Abstract: A four-stroke, piston-powered internal explosion (“IE”) engine for providing power output through a rotating crankshaft. The IE engine includes an engine block having power cylinders formed therein for receiving working pistons, bearing means for supporting the crankshaft, and a crankshaft supported within the bearing means having an output end extending outside of the engine block and a plurality of offset power cranks. The IE engine further includes connecting rods operably coupled to the power cranks and configured to transfer power from the working pistons to rotate the crankshaft, and working pistons that are received into the power cylinders and operably coupled to the power cranks. Each working piston has a head end positioned adjacent to a cylinder head to form a compression chamber and is configured to receive power from an explosion of a compressed volume of air/fuel mixture located within the compression chamber, and to transfer the received power to the connecting rods.

Abstract: A connecting rod for an engine may include a sleeve portion having a distal end including a distal aperture configured to be coupled to a piston, and a rod portion having a proximal end including a proximal aperture configured to be coupled to a crankshaft. The rod portion may be configured to reciprocate in the sleeve portion, such that a distance between a center of the proximal aperture and a center of the distal aperture is variable. An engine may include the connecting rod, a power train may include the engine, and a vehicle may include the power train.

Abstract: In a link type variable stroke engine in which a piston, a crankshaft and an eccentric shaft are linked by a linking mechanism, a counterweight part which is provided so that in a projection view on a plane orthogonal to an axis of a rotary shaft, a center of gravity of the counterweight part is located on an opposite side of the axis of the rotary shaft from an axis of the eccentric shaft rotates together with the rotary shaft. Accordingly, it is possible to effectively suppress and lessen half-order inertial exciting force occurring at the eccentric shaft.

Abstract: In a link type variable stroke engine in which a piston, a crankshaft and an eccentric shaft are linked by a linking mechanism, counterweights are provided on the crankshaft so that in a projection view on a plane orthogonal to a rotation axis of the crankshaft, centers of gravity of the counterweights are located on a straight line extending from the rotation axis of the crankshaft in an opposite direction to a direction of a total inertial exciting force when the total inertial exciting force becomes maximum, the total inertial exciting force being obtained by adding inertial exciting forces occurring respectively in movable components of the linking mechanism. Accordingly, it is possible to effectively suppress and lessen inertial exciting force.

Abstract: A piston and connecting rod assembly wherein the piston includes an inner cooling gallery defined in the body thereof beneath the crown of the piston, an outer cooling gallery defined between the skirt of the piston and the body and beneath the crown. A pin bore is formed in the body. A connecting rod is adapted to interconnect the piston and crankshaft where the connecting rod has at least one end with a bore extending therethrough and adapted to be aligned with the pin bore of the piston. At least one end of the connecting rod is in fluid communication with the inner cooling gallery of the piston and includes a reservoir formed on the end of the connecting rod which is adapted to collect coolant therein.

Abstract: An internal combustion engine may include a cylinder block defining a cylinder and a crankshaft including a crankpin. The crankshaft is rotatably received by the cylinder block and rotates along a longitudinal axis, and the crankpin defines a longitudinal axis parallel to and spaced from the longitudinal axis along which the crankshaft rotates. The engine may further include a piston configured to reciprocate within the cylinder and a connecting rod including a distal end and a proximal end, wherein the distal end is operably coupled to the piston. The engine may also include a rocker member including a pivot portion, a coupling portion, and a slot, wherein the pivot portion is operably coupled to the cylinder block, the coupling portion is operably coupled to the proximal end of the connecting rod, and the slot is operably coupled to the crankpin. The slot may be configured to vary a distance between the crankpin and the distal end of the connecting rod.

Abstract: A method of manufacturing a connecting rod assembly including the steps of defining a small end of a connecting rod assembly having a terminal end and then defining a pin bore extending through the small end of the connecting rod assembly. A pair of channels is formed on opposite sides of the small end of the connecting rod assembly wherein the axis of each of the channels is substantially perpendicular to the axis of the pin bore. At least partially annular grooves are formed within the pin bore adjacent the distal end of the pin bore. The connecting rod assembly is then machined to reduce the width of the small end between each channel and the terminal end to provide a small end having a reduced width configuration wherein the grooves are disposed along at least a portion of the distal end to reduce the need to deburr the area adjacent the pin bore.

