Monitors

From the Washington Naval Treaty to the end of the Second World War.
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marcelo_malara
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Re: Monitors

Post by marcelo_malara » Tue Apr 21, 2020 7:35 pm

Oh yes, I know the Rodmans quiet well, we have a pair of them in Argentina, 10", but of a post Civil War rifled version. The Rodmans were quiet obsolete at the end of the Civil War, they were cast iron muzzle loaders , while UK were then manufacturing Armstrong´s rifled breech loaders, and Krupp was finishing its first steel breechloader.

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Byron Angel
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Re: Monitors

Post by Byron Angel » Fri Apr 24, 2020 4:58 pm

The 15-in Rodmans actually remained in service for quite some time. Ultimately sleeved down into 12-inch rifled muzzle-loaders, they carried on into the 1880's as coast artillery. Also, they introduced a quite sophisticated (for the time) casting and cooling process that produced a very strong strong gun, even though of cast iron.

Rodman was also responsible for the post civil war development of 'prismatic powder', which considerably improved burn rate and pressure curve of its black powder propellant. This made a considerable difference in the later performance of the gun.

Byron

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marcelo_malara
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Re: Monitors

Post by marcelo_malara » Fri Apr 24, 2020 8:44 pm

Yes Byron, the Rodmans soldiered on until they were far surpassed by technology.

The guns were cast hollow, the mold contained a central insert that formed the bore of the gun, this insert had an inner piping thru which water was circulated during the cooling. This ensured that the casting cooled from the inside.

The prismatic powder actually diminishes the burn rate, presenting to the flame a smaller surface than spherical grains. This made the pressure increase more slowly during firing, allowing the shell to move forward and make space while the powder was still burning. This kind of powders almost duplicated the muzzle velocity, going from around 300 m/s for a black powder gun to about 600 m/s.

I am curious about the rifled 15" Rodman you mentioned. Do you have any more data? Only rifled Rodmans I know about were 8" made from 10" smoothbores by sleeve inserting, and the Argentine´s 10" with rifling cut directly on the cast iron core.

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Re: Monitors

Post by Byron Angel » Sat Apr 25, 2020 9:04 pm

marcelo_malara wrote:
Fri Apr 24, 2020 8:44 pm
I am curious about the rifled 15" Rodman you mentioned. Do you have any more data? Only rifled Rodmans I know about were 8" made from 10" smoothbores by sleeve inserting, and the Argentine´s 10" with rifling cut directly on the cast iron core.

Hi Marcelo,
My sincere apologies for relying upon an obviously poor memory; I should have checked my files first. No 15-inch Rodmans were ever sleeved, only the 10-inch as you mentioned.

Byron

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marcelo_malara
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Re: Monitors

Post by marcelo_malara » Sat Apr 25, 2020 11:05 pm

No need for apologies, memory can betray any of us :D :D :D .

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Re: Monitors

Post by Byron Angel » Mon Apr 27, 2020 3:48 pm

Hi Marcelo,
Quite by coincidence, the topic of modifications to Rodman guns came up in a different discussion with some other friends. I asked them what they might know of any such efforts connected to 15-in Rodmans and they very kindly shared some information which you may find interesting -


"1n 1878-79, a 15-inch smoothbore converted to 11 rifle was made and tested. As of the 1879 Report of the Chief of Ordnance, it seemed to be working OK. There is no record of this being adopted for service."

- - -

"Between 1862 and 1868, six 15in forms were cast as 12in and rifled. All failed endurance trials. I'm still inching my way through the Reports of the Chief of the Ordnance Department. In those lean years, Army Ordnance Department and Navy Ordnance Bureau cooperated and shared information. But it was not a seamless process. I read of a Navy gun (I think an 11in Dahlgren Palliser conversion to an 8in) was tried by the Army. Since the Army was doing the trials, the Navy did not have an observer to keep the detailed records, and since it was a Navy gun, the Army did not keep the details either."


FWIW

Byron

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marcelo_malara
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Re: Monitors

Post by marcelo_malara » Mon Apr 27, 2020 5:05 pm

Guau Byron, that´s very good info. You should comment this with the guy behind https://markerhunter.wordpress.com/, Craig I believe is his name. I contacted him about the Argentine Rodmans. Our Rodmans apparently were cast with the mold of the 13" experimental ones, as I could realize measuring one of them and comparing with the dimensions listed in the book The Big Guns: Civil War Siege, Seacoast, and Naval Cannon. The insert for the bore used was 10", and they were rifled directly on the cast iron.

Those reports you mentioned are invaluable, but it is time consuming going thru them. It is striking that what is now the most powerful military power was then playing with such obsolete technology, Krupp was by then manufacturing steel, breech loader rifled guns that became famous.

I share some photos of our Rodman:

Image

Image

Image

Just curious Byron, are you American or British?

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Re: Monitors

Post by Byron Angel » Mon Apr 27, 2020 7:33 pm

Hi Marcelo,
3rd generation American of Greek extraction. Three grandparents were native Greeks; one was a Hellene born in Ottoman Turkey.

Interesting photos of your Argentine Rodman. Thank you for sharing them. Quick question: You mentioned that the gun was cast from the 13-inch Rodman mold with an "insert" (a sleeve or liner?) inserted to reduce bore diameter to 10-inches. I'm assuming you are referring to the cooling insert used to create the bore at the time of casting. Is that correct?

