Abstract: A gas turbine engine according to an exemplary aspect of the present disclosure includes, among other things, a fan section including a fan rotatable about an axis and a speed reduction device in communication with the fan. The speed reduction device includes a planetary fan drive gear system with a planet gear ratio of at least 2.5. A fan blade tip speed of the fan is less than 1400 fps.

Abstract: The thrust load of an outer shaft is received by a contra-rotating thrust bearing provided in a boss of a front propeller and transmitted to an inner shaft. The combined thrust load of the outer shaft and the inner shaft is received by an inner thrust bearing provided on the bow side of the power transmission unit and transmitted to a ship body. The rotational force of an outer output shaft is transmitted to the outer shaft via a flexible joint (gear coupling). Thus, the thrust load of the outer shaft is transmitted to the ship body only via the inner shaft without being directly transmitted to the ship body, and the axial displacement and angular displacement are allowed by the gear coupling, so that it is possible to eliminate the influence of the change of hull deformation on the shaft center of the outer shaft.

Abstract: A propulsive fan system comprises a fan unit comprising a first stage array of rotatable blades upstream of a second stage array of rotatable blades. The first stage is coupled to a first drive means. The second stage is coupled to a second drive means. The first drive means is independently operable of the second drive means during operation of the fan system.

Abstract: A de-rotation system includes a planetary gear set, and a fairing support structure mounted for rotation with a first ring gear.

Abstract: The object is to facilitate the installation of a contra-rotating propeller on a mother ship. Disclosed is a contra-rotating propeller unit in which a predetermined part on the rear side of an inner shaft (12) is supported by a contra-rotating rear bearing (36) provided in a boss (13a) of a front propeller (13), and which includes an inner fixing tool (50) detachably attached to a tip of an outer shaft (11) to temporarily support a predetermined part on the front side of the inner shaft (12), and a contra-rotating thrust bearing (40) provided in the boss (13a) of the front propeller (13) to receive the thrust load from the outer shaft (11) to transmit the thrust load to the inner shaft (12).

Abstract: A turboprop propulsion unit includes at least one pusher propeller 5, 6 driven by an aircraft gas-turbine engine, with the aircraft gas-turbine engine being arranged in front of the pusher propeller 5, 6 in a direction of flight. A turbine outlet area 9 is arranged at the front in the direction of flight and a compressor area 14 faces towards the pusher propeller 5, 6.

Abstract: A turbine engine including two outer coaxial counter-rotating unducted propellers, of an upstream propeller and a downstream propeller, respectively. The blades of the downstream propeller are retractable in the lengthwise direction thereof so as to reduce the diameter of the propeller. The reduction in the diameter of the downstream propeller makes it possible to reduce noise caused by vortices generated by the upstream propeller.

Abstract: A self-contained counter rotating turbo prop system is driven by a gas turbine engine through a reduction gearbox. A gear train housed separate from the reduction gearbox provides the counter-rotation of a first and second pluralities of propeller blades. The entire counter-rotating propeller system is disposed within cowlings and is separate from the gas turbine engine and reduction gearbox. The example counter rotating propeller system includes a collective blade angle actuation system that provides for adjustment of blade angle of both the first and second plurality of propeller blades with a single actuator.

Abstract: The invention relates to a method for improving the propulsion efficiency of vessels. The improvement is obtained by utilizing wave induced variations in propeller inflow, i.e. the speed of water flowing towards the propeller. The wave induced water speed variation is used to calculate the propeller speed in a way so that the propeller speed is optimal with respect to the total propulsion efficiency. The optimal propeller speed is determined by solving an optimization problem formulated as the maximization of the ratio of energy delivered by the propeller and the energy delivered to the propeller. The method may be used for vessels with one or more propellers.

Abstract: It is provided to embody as a modularly constructed system, a waterwheel for power generation via generators with transversely extending water blades as hinged or folding blades. In this regard it is provided to arrange the water blades over a truss framework. The truss framework for each water blade is formed by a transversely extending prism-like arrangement of plural connected struts as transverse supports, whereby these are connected at node points by longitudinal rods, and at least one strut of the transverse supports is connected with the wheel rim. In that regard, a longitudinal rod located at the top and arranged over the transverse supports is embodied for the rotatable support of a pivotably received water blade via a mounting receiver and a longitudinal rod is allocated as a counter support for the water blade in its working position. Simultaneously this longitudinal rod serves for limiting a pivoting motion of the neighboring water blade in the turbulent region.