Abstract: A hydrodynamic bearing (1) for an internal combustion engine is composed of a sliding material whose average maximum roughness value leads an accelerated wear of the sliding material and an accelerated accommodation of a crankshaft during engine operation.

Abstract: A method for manufacturing a connecting rod for an engine contemplates creating a rough connecting rod from high carbon steel. The rough connecting rod is normalized to provide strength and toughness characteristics to the core of the connecting rod for functional operation. A first, second or both ends of the connecting rod are selectively induction hardened to create a durable martensitic structure in those ends. The connecting rod is then cracked and ground to form a final connecting rod for use in internal combustion engines.

Abstract: A force transfer mechanism is provided for an internal-combustion engine. In the most preferred configuration, the force transfer mechanism comprises two inter-connected first class levers that are driven by four pistons. Each of the pistons is driven through its non-powered strokes by the action of the piston in its powered stroke on the first class levers. The force transfer mechanism also drives the crankshaft through a single connecting rod. The force transfer mechanism provides for less frictional loss, and greater efficiency, than a typical internal combustion engine.

Abstract: The dwell cycle crank includes a reciprocating piston having a piston head or cylinder, a main body connected to the piston head, a cap detachably mounted to the main body, an S-shaped cam formed between the main body and the cap, a follower disposed in the S-shaped cam, a rotatable crankshaft, and an offset journal disposed between the connecting bearing and the crankshaft to thereby form a torque arm. The S-shaped cam and connecting bearing create periodic dwells and faster strokes in the crank cycle to maximize volumetric and geometric efficiencies of the engine.

Abstract: An internal combustion engine may include a cylinder block defining a cylinder and a crankshaft having a crankpin. The crankshaft is rotatably received by the cylinder block and rotates along a longitudinal axis, and the crankpin defines a longitudinal axis parallel to and offset by a distance with respect to the longitudinal axis along which the crankshaft rotates. The engine may further include a piston configured to reciprocate within the cylinder and a connecting rod operably coupled to the piston and the crankpin. At least one of the piston and the connecting rod is configured such that a distance between a cross-sectional center of the crankpin and an upper surface of the piston is variable via hydraulic operation.

Abstract: A lubrication system comprising a bore including an inlet for receiving lubrication, an outlet for distributing lubrication, and a inner passageway extending between the inlet and outlet is provided. The outlet may be provided with a wider opening than the passageway. The outlet may further include a groove having a radius of curvature, and defined by a pair of flat or curved sidewalls, and a pair of curved end walls each extending toward the inner passageway.

Abstract: A connecting rod and methods for making the same are disclosed. A connecting rod may include a shaft extending between a piston pin end and a crankshaft pin end. The piston pin end generally defines a bore opening extending along an axis. The connecting rod further includes a bore surface formed integrally with the piston pin end and extending about an inner circumference of the bore opening. The bore surface may define a plurality of dimples that extend axially along the bore surface. The bore opening further may further include profiled surfaces adjacent opposing ends of the bore opening.

Abstract: An internal combustion engine may include a cylinder block defining a cylinder, and a crankshaft defining a crankpin, wherein the crankshaft is rotatably received by the cylinder block and rotates about a longitudinal axis. The internal combustion engine may further include a piston configured to reciprocate within the cylinder, and a connecting rod operably coupled to the piston and the crankpin. The connecting rod may include a first rod element having a first distal end and a first proximate end, wherein the first distal end is operably coupled to the piston. The connecting rod may further include a second rod element having a second distal end operably coupled to the first proximate end of the first rod element, and a second proximate end operably coupled to the crankpin, wherein the first rod element and the second rod element are pivotally coupled to one another.

Abstract: The crankshaft-free internal combustion engine which is of the type that contains at least one cylinder having a longitudinal axis, at least one piston that has a pivot pin and is slidingly installed in the cylinder, a main driveshaft having a central axis, which is offset at a distance from the longitudinal axis of the cylinder, and a cylindrical eccentric which is eccentrically and non-rotationally secured on the main drive shaft A distinguishing feature of the engine is a connecting rod that has a substantially L-shaped configuration formed by one portion which is substantially straight and is pivotally connected to the pivot pin of the cylinder and a second portion which is substantially transverse to the first portion and pivotally receives the cylindrical eccentric. The distance from the central axis of the main driveshaft to the longitudinal axis of the cylinder is always greater than 0. Such a construction significantly improves efficiency of the engine.

