Herringbone gear is a combination of double helix gears, the two helices are arranged side to side of opposite hands. The teeth are arranged at an angle called helix angle with no gap in between the right and the left helix which appears in the shape of the letter ‘V'
The letters together form a pattern that resembles the structure of the bone of a fish such as a herring. Because of this structure more than two teeth meshes with each other at a moment, this advantage the power to transfer smoothly. The setup is designed to transfer power through its perpendicular axes.
The multiple teeth which always mesh reduce the load on each tooth, eventually help in the reduction of vibration and shock load.
The inclined teeth help in the production of axial forces and heat, axial force differs in proportion to the magnitude of the tangent of the helix. The angle made by the helices with the axis of rotation is 45 degrees, however, a larger helix angle delivers higher speed.
The setup of two teeth cancels out the thrust applied on each other which gives the advantage of smooth operation even at a higher speed.
The herringbone gear is difficult to manufacture due to its peculiar structure, the teeth arrangement increases the cost of manufacturing hence compared to other gears it is more expensive. They are mostly used in heavy machines.
Summing up the whole idea we can say that herringbone gears helps in providing smoother, quieter operation and provides high speed.
Difference between helical Gears and herringbone Gear
Gears are designed to transmit power at a small distance. It also can transmit heavy power without any positive drive. The amount of power transmission depends on the orientation of the driver, shaft, and teeth profile, this orientation makes it unique and of different use. Helical gear and herringbone gear both have parallel shafts and teeth are cut in a helical form on the cylindrical gear bank whereas in herringbone gear identical teeth are cut in two halves of the gear bank. The helix maintains the same number of teeth, module, and helix angle but in the opposite hand, just like a mirror image.
The radical thrust force of helical gear has a limited helix angle it can maximum reach 25°. The absence of thrust force in herringbone gear gives it provision to use a higher helix angle which can reach up to 45°.
Due to the structure, it imposes an axial thrust load on the bearing, and this thrust load limits the power, however, in herringbone gear the thrust load is eliminated because of the peculiar structure of teeth and helix angle, the thrust force produced by each half of the herringbone gear is equal and opposite thus the total thrust eliminates each other and help in transmitting higher power without much trouble as compared to helical gear.
The shafts are mounted at the ends using appropriate bearings that support the shaft and maintain an accurate position, it also takes away the vibration and load, and disseminates them to the ground. The bearings are employed in gear to handle the axial load, radial load, and thrust load reserve. The bearings required in helical gear can handle both axial load and thrust load. Since there is no thrust force in the herringbone gear the bearings are capable of handling the heavy radial load.
Herringbone gear has the capability to transmit very high mechanical power or torque as compared to helical gear.
The design of herringbone gear is complicated which extends the cost of manufacturing whereas helical gear is comparably simpler in design and manufacturing thus it is cheaper.
In heavy gears, the inertia of gears through acceleration and deceleration makes it harder to stop or reverse, whereas helical gears are comparably less heavy so it is easy to stop and reverse them.
The helical teeth of a helical gear are obtained by the process which cuts high productive gears called hobbing. However, this process of cutting is not preferred for herringbone gear as there is a risk of overstepping to the other half. So the gear requires a specialized hobbing cutter whose grove matches with the herringbone gear.
Uses of herringbone Gear
- The herringbone gears are used in the torque gearbox.
- Used in a steam turbine to marine propulsion.
- It is used in roller shafts in steel mills.
Everything needs to be cared for, maintaining the things we care for can expand their life, just like gadgets, machines also have some requirements which act as fuel to them. There are certain things which should be kept in mind to extend their life and performance.
For smoother, temperate operation lubricates the gear in a certain interval of time. Gears are exposed to the harsh environment and chemical that is why it should be protected with corrosion resistance.