Abstract: A turboprop having at least one propeller formed by a set of variable pitch blades. Each blade is swivel-mounted on a rotary support and carries a gearwheel meshing with an actuator annulus rotating on the rotary support and coupled to a control annulus via an epicyclic mechanism.

Abstract: A turbomachine having two unducted external fans mounted to contrarotate about a common axis, the fans constituting respectively an upstream fan and a downstream fan, is disclosed. At least some of the blades of the upstream fan carry an air guide device on their radially outer end portions, the air guide device being outwardly oriented on going from upstream to downstream and serving to deflect the vortices that are formed in the vicinity of the blade tips of the upstream fan radially to outside the blades of the downstream fan.

Abstract: A turbine engine having two contrarotating unducted propellers, an upstream propeller (12) and a downstream propeller (14), with a power turbine mounted axially between the two propellers (12, 14), the turbine comprising an outer rotor (56) constrained to rotate with the upstream propeller (12) and an inner rotor (54) driving rotation of an inlet shaft (62) of a step-down gearbox (52), the gearbox having an outlet shaft (64) driving rotation of the rotor (56) of the upstream propeller (12) and an outlet shaft (66) driving rotation of the downstream propeller (14).

Abstract: A hub of a propeller with variable-pitch blades for a turbine engine, for example for a propfan engine. The hub of the propeller includes a polygonal ring with substantially radial cylindrical recesses distributed about a central axis of the ring for receiving the blades, a turbine rotor element of the turbine engine, and a securing flange that is attached to the ring so as to connect the ring to the rotor element. The hub further includes a plurality of back-up hooks inserted with clearance in openings, the back-up hooks being connected either to the ring or to the rotor element, and the openings being connected to the other one of the two.

Abstract: A turbine driving a planet gear and an epicyclic gear train and including a planet pinion cage and a ring driving two propellers in rotation, is connected to the planet gear through a flexible sleeve surrounding a turbine support shaft rather than through a support shaft itself to achieve a flexible assembly with a limit stop position in contact with the shaft to limit parasite internal forces applied to the epicyclic gear train without tolerating a loose assembly or breakage of the sleeve due to a condition of the limit stop after a clearance has been eliminated.

Abstract: A system of contra-rotating propellers for an aircraft jet engine, including: a free power turbine; a first and second propeller, contra-rotating, the first propeller being placed in a predetermined direction relative to the second propeller, each including a hub, an outer ferrule, and coupling arms linking the two; and a casing inserted between the free turbine and the propellers, the propellers arranged in the predetermined direction relative to the casing and the free turbine arranged in the opposite direction relative to the casing, the casing including a casing extension in the given direction, rotatably supporting the hub of the propeller. The coupling arms extend in the opposite direction, radially towards the outside.

Abstract: A mechanical arrangement for an engine having two propeller stages, including: a first epicyclic gear stage including a sun gear, a planet gear, a planet carrier and an annulus, wherein the sun gear is driven by a shaft of the engine, the planet carrier is stationary and thereby permits static structure to be located there through, and the annulus outputs torque and/or drive; a second epicyclic gear stage including a second sun gear, a second planet gear, a second planet carrier and a second annulus, wherein the second sun gear is driven by the annulus of the first epicyclic gear stage and is annular to accommodate the static structure, the second planet carrier includes the output to one of the propeller stages and the second annulus includes the output to the other of the propeller stages; wherein the static structure provides mounting for static components on one or both sides of each epicyclic gear stage.

Abstract: A system of contra-rotating propellers for an aircraft turbomachine, including: a free power turbine including a first rotor; first and second propellers; and a mechanical transmission system including a planetary gear train fitted with a sun gear driven by the rotor, at least one planet gear driving the first propeller, and a ring driving the second propeller. The free power turbine also includes a second rotor that is contra-rotating relative to the first rotor, and rotating the ring.