Abstract: A process for manufacturing connecting rods is provided which comprises the steps of compacting, sintering, and powder forging a powder metal comprising a carbon source and a prealloyed powder consisting essentially of iron and copper. The connecting rods made from this process have sufficient hardness and strength to be used in an engine and do not require any additional quenching or tempering.

Abstract: The invention provides a method of manufacturing a ferrous monolithic component and the component that results from the method. The method of the invention utilizes selective rapid cooling of the portion of the component that is desired to have increased strength and selective controlled cooling of the portion or portions which are desired to be more machinable. The controlled cooling may include cooling, re-heating and re-cooling. The result is a component with local high strength in the rapidly cooled zones and locally altered metallurgical properties to improve machinability in the more slowly cooled zones.

Abstract: A connecting rod and methods of making a rod are disclosed. A method of making a connecting rod may include the step of providing a connecting rod blank, where the connecting rod blank includes a crankshaft end and a piston pin end. The method may further include forming a crankshaft pin recess in the crankshaft end of the connecting rod blank and a piston pin recess in the piston pin end, and forming at least one lubrication recess in the piston pin end of the connecting rod blank. The lubrication recess and the piston pin recess may both formed concurrently.

Abstract: The Internal-Combustion Engine is set forth, in which when in use there is no lateral component of the force on the piston which is taken up by the slider rolling by the bearings. As a result of this the cylinder compression is improved, power losses on friction are reduced and wear out of the cylinder is decreased. Also due to the absence of the lateral component of the force on the piston, the latter can be made in a relieved version, e.g. without a skirt and with two compressing rings in one groove.

Abstract: A sliding component for an internal combustion engine includes a component main body made of titanium or a titanium alloy, a surface hardened layer provided on a surface of the component main body, a diamond-like carbon film provided on the surface hardened layer, and a titanium layer provided between the surface hardened layer and the diamond-like carbon film.

Abstract: A four cycle piston engine has a crankshaft that includes a crank pin and a guide pin rotatable as a unit around the crankshaft rotational axis. The connecting rod has a linear trackway that slidably engages the guide pin so that the rod has linear slidable motion relative to the crankshaft. During the power stroke the connecting rod applies a pulling force to the crank pin via a special force-transmitting linkage.

Abstract: A connecting rod assembly includes a first end and a second end having bore extending therethrough and adapted to be aligned with a piston pin bore and receive a piston pin. The second end further includes a terminal end and has a reduced width configuration. The reduced width configuration is formed by machining a pair of channels that are formed on opposite sides of the second end between each channel and the terminal end. The bushing includes at least partially annular grooves disposed on the contact surface along at least a portion of opposed distal ends, where the grooves substantially eliminate the need for the small end to undergo a deburring process after the second end is machined to provide a reduced width configuration.

Abstract: A connecting rod includes an elongate rod shank with a small end at a first axial end of the rod shank and a big end at the second axial end of the rod shank. The big end includes a body part and a cap part adapted to releasably couple to the body part. When the cap part is coupled to the body part, the cap part and body part cooperate to define a crank pin receiving bore and abut at first and second spaced apart interfaces. The cap part defines an aperture proximate the first interface that is adapted to receive a threaded fastener that engages and clamps the cap part to the body part. The cap part includes a side portion that extends radially beyond a largest radius from a crank pin bore center to the first interface. The side portion is substantially radially concentrated adjacent the first interface.

Abstract: Disclosed is a connecting rod for a combustion engine, comprising a small connecting-rod eye that is provided with a plain bearing surface and is used for accommodating a piston pin, and a large connecting-rod eye which is provided with a plain bearing surface and embraces a crankshaft journal. In order to very effectively and inexpensively prevent the piston pin and the crankshaft journal of the connecting rod from jamming and wearing off, a self-lubricating coating made of a thermally cured resin which contains embedded solid lubricant particles is applied directly to at least one of the plain bearing surfaces by means of rotary atomization.

Abstract: An improved two-piece connecting rod (800) that connects a reciprocating piston with a crankshaft in an internal combustion engine. The connecting rod (800) has a shank portion (810, 860), a cap portion (820, 870) and projections (830, 880, 882) extending from one or both of the shank (810, 860) and cap portions (820, 870). When the shank (810, 860) and the cap (820, 870) are connected, the projections (830, 880, 882) mate with the opposite side with an interference fit, thereby resisting relative motion between the shank (810, 860) and the cap (820, 870) along the split-line (A?).

