Bevel Gear Boxes for Agricultural Harvesters

The high load capacity of bevel gearing makes it widely used in mechanical transmission systems, such as tractor transmission systems.  For large agricultural equipment such as modern harvesters, high-performance gearboxes are critical to ensure maximum availability during the harvesting process. This means that agricultural equipment OEMs must use high-performance gearboxes.

For optimum performance, these machines require reliable, efficient drive and control systems that are easy to operate. Leading agricultural equipment manufacture’s worldwide trust Superior Gearbox Company to provide solutions that optimize the performance of the machine to ensure the equipment can yield maximum productivity, all season long.  

Our diverse product selection allows Superior gearbox to provide complete systems from a single source.  Precision engineering and rigorous testing ensure that every unit meets the most demanding requirements. Field-proven solutions convert the rotational energy supplied by your equipment into energy levels required by each application at the optimal speed and power. In order to maximize performance, most farm machines require custom gearboxes. As part of Superior’s development process, our engineers can work with you to design and develop a custom gearbox solution that perfectly meets your needs and provides a mechanical advantage to improve torque and performance.

What is a Bevel Gearbox?

The name Bevel Gearbox refers to the gearing within the gearbox itself.  This commonly used gearbox is used in a variety of applications across many industries as a single-stage unit which simply interlocks the beveled edges of two gears to transfer the rotation or torque from one gear to the other.  

In mechanical power transmission, gear drives transmit power and motion by successively engaging and disengaging the teeth of driver and driven gears. Gears can be categorized into four types: spur gears, helical gears, bevel gears, and worm gears. The spur gear and helical gear are applicable for power transmission between two parallel shafts, whereas bevel gear is useful for two intersecting shafts (not necessarily perpendicular). For non-parallel non-intersecting shafts, worm gear can be employed.

Similarities and differences of straight and spiral bevel gears.


As the name suggests, a straight bevel gear has straight teeth like a spur gear that are cut along the axis on a cone. For this reason, it can be quite noisy as the teeth of the mating gears collide upon making contact. 

On the other hand, a spiral bevel gear has spiral teeth that are cut in a spiral curve across the pitch cone. Unlike its straight counterpart, the teeth of two mating spiral bevel gears come in contact more gradually and do not collide. This results in less vibration, and quieter, smoother operations.


Due to the sudden contact of the teeth with straight bevel gears, it is subject to impact or shock loading. Inversely, the gradual engagement of the teeth with spiral bevel gears results in a more gradual buildup of the load.

Axial Thrust

Because of their cone shape, bevel gears produce axial thrust force — a type of force that acts parallel to the axis of rotation. A spiral bevel gear exerts more thrust force on bearings thanks to its ability to change the direction of thrust with the hand of the spiral and its rotation directions.

Bevel Gearing in Harvesters

Grain Conveyor 

Agricultural vehicles such as agricultural harvesters convey crop material (grain or MOG) from subsystem to subsystem. The conveyors that move crop material are driven by a variety of means. Various drive arrangements are provided to connect the internal combustion engine (typically the source of power in most agricultural vehicles) to these conveyors. Hydraulic means, mechanical means, and electrical means may be used. One element used, particularly with conveyors that elevate grain (i.e. elevators) such as auger conveyors, are bevel gear drives.  The bevel gear drive drives the auger in rotation, rotating the auger and conveying crop upward.

Bevel Gear Drives

Multiple Row Harvester

A row-crop harvester has a frame displaceable in a predetermined travel direction and formed with a plurality of forwardly open throats each provided with a respective conveyor chain each in turn spanned over a respective drive sprocket. Each such drive sprocket is carried on a respective drive shaft having a drive gear that meshes with the drive gears of the conveyor chains to each side. Each driveshaft with its respective sprocket and gear are together mounted in a respective housing bolted to the frame of the harvester and having a mounting flange whose outer periphery corresponds to the pitch circle of the respective drive gear. A main gear meshing with one of the drive gears rotates all of these drive gears simultaneously, and each conveyor chain has a stretch exposed in a respective throat of the machine which is opposite the stretch of the flanking chains for backward advance of cut crop.

Power Take Off 

PTO Drives, or power take-off drives, are used to transfer power from an engine to a secondary source. Often, they are used on heavy-duty equipment that needs to send power to a hydraulic pump. The tractor PTO goes back pretty much as far as tractors. Most early PTOs were driven from the transmission, which being located at the back of the tractor, allows for easy location of an output shaft. The transmission type of PTO is only engaged when the transmission clutch is also engaged and is coupled directly to transmission so that when the clutch is depressed, the PTO isn’t driven.

Choosing the right PTO for your application is important, as the product specifications should vary depending on your industry application, method of PTO engagement, speed output goals, and more. Superior’s Right Angle Bevel gear drives are driven by a PTO shaft at an input speed of 540rpm or 1000 rpm. The traditional simple planetary when driven from output to input will act as a speed increaser, thus, providing the needed speed up to optimize hydraulic pump speed for efficiency.

Even with the high torque able to be transmitted by tractor PTOs, there are occasions when even more torque is demanded than a tractor can transmit (or slower speed than a standard 540 or 1000 rpm PTO). Although implements often employ pulleys and chain drives, which can be used for torque multiplication, the heaviest of demands require a gearbox for reliable and efficient operation. Of course, the use of gearboxes is not limited to farm applications and are most often seen in wheel drives and other massive-torque low-speed applications.

Common Bevel Gearbox Applications in Ag

Superior Gearbox offers bevel gearboxes in a wide range of HP capacities. Choose from existing ratios and shaft configurations or customize them to meet your specific application needs. Our engineers will work with you to fully understand your requirements and size the appropriate gearbox for your application. If your application requires a custom drive solution, our engineers will team with you to design a bevel gearbox that meets your exact application to minimize stress and wear on your equipment and extend service life. Contact us to learn more!