Abstract: An improved coaxial rotor assembly for a helicopter includes an upper rotor system having a multiple of upper rotor blades each having outer tips and mounted on and extending outwards from a central rotor shaft and a lower rotor system having a multiple of lower rotor blades each having outer tips and mounted on and extending outwards from the central rotor shaft with the upper rotor system spaced an axial distance from the lower rotor system on the central rotor shaft. A rotor blade support ring extends circumferentially around each of the upper and lower rotor systems which movably engages and supports the outer tips of the upper and lower rotor blades in spaced apart relation such that the upper and lower rotor systems rotate in opposite directions and the rotor blade support ring means prevents contact between the upper and lower rotor systems during operation thereof.

Abstract: An aircraft having counter-rotating, ring-type wing rotors that are driven by engines located at the wing tips is disclosed. The aircraft incorporates large span, high aspect ratio wings that are configured in a joined-tip design to improve the structural characteristics of the wings. One of the wings counter-rotates inside the other wing to enable vertical take-off and landing. The wings may comprise elliptical shapes, each having upper and lower sections that are separated from each other.

Abstract: The thrust load of an outer shaft (11) is received by a contra-rotating thrust bearing (40) provided in a boss (13a) of a front propeller (13) and transmitted to an inner shaft (12). The combined thrust load of the outer shaft (11) and the inner shaft (12) is received by an inner thrust bearing (41) provided on the bow side of the power transmission unit (20A) and transmitted to a ship body (2). The rotational force of an outer output shaft (24) is transmitted to the outer shaft (11) via a flexible joint (19) (gear coupling (19A)). Thus, the thrust load of the outer shaft (11) is transmitted to the ship body (2) only via the inner shaft (12) without being directly transmitted to the ship body (2), and the axial displacement and angular displacement are allowed by the gear coupling (19), so that it is possible to eliminate the influence of the change of hull deformation on the shaft center of the outer shaft (11).

Abstract: A system of counter-rotating propellers for an aircraft turbine engine including a first and a second propeller, each including a stalling control system for the blades, a rotating actuating mechanism for sliding an element to move the angle of attack of the blades, and a disengaging mechanism for rigidly fixing in rotation the rotating actuating mechanism. The system is designed so that when the disengaging mechanism is engaged, a relative rotation speed is created between the elements and the associated rotating actuating mechanism thereof, bringing the blades into a neutral position thereof for feathering.

Abstract: A transmission device includes: a transmission shaft having first and second shaft sections and a gear mounting portion; a first tube sleeved rotatably on the first shaft section, and including a tube body and an annular portion; a second tube sleeved on the second shaft section; a plurality of first planetary bevel gears mounted rotatably on the gear mounting portion; a plurality of second planetary bevel gears mounted rotatably on the annular portion; a transmission gear disposed rotatably on the tube body and meshing with the first and second planetary bevel gears; a first output bevel gear disposed rotatably on the second tube and meshing with the first planetary bevel gears; and a second output bevel gear disposed rotatably on the tube body of the first tube and meshing with the second planetary bevel gears.

Abstract: A turboprop propulsion unit includes at least one pusher propeller 5, 6 driven by an aircraft gas-turbine engine, with the aircraft gas-turbine engine being arranged in front of the pusher propeller 5, 6 in a direction of flight. A turbine outlet area 9 is arranged at the front in the direction of flight and a compressor area 14 faces towards the pusher propeller 5, 6.

Abstract: A method of operating a contra-rotating propeller engine that preferably comprises a 12 bladed front and a 9 bladed rear propeller. As is conventional, the engine is operated during at least a take-off phase, a cruise phase and an approach phase; during the cruise phase the engine operates with a generally constant propeller tip speed. The method is characterised by the step of operating the engine such that the tip speed of either or both of the propellers, during at least one of take-off, climb or approach, at least 10% greater than cruise tip speed. With a specific front to rear propeller spacing, increasing the tip speed reduces overall noise generated by the propellers.

Abstract: This turbine engine compressor comprises a separating nose extended by inner and outer annular walls defining in cooperation an annular volume (V) of separation of a primary flow (F1) and a secondary flow (F2). This volume (V) comprises a plurality of annular segments in the form of cells separated in pairs by blades of a first fan, these blades passing through both the primary flow (F1) and the secondary flow (F2). These cells are fixed to an upstream annular collar and a downstream annular collar driven rotationally by the aforementioned blades.

Abstract: A novel, more sophisticated steam turbine design is proposed with reaction stages that have full admission, compounded by counter rotating axial blades, with impulse ignition utilizing sodium injection.