Abstract: In an opposed piston, compression ignition engine two crankshafts are single-side mounted with respect to a row of cylinders, which is to say that the crankshafts are mounted so that their axes of rotation lie in a plane that is spaced apart from and parallel to a plane in which the axes of the cylinders lie. Each piston of the engine is coupled to one of the crankshafts by a single linkage guided by a crosshead. The piston has a piston rod affixed at one end to the piston. The other end of the piston rod is affixed to the crosshead pin. One end of a connecting rod swings on the pin and the other end is coupled to a throw on a crankshaft. Each crosshead is constrained to reciprocate between fixed guides, in alignment with the piston rod to which it is coupled.

Abstract: This is a method of forming a fracture start portion of a ductile metal part on an inner circumferential face of a through hole by irradiating laser to an opposing position of the inner circumferential face of the thorough hole of the ductile metal part having a predetermined through hole and by forming a large number of recess portions separated with a predetermined distance at a predetermined interval from one opening to the other opening of the through hole, in which a recess part is formed, instead of by focusing the laser exactly onto the inner circumferential face of the through hole, by irradiating it onto the inner circumferential face of the through hole while defocusing from the inner circumferential face of the through hole by a predetermined amount as well as by supplying an assist gas to a position of the laser irradiation, and the laser is moved linearly at a predetermined speed from one side opening to the other side opening on the inner circumferential face of the through hole while irradiatin

Abstract: The invention relates to a method for producing a bearing surface (5) of a radial shaft bearing from electrically conductive material. In said method, the contour of the bearing surface (5) is machined down in a first machining step, and the bearing surface (5) is electrochemically machined in a subsequent step. Also disclosed are an electrode for electrochemical machining as well as a connecting rod (1) to be used in machines.

Abstract: A connecting rod for a piston assembly includes first and second guidance members for guiding a piston assembly within a cylinder during piston stroke along a first axis. The guidance members are supported by first and second support ribs extending from a shaft of the connecting rod and include first and second sliding surfaces for contacting side walls of the cylinder. The connecting rod includes an attachment boss disposed at a first end of the shaft and defines a second axis perpendicular to the first axis. The first and second support ribs extend radially outwardly from the attachment boss and are spaced radially about the second axis by approximately 180 degrees.

Abstract: A method for forming a remateable cracked titanium powder base alloy connecting rod using a titanium alloy powder processed to produce a connecting rod.

Abstract: The efficiency of a multi-cylinder engine is optimized by coupling the volume change in each cylinder to a common coordinate under conditions such that, at each point in the engine's cycle, the energy necessary to produce a differential volume change is reduced substantially to zero. Each cylinder is coupled to the common coordinate through a cam or through a variable-length connecting rod. The same efficiency optimization may be achieved with various combinations of cylinders in a two-cycle engine, a four-cycle engine, or a multi-cylinder compressor.

Abstract: A rotary shaft, such as an automotive crankshaft, for rotation about an axis carries an eccentric substantially circular section, radially extending flap (6), connected to the radially outer surface of which is an annular housing (16) affording a cavity defined in part by radially inner and radially outer coaxial cylindrical surfaces. The axis (22) of the cavity is offset from the axis (4) of the shaft. The cavity accommodates an annular inertia mass (20) and the radially inner and outer surfaces of the cavity are opposed to radially inner and outer surfaces, respectively, of the inertia mass whereby there are two pairs of opposed surfaces. One of the said pairs constitutes bearing surfaces guiding relative motion of the inertia mass and the housing (16) about the axis (22) of the coaxial cylindrical surfaces.

Abstract: The present invention relates to a connecting rod assembly and method of manufacturing same. The method includes defining a small end of a connecting rod having a terminal end and defining a pin bore extending through the small end. A pair of channels is forged on opposite sides of the small end, such that each of the channels is substantially perpendicular to the pin bore. A bushing having a contact surface including at least partially annular grooves and opposed distal ends is subsequently formed and installed into the pin bore of the small end. Following installation of the bushing, the connecting rod is machined to reduce the width of the small end between each channel and the terminal end to where at least a portion of the grooves are disposed along the distal ends to reduce the need to deburr the area adjacent the pin bore.

