Abstract: An antivibratory system is provided by means of a servo motor driven shaker affixed to the head or bed frame of a tufting machine and programmed for rotation of a balancing weight to minimize vibration caused by operation of tufting machine at a particular speeds and needle stroke lengths.

Abstract: A noise and vibration damper for use with a rotatable structure, such as a driveshaft assembly for a vehicular drive train system, includes an inner member, an elastomeric member that extends about the inner member, and an outer member that extends about the elastomeric member. The inner member is formed from a sheet of material that has been deformed to a desired shape, while the outer member is formed from a tube of material having a length that is selected to provide the desired dampening frequency. The natural resonant frequency of the noise and vibration damper can be adjusted by varying either or both of the shape of the inner member or the axial length of the outer member of the noise and vibration damper. In both instances, the weight distribution of the components of the noise and vibration damper is altered.

Abstract: The invention relates to a crank shaft having a guide groove allowing the movement of a crank pin so as to adjust the reciprocating distance of a piston according to the rotating direction. The crank shaft comprises a rotation shaft for inducing the rotating movement; and a crank arm connected to the rotation shaft at the center and having at one side a guide groove provided horizontal in the radial direction for allowing free movement of a crank pin and elastic means provided within the guide groove to enhance the performance of sucking and compressing fluid. Accordingly, smooth and soft compression is enabled to prevent the overpressure loss. Also, the sucking performance is improved by using additional retreat due to the elastic means.

Abstract: A crankshaft is provided with a plurality of counterweights which are asymmetrically formed so that one surface has a shape which induces a flow of air and oil mist in a preselected and preferred direction. This shape also improves the aerodynamic characteristic of the counterweight and reduces the friction that the counterweight would otherwise experience as it rotates about the rotational axis of the crankshaft. A tapered surface is provided on a lower surface of each crankshaft and the tapered surface is positioned at a leading edge of each counterweight.

Abstract: A torsional vibration damper for the crankshaft of an internal combustion engine. The damper includes a housing and a damper mass arranged in the housing and embedded in a fluid. The damper mass is joined to the housing by a spring device. The spring device is embodied and arranged in such a way that the damper mass is prevented from knocking against the housing.

Abstract: An internal combustion engine for an aircraft is described. The internal combustion engine includes a crankshaft defining first and second ends, a propeller, and a transmission disposed between the first end of the crankshaft and the propeller, operatively connecting the propeller to the crankshaft. A torsion bar is disposed between the first end of the crankshaft and the transmission, operatively connecting the crankshaft to the transmission. A torsional vibration damper is operatively connected at one of the first and the second ends of the crankshaft.

Abstract: A torsional vibration damping apparatus, especially a web damper for mounting on a crankshaft of a piston engine, particularly an internal combustion engine for suppression of natural torsion frequencies from crankshafts can now be economically produced. The apparatus comprises a housing fastened to the engine crankshaft to which at least one rotary mass is coupled with spring elements disposed between the housing and the rotary mass allowing the apparatus to be pre-assembled. Advantageously, multiple parts of the torsional vibration damping apparatus, such as the housing can now be fabricated from more economic sheet metal in place of more costly cast parts.

Abstract: An internal combustion engine comprises a crankshaft having at least one rod journal and at least one main journal, a cylinder block rotatably supporting the crankshaft, at least one coupling member rotatably coupled to the crankshaft. The at least one coupling member has an annular, substantially cylindrical inner wall defining a crank bore circumscribing one of the main journals and/or one of the rod journals of the crankshaft. Moreover, the inner wall of the crank bore has at least one substantially annular recessed portion formed therein which is axially spaced from opposite ends of the inner wall. The internal combustion engine further comprises a vibration dampener assembly disposed in the recessed portions formed in the coupling member thereby substantially dampening and isolating transmission of vibrations between the connecting rods and the crankshaft and between the connecting rod and the cylinder block.

Abstract: A crankshaft assembly (18) for a VDIC engine (16) of an automotive vehicle (14) includes a crankshaft (44) integrated within an internal combustion engine (16). The crankshaft (44) has at least two pendulum vibration absorber assemblies (58) integrated therein. Each pendulum vibration absorber assembly (58) includes a counterweight member (60) integrally formed within the crankshaft (44). The counterweight member (60) has a desired counterweight mass for providing, in conjunction with the mass of the assembly (58), first order engine balance. The counterweight member (60) has a pendulum (64) pivotally coupled thereto. The pendulum (64) has a desired mass and geometry for attenuating torsional fluctuation.