Abstract: An upper rotor control system is contained within an upper rotor shaft and upper hub assembly of a contra-rotating rigid rotor system. A collective servo assembly includes a hydraulic actuator that provides collective pitch to all blades through axial extension/retraction of the control rod relative the upper rotor shaft for collective pitch control of the rotor blades. The collective servo assembly includes a spherical bearing for attachment of the control rod to aircraft structure. An X-Y positioner assembly includes a bearing arrangement which allows the shaft to rotate, while the X-Y positioner assembly remains non-rotational therein. The X-Y positioner assembly includes a multitude of hydraulic actuators, orthogonally positioned, to tilt the control rod about the spherical bearing off the axis of rotation of the upper rotor shaft for cyclic pitch control of the rotor blades.

Abstract: A turbomachine comprising: a gas generator for producing combustion gas; a turbine section through which the combustion gas passes and comprising first and second rows of contrarotating turbine rotor blades respectively driving first and second low-pressure shafts in rotation; and a fan section comprising a first row of fan blades mounted on a front fan shaft that is connected to an upstream end of the first low-pressure shaft, and a second row of fan blades axially offset from the first row and mounted on a rear fan shaft that is connected to an upstream end of the second low-pressure shaft, the front fan shaft being connected to the upstream end of the first low-pressure shaft via a removable sleeve for transmitting torque.

Abstract: A multiple counter-rotating propeller assembly includes a drive shaft, a first propeller and a second propeller. The first propeller has a first hub which is supported on the drive shaft and which is freely rotatable with respect to the drive shaft, a plurality of first blades mounted on the hub, and a gear set connected to the drive shaft and to the hub, the gear set rotating the hub in a direction opposite to the direction of rotation of the drive shaft. The second propeller has a second hub which is supported on the drive shaft and which is freely rotatable with respect to the drive shaft, and a plurality of second blades mounted on the second hub, the second hub connected to the gear set in the first hub to rotate the second hub in the same direction as the rotation of the drive shaft. The entire propeller assembly is supported solely on the drive shaft, and the inclusion of the gear set which provides all of the gear reduction completely within the propeller hub provides a compact design.

Abstract: A method for assembling a gas turbine engine that includes providing a low-pressure turbine inner rotor that includes a first plurality of rows of turbine blades configured to rotate in a first rotational direction, providing a low-pressure turbine outer rotor that includes a second plurality of rows of turbine blades configured to rotate in a rotational direction that is opposite the first rotational direction, and coupling a support structure between the outer rotor and a turbine mid-frame such that the support structure supports a forward end of the outer rotor, and wherein the support structure includes a first portion that has a first coefficient of thermal expansion and a second portion that has a second coefficient of thermal expansion that is different than the first coefficient of thermal expansion.

Abstract: A rotor system (12) for a helicopter (10) includes a rotating shaft (82). A gimbaled hub assembly (56) is coupled to the rotating shaft (82). Rotating blades (24) and non-rotating blades (33) are coupled to the gimbaled hub assembly (56). The non-rotating blades (33) provide lift for the helicopter (10) in forward flight unloading the rotating blades. The rotating and non-rotating blades (24, 33) provide equal and opposite rolling moments for lift offset operation.

Abstract: A compressor or pump employs principles of unsteady delayed stall to enhance the head increase produced by the compressor or pump. Plural airfoil-shaped lifting elements are spaced from each other in a cascade and the fluid is directed into the cascade by a device that varies a parameter of the flow relative to each lifting element in repeating cycles to cause the flow relative to each lifting element to begin to separate from the lifting element and then reattach thereto during each cycle. The cascade can comprise an axial flow impeller with plural impeller blades arranged around a hub capable of rotating on an axis. The device for varying the flow parameter can be a stator with a plurality of stator blades upstream of the impeller, or a second, counter-rotating axial flow impeller. In either case, the parameter is a flow angle at which the flow is directed to the downstream impeller.

Abstract: A pulling marine propeller (1) including multiple propeller blades (4) attached to a propeller hub (5). The propeller hub (5) is attachable to a propeller shaft (9) extending from a drive housing (10) located downstream of the propeller (1). The invention is especially characterized by the fact that the propeller hub (5) is provided with an annular, radially outwardly flared peripheral portion (11) at an aft end (12) thereof. The flared portion (11) is arranged to axially overlap a front end shoulder portion (13) of the drive housing (10).

