Slewing drives are gearboxes with the ability to handle both radial and axial loads and deliver a high rotational torque. These mechanisms generate a rotational movement along either a single axis or multiple combined axes. A finished gearbox is assembled from seals, bearings, housing, gearing, motors, and other manufactured components.

Slewing drives work well in applications requiring high torque supplied at reduced speeds. They provide superior precision in positioning accuracy and rotating movement due to their zero-backlash and smooth component operation. These mechanical devices are ideal for applications such as cranes, satellites, radar trackers, oil tool equipment, and various fields dependent on similar functionality. They are made of phosphor bronze and steel or materials with related wear and deformation properties. Slewing drives feature enclosures that provide protection against environmental factors including dirt, dust, and water.

Types of Slewing Drives

Slewing drives offer a myriad of sizes, capacities, and mounting features to fulfill a multitude of functions. Standard models have dual-axis drives turning simultaneously, or two drives positioned on the same axis. The two-drive setup allows two worm threads to drive a ring gear along one axis.

Emerging technologies led to an increase in popularity of the hourglass design in slew drive manufacturing. The new design offers superior performance by employing multiple gear teeth at the same time. Slewing drives, designed to handle heavier loads, utilize double-row slew bearings instead of single-row bearings.

With a specialized application in solar tracking systems, slewing drives assist in generating a higher solar power output. This is achieved by facilitating equipment mobility with a focus on the sun. Custom solutions are made for applications requiring exceptional load capacity utilizing dynamic and static torque.

How Slewing Drives Work

Slewing drives depend on worm gear technology, whereby a horizontally mounted worm acts as a driver for the gear. As the horizontal screw rotates, it turns the gear around the axis oriented perpendicularly to the screw axis. As a result, the gear speed is reduced while the torque is multiplied proportionately. The number of worm threads and gear teeth determine the applicable speed ratio.

The hourglass mechanism resembles the traditional worm gear technology and offers an improvement in gear functionality. Instead of relying on a single point of contact as with traditional models, the hourglass worm profile allows up to 11 gear teeth to make contact with the worm shaft. The ability to engage multiple teeth at once makes hourglass slewing drives durable, stronger, and more efficient.

Features

Slewing drives offer a multitude of features, including:

• Single or double row ball
• Hardened and ground worm gear (for an extended life)
• Self-locking capability
• Single worm drive
• Double worm drive
• Hydraulic motor
• Electric motor
• Pneumatic motor
• Modular design
• Encoders
• Open chassis
• Enclosed chassis
• Brakes
• Hourglass design
• Gearbox reduction ratio
• Horizontal mounting
• Vertical mounting
• Horizontal/vertical mounting combination

Applications

A slewing drive's ability to handle varying loads and provide rotational torque strength makes it suitable for a wide range of applications. These include:

Metal cutting and forming: These applications need full precision in positioning the workpieces. Slewing drives with a reduced backlash option deliver high accuracy results under varying conditions.

Mining: Slewing drive mechanisms are ideal for applications demanding a maximum torque capacity along with shock loading resistance. They also offer ratio reduction and present a profile low enough to support an extensive selection of mining equipment.

Construction: Slewing drives operate with systems providing power to construction equipment that is subject to heavy loads of variable operation. They are appropriate for this field due to the ability to produce high torque and smooth operation in limited spaces. Crowded construction areas are typical with equipment such as winches, hoists, and cranes.

Printing: Printing press rolls keep precision print registration at top speeds. A slewing drive supports rapid changes in the operating speed. Compact drives with low inertia perform better where rapid starting and stopping is necessary than devices with heavier gearing featuring multiple stages.

Additional applications featuring slewing drives include:

• Solar trackers
• Man lifts
• Wind turbines
• Hydraulic machinery
• Automotive lifts
• Digger derricks
• Telescopic handlers
• Military equipment
• Drilling equipment
• Cranes
• Satellite and radar dishes
• Utility equipment
• Paper
• Plastic
• Oil tool equipment
• Packaging equipment
• Iron and steel production equipment
• Tire handlers

Specifications

Slewing drive specifications provide specific details necessary for meeting critical requirements, such as:

• Output torque
• Tilting moment
• Holding torque
• Static axial
• Dynamic axial
• Dynamic radial
• Gear ratio
• Tracking precision
• Unit weight

References

Image credits:

Dalian Running Engineering | The Precision Alliance | Potesta & Company, LLC