“Pig” or “Chariot”, SLC (Siluro Lenta Corsa)
The SLC (Slow Moving Torpedo) was the best known assault weapon of the Regia Marina during World War II. This new torpedo, nicknamed “maiale” (pig or hog, depending on the author), was equipped, amongst other things, with diving planes, ballast tanks, and compressed air for the release of ballast, thus allowing for full underwater navigation, just like a submarine.
SLC (Slow Moving Torpedo also knows as maiale or pig).
Museo Navale di Venezia, Italy.
(Photo Cristiano D’Adamo)
The models built after the original 1936 prototype employed an electric motor with power increased from 1 to 1.6 HP. Batteries were increased to a total of 150 Amp. Specific efforts were made in bettering equipment; a magnetic compass, for instance, was preferred to a gyroscopic one, due to the difficulties encountered in miniaturizing such a complex device. The magnetic compass was improved, rendering it less susceptible to magnetic interference.
Tail section.
Museo Navale della Spezia, Italy.
(Photo Cristiano D’Adamo)
The breathing apparatus used by the operators was also notably improved. After having noted the unreliability of the Davis hoods used on submarines, studies were began on specific apparatuses capable of providing longer autonomy and complete safety.
To avoid bubbles rising to the surface, which would have revealed the presence of a diver, the Regia Marina employed special devices, specifically built by Pirelli, which utilized a sealed system. These breathing apparatuses were not fueled by compressed air, but instead used pure oxygen. The use of oxygen eliminated the presence of bubbles since it did not produce exhaust gases. During breathing, the expended oxygen is turned into carbon dioxide (CO2) which is then purified by a lime-based filter (sodium carbonate and lime). A closed system allows for the apparatus to function until the lime is saturated and cannot any longer absorb the carbon dioxide (CO2). The ARO, as it was designated by the Navy, eliminated the risk of the bends typical of the compressed air apparatus (designated as ARA), and the fastidious decompression stages required during ascent.
Head gear.
Venice Naval Museum, Italy.
(Photo Cristiano D’Adamo)
Nowadays we know that breathing pure oxygen stresses the central nervous system and can cause epileptic episodes, but no one recollects such occurrences during the training conducted by the Italian divers. Therefore, it is believed that the oxygen in use was not 100% pure. As a matter of fact, it is recorded that divers experienced “breathlessness” typical of carbon dioxide (CO2) intoxication. Regardless, divers experienced some maladies caused by oxygen breathing at certain depths. The maximum submerged depth of an ARO apparatus should have not exceeded -15 meters (- 45 feet), but it was known that depths of up to -30 meters (-90feet) were often reached.
Adapted from: ‘Imagini di Storia – Decima MAS: I mezzi d’assalto della Marina Italiana – N7 gennaio 1995
Modified Touring Boat MTM – Barchino
Also known as “barchini” (little boats), the M.T.M represented an evolution of a fast surface attach vessel conceived in 1936 as the M.A. (assault motorboat) and the M.A.T. (airborne assault motorboat) and built in 2 exemplars by the Biglietto Varazze shipyard. The same shipyard, in 1938-39, built two series of the new type M.T.; the first of 6 units, and the second, slightly larger and with motor of 95HP, of 12 units.
MTM.
Venice Naval Museum, Italy.
(Photo Cristiano D’Adamo)
This last experience allowed, in 1940-42, for the tuning and the construction of the M.T.M. of which about 50 were built. From the M.T.M. derived, in 1942-43, the M.T.R. and the M.T.R.M. of which about 20 were laid down, but only one entered service with the navy of the Republica Sociale Italiana.
MTM.
Venice Naval Museum, Italy.
(Photo Cristiano D’Adamo)
Admiral Iachino, in his book “Sunset of a Great navy” describes the M.T.M. as small motorboat-torpedo (M.T.S.M. invented by Capt. Guido Cattaneo), and commonly known as “barchini”, piloted by a single man who would through himself into the water about 100 meters before hitting the target, abandoning the vessel in full speed.
MTM.
Venice Naval Museum, Italy.
(Photo Cristiano D’Adamo)
Adapted from: “Imagini di Storia – Decima MAS: I mezzi d’assalto della Marina Italiana” – N7 January 1995
Modified and Enlarged Touring Boat – MTMSA
After the construction of the first “barchini” (small boats) M.T.S. (Modified Torpedo Touring Boats) in summer of 1941, the Regia Marina studied some improvements which produced the the M.T.S.M.A., an enlarged version of the previous model. The first version had a displacement of 1.75 tons and dimensions of 7.1 x 2.1 x 0.5 meters. The engine was a gasoline-powered 90HP which produced a maximum speed of 28 knots with an range of 90 miles.
MTMSA
Museo Navale della Spezia, Italy.
(Photo Cristiano D’Adamo)
In the “modified” version, produced in 1941, the displacement was increased to 3 tons and the dimensions to 8.4 x 2.2 x 0.6 meters. The power plan was doubled and the output was increased to 190 HP total for a speed of 32 knots and a range of 200 miles. The version M.T.S.M.A. was further improved with the installation of a single cabin for both operators which differed from the previous version which had two distinct cockpits built in tandem.
Cockpit
Museo Navale della Spezia, Italy.
(Photo Cristiano D’Adamo)
Translated from: “Imagini di Storia – Decima MAS: I mezzi d’assalto della Marina Italiana” – N7 gennaio 1995
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