Abstract: A modular propeller comprises a center hub with an integrated front cap and an aluminum core encapsulated with fiber-reinforced composite polymer resin. A set of replaceable blades have bases that slip into and interlock with corresponding slots in the center hub. An elongated rear cap retains the blades in the center hub. The rear cap includes a nozzle section for expelling exhaust gasses that pass through the center parts of the hub and blade bases.

Abstract: A counter-rotating 2 cycle piston engine with a combustion chamber and an output shaft rotatably mounted to rotate independently about the same propeller centerline of an aircraft. The Internal combustion power is transmitted to the output shaft by means of a conventional piston, rod, crankshaft configuration journaled to the combustion chamber or engine block in the traditional manner thereby producing concurrent rotation of the shaft and counter-rotation of the engine block. Interior surfaces of the combustion chamber and pistons are angled to control the oil flow inside the crankcase and eliminate unwanted ponding. The pistons are modified to transfer fluid accumulations to the combustion chamber. A throttle is located at the axis of rotation to function normally without the effects of centrifical force.

Abstract: The present invention is a novel hydraulic/electric, rotating interface for torque producing engines, including internal combustion engines, which enables a rigidly mounted motor to isolate the power/torque producing components from other stationary accessories, to provide advantageous crankshaft/block counter-rotational output, suitable for torque free power applications, torque free propulsion and torque sensitive environments.

Abstract: A gas turbine engine turbine assembly includes a high pressure spool having a high pressure turbine drivingly connected to a high pressure compressor by a high pressure shaft which is rotatable about an engine centerline. A low pressure turbine has counter rotatable low pressure inner and outer shaft turbines with a row of low pressure variable vanes disposed therebetween and drivingly connected to coaxial low pressure inner and outer shafts respectively which are located radially inwardly of the high pressure spool. The low pressure inner and outer shaft turbines are drivingly connected to a forward and aft fan blade rows by the low pressure inner and outer shafts. A single direction of rotation booster is drivenly connected to the low pressure outer shaft and axially located aft and downstream of the aft fan blade row.

Abstract: A counter-rotating rotary-piston engine has an output shaft with a cylindrical inner cavity rotatably mounted on a single support spindle in the frame of an aircraft. The output shaft extends substantially through the length of the engine block, which is suitably journaled on the shaft or the spindle to permit its counter-rotation. Internal combustion power is transmitted to the output shaft by means of an inner rotary piston fixed to the shaft which cooperates in conventional manner with an outer working chamber in the engine block, thereby producing concurrent rotation of the shaft and counter-rotation of the engine block. Dual propellers mounted on the shaft and on the block improve thrust performance, balance the torques and moments of inertia of the two counter-rotating masses, and virtually eliminate any resultant torque to the aircraft.

Abstract: A rotor through which a fluid flows in a main direction of flow, provided with at least one rotor blade, the rotor blade being arranged to rotate about a rotor axis. The rotor blade extends away from the axis of rotation into the field. To reduce the trailed tip vortex at the end of the rotor blades, the fluidic losses, and flow noise, the rotor blade is split in at least two partial blades at a set distance from the axis of rotation and forms a loop. One partial blade extends in the direction of rotation in relation to the rotor blade. The other partial blade extends in a direction opposite the direction of rotation to the rotor blade. The two partial blades are interconnected in one piece at their ends, to encompass a loop surface extending essentially crosswise to the main direction of flow, through which the fluid flows.

Abstract: An aircraft gas turbine engine includes a low pressure turbine having a low pressure turbine flowpath and counter rotatable low pressure inner and outer shaft rotors having inner and outer shafts, respectively. The low pressure inner and outer shaft rotors include low pressure first and second turbine blade rows disposed across the turbine flowpath and drivingly connected to first and second fan blade rows by low pressure inner and outer shafts, respectively. At least one of the low pressure first and second turbine blade rows is interdigitated with an adjacent pair of one of the turbine blade rows. At least one row of non-rotatable low pressure vanes is disposed across the low pressure turbine flowpath between a non interdigitated adjacent pair of one of the turbine blade rows.