Abstract: An engine suitable for mounting in a small planing boat, which both lowers the center of the gravity of the boat, and enables a degree of freedom in arranging accessories. Balancers are arranged on the left and on the right of a crankshaft on a parting face of an engine. The engine is mounted in the body of the small planing boat surrounded by a hull and a deck. A starter motor and an idle gear of one balancer are arranged on the side opposite the starter motor, with the crankshaft between them. Also disposed between the idle gear and the starter motor is a cylinder. An oil tank is provided at the front of the engine, and two oil supply passages leading to the balancer supports are formed in the case of the oil tank.

Abstract: A shaft damping device includes a damping ring having a splined bore, a shaft having at least one spline, and a fluid feed system. The shaft is disposed within the splined bore such that the splines of the shaft mesh with the splined bore, forming a damping space therebetween. The fluid feed system is operable to control a quantity of a fluid within the damping space.

Abstract: In an engine operated machine system including a hollow support rod connected at one end to an engine through a vibration insulator, an auxiliary weight is mounted at the other end of a crankshaft for generating a centrifugal force in the same direction as an inertia force of a piston, when the piston reaches top and bottom dead centers. Thus, it is possible to bring a center of gravity of the engine closer to the position of the vibration insulator, thereby suppressing the application of the vibration from the engine to the support rod to the utmost.

Abstract: An improved counterweight for a crankshaft having a main body which is adapted to rotate about a predetermined axis. The main body includes a major lobe on one side of the axis and a diametrically opposed minor lobe. Two recessed surfaces extend on opposite sides of a diametric line bisecting the major and minor lobes so that the recessed surface forms a portion of the outer periphery of the crankshaft. A pair of inserts is provided and each insert has a surface complementary to one of the recessed surfaces on the main body. Each insert is inserted into the main body to form a generally cylindrical counterweight.

Abstract: A working device, especially a ramming device for compacting soil, or a hammer, has a crank mechanism for producing a controlled vibration. The crank mechanism is coupled with a set of springs. According to the invention, the crank disk belonging to the crank mechanism is provided with a counter-mass whose center of gravity is shifted around an angle not equal to 180° from the center of gravity of a crank pin on the crank disk, in relation to the axis of rotation of the crank disk. This prevents vibrations which would be unpleasant for the person operating the device from occurring.

Abstract: An oil pump attachment structure is provided for an engine. The oil pump attachment structure includes an oil pump 9 coaxially driven by the crankshaft 2. A pump housing 10 of the pump 9 is disposed between a front cover 7 for covering timing chains 5a, 5b and crank sprockets 3a, 3b while leaving a clearance against the front cover 7. The pump housing 10 is also fastened to a cylinder block 1 so as to straddle the timing chains 5a, 5b, through stays 11a, 11b, 11c by bolts 12. With this arrangement, pulsation produced during the operation of the oil pump 9 is not transmitted to the front cover 7 directly, so that noise radiated from a front face of the front cover 7 can be reduced.

Abstract: A locator bushing member for assembling a damper/pulley member to a crankshaft as part of a modular housing assembly. The locator bushing temporarily secures a damper member to a housing assembly until the housing assembly is secured to the front of a vehicle engine and the damper member is subsequently secured to the nose of the crankshaft. A seal member is typically provided in order to seal the joint between the damper member bushing and housing member. Mating ridge and groove mechanisms, or equivalent mechanisms, can be provided to more securely affix the damper member, locator bushing member and housing member together.

Abstract: A balancing mechanism for an engine that has a rotating crankshaft and reciprocating pistons such as those engines used in automobiles, aircrafts, boats, piston-driven compressors, piston-driven slider crank mechanisms, etc. The present balancing mechanism may comprise a first balance mass non-rotatably affixed to the crankshaft and a second balance mass rotatably supported on the crankshaft. A driver assembly is affixed to crankshaft to cause the second balance mass to rotate in a direction that is opposite to the direction in which the crank shaft is rotating. The driver assembly may include auxiliary gears configured to transport rotary power to auxiliary components.

Abstract: The engine balancer unit includes a first oil pan attaching to the bottom of an engine cylinder block, a second oil pan attaching to the first oil pan to close a bottom of the first oil pan, and a unitary case inserted in the first oil pan to support counterbalance shafts with balance weights. The cylinder block does not need to be modified to install the engine balancer unit because the first oil pan which encloses the unitary case is attached under the cylinder block. Further, fluid tightness between the first oil pan block is not spoiled by the unitary case because the unitary case is provided inside the first oil pan. Furthermore, fluid tightness between the first oil pan and the second oil pan is not spoiled by conventional fastening structure.

