Herringbone gears!!!

What are Herringbone gears and where they should be used ?                                     
                 
                                              

• Herringbone gears, also called double helical gears, are gear sets designed to transmit power through parallel or, less commonly, perpendicular axes.

• In normal helical gears there is no problem of impact stresses but there are axial thrusts on the bearings of shafts on which they are mounted.these gears are good for moderate power transmission because bearing can be designed.

• But in very high power transmission design of bearing for a small and compact system becomes very tough and unemployable.Thus herringbone gears were designed to eliminate these axial thrusts.This gear contains both right hand helical profile and left hand helical profile on same gear as you can see in diagram.

• The axial components of transmission force is cancelled by each other on same gear.Thus eliminating the problem of thrust force.

• These gears are used in racing cars where high power transmission is required and bearing size can not be increased after certain limit.

Herringbone Gear Applications

• Application requirements should be considered with the workload and environment of the gear set in mind.

• Power, velocity and torque consistency and output peaks of the gear drive so the gear meets mechanical requirements.

• Inertia of the gear through acceleration and deceleration. Heavier gears can be harder to stop or reverse.

• Precision requirement of gear, including gear pitch, shaft diameter, pressure angle and tooth layout. Herringbone gears' precise teeth can make them expensive.

• Gear lubrication requirements. Some gears require lubrication for smooth, temperate operation.

Mounting requirements.

•  Application may limit the gear's shaft positioning.

Noise limitation. 

• Commercial applications may value a smooth, quietly meshing gear. Herringbone gears offer quiet operation.

• Corrosion resistance. Gears exposed to harsh environments or chemicals should be especially hardened or protected.

• Temperature exposure. Some gears may warp or become brittle in the face of extreme temperatures.

• Vibration and shock resistance. Heavy machine loads or backlash, the deliberate surplus space in the circular pitch, may jostle gearing.

• Operation disruption resistance. It may be necessary for some gear sets to function despite missing teeth or misalignment.

Herringbone Gear Materials

• Gear composition is determined by application, including the gear's service, rotation speed, accuracy and more.

• Cast iron provides durability and ease of manufacture.

• Alloy steel provides superior durability and corrosion resistance. 

• Minerals may be added to the alloy to further harden the gear.

• Cast steel provides easier fabrication, strong working loads and vibration resistance.

• Carbon steels are inexpensive and strong, but are susceptible to corrosion.

• Aluminum is used when low gear inertia with some resiliency is required.

• Brass is inexpensive, easy to mold and corrosion resistant. Copper is easily shaped, conductive and corrosion resistant.The gear's strength would increase if bronzed.

• Plastic is inexpensive, corrosion resistant, quiet operationally and can overcome missing teeth or misalignment.

•  Plastic is less robust than metal and is vulnerable to temperature changes and chemical corrosion.

•  Acetal, delrin, nylon, and polycarbonate plastics are common. Other material types like wood may be suitable for individual applications.