Abstract: A counterrotatable booster compressor assembly for a gas turbine engine having a counterrotatable fan section with a first fan blade row connected to a first drive shaft and a second fan blade row axially spaced from the first fan blade row and connected to a second drive shaft. The counterrotatable booster compressor assembly includes a first compressor blade row connected to the first drive shaft, a plurality of fan shaft extensions connected to the second drive shaft for driving the second fan blade row, and at least one compressor blade integral with each fan shaft extension so as to form a second compressor blade row interdigitated with the first compressor blade row.

Abstract: A propeller propulsion unit comprising a prime mover, propellers, and rotating force transmission for transmitting the rotating force of the prime mover to the propellers, wherein a counter propeller is fixed to a main shaft and a forward propeller is mounted to be rotatable on the main shaft, and these propellers are rotated in the directions reverse to each other by a belt transmission mechanism having forward and reverse running belts, whereby a lightweight moving body susceptible to an effect by a torque reaction can be steered stably.

Abstract: An engine with counter-rotating rotors, which are coaxially arranged and are driven via a shaft by a turbine whose working medium is supplied by a gas generator with an air inlet, the air inlet (3) being arranged between (in the axial direction) the rotors (1, 2) in order to reduce the noise annoyance (FIG. 1), the rotors driven by an epicyclic gear, the internal gearwheel driving the rear rotor the plant carrier driving the front rotor.

Abstract: A plurality of rotors are individually measured for determining relative eccentricity between forward and aft annular mounting ends thereof. The measured rotor eccentricities are stacked analytically to minimize eccentricity from a centerline axis. The rotors are then assembled axially end-to-end to correspond with the stacked measured eccentricities thereof.

Abstract: Contra-rotating members are used for straightening a fluid flow. The members may take the form of propellers, fans or impellers. The contra-rotation eliminates tangential flow components, and most importantly, eliminates cylindrical vortices. The present invention finds specific use in applications in which toroidal vortices are employed and/or generated.

Abstract: A gear-based airboat transmission is provided for driving a pair of coaxial, counter-rotating propellers. The transmission includes a fore output gear rotatably affixable within a housing and affixable to the inner shaft for rotating the outer propeller. An aft output gear is rotatably affixable within the housing and is affixable to the outer shaft coaxial with the inner shaft for rotating the inner propeller opposite the outer. The aft output gear is generally coaxial with the fore output gear. An intermediate gear shaft has a fore end and an aft end, and both ends are opposedly and rotatable affixable within the housing. This bracing confers additional stability to the transmission, conferring longer life and decreased vibration. An intermediate gear is mounted thereon, and is positioned in driving relation to the fore output gear. A drive gear is rotatably affixable within the housing and is affixed for corotation with a drive shaft.

Abstract: In a rotary engine having rotating cylinders which burns a fuel which is not mixed with oil there is a real problem of centrifugal force form the rotating engine causing oil to flow into the combustion chambers. The disclosed rotary engine has oil reservoirs which are positioned radially outwardly from the pistons so that centrifugal force resulting from engine rotation tends to keep oil out of the combustion chambers.

Abstract: A propulsion device having fins rotating in opposing directions which are adjustable to avoid collision yet which provide opposing strokes similar to fishtails. At least one adjustable fin is connected at an end of a rotatable hollow primary axle which coaxially encompasses a secondary rotatable axle extending a distance from the end of the primary axle and having at least one adjustable fin at that end. Primary fins are adjusted distally during their trust segment of rotation and secondary fins are adjusted proximally during their thrust segment of rotation to enter a common thrust sweep zone. Fins are adjusted in a timed relationship to provide thrust while occupying the thrust sweep zone and thereafter adjusted out of the thrust sweep zone to avoid collision with opposing fins. Fins are additionally adjusted to assume a low resistance configuration during non thrust segments of rotation in order to reduce drag.

Abstract: An improved hydraulic system for a twin propeller marine propulsion unit. A vertical drive shaft is operably connected to the engine of the propulsion unit and carries a pinion that drives a pair of coaxial bevel gears. An inner propeller shaft and an outer propeller shaft are mounted concentrically in the lower torpedo section of the gear case and each propeller shaft carries a propeller. To provide forward movement for the watercraft, a sliding clutch is moved in one direction to operably connect the first of the bevel gears with the inner propeller shaft to drive the rear propeller. A hydraulically operated multi-disc clutch is actuated when engine speed reaches a pre-selected elevated value to operably connect the second of the bevel gears to the outer propeller shaft, to thereby drive the second propeller in the opposite direction.