Gear Basics

Gears have teeth that mesh with other gears in order to transmit torque. Gears can be used to change the speed, torque (turning force), or direction of a motor’s original output. For gears to be compatible with each other, the meshing teeth must have the same shape (size and pitch). Gears are ideal for use in more compact spaces and are also used for changing the direction of rotation.

Gears offer more flexibility in transforming motion than sprockets and chain because there are a larger variety of gear sizes available.

There are many different types of gears; one of the simplest and most commonly used is a spur gear, and that is the gear type used in the REV ION System. Spur gears consist of a disk with straight teeth projecting radially (outward from the center) and these gears will only mesh correctly with other gears if they are on parallel shafts.

Anatomy of a Spur Gear

Documentation Coming Soon!

20DP Pocketed Gears

All REV ION Gears are 20DP, made of 4140 Steel, and pocketed to reduce weight. Our REV ION 20DP Gears (Product Family Page) come in a wide range of sizes and bores including MAXSpline, 1/2in Hex, and 1/2in Rounded Hex. Larger gears include #10 clearance hole patterns, 2in bolt circle, and MAXTube mounting pattern.

DP stands for Diametral Pitch. The diametral pitch of a gear is the number of teeth in the gear for each inch of pitch diameter. So, a 20DP gear has 20 teeth per inch.

Gear Alignment Mark

Sometimes in a design it may be desirable to stack together multiples of the same gear on a shaft to increase the load carrying capacity of the gears. In the case where the number of teeth on the gear is not divisible by six, because of how they are oriented when put onto the hex shaft, the teeth may not be aligned between the two gears. To ensure all of the gears are clocked the same way, use the alignment shaft notch to put all the gears on the shaft with the same orientation.

Using Gears as a Powertrain

Meshing two or more gears together is known as a gear train. Selecting the gears in the gear train as larger or smaller relative to the input gear can either increase the output speed, or increase the output torque but the total power is not affected.

A gear ratio is the ratio of the sizes of two gears. For instance, in the image below, the input gear is a 15 tooth gear and the output gear is a 72 tooth gear. So, the gear ratio is 72T:15T. The ratio in size from the input (driving) gear to the output (driven) gear determines if the output is faster (less torque) or has more torque (slower). The gear ratio is proportional to the speed and torque changes between them.

In the image above, the 15 tooth input gear is rotating clockwise. As the input gear rotates, it pushes down on the output gear where the teeth are meshed. This action transmits the motion to the output gear, but forces the output gear to rotate in the opposite direction of the input gear.

When assembling the gear train we recommend adding grease during assembly and re-applying as needed for the maintenance of your mechanism. For most applications, using White Lithium Grease or Red Tacky Grease will provide sufficient lubrication.

Gear Spacing

In order for gears to work effectively, and not become damaged, it’s important that the center-to-center distance is correctly adjusted. The gears in DETAIL A of the figure below may work under very light load, but they will certainly not work and will skip under any significant loading. The gears in that example are too far apart, and the teeth of each gear barely contact each other. The gears in DETAIL B are correctly spaced and will provide smooth and reliable operation.

To learn more about calculating center-to-center distance for Gears visit the Center-to-Center Distance Section.

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