Gun-only AAW conversion of light cruiser Giuseppe Garibaldi?

[Phoenix_jz]

Hello all;

I recently got my hands on a Storia Militare 'Dossier', the first part of a series covering the Italian navy from 1945 to 2015 (first part being from 1945 to 1970, issue no.14, Sept-Oct 2014) by Michele Cosentino and Maurizio Brescia.

Within the SM 'Dossier' there is mentioned, in passing, about a 1950s project for converting the cruiser Giuseppe Garibaldi to an anti-aircraft cruiser. This design pre-dated the guided missile cruiser conversion plans, and involved the new automatic 135/45, and a planned 76/62 quadruple mount, based off the new 76mm 'Sovrapposto' twin mounts. Needless to say, this plan was never carried out, and when they were able to convert Giuseppe Garibaldi, it was to a far superior design utilizing the RIM-2 Terrier. This is probably for the best too, as the year work started (1957) was the same year the 76mm Sovrapposto mounts entered service on the Centauro-class frigates, and they proved extremely unreliable - the better known and vastly more widely used 76/62 Allargato followed soon after, leaving the Sovrapposto isolated to just the Centauro's, and even those mounts were replaced by the Allargato mounts in the late 1960s.

Unfortunately, as the design is only mentioned in passing, there are literally no details mentioned beyond the fact that;

• The design emerged in the mid-1950s
• It involved the new 135/45 and a planned quadruple 76mm mount based on the Sovrapposto
• It remained on paper and was replaced by the plans for the conversion to a guided missile cruiser

I was wondering if anyone here had any more information on this ballistic-only AAW cruiser?

 

[Tzoli]

Ohh! Fascinating! A Double Twin Sorapposto? Sounds like a side by side Sovrapposto! I'm intrigued!
For those who don't know how the original Sovrapposto looked like (Basically an elevated twin mount) here are the only photos of it:
Official designation 76mm/62 Pozzuoli SMP-3 Sovrapposto

https://i.redd.it/5q8un3zh4y761.jpg

https://pbs.twimg.com/media/D9Lo3bjXsAErugC?format=jpg&name=small

SMP.3 - L’ultimo cannone di Pozzuoli

SMP-3 L’ultimo cannone di Pozzuoli A quelli come me che nei primi anni ‘50 iniziavano a percorrere la provinciale Via Miliscol...

giuseppe-peluso.blogspot.com

 

[JohnR]

This is the second mention of a quad 76mm mount. In an article written by George Moore in Warship; I can't look up which edition as those are books are in storage. The article was about the immediate post war cruiser porjects a number of which featured quad 76mm mounts, which given the weight of the twin 76mm MK6 could have worked out extremely heavy. What was the projected of the twin Sovrapposto?

 

[_Sarcasticat_]

Oh my, a quad 76mm/62. If that doesn't inspire true fear, I don't know what will.
Though Garibaldi with a bunch of 13.5cm as a main battery sounds beyond fun.

 

[Phoenix_jz]

Ohh! Fascinating! A Double Twin Sorapposto? Sounds like a side by side Sovrapposto! I'm intrigued!
For those who don't know how the original Sovrapposto looked like (Basically an elevated twin mount) here are the only photos of it:
Official designation 76mm/62 Pozzuoli SMP-3 Sovrapposto

https://i.redd.it/5q8un3zh4y761.jpg

https://pbs.twimg.com/media/D9Lo3bjXsAErugC?format=jpg&name=small

SMP.3 - L’ultimo cannone di Pozzuoli

SMP-3 L’ultimo cannone di Pozzuoli A quelli come me che nei primi anni ‘50 iniziavano a percorrere la provinciale Via Miliscol...

giuseppe-peluso.blogspot.com

Coupling the mounts is exactly what was intended, yes. The design of the mounts was intended to act as a prelude to that eventuality. Ex, as stated by the source I mentioned in my OP;

"La configurazione a canne sovrapposto avrebbe dovuto preludere alla realizzaione di un impianto quadruplo da 76/62, inizialmente previsto per l'imbarco sull'incrociatore Giuseppe Garibaldi trasformato, assieme ai nuovo impianti binati da 135/45;"

Note that the text specifically states that the Sovrapposto's arrangement should have been the prelude to the quadruple mount (had the later mount actually have been built).

Another text I have, a USMM publication from 1970 (Esploratori, Fregate, Corvette, ed Avvisi Italiani by Franco Bargoni & Franco Gay), states;

"...erano armi modernissime progettate per un eventuale complesso a quattro canne mediante accomppiamento di unità binate."

Bold part stating that they were designed for a possible four-gun mount via the coupling of two twin 'units'.


That being said, I would emphasis that the SMP-3 was a project of Stabilimenti Meccanici di Pozzuoli, while the Sovrapposto was a project of OTO Melara, albeit derived from the SMP-3, with a very different loading system, so it would be incorrect to describe the Sovrapposto as a Pozzuoli project. As far as I can tell the gun itself should be the same, at least in regards to ballistics, but needless to say the mount is very different, and so is the reloading system. It seems for the subsequent 76/62 Allargato developed by OTO-Melara, however, the gun itself did change, as the ballistics are different (heavier shell, lower MV, slightly greater range, according to the latter book).