Abstract: A needle roller bearing comprises a plurality of needle rollers and a retainer. The retainer includes a pair of annular parts and pillar parts connecting the pair of annular parts so as to form pockets in which the needle rollers are housed. A sidewall surface of the pillar part has a sheared surface punched by a punching blade so that the pockets are formed, and a fractured surface fractured by a material pressed by the punching blade. The needle roller is guided by the sheared surface.

Abstract: The piston is connected to the crankshaft via a connecting rod, while the crankshaft is disposed between the wrist pin and the combustion chamber. This way the combustion is shifted to the slow dead center, enabling the diesel to perform at higher revs, improving the spark engine efficiency and making HCCI combustion easier. Though the crankshaft is of one piece, more connecting rods can be used for a piston. As opposed piston, the PRE engine further combines top specific power, top thermal efficiency, built in scavenging pumps, and compactness.

Abstract: A method of jointly fitting or removing a piston and a cylinder liner in or from an engine block of an internal combustion engine is provided. During the fitting or removal operation, the cylinder liner is supported or held on a contact shoulder which is arranged at a connecting rod of the piston or at the piston.

Abstract: The present invention relates to a method of manufacturing a connecting rod assembly having a stepped small end. The method includes defining a small end of a connecting rod assembly having a terminal end and defining a pin bore extending therethrough. A pair of channels are formed on opposite sides of the small end, perpendicular to the pin bore and a bushing is subsequently installed into the pin bore. Where a connecting rod assembly does not include a bushing the method includes defining a small end having a pin bore and forming pair of channels on opposite sides of the small end. A contact surface is then defined within the pin bore to engage a piston pin and the small end is machined to provide a stepped configuration. The connecting rod assembly is then machined to reduce the width of the small end to provide a stepped configuration.

Abstract: The present invention relates to a connecting rod (10) for an internal combustion engine, having a small connecting rod eye (20) for holding a piston pin and having a large connecting rod eye (30) for holding a crank pin, wherein at least one connecting rod eye (20; 30) has at least one geometric deviation from a cylindrical inner contour. It is provided according to the invention that the at least one connecting rod eye (20; 30) is formed by a bore (22; 32) with a cylindrical inner contour, that the bore (22; 32) is provided with a coating (23; 33) comprising a resin with solid lubricant particles embedded therein, and that the coating (23; 33) forms the at least one geometric deviation from the cylindrical inner contour of the at least one connecting rod eye (20; 30). The present invention also relates to a method for producing a connecting rod of the type.

Abstract: A reciprocating device which may be operated either as a compressor or an engine. Each cylinder has a reciprocating piston connected to a piston rod. Dual cylinder chambers are located in each cylinder on opposite sides of the piston. The pistons are connected to a scotch yoke which translates the reciprocating motion of the pistons to rotary motion at a shaft in the engine mode. In the compressor mode, the shaft is connected to a power source. The engine components such as the pistons, rods, bushings and cylinder lines may be high quality steel or a ceramic.

Abstract: A connecting rod of an internal combustion engine, comprising a connecting beam section serving as a main body of the connecting rod. Big and small ends are located at the opposite ends of the connecting beam section. A first joining section is located between the connecting beam section and the big end to connect the connecting beam section and the big end. A second joining section is located between the connecting beam section and the small end to connect the connecting beam section and the small end. In this connecting rod, each of the first and second joining sections gradually and continuously decreases in cross sectional area toward the connecting beam section and has a strength distribution in which a strength increases with a decrease in the cross sectional area.

Abstract: A multiple watt-linkage force transfer mechanism is provided for an internal-combustion engine. The force transfer mechanism comprises two “bell cranks” that are used to drive a single crankshaft through a watt linkage mechanism. Each bell crank, in turn, is driven by two pistons through corresponding watt linkage mechanisms. The watt linkages connected to the pistons enable the connection ends of the pistons to travel along substantially straight paths, significantly reducing side loads against the piston walls. Also, all four pistons preferably drive a single connecting rod. This changes the role of the crankshaft—and the corresponding strength and rigidity requirements for the crankshaft—by reducing the necessary number of rod journals and main journals on the crankshaft.

