The Boats of the Early
Bernardis Type

by Cristiano D'Adamo

Propulsion Plan

Diesel Engines
The "Pisani" class was powered by two Franco Tosi "K 6" six cylinder diesel engines capable of producing 1,350 HP. These were four-stroke motors with a primary crankshaft to which were connected the pistons; they could not be reversed (they only rotated one way). The engines were directly connected to a four-stage air compressor which produced air at a pressure of 70 Kg/cm2 m (995.6 psi) and which was also used (in reverse) to start the engines.


The diesel engines on the "Pisani"

The "Bandiera" and the “Squalo”were equipped with the new FIAT Q 426, a six-cylinder, two-stroke reversible 1,500 HP (xxxx Kw) diesel engine. The two power plants did not directly effect the surface speed of the boats, but rather their endurance.

The three classes had almost similar performances with the “Pisani” rated at 15 knots, and the “Bandiera” and “Squalo” at 15.1 knots. With continuous use and the general aging of the boats, these values became hardly achievable, especially toward the end of their operational lives. On surface navigation, the engines were connected to the primary axels via a clutch joint, while the axels were connected to the propeller shafts by a geared joint. The geared joints could be disconnected from the propeller shaft and connected to the electric motors, thus turning them into dynamos for the production of direct current. While submerged, the clutch joints were fully disengaged. The two diesel engines received their supply of fresh air from an intake place above deck within the cunning tower. The intake was protected by a large valve, which, while the boat was submerged, was sealed.

Electric Motors
On the "Pisani" the two electric motors (double coaxial armature winding) were produced by C.G.E. (Compagnia General Elettricità, Milan) and capable of producing up to 550 HP (410.1 Kw) each. The “Bandiera” were fitted with motors produced by Savigliano, while the “Squalo” received motors produced by C.R.D.A.

Electric motors on the "Pisani"
The motors on the "Pisani" were powered by direct current and could be supplied with 55, 110 or 220 volts. Each motor could be run at full speed (550 HP) for one hour, at 416 HP for three hours and at 66 HP in continuous motion. The Savigliano installed on the "Bandiera" could produce 650 HP each; those on the "Squalo" were also capable of 650 HP (522 Kw). The difference between the various power plant solutions allowed for various endurance at maximum speed; the "Pisani" and the “Bandiera” were capable of 8.8 miles at 8.2 knots, while the "Squalo" was only capable of navigating 7 miles at 8 knots.

Batteries
On the "Pisani", “Bandiera” and :Squalo” there were two 56 cell storage batteries; later Bernardis had them increased to 132. On the “Pisani”, each cell was of the type 30 M.A.S. 870-5 produced by the SGIAE of Melzo (near Milan) and weighed 750 kg (1653 lb) The total weight of all cells was 84 tons (92.59 short tons). The batteries could deliver 5,150 amps in one hour, 7,500 amps in three (2,500 amps/hour), and 11,500 amps in twenty hours (575 amps/hour).

The batteries holds

This configuration was identical to the “Mameli”, a class designed by Cavallini. This configuration was altered on the "Bandiera" and these boats were fitted with 112 Hensemberger R.M 865/28, batteries these with slightly different performaces (5,200 amps for one, 7,680 for 3 hours, 10,000 for10 hours and 11,000 for 20 hours). The “squalo” received batteries with far less performance; 4,270 amps for one, 6,380 for 3 hours, 8,400 for10 hours and 9,350 for 20 hours

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