Types of Gear Drives

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Article Tags:
3 types of gear drives
concentric
concentric gear drive
gear box
gear drive
parallel
parallel gear drive
right angle
right angle gear drive
shaft arrangement
types of gear drives

Gear drives tend to be described by either the arrangement of their shafts or the way that they mount to the driven equipment. It’s important to realize that the shaft arrangement and the mounting are two different characteristics of the drive. Asking a supplier for a “shaft mounted” drive or a “right angle” drive is not enough information for selection by itself!

Shaft Arrangement:

The shaft arrangement on a gear drive is the location of the high speed and low speed shaft extensions relative to each other. This is dictated by the position of the motor and driven equipment and sometimes constrained by the physical space of the application.

1) Concentric

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A concentric gear drive, also commonly referred to as an inline gear drive, and 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.

2) Parallel

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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, high horse power applications.

3) Right Angle

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A right angle gear drive is one in which the high speed and low speed shaft have a 90 degree relationship, or a right angle. 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 in order 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.  Its typically used in mixing or crushing applications, with the gear drive mounted above or below the equipment.
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The orientation of high and low speed shafts as they relate to the naming of the different types of gear drives may seem very simple, but there are reasons why you would choose one over the others when determining the best gear box for your application.  The primary reason that you would differentiate between a concentric, parallel, or right angle drive during your selection is space limitations that you have in your system. Because the shafts are oriented differently, your driving equipment, or motor, will be in a different location depending on which type of gear drive is selected.

Mounting:

There are two ways to mount a gear drive 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 that the foundation is 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 aren’t 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’s 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. When selecting and sizing a gear drive, keep in mind that the orientation of the shafts and the type of mounting must both be used to fully specify the gear drive!

How to Select the Right Gear Drive

Regardless of what type of gear drive is right for your application, having the right information and specifications for your operation is crucial to choosing the correct gear drive. Learn what you need to make the right choice in this whitepaper.

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Robin Olson

Robin is the Director of Applications Engineering at Rexnord Industries, Gear Group. In 1995, Robin joined Falk, which was acquired by Rexnord in 2005, and has previously worked in the Engineering Technical Services, Warranty, Product Engineering, and Marine Product groups during her career.  She is active in the American Gear Manufacturers Association (AGMA), acting as a contributing member of the Helical Gear Rating Committee, Chairperson of the AGMA 925 (Gear Surface Distress) subcommittee, and is honored to act as US delegate to ISO Working Groups 6 (Gear calculations) and 15 (Micropitting).  Robin holds a Bachelor of Science in Physics from the University of Wisconsin -- LaCrosse and a Master of Science in Physics from the University of Wisconsin -- Madison.