

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Bolted in position temporarily.  Tomorrow I will make the top half of the bracket.  The gap between the bracket and the carriage caused by the metal folding will eventually be filled, and invisible.  A millimeter or so will be removed from the width of the bracket and bearing.

I had a bit of milling excitement while cutting out the steel components.   I was using a 6.35mm 4 flute carbide cutter, and when I started the program the machine plunged into the shape at extremely high speed.  When I checked, the feed speed was 60 times higher than I had specified.  Somehow, the units had changed from mm/minute, to mm/SECOND.  Amazingly, the cut was close to perfect with no damage to the workpiece.  But, alas, it wrecked the carbide cutter.

I had recently upgraded the CNC software (Vectric V-Carve Pro) from version 10 to 10.5.  Maybe some of my settings in the program had been changed in the upgrade?  I never use mm/second.  That is a woodworking CNC router unit.

Using a Banggood tool to make spacers

I needed 20 spacers, 2mm thick, 13mm OD, 5mm ID, to finish the carriage axles for the Armstrong model 80pounder RML.

I could have turned some 13mm OD, drilled a 5mm hole, and parted off the spacers in my lathe, but I know from experience, that the pieces never end up exactly the same thickness (in this case, 2mm thick).

So I decided to try a Banggood tool which has sat unused since I bought it many months ago.

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It is a HSS hole cutter.  18mm OD, but the disk removed is 14mm OD, just a bit bigger than I wanted.  2mm thick waste brass plate.

So I cut off 25 disks, from a piece of waste brass, 2mm thick.  The Banggood tool worked well, except that it need swarf picked out after almost every disk.   But it was quick, reasonably accurate, and the central drill bit was 5mm, just what I wanted.

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The disks were slid onto a 5mm capscrew bolt, and nutted down hard.

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The head of the capscrew was held in the lathe chuck, and the tail of the threaded end in a shop made tapered tailstock socket.  And turned to 13mm diameter. 

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About 12 spacers made per run.   Very quickly.  Reasonably accurately.  A bit of tidying to follow.

The Banggood tool worked pretty well.  I will buy some more of these.  They were quite inexpensive.

Today I polished the ends of the trunnions, being careful not to remove the lasered lines and markings.  I used a 200grit sanding pad in a sponge backed sanding disk in my milling machine.   Also worked very well.  I removed about 0.1mm of steel, without destroying the markings.

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Axles for a Cannon Carriage

How fascinating is that for a topic!

Well, I found it interesting.  Maybe says something about me.

My 2 carriages have 20 wheels and 20 axles between them.  Plus the 4 big ones under the chassis’.  I had made the wheels.  The axles required some planning and thought, after all, whatever I did was going to be repeated at least 20 times.

I decided on stainless steel for the axles, and brass for the end caps.  The originals were steel, but they will be painted, so the appearance of the metal is irrelevant.

First steps were to cut up 20 pieces of 5mm stainless steel, 25mm long, and drill 5mm holes in 12.7mm brass rod, and part off 20 pieces 5mm wide.  With a few spares.

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The the brass end caps need to finish 4mm wide, so there was a machining allowance of only 0.5mm on each face.  So the silver soldering of the 2 parts needed to be reasonably precise.

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To assist with keeping the brass disks square to the rods while soldering, I drilled some 5mm holes in an aerated concrete block, exactly 21mm deep.

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Fluxed the mating parts, and silver soldered 5 at a time.  Very quickly.  I could have used Loctite 620, but would have had to wait until it cured before machining.

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A soak in sulphuric acid for a few minutes, then a water rinse.

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Then turned the end cap shape on the Boxford TCL125

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Not quite finished. M2 Holes to be drilled through the end caps, and threaded to the brackets.  I will use the CNC toolpost milling attachment which I made in 2019.  That might warrant a short video.

A short video.  Well, a bit over 5 minutes…

 

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The capscrews are not kosher.  The original cannons had large slot screws.  But will anyone notice?  (idea…  I could fill in the hex hole with JB Weld, and machine a slot?!).  Maybe.

In retrospect I could have done the entire shaping and drilling and milling of the brass end cap using the toolpost mill on the CNC lathe.   Would have been a lot more efficient.

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.

 

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.