A concentric gearbox, also referred to as an inline gear drive, is one in which the high and low speed shafts are on the same horizontal and vertical planes. These units allow several units to be placed in a row because of the straight-line alignment of their shafts. A planetary gearbox is a type of concentric inline gear drive that is typically used in applications requiring higher torque due to its rugged design.
A parallel gear drive is one in which the high and low speed shaft are on the same horizontal plane and parallel to each other. Parallel shaft gear boxes are usually selected for high torque and high horsepower applications.
A right-angle gear drive is one in which the high speed and low speed shaft have a 90 degree, or right angle, relationship. These drives are often used on conveyors or other applications that require the driving equipment to be close to the driven equipment. The 90-degree orientation also makes right angle gear drives ideal when using a large drive that is mounted directly to the shaft to minimize shaft bending loads.
The right-angle vertical drive is a right-angle gear drive with the low-speed shaft oriented in the vertical direction. It is typically used in mixing or crushing applications, with the gear drive mounted above or below the equipment.
There are two ways to mount a gearbox into a system: foot-mounted or shaft-mounted. Like shaft arrangement, mounting is determined by the space and structure limitations in the system. Foot-mounted gear drives are mounted to a foundation or baseplate through bolt holes in their feet. That may seem simple, but it requires the foundation to be sufficiently rigid to support the drive and the torque passing through it. These drives are sensitive to soft-foot, a condition that occurs when the feet are not level to each other which causes misalignments between the shafts. Foot mounted drives should also be on foundations that are well connected to the motor and driven equipment foundations. This prevents the equipment from moving independent of each other, which also causes misalignment and vibration.
If it is not possible to place a foundation for the motor, gear drive, and driven equipment into the application, the gear drive may be shaft-mounted to the application. In this case, the gear drive low speed shaft is rigidly connected to the driven equipment shaft. This can be done by making the low-speed shaft of the gear drive hollow and securing it in place around the solid shaft of the drive equipment with a bushing and keeper plate. It can also be done with a rigid flange coupling that connects the sold shafts of the gear drive and driven equipment together.
When a gear drive is shaft-mounted, it hangs in space by the low-speed shaft connection. The motor can be direct coupled to the gear drive via an adapter, a scoop mount, or a swing base. It can also be mounted on top of or next to the reducer via belts or chains. The gear drive and motor system will want to rotate about the gear drive’s low speed shaft, so a torque arm is required to bolt into some structure and prevent rotation.
Over time, the term “shaft mount” has become nearly synonymous with relatively small gear drives that are designed without feet for light conveying applications.