This is the second mention of a quad 76mm mount. In an article written by George Moore in Warship; I can't look up which edition as those are books are in storage. The article was about the immediate post war cruiser porjects a number of which featured quad 76mm mounts, which given the weight of the twin 76mm MK6 could have worked out extremely heavy. What was the projected of the twin Sovrapposto?

Unfortunately none of my sources give a weight for the Sovrapposto.

 

[Tzoli]

Ohh? Looks like I remembered incorrectly about the Pozzouli mount being the Twin one.
Though it is indeed difficult to get info on early cold war Italian guns. Adds to the confusion that both Pozzuoli and OTO-Malera developed a Sovrapposto gun/mount

To my knowledge the Sovrapposto was mounted on these vessels:
Indonesian Pattimura class corvettes: 2x1 OTO-Melara Sovrapposto
Italian Albatros class corvettes: 2x1 Pozzuoli SMP-3 Sovrapposto
Italian Centauro class frigates: 2x2 OTO-Melara Sovrapposto
Dutch Lynx class corvettes: 2x1 OTO-Melara Sovrapposto
Portoguese Pêro Escobar class frigate: 2x1 OTO-Melara Sovrapposto

 

[Tzoli]

Previously I've already drawn the elevated twin mount, now I imagine the quad would look like this:

 

[_Sarcasticat_]

Previously I've already drawn the elevated twin mount, now I imagine the quad would look like this:
View attachment 647382

This reminds me a lot of Russian quadruple mounts. Is there any known inherent flaws with choosing this stacked arrangement?

 

[Tzoli]

With the loading.
It is complex and difficult to repair or maintain.
And if you add first generation auto loading mechanisms, prone to jam or breakdown, add the difficulty to maintain and you can see why it wasn't continued.
Pro is that it requires basically the same deck space as a single mount

 

[Phoenix_jz]

Ohh? Looks like I remembered incorrectly about the Pozzouli mount being the Twin one.
Though it is indeed difficult to get info on early cold war Italian guns. Adds to the confusion that both Pozzuoli and OTO-Malera developed a Sovrapposto gun/mount

To my knowledge the Sovrapposto was mounted on these vessels:
Indonesian Pattimura class corvettes: 2x1 OTO-Melara Sovrapposto
Italian Albatros class corvettes: 2x1 Pozzuoli SMP-3 Sovrapposto
Italian Centauro class frigates: 2x2 OTO-Melara Sovrapposto
Dutch Lynx class corvettes: 2x1 OTO-Melara Sovrapposto
Portoguese Pêro Escobar class frigate: 2x1 OTO-Melara Sovrapposto

The Sovrapposto should refer exclusively to the twin mounts - the name refers to how the guns are arranged in the twin mounts, in fact. Thus, as far as I know the armament of all the other ships - Lynx, Pêro Escobar, the Pattimura-class, and of course the Albatros-class, should all be armed with Pozzuoli-produced single mounts for their SMP-3. The actual 'Sovrapposto' mount produced by OTO-Melara is unique to the Centauro-class, and the first single-gun 76mm mount from OTO-Melara is the much better known Allargato.

Pozzuoli's single mount designs are rather distinctive looking, which makes them pretty easy to recognize, fortunately (and personally, I find them a lot cooler-looking than the Allargato, even if the latter was the better weapon system). Imagine of one of these mounts below;



You can also see some nice phots of the mount on Pêro Escobar here.

Another view here (via Esploratori, Fregate, Corvette, ed Avvisi Italiani);

https://imgur.com/XQ2TUm2

The book also includes line drawings for the Albatros-class corvettes and Centauro-class frigates, which I'll spoiler below;

Spoiler

Previously I've already drawn the elevated twin mount, now I imagine the quad would look like this:
View attachment 647382

Very nice work! The only thing I can really think to critique is that the stalk should be slightly further forward - if you see the line drawing above, you can see the overhang of the rear of the turrets are greater, and the front of the turret is nearly flush with the 'barbette'.

Previously I've already drawn the elevated twin mount, now I imagine the quad would look like this:
View attachment 647382

This reminds me a lot of Russian quadruple mounts. Is there any known inherent flaws with choosing this stacked arrangement?

As Tzoli said, such arrangements greatly complicate the internal arrangement and mechanisms of the turret. Ex, in this example the elevation mechanisms lie between the two guns. The SMP-3 single was guilty of being overly complex too. Unfortunately, I don't have an internal view of the Sovrraposto - just the Pozzuoli SMP-3 and the OTO-Melara 76/62 Allargato.

