Technical Articles

Double Helical Gear Note

Posted: 2013-12-05 11:51:33  Hits: 1821
These overcome the problem of axial thrust presented by "single" helical gears by having two sets of teeth that are set in a V shape. A herringbone gear (double helical gears) can be thought of as two standard mirror image helical gears bonded together side-by-side to form a single gear. This cancels out the thrust load along the gear shaft, since each half of the gear thrusts in the opposite direction. As a result of their more complicated shape, double helical gears are more difficult to manufacture, and therefore tend to be more expensive.

  For each possible direction of rotation, there are two possible, opposite orientations for the gear faces. In one, the double helical gears faces are oriented so that the axial force generated by each is in the axial direction away from the center of the gear. This arrangement is unstable. In the other, which is stable, the helical gear faces are oriented so that each axial force is toward the mid-line of the gear. In both arrangements, alignment is critical to ensure correct teeth engagement. When the gears are aligned correctly, the total (or net) axial force on each gear is zero.

  If the gears become misaligned in the axial direction, the unstable arrangement will generate a net force  for disassembly of the gear train, while the stable arrangement will generate a net corrective force. If the direction of rotation is reversed, the direction of the axial thrusts is also reversed. Thus a stable configuration becomes unstable, and vice versa.

 Double helical gears – These types of gears are arranged in parallel position. There is the same tooth sectioning. When the gears move, the same section of the teeth merge and thus producing a strong torque effect. The load tension and the thrust are eliminated with the two converging gears. This type of gear eliminates the tension produced by sideways movement. It can operate smoothly through the proper exchange of torques even on high velocity. It moves in 30 degrees angle giving large space to overlap. Further, it moves efficiently on and rapidly on these gaps. One disadvantage of the double helical gear arrives when the gears do not match in pacing and teeth arrangement. The gear that is floating axially continues to shift as its response to the misaligned load.

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