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  #101  
Old 11-06-2019, 01:48 PM
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airdave airdave is offline
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Close up of the finished front Barrel hold-down.
The strip around the barrel is still place,
but the side elements and lower cradle are assembled separately and then installed.



...
This was my biggest source of frustration...
figuring out the swivel pins/supports that conect the Gun Barrel assembly to the Frame Cradle.

On the real thing, the swivels are thick walled, short tubes...laid flat on the side brackets (of the Recoil mechanism).
These tubes are securely welded in place, but very little material is actually supported over the brackets.

I couldn't run a supporting dowel or tube across the entire gun barrel, and paper parts are a lot more flimsy than solid milled steel.
I am stuck with two short pivoting tubes that must be securely attached to the gun barrel brackets.

In the end, I decided to enlarge the surface area of the top plates
(you can see in the photo, I am adding additional plates, rather than rebuild the entire assembly).
The final design will not require this.

But the builder will need to add a split second layer to the top, which creates a small cut-out for the pivot tube.
You can fill up the gap with glue and lay the pivot tube in place and this should help locate the pivot and give a stronger connection.



...
Here are the two completed pivot tubes glued in place.



...
The entire recoil mechanism can be set in place on the Frame Cradle.
To hold it in place, there are two brackets to go over the swivel tubes.
This should allow the Gun to swivel once everything is glued.

Second photo...with the Gun Barrel in place (not actually glued yet).



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  #102  
Old 11-06-2019, 03:39 PM
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outstanding work sir
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  #103  
Old 11-06-2019, 06:38 PM
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Don Boose Don Boose is offline
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Superb model.

Don
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  #104  
Old 11-08-2019, 06:29 AM
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Michael Mash Michael Mash is offline
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Great work. Highly detailed.
When adding this to the Limber and the Field Artillery Tractor, it represents quite an extensive project.
Mike
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  #105  
Old 11-08-2019, 05:47 PM
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airdave airdave is offline
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As you can see, I plan on including a Muzzle Brake as part of the Gun Barrel.
It lengthens the barrel and makes it more visually appealing I think.
It also helps detract from the lack of taper in the barrel
(yes, the two sections of the gun barrel should be slightly tapered, but for build simplicity, I eliminated the taper)

I experimented with a 3D Brake...cut out holes, hollow inside, etc.
But the real thing is a solid chunk of metal, drilled through from three directions, leaving very thick walls.
Trying to recreate this in paper is virtually impossible at any scale.
And the thin walled paper assembly I created was flimsy and easily distorted and/or crushed.

As you can see, I decided to continue with 3D virtual artwork instead.
I like it...and its a LOT easier to build!



...
Next step is the Loader/Breech and its connecting elements.

The Breech box and that box on top of the Barrel are fairly straightforward box assemblies.
However the Breech has a cutout for the sliding Breech block, as well as some surface detail parts.



...
Some of the surface layers are optional, and some aren't.
I took my time...prescored and prefolded everything...then edge coloured.
The main Breech block has its insert installed first, and then close up the box.

The box on the top of the Barrel is scored, folded and the ends are glued down.
Its cut out to fit the barrel and just sits on top (glued in place).



...
A small tube (sleeve) is created first, that slips over the rear end of the main barrel.
It is butted up to the mounting block and this sets the distance for the Breech assembly.
It is just glued to the back end of the barrel.
Its also aligned to the upper box thingy, so its best to glue that one in place first.



...
Only thing I didn't account for is the weight balance of the gun.
The paper Breech is too light to balance the barrel.
It needs about 2-2.5 grams of extra weight.
(about one US penny...which could have been added inside the breech, had I thought about it!)

But when the gun swivel is clamped down with the top plates, it will probably provide enough friction
to hold the Gun in any position.



...
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  #106  
Old 11-08-2019, 06:20 PM
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Michael Mash Michael Mash is offline
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The muzzle brake gets my vote.
Nicely done.
Mike
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  #107  
Old 11-08-2019, 06:31 PM
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CharlieC CharlieC is offline
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Did Canadian 25 Pounders have muzzle brakes in WW2? Australian 25 Pounders didn't get muzzle brakes until 1946. The brake allows the gun to fired with larger propellant loads which would damage the recoil system otherwise.


I'm just gobsmacked watching the development of this model - just amazing.


Regards,


Charlie
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  #108  
Old 11-08-2019, 09:19 PM
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airdave airdave is offline
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No idea about Canadian 25 pdrs specifically...or Australian for that matter.
Who said my model was Canadian? Maybe the Quad crew borrowed it?
Who said it was a WW2 piece? Maybe it was added to the Quad after the war?
Who said it was gonna be accurate to any particular Gun?
Actually, I've been using the two local 25pdrs (both on Mk2 carriages) for reference and whatever photos I can find online of 25pdrs in general.
I wasn't really concerned about making sure its accurate to any one particular Gun.


it looks better with the muzzle brake...lol...thats all that matters.

One of the local Museum guns was built in 46 and has a polished muzzle brake that may or may not be original, I don't know.

The Gun outside the Museum is from 1942, and does not have a brake fitted (but that gun is quite incomplete).
Attached Thumbnails
1/16 Scale Field Artillery Tractor Part Deux-guns.jpg  
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  #109  
Old 11-09-2019, 08:33 AM
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airdave airdave is offline
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I did a very quick image search for wartime 25pdrs....
I found quite a few undated pics that appear to be wartime, featuring muzzle brakes on the guns.
But theres no way to verify what you are seeing in these photos,
so I won't reference any of them or argue the point based on those photos.

Since this equipment stayed in use long after the war, there can be no argument
that Guns of this type were in service and equipped with muzzle brakes.
Canadian too!
And even though they were only used in training after that, its still valid.

So I am happy with that.

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  #110  
Old 11-10-2019, 10:49 AM
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Kevin WS Kevin WS is offline
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The muzzle brakes were introduced in 1942 after a "super" cartridge was introduced towards the end of that year.

The "super" raised the muzzle velocity considerably, so the muzzle brakes were retrofitted, mainly from 1943 on...

-----------------------------

As an aside, it was known as the G1 in South Africa where post-war it was modified to 90mm and manufactured locally with some mods.
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