The SMP-3 operated as either a single fire or burst-fire system, reliant on a 14-round drum. When fired in burst, rate of fire was 50 rpm (aka, a round every 1.2 seconds, or about 16.8 seconds to empty the drum). Once the drum was depleted, the gun would have to elevate up to +90°, where the drum was reloaded (which took 3 seconds). The system in practice, fully automatic, was quite complex - too much for the time. In particular, the speed of reloading the drum proved to be a particular point of issue, and this had fatal consequences. On the Dutch corvette Lynx, a failure in the reloading mechanism occurred in the continuous elevator feeding the drum, where a cartridge was blocked, and the movement of the rollers against this blocked cartridge cause such friction as to cause the overheating and explosion of the cartridge. Believed to have been due to an incorrect amount of lubrications, this ultimately lead to the replacement of the guns on the ship with 40mm/70's, which was also in part a measure to fight topweight issues on the Albatros-class as a whole.

OTO-Melara ditched the drum system entirely when they developed the Sovrapposto mount, and each gun had its own replenishment system. This consisted of a hydraulic elevator, a carousel containing 11 cartridges, and a pair of oscillating arms. This system, when functioning properly, could allow the guns to be continuously reloaded without any interruption at any angle of elevation, and thus in theory a rate of fire of 55-60 rpm could be maintained until the magazines ran dry. Practically speaking, the only limit was the need to pause for ten seconds every 50-60 rounds to allow the barrel to cool. The system seems to have been safer, but was apparently still not satisfactory. Unfortunately, none of my sources actually specify what was unsatisfactory about them.

Whatever the case, the ultimate solution the MMI found seems to have been just using the 76/62 Allargato singles and slaving them in pairs to directors, which allowed for the same effective output - higher on paper, really, since the Allargato are sometimes credited with higher rates of fire (55-60 rpm usually, but I have a contemporary source that credits them with 70-80 rpm), and they incorporate a water-cooling system.

 

[Tzoli]

As I don't speak Italian and the very rare info I could find on the guns I might have incorrect info.
Still to my knowledge these are/were the post WW2 76mm Guns of the Italian Navy:
Pozzuoli SMP-3 Sovrapposto? from around 1951
OTO-Melara Sovrapposto from around 1952
OTO-Melara Allargato from around 1961
OTO-Melara Compact from around 1963
OTO-Melara Super Rapid from around 1988
and the final OTO-Melara Sovraponte from around 2019

all of them are 76mm/62

Also thanks for the drawings. My turret drawing was based on a ship drawing I've found on a Russian forum.

 

[Phoenix_jz]

As I don't speak Italian and the very rare info I could find on the guns I might have incorrect info.
Still to my knowledge these are/were the post WW2 76mm Guns of the Italian Navy:
Pozzuoli SMP-3 Sovrapposto? from around 1951
OTO-Melara Sovrapposto from around 1952
OTO-Melara Allargato from around 1961
OTO-Melara Compact from around 1963
OTO-Melara Super Rapid from around 1988
and the final OTO-Melara Sovraponte from around 2019

all of them are 76mm/62

Also thanks for the drawings. My turret drawing was based on a ship drawing I've found on a Russian forum.

No worries! The language barrier can definitely be harsh, especially given the lack of coverage of period Italian armaments (especially in English, but even in Italian a lot of the niche technical stuff isn't a huge focus).

Your summary is correct for the most part. The only things I'd like to distinguish are that;

As mentioned before, the SMP-3 singles were just known as the SMP-3. Development on these started development around 1951 iirc, and entered service in 1955 with the first corvettes of the Albatros-class.

The Sovrapposto was a development of OTO-Melara, and though the gun is derived from the SMP-3, to my knowledge Pozzuoli had nothing to do with the Sovrapposto mount itself - and 'Sovrapposto' refers exclusively to this twin mount (due to how the guns are positioned). Unfortunately I'm not sure what year it started development (1952 doesn't seem unlikely), though its entry into service can be dated to 1957 with Centauro.

OTO-Melara's 76/62 Allargato, which used a new version of the gun (different ballistics, as mentioned previously) began development in 1958 and entered service in 1961 on Giuseppe Garibaldi.

 

[Tzoli]

I've tried to determine their design date which of course not equals to when they started the design process nor when they were first entered service.
But yeah I only have muzzle velocity and shell weight data on the Compact and Super Rapid guns/mounts though for the Allargato the muzzle velocity should be 900m/s
By the way I based my turret drawing on this:

https://2014.f.a0z.ru/06/07-3503685-cigno1.jpg

from:

Итальянские корабли [5] (61/156) [Форумы Balancer.Ru]

Mare Nostro: … (стр. 61 из 156)

forums.airbase.ru

 

[Phoenix_jz]

According to Esploratori, Fregate, Corvette, ed Avvisi Italiani, the SMP-3 fired a 6 kg round at 950 m/s, with a range of 16,000 meters and a ceiling of 11,500 meters. The new OTO-Melara gun adopted for the Allargato is credited with a 6.2 kg round fired at 925 m/s, with range and ceiling increased to 16,300 meters and 11,800 meters respectively.

Which makes me curious if the figures given by navweaps (6.296 kg at 850 m/s to 18,400) are maybe a later round? Said data does match that which was eventually used on the 76/62 Compatto (Compact), and my source for obvious reasons isn't going to be able to account for anything past 1970.