Abstract: In a reciprocating machine having piston/cylinder units arranged in line, a cam member having diametrically opposed cams is fixed to a crankshaft with the cam member arranged in a central transverse plane. A balancing mass is in contact with the cam member by way of a cam roller. The cam roller is maintained in permanent contact with the cam member by a compression spring which is seated against the machine. The cams are identical and neutralize second order free inertial forces.

Abstract: A method and apparatus for internally damping vibration and impulse within a crankshaft utilizes the mass of high density inserts and an energy absorbing medium. By placing the inserts into bores in the counter balance weights and surrounding the inserts with the energy absorbing medium, the inserts are allowed to "float" within the counter balance weight, achieving a pendulum damping effect as the inertial mass of the insert responds to vibration propagating along the crankshaft in both directions. In one embodiment the energy absorbing medium is solid but flexible material; in another embodiment the energy absorbing medium is viscous fluid. Because counter balance weights are located at different points along the crankshaft, the present invention damps vibration closer to the sources of the vibration than conventional dampers, thus reducing the propagation of vibration throughout the length of the crankshaft.

Abstract: An adjustable counterweight apparatus for use in vibratory machines, such as concrete molding machines, where a rotating shaft is engaged with a vibrating or oscillating load. The counterweight includes a first bore for receiving a rotating shaft, and a second bore for receiving a plug having a weight selected to dynamically balance the rotating shaft and oscillating load.

Abstract: A double-mass type dynamic damper mounted on a rod-shaped oscillating member, which includes a first damper system and a second damper system that are tuned to two different frequency ranges. Each of the damper systems includes a cylindrical mass member disposed radially outwardly of the oscillating member, and an elastic support member for elastically supporting the mass member with respect to the oscillating member. The elastic support members of the two damper systems are disposed in series and connected to each other in the axial direction. The dynamic damper further includes an elastic connector formed by adjacent parts of the two elastic support members, for elastically connecting axially opposed faces of the two mass members.

Abstract: An improved engine gear drive train arrangement is provided which effectively minimizes the crankshaft torsional vibrations at the location of the gear train, for engines with a front gear train. A flywheel is resiliently connected to the rear end portion of the crankshaft so as to resiliently connect a driven unit to the crankshaft. An extra inertial device is connected to the front end portion of the crankshaft and includes an inertia so selected as to cause a nodal point of the first torsional vibration mode of the crankshaft to be located in the vicinity of the crank gear to minimize the amplitude of torsional deflection of the crankshaft at the crank gear. Also, the device for resiliently connecting the flywheel to the rear end portion of the crankshaft may include resilient members positioned in cavities formed by engaging rings.

Abstract: A reduction in size and weight of an engine block is achieved by the described balancer shaft arrangement in which the balancer shaft bearing balancer weights at opposite ends is rotatably mounted in a pipe member fixedly attached to an exterior wall of the engine block. The balancer shaft contains an axial opening which communicates with the lubricating oil supply system of the engine in order to conduct lubricating oil to associated parts of the arrangement.

Abstract: In an energy generating system, which is preferably suitable for satellites and space stations, a total of four Stirling engines are combined together into a cross-shaped unit, in the center of which is arranged a cross-gear drive that is acted upon by the pistons of the Stirling engines. Therein, two planet gears revolve around in internally toothed annular gears. The common shaft of the annular gears is connected with the piston rods of the Stirling engines by an inner crankshaft, which simultaneously carries the planet gears, and by an outer crankshaft articulately connected with the inner crankshaft. Both crankshafts comprise counterweights as balancing masses, whereby a complete mass balancing of the cross-gear drive and therewith a vibration-free operation of the entire arrangement is achieved.

Abstract: In a method and apparatus for detection of reciprocating machine faults and failures, data representing velocity variation waveforms of a reciprocating machine having a plurality of cylinders is acquired. The acquired data is transformed using a computer to produce torque waveforms corresponding to the acquired velocity variation waveforms. An optimization algorithm is used to obtain a number of parameters corresponding to the number of cylinders of the machine for both compression and expansion cycles of the machine in an independent manner and for each cylinder. The optimized parameters and the transformed torque waveforms are then presented to the user to identify each cylinder's condition.

