A flat plane crankshaft for an in-line four cylinder engine includes eight crank arms. A fourth crank arm and a fifth crank arm are respectively provided with counter weights. Each of a width of the fourth crank arm and a width of the fifth crank arm is configured to be smaller than a width of a second crank arm. Each of a width of the third crank arm and a width of the sixth crank arm is configured to be greater than the width of the second crank arm.

A shaft balancing device for insertion into a shaft including a generally flat cylindrical band having an outer surface, an inner surface and a set of two crush points thereon. A balancing weight is attached to the outer surface of the band between the set of crush points. The device is inserted into the shaft and the crush points are plastically deformed radially outward creating spring force which holds the balancing weight to the inner surface of the shaft. The band has a curved connecting portion between the two crush points having a radius of curvature slightly greater than the curvature of the shaft. The balancing weight has a radius of curvature slightly greater than the radius of curvature of the curved connecting portion and slightly less than the radius of curvature of the shaft.

A computer program and method for pre-balancing a crankshaft. The method includes receiving data related to a three dimensional scan of the crankshaft; generating a model based on the data; and providing instructions, based on the model, for defining a pre-balancing machining axis.

A computer program and method for pre-balancing a crankshaft. The method includes receiving data related to a three dimensional scan of the crankshaft; generating a model based on the data; and providing instructions, based on the model, for defining a pre-balancing machining axis.

An internal combustion engine including a first set of cylinders includes: a first two-stroke compression cylinder housing a first compression piston connected to a first crank shaft; a first four-stroke combustion cylinder housing a first combustion piston connected to a second crank shaft, the first four-stroke combustion cylinder being configured to receive compressed gas from the first two-stroke compression cylinder; and a first two-stroke expansion cylinder housing a first expansion piston connected to the first crank shaft, the first two-stroke expansion cylinder being configured to receive exhaust gas from the first four-stroke combustion cylinder, wherein the first compression piston is positioned to reach a lower end position within the first compression cylinder and the first expansion piston is positioned to reach an upper end position within the first expansion cylinder when the first combustion piston reaches a lower end position within the first combustion cylinder; wherein the second crank shaft is configured to rotate with a speed of at least twice the speed of the first crank shaft.

An internal combustion engine including a first set of cylinders includes: a first two-stroke compression cylinder housing a first compression piston connected to a first crank shaft; a first four-stroke combustion cylinder housing a first combustion piston connected to a second crank shaft, the first four-stroke combustion cylinder being configured to receive compressed gas from the first two-stroke compression cylinder; and a first two-stroke expansion cylinder housing a first expansion piston connected to the first crank shaft, the first two-stroke expansion cylinder being configured to receive exhaust gas from the first four-stroke combustion cylinder, wherein the first compression piston is positioned to reach a lower end position within the first compression cylinder and the first expansion piston is positioned to reach an upper end position within the first expansion cylinder when the first combustion piston reaches a lower end position within the first combustion cylinder; wherein the second crank shaft is configured to rotate with a speed of at least twice the speed of the first crank shaft.

A crankshaft includes: journals that define a central axis of rotation; crank pins that are eccentric with respect to the journals; and crank arms for connecting the journals and the crank pins, wherein each of the crank arms or at least one of the crank arms integrally includes a counterweight. The crank arms have a recess in a surface adjacent to a corresponding one of the journals, the recess disposed inward of a peripheral region along a periphery of the surface, the recess disposed along the peripheral region. With this configuration, it is possible to provide a crankshaft which has reduced weight and increased torsional rigidity in combination with increased flexural rigidity.

A crankshaft includes: journals that define a central axis of rotation; crank pins that are eccentric with respect to the journals; and crank arms for connecting the journals and the crank pins, wherein each of the crank arms or at least one of the crank arms integrally includes a counterweight. The crank arms have a recess in a surface adjacent to a corresponding one of the journals, the recess disposed inward of a peripheral region along a periphery of the surface, the recess disposed along the peripheral region. With this configuration, it is possible to provide a crankshaft which has reduced weight and increased torsional rigidity in combination with increased flexural rigidity.

A vibratory compactor is described that includes a drum, a frame supporting the drum, an eccentric shaft configured to be rotated by a vibration motor, and a primary eccentric weight attached to the eccentric shaft inside the drum. At least one active isolation eccentric weight is located outside the drum so that when the eccentric shaft is rotated, a phase of a vibration generated by the at least one active isolation eccentric weight is substantially opposite to that of a vibration generated by the primary eccentric weight.

A vibratory compactor is described that includes a drum, a frame supporting the drum, an eccentric shaft configured to be rotated by a vibration motor, and a primary eccentric weight attached to the eccentric shaft inside the drum. At least one active isolation eccentric weight is located outside the drum so that when the eccentric shaft is rotated, a phase of a vibration generated by the at least one active isolation eccentric weight is substantially opposite to that of a vibration generated by the primary eccentric weight.