Kasimo,

(GENERAL DESCRIPTION) - A twin screw propulsion arrangement is instaled on the IXC class boats. Each of the diesels when running at rated speed (470 RPM) transmite 2200 HP to the main shaft. The friction clutch forward of the main motor is operated by pneumatic hydraulic action while that aft is hand-operated. the main propeller thrust bearing and shaft brake are both standard design. The stern tube and strut bearings are inlaid with lignum vitae. The outboard shaft is rubber covered; that part between the stern tube and strut bearings is wrapped with light wire.

(INDIVIDUAL COMPONENTS) - (a). (Shafting) - The shaft line runs at an angle of 0 40' to the centerline and 0 0' to the base line. The main and propeller shaft dimensions are as listed:

Outside diameter on the main shaft is 8.67 ins. and 7.88 on the propeller shaft.

Inside diameter on the main shaft is 4.73 ins and 3.94 ins on the propeller shaft.

The length is 482 ins.

The shafts are made from a martinsitic forged steel with the following characteristics:

Ultimate strength is 60,000 to 75,000 psi. The yield point is 40,000 psi and the elongation ( in length of 5 dias.) 23%

(b). (Stern tube) - The stern tube consists of a forward and after cast steel bearing connected by a steel tube. The bearings have bronze bushings inlaid with lignum vitae on the lower thrid of the bearing. A circulating water connection is led to the bearing for flushing and cooling purposes. A standard stuffing gland is employed for the insertion of the packing rings. The gland is tightened by means of a spur gear arrangement which insures uniform tightness of all tightening bolts. The desiged stern tube abd strut bearing clearance is 1mm (0.40 ins); operating instructions available call for renewal after 3.5mm (.140ins) of wear.

(c). (Main thrust bearing) - A standard main thrust bearing is installed employing ten individuel shoes and capable of absorbing 33,000 lbs. thrust at 500 shaft RPM. It is self-lubricarted and has a built in cooling system for cooling the lubricant. The gearing for the shaft revolution indicator is built into the thrust bearing housing.

(d). (Main and diesel couplings) - Standard cone type friction couplings are used. To provide the quick operation necesarry for uncoupling of the diesel from the main shaft a combined pneumatic-hydraulic setup is employed. This consists of a hydraulic piston and cylinder operating in conjunction with an air on oil cylinder, a common German practice. Hand operation is also provided for emergency use. The main coupling is operated by a hand crank arrangement. Both of the units aredesigned to function at a maximum torque of 94,000 lbs. ft; equivalent to 25% overload. Operating instructions state that the clutches should not be ebgeged when turning the shaft above 350 RPM. They may be disengaged at any RPM.

(CONCLUSIONS) - The shafting arrangement is standard in nature for a direct drive submarine. The major deviation from normal U.S practic is in the use of lignum vitae for the lower third of the strut and stern tube bearings. This provids a conservation of lignum vitae but results in an undesirable "combination" bearing.

A similar tightening arrangement for the stern tube gland to that installed on the IX-C boats has been installed on some U.S. submainres and is recommended for adoption on all submarines, especially inasmuch as it provides a ready means for changing the pressure on the packing under varying operating conditions.