Abstract: A piston/connecting rod arrangement for an internal combustion engine has a piston upper part with hub supports which lie opposite one another and have hubs and hub holes which delimit a recess, in which the small connecting-rod eye of a connecting rod is arranged. A piston pin is mounted in the small connecting-rod eye and the hub holes. There is at least one oil-guiding face to be provided on that face of the hub support which faces the recess. At least one oil-guiding face opens into at least one oil-collecting space which is arranged in the hub hole, in such a way that the oil-guiding face guides oil into the oil-collecting space.

Abstract: A Stirling cycle machine. The machine includes at least one rocking drive mechanism which includes: a rocking beam having a rocker pivot, at least one cylinder and at least one piston. The piston is housed within a respective cylinder and is capable of substantially linearly reciprocating within the respective cylinder. Also, the drive mechanism includes at least one coupling assembly having a proximal end and a distal end. The proximal end is connected to the piston and the distal end is connected to the rocking beam by an end pivot. The linear motion of the piston is converted to rotary motion of the rocking beam. Also, a crankcase housing the rocking beam and housing a first portion of the coupling assembly is included. A crankshaft coupled to the rocking beam by way of a connecting rod is also included. The rotary motion of the rocking beam is transferred to the crankshaft.

Abstract: Disclosed is a connecting rod for a combustion engine, comprising a small connecting-rod eye that is provided with a plain bearing surface and is used for accommodating a piston pin, and a large connecting-rod eye which is provided with a plain bearing surface and embraces a crankshaft journal. In order to very effectively and inexpensively prevent the piston pin and the crankshaft journal of the connecting rod from jamming and wearing off, a self-lubricating coating made of a thermally cured resin which contains embedded solid lubricant particles is applied directly to at least one of the plain bearing surfaces by means of rotary atomization.

Abstract: A powertrain for an internal combustion engine having a connecting rod with a piston supported at one end which is adapted for easy assembly and disassembly without expensive tools. The piston is supported on the connecting rod by a universal joint defined by a spherical surface of an integral connecting rod end and an end plate of the piston having a correspondingly configured spherical recess. The connecting rod end is formed with flat surfaces on opposed sides for engagement by releasable securement members which maintain the piston in proper seated position on the connecting rod during normal usage, but which are releasable to permit removal of the piston upon rotation of the connecting rod 90° about its longitudinal axis.

Abstract: F&C engine includes a central shaft mounted a cylindrical cam, that formed with two pieces of different diameter steel tubes, as the inner and outer walls, the upper end of the outer wall, placed a driving flange, to drive the engine timing devices. on the two layer walls (for light duty or small engine the single layer wall is acceptable) with pairs of peak and valley channel, a overdrive clutch; inside the cam contained a dynamotor to form a hybrid; a magnetic clutch, for engaging or disengaging the cylindrical cam; a driving plate for driving the devices that not related to the engine timing; a cylinder to produce power and transfer the power to the cam through a push rod; a guide plate to guide the push rod; many support rollers for supporting the cam; a tubular case with foot for contain and support the engine.

Abstract: A small end member constituting a small end, a column member constituting a column portion, and a big end member constituting a big end of a connecting rod are formed as separate members. In addition, the small end member and the big end member are each made of a high-rigidity material, and the column member is made of a high-strength material. These members are integrally bonded by liquid phase diffusion bonding, thus providing a connecting rod that can achieve suppression of stress concentration.

Abstract: A cast metal connecting rod of the type used in a reciprocating piston engine has a beam section between two end sections. The beam section and the end sections are integral with one another and are at least partially made of a cast metal material. At least the beam section of the connecting rod includes an insert made of a sintered powder metal material. The insert is at least partially encapsulated by the cast metal material of the connecting rod. The insert reinforces the connecting rod and can help match characteristics of surrounding or mating parts of the engine that are made of materials more similar to the material of the insert than the cast metal of the connecting rod. The cast metal material, for example aluminum alloy, of the connecting rod can also provide localized regions of high machinability where needed.

Abstract: An internal combustion engine which includes two parallel crankshafts positioned in crankcases, a cylinder positioned on a side of the crankcases, a piston movably disposed within the cylinder, and connecting rods linked to the piston and extending from respective crankshafts. Positions at which the two connecting rods are linked to the piston and the crankshafts are constantly kept symmetrical with respect to a cylinder axis when the two crankshafts rotate in opposite directions.