Abstract: A camshaft vibration damper comprises an inertia ring having a friction clutch surface disposed in driving contact with a complementary clutch surface and a spring for biasing the clutch surfaces toward one another. The complementary clutch surface may be disposed on a drive member, for example, a camshaft sprocket or similar structure rotating with the camshaft. The spring is a compression spring, preferably a Belleville spring washer, which biases the two friction clutch surfaces together. The inertia of the inertia ring opposes the instantaneous variations in rotational speed (d.theta./dt) of the camshaft causing relative rotation between the inertia ring and the drive member thereby reducing vibration without resisting camshaft rotation. Relative motion at the clutch face between the inertia ring and the drive member results in energy absorption and dissipation thereby minimizing unwanted vibration.

Abstract: A crankshaft of a V-type 6-cylinder internal combustion engine including first to sixth crank pins connected with connecting rods, having first to fourth crank journals between the first to sixth crank pins, and first to ninth crank arms between first to sixth crank pins and the first to fourth crank journals, the combination including a first balance weight provided to the first crank arm, a center of gravity of the first balance weight being mal-distributed to a lower part with respect to a center axis of the crankshaft, a second balance weight provided to the second crank arm, a center of gravity of the second balance weight being mal-distributed to a lower part, and deviated from the first balance weight in a counterclockwise direction, third and fourth balance weights provided respectively to the fourth crank arm and sixth crank arm, the centers of gravity of the third and fourth balance weights being mal-distributed to be orthogonal to the center of gravity of the first balance weight in a clockwise dir

Abstract: The disclosure teaches a piston engine having at least one reciprocating piston, a crankshaft rotatable within a support bracket, and a piston rod connecting the piston with the crankshaft, with an inertial mass mounted on the support bracket for movement with three degrees of freedom. A method for retrofitting a piston engine is also provided.

Abstract: A damping mass is housed in a rolling chamber formed in a flywheel body, and executes a pendulum motion in a radial direction according to torque fluctuations. If md is the mass of the damping mass, Id is tile moment of inertia of the damping mass, rd is the radius of tile damping mass, n is the order of torque fluctuations of a rotating drive mechanism, R is the distance from the center of rotation of the body to the center of the pendulum motion of the damping mass, and L is the distance from the center of the pendulum motion of the damping mass to the center of gravity of same, the actual ratio R/L is set larger than a value Ro/Lo obtained from the theoretical relation Ro/Lo=n.sup.2. [1+{Id/(md.multidot.rd.sup.2)}] to reduce rotational fluctuations. In this way, the effect of manufacturing defects and dimensional variations due to wear on rotational fluctuations is reduced.

Abstract: The disclosure relates to a damper pulley that exhibits a good damping effect and has a preferable resonance ratio. An annular damper-mass member is joined to an annular surface of a plate portion of a pulley through a first resilient rubber member. Two fan-like concave portions are formed in the surface of the annular damper-mass member, which faces the annular surface of the plate portion, at symmetrical positions with respect to the center of rotation of the pulley. Two projections are formed on the annular surface of the plate portion so as to perpendicularly project into the fan-like concave portions. A second resilient rubber member is interposed between each concave portion and projection. When torsional vibrations are exerted, each second resilient rubber member produces compression deformation, thereby generating a large spring force, whereby the resonance frequency against the torsional vibrations sufficiently increases even when the inertia moment of the mass member is increased.

Abstract: A balancing apparatus for suppressing engine vibrations is disclosed. The balancer apparatus includes a helical drive gear that is rotatable together with the crank shaft. A first driven helical gear for is driven by the drive gear and a second driven helical gear is driven by the first driven gear. Support shafts are provided to carry each of the driven gears and a weight associated therewith. A case is provided about the driven gears and carries the support shafts.

Abstract: A system for absorbing torsional vibration in a shaft which is drivingly rotated about an axis and wherein the shaft is exposed to torsional disturbances which tend to cyclically increase and decrease the rotational speed of the shaft utilizes a body attachable to the shaft for rotating therewith as the shaft rotates about its axis of rotation and cylindrical rolling elements positioned within cavities disposed in the body. During operation of the system, the torsional disturbances induce pendulum-like motion of the cylindrical elements within the cavities in a manner which absorbs torsional vibration of the shaft. The cylindrical elements, the cavities and the torsional disturbances are related to one another in accordance with an equation which optimizes performance of the system and circumvents time-consuming trial and error techniques during design of the system.

