Engineered chain offers an alternative to roller chain in many heavy-duty applications, such as conveyors, drum drives, and elevators. These applications often require engineered chain drives because they are more durable and able to withstand adverse operating conditions.

On the other hand, these systems operate at lower speeds, which means that the engineered chain and sprockets can be less precise than roller chain types.

To ensure the best match of chain and sprocket for optimum performance, obtain both components from the same manufacturer, if possible. Also, make sure they are both manufactured to a well-accepted standard such as ANSI B29.1.

Sprocket types

There are many types of sprockets to fit the various engineered chain versions, and the number of choices may surprise you. In general, these sprockets have hub configurations similar to those used with roller chain. Spokes or lightening holes are commonly used to reduce the weight of these sprockets, which are often larger and heavier than roller chain sprockets.

To accommodate special needs, the options go beyond those found in ANSI standards. Following are some of the specific types that are designed to handle different installation and operating conditions.

One type of sprocket is split into two 180-deg segments, Figure 1, to simplify installation and removal, particularly of large sprockets that are installed between bearings. This lets a technician place them on the shaft and bolt them together without removing bearings or disturbing the shaft alignment.

Sprockets with removable rim segments, Figure 2, enable replacing wear surfaces without removing the sprocket hubs or bearings, or moving the shafts. These come in both split and non-split versions.

Wide-flange, drum-type sprockets, Figure 3, support the wide offset chain commonly used in drag conveyor applications. These sprockets are generally made of cast steel or flame-cut steel plate.

Another type of sprocket, called a traction wheel, Figure 4, is used in bucket elevators instead of conventional chain and sprockets. It has a smooth OD, rather than teeth, and it functions by frictional engagement with the bushings in the chain links.

Elevator drive applications tend to cause rapid tooth wear due to a scrubbing action between conventional sprocket teeth and the chain rollers or bushings. Traction wheels eliminate this effect, so they last longer. Also, many of them have segmented rims to facilitate replacing wear surfaces.

In the event of an obstruction or overload, the chain slips on the OD of the traction wheel, thereby preventing damage to elevator components. Because slippage may generate heat and sparks, don’t use traction wheels in applications where an explosion might result, such as in grain elevators.

The frictional grip of a traction wheel must be sufficient to transmit the power needed. Therefore, make sure elevator height, material lubricity, and chain tension are within a range that ensures the necessary traction.

Tooth shape

Teeth come in different shapes to accommodate various types of engineered chain and operating conditions. For example, the tooth profile for engineered drive chain, Figure 5, is approximately the same as for roller chain. But conveyor chain and engineered bar chain require different profiles. Sprocket tooth profiles for engineered chain are specified by ANSI Standard B29.10.

Some sprockets used with longpitch conveyor chains resemble bar chain sprockets but include pockets at the tooth corners to accommodate the chain rollers. Conveyor chains normally have attachments on the top side, which, if used with a drive chain sprocket, would interfere with the tops of the teeth. Therefore, make sure the sprocket matches the chain type.

Engineered chain drives often operate in contaminated environments, which requires a modified tooth form to accommodate foreign elements that get between the chain and sprocket teeth. Unlike a roller chain sprocket tooth, which has minimal pitch line clearance, the sprocket tooth for engineered chain is narrower to provide more clearance, Figure 6. This clearance between the tooth and the chain roller or bushing allows contaminants to pass through.

Accuracy. The operating characteristics and speed of roller chain and engineered chain call for different levels of sprocket tooth accuracy. Steel or cast-iron sprockets with machined teeth are typically required in high-speed roller chain or silent chain drives.

But the long chain pitches and slower speeds of engineered chain usually do not require the precision of machined teeth. Sprockets with cast or flame-cut teeth provide adequate life and cost less.

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