A propulsion unit includes a housing supported on a vessel. A propeller shaft extends in the housing. The propeller shaft is rotatably supported with a first bearing and a second bearing. A propeller is attached to at least one end of the propeller shaft. The first bearing includes a first radial bearing and a first thrust bearing. The first radial bearing is a sliding bearing positioned axially inside the first thrust bearing. The first bearing is positioned at the first end of the housing and the second bearing being positioned at the second end of the housing or vice a versa.

The stub shaft bearing for a stub shaft can be replaced while the stub shaft remains installed in a hydroelectric unit. A runner hub lifting device may be positioned within a discharge ring surrounding a runner hub. The runner hub lifting device may lift the runner hub, and a stub shaft bearing may be removed from a stub shaft. The stub shaft bearing may be disassembled into bearing sections while located in a chamber in the hydroelectric unit. The bearing sections may be removed from the chamber through a service hatch in the chamber. A replacement stub shaft bearing may be moved into the chamber and installed on the stub shaft. The runner hub lifting device may lower the runner hub.

A gyroscopic roll stabilizer for a boat includes an enclosure mounted to a gimbal for rotation about a gimbal axis and configured to maintain a below-ambient pressure, and a flywheel assembly including a flywheel and flywheel shaft, with the flywheel assembly rotatably mounted inside the enclosure for rotation about a flywheel axis. The gyroscopic roll stabilizer also includes a motor operative to rotate the flywheel assembly and disposed inside the enclosure. A motor cooling circuit is configured to transfer heat away from the motor. The motor cooling circuit has a closed fluid pathway for recirculating cooling fluid therein. The fluid pathway includes a fluid channel jointly defined by the motor and the enclosure and having the cooling fluid therein. The gyroscopic roll stabilizer is configured to transfer heat away from the motor to the cooling fluid. Related methods are also disclosed.

A slew bearing includes a stationary bearing ring to be fixed to a base, and a moveable bearing ring to be fixed to a moveable object, wherein the stationary bearing ring and the moveable bearing ring are configured to enable rotation of the moveable bearing ring relative to the stationary bearing ring about a rotation axis. A main axial bearing and an auxiliary bearing are provided between the stationary bearing ring and the moveable bearing ring, wherein the moveable bearing ring includes one or more main portions and one or more auxiliary portions, which one or more main portions are moveable relative to the one or more auxiliary portions between an operational position, in which the main axial bearing transfers the axial loads between moveable bearing ring and stationary bearing ring, and a raised maintenance position, in which the auxiliary axial bearing transfers the axial loads between moveable bearing ring and stationary bearing ring and the main bearing is allowed to be inspected and/or maintained so that the slew bearing during inspection and/or maintenance is still operational.

Systems and methods are provided for using an additively manufactured vehicle, such as an UUV, with additively manufactured modules. The vehicle may be configurable such that additively manufactured modules or components may be detachably connected to the vehicle by hand, without the use of tools. Such modules may include connectors adapted to securely attach additional modules that may be detached by hand, without the use of tools. The additively manufactured modules may include ball bearings for rotating modules such as propellers and thrusters, and clips or tabs for detachable connection. The modules may include optical components for communications between a swarm of unmanned vehicles. Such optical modules for underwater vehicles may utilize nephelometry and/or turbidimetry to improve communications parameters based on scattered light measurements.

A hinge assembly includes: a body; a first arm pivotally mounted on the body and movable between a first position and a second position, the first arm including a plurality of teeth formed thereon; a pawl mounted on the body proximate to a portion of the first arm, the pawl shaped to releasably engage the plurality of teeth of the first arm. In a collapsed position of the hinge assembly the pawl is disengaged from the plurality of teeth of the first arm such that the first arm is pivotable relative to the pawl. In a deployed position the pawl engages the plurality of teeth of the first arm to releasably secure the first arm in the second position.

The stub shaft bearing for a stub shaft can be replaced while the stub shaft remains installed in a hydroelectric unit. A runner hub lifting device may be positioned within a discharge ring surrounding a runner hub. The runner hub lifting device may lift the runner hub, and a stub shaft bearing may be removed from a stub shaft. The stub shaft bearing may be disassembled into bearing sections while located in a chamber in the hydroelectric unit. The bearing sections may be removed from the chamber through a service hatch in the chamber. A replacement stub shaft bearing may be moved into the chamber and installed on the stub shaft. The runner hub lifting device may lower the runner hub.

An arrangement and a method for sealing a propeller shaft of a marine vessel. The arrangement including a shaft seal arrangement and a lubrication arrangement including a lubricant circulation line for conducting lubricant to and from the shaft seal arrangement and a lubricant circulator. The lubricant circulation line includes a connection line that is connected in fluid connection with the lubricant circulation line downstream of the lubricant circulator and upstream of the shaft seal arrangement, and that is connected in fluid connection with a second part of the lubricant circulation line so as to selectively conduct a part of the flow of lubricant past the shaft seal arrangement. At least one hydraulically operated pressure relief means is configured to control the flow of lubricant in the connection line.

A water lubrication type bearing material contains 12 wt. % to 25 wt. % of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA resin), 18 wt. % to 33 wt. % of a carbon fiber, and a remainder including a polytetrafluoroethylene (PTFE) resin and/or a modified PTFE resin. The bearing material has excellent wear resistance and sliding characteristics for a water lubrication type bearing.

A bearing system including a wheel assembly transmitting load to a damping assembly, wherein the wheel assembly is configured to rotate angularly relative to the damping assembly.