Byron

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marcelo_malara
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Re: Monitors

Post by marcelo_malara » Mon Apr 27, 2020 8:27 pm

So you are descendant of those who created Occidental civilization and democracy, good!

As I was writing I knew that it was to be confusing :D :D . Those that have been inserted with a sleeve are clearly distinguishable:

Image

In our Rodman, I was referring to the inner water cooled mould. I presume that an external mold of a 13" smooth bore combined with a 10" bore would give the wall thickness to withstand the higher pressures resulting from the heavier elongated shells and the friction of the rifling. Unfortunately, no 10" shell appears to survive, I could not locate any in local museums so far.

In Chile there are three surviving 15" Rodman in a coastal fort:

https://filanaval.blogspot.com/2013/04/ ... ralda.html

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paul.mercer
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Re: Monitors

Post by paul.mercer » Fri May 08, 2020 9:25 am

Gentlemen,
As always many thanks for your expertise, I regret that due to a short spell in hospital i have been 'out of action' for a while.
Re the picture of the Rodman and it's huge bottle shaped chamber which make the whole gun appear almost medieval, to be that sort of size it seems that it must have has a massive charge to fill that chamber, i note the thickness of the metal, but I wonder if they had any explosions?
Also, on the question of WW1/2 Monitors, even though they appear to have been set very high on the trunking, did they have greater elevation capabilities than that on a more modern battleship?

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marcelo_malara
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Re: Monitors

Post by marcelo_malara » Fri May 08, 2020 4:44 pm

Hi Paul, hope it was nothing serious, glad you are back.

The Rodmans are so fat not because of an oversized chamber, but for the thickness of the walls, as you can see in this plan of one:

Image

I believe that explosions were uncommon (even may be there was none) in Rodmans as well as in Dahlgrens. Dahlgrens were constructed differently than Rodmans. Instead of the casting having an insert for the bore ("cast hollow") they were cast as a solid piece ("cast solid"), with the cast having the form of a cylinder, with parallel walls. After the piece was cold it was machined internally for the bore and externally to the soda bottle shape carachteristicall of the them.

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Re: Monitors

Post by Byron Angel » Sat May 09, 2020 2:01 am

Firing charge for the Rodman 15-inch (IIRC) was originally 35 pounds of standard cannon powder. Rodman later developed slower burning "Mammoth" (pelletized) powder and then compressed and perforated "hexagonal" powder in cake form, both of which burned more steadily and slowly without a great initial pressure spoke.

(go here - http://firearmshistory.blogspot.com/201 ... owder.html )

With the newer type powders, the 15-inch Rodman was successfully tested with charges of 60 lbs up to 100 lbs.
Working from memory here, so please check my details.

Byron

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Re: Monitors

Post by wadinga » Sun May 10, 2020 1:45 pm

Fellow Contributors,

A Google search https://books.google.co.uk/books?id=Ul6 ... &q&f=false

got me access to a chunk of Ian Buxton's excellent book (thanks Byron) which I will try to buy if possible.

In it it is described how the 12" guns repurposed from obsolete pre- dreadnoughts were given new mounts in the WWI "General" class monitors going up from 13.5 degrees (13,700 yds range) to perhaps 30 degrees giving over 21,000 yds. Others had 14" American guns never delivered to their Greek customers. A photo says they had a maximum elevation of 15 degrees but I measure 25 at least on the photo.

Other pictures confirm the ships were routinely heeled to increase elevation, range and angle of fall (for targets behind obstructions).

The bizarre bulged hull forms are also presented in drawings and photos, and emphasize what appalling sea boats they must have been, which when combined with slow speed they had, made them very specialized warships.

All the best,
"There seems to be something wrong with our bloody ships today!"

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Re: Monitors

Post by HMSVF » Sun May 10, 2020 10:17 pm

wadinga wrote:
Sun May 10, 2020 1:45 pm
Fellow Contributors,

A Google search https://books.google.co.uk/books?id=Ul6 ... &q&f=false

got me access to a chunk of Ian Buxton's excellent book (thanks Byron) which I will try to buy if possible.

In it it is described how the 12" guns repurposed from obsolete pre- dreadnoughts were given new mounts in the WWI "General" class monitors going up from 13.5 degrees (13,700 yds range) to perhaps 30 degrees giving over 21,000 yds. Others had 14" American guns never delivered to their Greek customers. A photo says they had a maximum elevation of 15 degrees but I measure 25 at least on the photo.

Other pictures confirm the ships were routinely heeled to increase elevation, range and angle of fall (for targets behind obstructions).

The bizarre bulged hull forms are also presented in drawings and photos, and emphasize what appalling sea boats they must have been, which when combined with slow speed they had, made them very specialized warships.

All the best,
Highly recommend it - brilliant book,one of my favourites.

Byron Angel
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Re: Monitors

Post by Byron Angel » Mon May 11, 2020 2:30 am

My pleasure, Sean. You will enjoy Buxton. As HMSVF says - "brilliant book".

If perchance you are interested in some of the nuts and bolts and issues of WW1 monitor operations, hunt up a copy of "The Dover Patrol 1915-1917" (two volumes) by Vice-Admiral Sir Reginald Bacon.

Byron

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