Abstract: A balancer device installed to an in-line engine comprises a balance shaft which includes first and second journals at which the balance shaft is supported through first and second bearings. The first bearing is disposed near the front side of the engine and set in a retainer for rotatably fixing the balance shaft. The second bearing is disposed near a generally center portion in the axial direction of the crankshaft and secured to a cylinder block. A pair of unbalance portions are disposed near the second journal. The diameter of the first journal is formed smaller than that of the second journal to suppress the friction loss of the first journal.

Abstract: Three balance mechanisms for a press machine are described. The first balance mechanism for a press machine comprises a balance weight 91 mounted on a crankshaft 86 of the press machine, a balance weight 92 mounted on a balance mechanism shaft 93, a motor for rotating the shaft 93 and a control system for the motor. The control system ensures that the balance mechanism shaft 93 rotates in the opposite direction to, but at the same speed as, crankshaft 86. The balance weights 91 and 92 balance the primary shaking forces which arise in the press machine along the axis of movement of its ram 83. In the second balance mechanism, balance weights are mounted on two separate shafts rotated by a motor and connected by a gear mechanism. In the third balance mechanism, one balance weight is mounted on the crankshaft, another balance weight is mounted on a shaft rotated by a motor, and a further pair of balance weights are mounted on a pair of shafts rotated by a motor at twice crankshaft speed.

Abstract: A crankshaft vibration damper which has an unique elastomer member positioned between a hub and outer annular inertia member. The hub is configured for connection to the accessory drive end of the crankshaft. The inertia member may or may not be grooved to accept an accessory drive belt. The resilient elastomer member is dimensionally and chemically developed to dampen torsional and bending vibrations when assembled between a corresponding curved hub and inertia member. The radially outward or inward curvature of the hub and inertia member is selected to be sufficient to effectively reduce crankshaft bending vibration.

Abstract: A high gain and high torsional stiffness servo axis drive system for machine tools is described as providing improved stability. This system includes a servo motor mounted on a base and connected to a C-Axis spindle drive arrangement via a toothed drive belt. A first by-damper is attached to the spindle drive pulley and tuned for damping torsional oscillations of the servo output shaft, belt, and spindle when the system is not fitted with a workpiece. An independent second damper is attached to the driving pulley of the servo motor and tuned for damping torsional oscillations of the entire servo drive system when the system is loaded with a workpiece. The resulting servo axis drive system features improved stiffness and can be adapted to a variety of predetermined loading conditions by convenient retuning of the second damper. At least the second damper is provided as a combination of a damper mass ring attached to the servo motor pulley by a plurality of viscoelastic damping elements.

Abstract: Three balance mechanisms for a press machine are described. The first balance mechanism for a press machine comprises a balance weight 91 mounted on a crankshaft 86 of the press machine, a balance weight 92 mounted on a balance mechanism shaft 93, a motor for rotating the shaft 93 and a control system for the motor. The control system ensures that the balance mechanism shaft 93 rotates in the opposite direction to, but at the same speed as, crankshaft 86. The balance weights 91 and 92 balance the primary shaking forces which arise in the press machine along the axis of movement of its ram 83. In the second balance mechanism, balance weights are mounted on two separate shafts rotated by a motor and connected by a gear mechanism. In the third balance mechanism, one balance weight is mounted on the crankshaft, another balance weight is mounted on a shaft rotated by a motor, and a further pair of balance weights are mounted on a pair of shafts rotated by a motor at twice crankshaft speed.

Abstract: A bearing for compensating masses for compensation of forces due to inertia as well as moments of inertia is in the form of a constructive unit made of the compensating masses and the support, whereby the outer mantle surface of the compensating masses provide the support surface. Furthermore, the compensating masses and the gear wheel comprise a unit whereby the exact angular coordination of crank shaft and compensating mass is ensured. The bearing arrangement results in a secondary mass compensation.

Abstract: A torsional-vibration damer is fastened on a crankshaft. It comprises a hub and a mass-body which is arranged to be offset in radial direction with respect to the hub. Between the torsional-vibration damper and the crankshaft are separate connections, one for torque transmission and the other for absorbing bending moments through radial supporting elements.

