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: Historic Model

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.

 

 

First Bronze Castings

Bevel gears seem to me to be rather difficult, even with CNC control of X,Y,Z and A axes.  The bevel gears on the model Armstrong cannon are rather small, being 32mm and 14mm outside diameter.

I read Ivan Law’s book on the subject, and I think that I understand the requirements, and I was prepared to try and cut the gears.  But, first, I decided to try to cast them.

That involved…

  1. Using “Gearotic” to design the gears, and save them as an STL file which was able to be imported into the 3D printer.
  2. Made PLA gears with the 3D printer.
  3. Attached the gears to a wax “tree”.
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3 pinions and 3 gears.  I need 2 of each.  1 spare of each.  Plenty of venting sprues.  And a head of about 70mm.

4. Then mixed the investment, poured it into the flask.  At least that was the intent.  The investment makers specify exactly 40:100 by weight of water:powder.  But the bloody scales switched themselves off while I was adding the powder to the water, so I had to guess the quantity of powder.   This was not looking promising.  First bronze casting pour not off to a good start.

5. Dry the mold flask in the potter’s oven for 2 hours, then 2 hours of burning out the PLA and wax, then 2-3 hours of baking at 750ºc.  A few minutes into the burnout phase, the oven died.   ?heating coil failure, ? control box failure?, ?thermocouple failure,  something else?    So I replaced the control unit and thermocouple (I had a spare of each), but problem persisted.  I rang my expert friend for advice.  “sounds like a broken wire” he says.  Suggested 3 or 4 things to try.  And the 4th suggestion worked!  The oven was working again!  Brilliant!   Thanks Stuart Tankard.  So I restarted the oven at the burnout temperature (400ºc) and continued.  Nothing to lose, after all.

6. Melted a couple of bars of LG2 bronze at 1100ºc in the melting furnace.  Added a pinch of Borax.  Let the investment oven cool to 710ºc for 1 hour to let the core of the mold cool to 710ºc.

7.  Without any great expectations of success, considering the various problems, I poured the molten bronze into the mold flask.  It seemed a bit more viscous and thick than I was expecting.  Oh well.  It is experimental.

8.  When the mold flask had cooled to 150ºc, I plunged into cold water, and flushed out the investment.

THE RESULT….

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Unbelievable.  No voids.  Hardly any surface bubbles.  ALL teeth intact and complete.  6 good gears!   You can see the head of molten bronze between the funnel and the top gear.  It did not need vacuum or positive pressure.

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I will turn the faces, bore the shaft holes, and if necessary file the teeth.

Totally delighted with this result.  Beginner’s Luck.

 

 

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.

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.

 

 

 

Bucket List. A Book Review leading to..

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GLASGOW MUSEUMS THE SHIP MODELS

A HISTORY AND COMPLETE ILLUSTRATED CATALOGUE

Emily Malcolm and Michael R Harrison

Large format, hardcover.  £35 RRP

 

Doesn’t sound particularly interesting?  That was my thought when I read that this book is a catalogue.  After all, who reads a catalogue?

 

However, the artwork on the covers is attractive and interesting, and I do have an interest in ships, models, modelling and history, so I opened a few pages at random.   And was transfixed!  This book is glorious!   Back to page one, read a few pages, then worked through every one of the 373 pages.

 

The photographs of the models are beautiful and expert.  Most are laterals, but some are of smaller details.  There are many historical photographs, pictures of modelers in action, previous exhibitions.  To describe the pictures as “lavish” would be an understatement.

 

Glasgow and the River Clyde was (and is?) famous for ship building.  Most of the 676 models in the Glasgow Museum’s collection are of ships built or owned in this region, over the past 150 years.  So this book includes models from the age of clippers and steam dredges, through the age of steam and dreadnoughts, to Queens Mary and Elizabeth, and later.  A wonderful historical tour.

 

Chapter 1.  Models in Shipbuilding (the whys and wherefores of making model ships)

Chapter 2. Professional Model Making (there were companies which made models for ship builders and owners for industrial and marketing reasons)

Chapter 3.  Amateur Models.  (including models made by French prisoners of the Napoleonic wars)

Chapter 4.  Ship Models and Exhibitions

Chapter 5. Building the Collection

The Catalogue  (220 pages)

 

Glasgow is now on my bucket list.

A few random pages to tempt you.

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Yes, I do find dredgers interesting.  Note who bought this one.

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101 years ago, today.

At 11am, on November 11, 1918, World War 1 ended.  Or as many historians claim,  phase 1 of WW1 ended.  Phase 2 became known as WW2.

The following text and photos are about one of the allies main artillery weapons, and the modelling of it by reader Robert Irving, of NSW.

 

The 1916 Vickers 8” Howitzer.

The United Kingdom entered WWI with its traditional lack of preparedness. Defence funds had been lavished on the Royal Navy to maintain the ‘Two Fleet’ policy, whereby Britain could deter attack by having a fleet more effective than the combined force of the world’s next two largest navies. The Kaiser wanted a fleet to rival his cousin Edward’s and later cousin Georges. The ensuing arms race drained the tax revenue leaving little in the budget for the army. The army was still equipping itself for mobile warfare after the needs of the Boar War and had a good supply of very mobile light field artillery, very few machine guns and an inadequate inventory of mobile heavy guns.

