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Italian Submarines
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Diesel Engines |
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The various series of the “600” class were equipped with diesel engines
similar in performances, but produced by different manufacturers. The "Argonauta"
were able to develop 1,250 HP, later increased to 1,350 HP on the "Sirena",
and 1,400 HP on the "Perla", "Adua" and "Platino". Some of the boat of the "Platino"
class received power plants capable of producing 1,500 HP. All these engines
were in general two-stroke reversible and produced by FIAT, TOSI or C.R.D.A.
The engines on the “Perla” had four cylinders; the “Argonauta” and the
“Adua” had engines with six cylinders. The “Platino” had five. In the long
run, the engines produced by C.R.D.A. appeared to be the most efficient. The surface speed of all the "600" boats was around 14 knots, while submerged speed was 7.5 knots excluding the first series, the "Argonauta", capable of 8 knots. Throughout the evolution of the various power plants, endurance remained somewhat similar with the boats capable of reaching 5,000 miles at 8.5 knots, and 2,300 miles at the maximum speed of 14 knots. The diesel engines were connected to the electric motors via a joint, which could be disconnected. The maximum operating RPM (revolutions per minute) was usually 420, but the engines could be pushed to 460 RPM for a limited period of time. |
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After intense use, the diesel engines were prone to failures and required extensive maintenance. The limited speed of the “600” was not a great factor, but in bad weather the engines intake valve, situated just above the engines on the deck instead of inside the cunning tower as in foreign design, would easily flood. To give a general idea of fuel consumption, the following is a chart created by the Allied after the capture of the Smg. Bronzo: |
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In general, as for most Italian submarines, the surface speed of all the class “600” submarines was very limited and could not be improved with the installation of new engines. A German type VII A submarine, somewhat similar to the “600”, could reach 17 knots versus the 14 of the Italian boats. |
Electric Motors
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Similarly to the diesel engines, different manufacturers produced the
electric motors. Some received motors produced by C.R.D.A., while others
received similar units produced by Marelli and Ansaldo. These motors could
operate at 45, 90 and 180 volts. The maximum output was obtained running 180
volts and 330 RPM. When not in use for propulsion, the electric motors could
be used to generate D.C. (direct current) to recharge the batteries. Each
motor was capable of producing up to 400 HP. |
Batteries
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On the “600” there were two holds capable of 52 batteries each. On the "Sirena",
each cell was of the type Ironclad N 7320 produced by the Tudor and weighed
700 kg (1543 lb) each. The total weight of all cells was 72.8 tons (80.25
short tons). The batteries could deliver 4,750 amps in one hour, 7,050 amps
in three (2,350 amps/hour), and 9,720 amps in twenty hours (485 amps/hour).
On the first series, the “Argonauta", each battery was capable of producing
only 4,270 Ampere/Hour. When captured, the Smg. Bronzo was equipped with
batteries produced by Marelli of Milan of the type Quaroldo M.51. These
batteries had been installed in September 1941, and at the time of the
boat’s capture, they were in perfect conditions, thus confirming that their
operational life was relatively long. Each cell was made of multiple positive and negative plates made of lead, each with common terminals, separated by insulators. The plates were immersed in an electrolyte solution made of pure water (distilled water) and pure sulfuric acid with a specific gravity of around 1.25 when fully charged. Each cell produced approximately two volts and was permanently wired in series. Each of the two battery groups could be operated independently or in parallel. On the “600” each battery group was divided into two busses, each composed of 26 cells (26 x 2 volts = 52 volts). |
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