Abstract: A vibrational dampening system in a cutter head having an elongate knife reciprocated to cut a ply or a stack of plies of sheet material comprises a drive pulley having an eccentrically mounted pin on which is journalled a linkage connecting the drive pulley to the knife, and two driven pulleys located on either side of the drive pulley synchronously interconnected with the drive pulley by a belt having spaced apart teeth formed on each side. The drive pulley and each of the two laterally disposed driven pulleys has a counterweight which rotates 180 degrees out of phase with the rotation of the eccentric pin in order to cancel the vertical forces generated by the reciprocating knife and its associated connecting linkage. The two laterally disposed driven pulleys rotate in an opposite direction relative to the rotational direction of the drive pulley in order to cancel any side-to-side forces generated when the counterweights move between vertically oriented positions.

Abstract: A dynamic damper of this invention comprises: a pair of ring-shaped fixing members disposed at a predetermined interval, inserted onto and supported by a rotary shaft; a cylinder-shaped mass member having inner surface larger than the outer surface of the rotary shaft, the cylinder-shaped mass member inserted onto the rotary shaft and disposed between the pair of ring-shaped fixing members; and elastic members integrally connecting the ends of the fixing members with the ends of the cylinder-shaped mass member. The dynamic damper has enabled to down-size the configuration thereof while maintaining the performance thereof and to make the installation thereof easier.

Abstract: A balancer arrangement for a two cylinder in-line internal combustion engine that includes a drive gear formed on the crankshaft between a pair of throws and between a pair of bearing surfaces. A pair of balance shafts are driven from this drive gear and have inertial masses coupled to them through a torsional vibration damper. The inertial masses are disposed between the adjacent pair of cylinders and within the crankcase so as to provide a compact engine.

Abstract: A crankshaft used in piston engines has vibration and noise level normally associated therewith substantially reduced. The natural frequencies of torsional vibration of individual cranks are made unequal by making main journals of different outside diameters.

Abstract: A large compressor has a four throw crankshaft, four connecting rods, four crossheads, and four horizontally opposed pistons. As usual, each piston is offset from its opposing piston and this causes the usual inertia force couples (primary couples and secondary couples). The crankshaft has counterweights thereon. A parallel oppositely rotating countershaft has balance weights thereon. These rotating weights balance the two primary inertia force couples. The crank sequence and the crosshead/piston locations are such that the two secondary inertia force couples counteract each other and no other secondary balancing device is needed. Further, the same counterweights also serve to balance the four crankpins and the large ends of the four connecting rods. Thus, the whole machine has near perfect balance with no unbalanced reciprocating primaries, reciprocating secondaries, primary couples, secondary couples, or rotating unbalance.

Abstract: An automotive engine crankshaft has a pair of vibration balancing masses pivotally secured to and depending from a main bearing cap for oscillatory movements in response to being driven by contoured cam wheels on the cheeks of the crankshaft, the cam wheels engaging rollers or cam follower sliding shoes on a bell crank type balancing mass, the vertical movements of the balancing mass centers providing forces in direct opposition to the forces caused by the engine second order vertical shake unbalance, to cancel the same.

Abstract: In a cutting machine having a reciprocating blade driven by a crank mechanism which includes an angularly balanced crank, the blade, the connecting rod which drives the blade and the connecting member which connects the blade to the connecting rod are dynamically counterblanced by a passive load, pair of connecting rods which drive the passive load in a direction opposite the direction of blade movement, and a pivoted link which cooperates with the pair of connecting rods to maintain the passiive load for movement in a predetermined path.

Abstract: A flywheel weight for removable attachment to a threaded component of a flywheel or crankshaft of an engine to supplement the weight of the flywheel. Set screws additionally lock the weight to the flywheel.

Abstract: A crankshaft for a 90.degree. V-type eight-cylinder internal combustion engine having eight balance weights of No. 1 through No. 8 balance weights and supported by five supports. An angle defined between the No. 1 and No. 2 balance weights is set at the range of 15.degree.-45.degree. and an angle defined between the No. 1 and No. 3 balance weights is set at the range of 45.degree.-75.degree.. The mass of each of No. 1 and No. 8 balance weights is greater than the weight of any one of No. 2 through No. 7 balance weights. These relationships can reduce the weight of a crankshaft and bearing loads.

Abstract: A crankshaft assembly for an internal combustion engine includes a crankshaft, an elastic member fixed to the crankshaft, and a flywheel fixed to the elastic member such that the flywheel is supported in an elastic relationship with the crankshaft. The elastic member has a rigidity in its rotating direction large enough to effectively transmit a driving power to a transmission through a clutch. On the other hand, the elastic member has a rigidity in an axial direction of the crankshaft small enough to shift a resonance frequency of a bending vibration out of a target frequency band of a forced vibration, while ensuring to prevent a failure of disengagement of the clutch.