The failure of the Schlieffen plan to take Paris and the channel ports, against stubborn resistance, resulted in the continuous trenches from the channel to Switzerland. German policy was to build a strong defensible line and hold their gains. To this end they employed their normal thorough approach and by 1916 had fortified their numerous layers of trenches with deep concrete dugouts to give protection and a modicum of comfort to their frontline forces. They had also retreated to gain the tactical advantage of high ground where applicable. France and Britain, understandably had an offensive policy and didn’t build strong or comfortable trenches. Break through, then attack with cavalry thinking dominated strategy and tactics . Germany began attacking the Verdun Forts in late February 1916. General Falkenhayns stated objective being to “Bleed France Dry”and this they were close to achieving. The British were rushed into the long planned attack between Serre and Montauban, nine miles of front, to relieve pressure on the French. The French were to attack on the British right flank, though this was scaled down due to the huge losses at Verdun. The British attack  plus the diversionary attack at Gommecourt were together, known as the Big Push. This being the first major attack by Field Marshal Kitchener’s Volunteer Army, morale was at peak, despite the average three months the new battalions had spent rotating through front line duty; the sector was a quiet one.

In August 1915 the Vickers 8” Howitzer was approved however an order for 50 was not placed until March 1916 and delivery began in July 1916. The Howitzer fired a 91kg, 8” diameter shell a maximum distance of 11,000 yards, it’s trajectory was high and therefore it gave plunging fire, ideal, with appropriate fusing, to penetrate deep dugouts. There were a few makeshift large calibre pieces in operation in June 1916 but these were thinly spread along the nine mile front, they were mainly stopgap weapons made by modifying old naval guns. The Royal Field Artillery staple weapon was the quick firing 18 pounder, firing a projectile weighing 8kg with a range of 6500 yards.

1B Mod 1918

1918  Vickers 8″ Howitzer.

 

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Australian 8″ Howitzer battery

The attack was scheduled for the morning of July 1st  and preliminary bombardment began one week earlier. Huge stocks of shrapnel and high explosive shell for the 18 pounders were in place, far fewer heavy shells were available. The plan was that the new spigot mortar, firing a basketball sized high explosive projectile, together with the 18 pounders would break up the fields of barbed wire and kill sufficient front line defenders to make the 100yard to one mile crossing of no-mans-land, without cover, survivable. Results on the wire were patchy and on the dugouts feeble at best. Only British forces adjacent to the French sector, with a high density of artillery, had a real chance success, near the villages of Fricourt and Montauban

The Attack began at 7.20am on that clearing misty July morning, with the explosion of a large mine under the German front line at Hawthorn ridge near Beaumont Hamel, followed by a series of similar mines at 7.30am. Orders to the first waves of infantrymen were to advance at walking pace with rifles at high port and occupy the German frontline. Later waves were to attack the second and third lines to facilitate a cavalry breakthrough. These orders ignored reports all week, from trench raiders, saying that the dugouts and occupants were intact and only the odd lookouts were killed by the bombardment. Also that the majority of the wire was undamaged.

In the first two hours of the attack, most of the 19,000 attackers who died on the first day were dead, or lying mortally wounded, without reaching the German lines. Likewise a further 40,000 casualties had occurred and the trenches were blocked by walking wounded and dead men. The storm of machine gunfire and precisely zeroed German shell fire, cut down attacking companies and battalions in rows that represented the waves leaving the trenches. The Battle of the Somme, as it was later known was doomed on the first day, the squadrons of lancers and hussars remained behind the British trenches unable to take part in the planned big break through. 1st July 1916 had the highest number of casualties for any attack by British forces.  By comparison on the first day of the landings in Normandy in 1944, there were 4,500 total allied forces killed.

The failure of this attack is attributed by most historians to the lack of sufficient heavy artillery in the preliminary bombardment like the Vickers 8 inch howitzer,. Had the 50 guns been ordered three months earlier, who knows what lives would have been saved on both sides by shortening the war.

1i Near complete Test Assembly
The almost complete model.   OAL 450mm

THE MODEL

The model was built to a firm budget for an individual in the U.K. The agreement was to build a fair representation of the Vickers 1916 8” Howitzer with no more than 250 rivets. The final number of rivets was over 500. Construction took just under 900 hours and only the nuts, bolts, two hand wheels and main gears were purchased. The model was not capable of firing having a rifled liner in the barrel (like the original) that did not extend to the breech. The breech was a four segment rotating thread type operated by moving a lever through an arc of 45 degrees. The upper chassis had elevation and traverse mechanisms and the barrel had a spring loaded recoil ability. Rifling the barrel liner was a problem. Testing the single cutter broach showed location and spacing problems. Multi cutter broaching exceeded the pushing power available, even on aluminium. These techniques work well on large production machinery cutting four or five groove barrels. This barrel needed thirty plus grooves. Having seen a toolmaker friends EDM set up I had the idea of making a copper male button to be passed spirally down a steel liner cutting electrically in the electrolyte. It worked splendidly first go and took about 20minutes. (editor’s note… “wow”)

The wheels were approximately 7” in diameter, classic traction engine types, with the rims machined from thick walled steel pipe and the spokes laser cut. The chassis, upper and lower, were cut from solid plate rather than fabricated, this was due to budget constraints.  The scale of the model was 11:1 and resulted in dimensions of : bore 19mm, overall length 450mm.

There were no engineering drawings used for the build only the line drawing shown and lots of web photographs, all of these were of later marks of the 8 inch and some were complicated by being shown in reverse from glass plates. The gun was still in service in 1939 though by then it had pneumatic tyres and lots of refinements.

Robert Irving 2019.

1a Best Drwg

The drawing which was used to make the model..

1 Boring The Barrel

Boring the barrel

1 Front

Note the rifling.

1 Gearbox

Wide track

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1f Hub Drill Jig.JPG

Wheel hub drilling jig

1g Laser cut Spokes

The spokes were laser cut

1h Rim Bolts 10BA.JPG

 

 

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Turning the barrel

7 In recoil

In recoil

8inch Breech

Breech

Early Assembly

Early assembly

1j Later Assembly

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Completed model

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Hand for scale

Rims 2

The rims

 

So, again, thanks to Robert for the photos and historical context of this superb model.