The slewing drive is a gearbox that can safely hold radial

Radial axle

A radial axle is an axle on a railway locomotive or carriage which has been designed to move laterally when entering a curve in order to reduce the flange and rail wear....

 and axial loads

Rotation around a fixed axis

Rotation around a fixed axis is a special case of rotational motion. The fixed axis hypothesis exclude the possibility of a moving axis, and cannot describe such phenomena as wobbling or precession. According to Euler's rotation theorem, simultaneous rotation around more than one axis at the same...

, as well as transmit a torque

Torque

Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

 for rotating. The rotation can be in a single axis

Rotary stage

A rotary stage is a component of a motion system used to restrict an object to a single axis of rotation. The terms rotary table or rotation stage are often used interchangeably with rotary stage...

, or in multiple axes together. Slewing drives are made by manufacturing gearing, bearings

Bearing (mechanical)

A bearing is a device to allow constrained relative motion between two or more parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can...

, seals, housing, motor

Powertrain

In a motor vehicle, the term powertrain or powerplant refers to the group of components that generate power and deliver it to the road surface, water, or air. This includes the engine, transmission, drive shafts, differentials, and the final drive...

 and other auxiliary components and assembling them into a finished gearbox.

History

The slewing drive is a modernized take on the worm drive

Worm drive

A worm drive is a gear arrangement in which a worm meshes with a worm gear...

 mechanism that dates back many centuries and was widely used during the Renaissance Era

Renaissance

The Renaissance was a cultural movement that spanned roughly the 14th to the 17th century, beginning in Italy in the Late Middle Ages and later spreading to the rest of Europe. The term is also used more loosely to refer to the historical era, but since the changes of the Renaissance were not...

. Pappus of Alexandria

Pappus of Alexandria

Pappus of Alexandria was one of the last great Greek mathematicians of Antiquity, known for his Synagoge or Collection , and for Pappus's Theorem in projective geometry...

(3rd century AD), a Greek mathematician is credited for an early version of the endless screw

Screw (simple machine)

A screw is a mechanism that converts rotational motion to linear motion, and a torque to a linear force. It is one of the six classical simple machines. The most common form consists of a cylindrical shaft with helical grooves or ridges called threads around the outside...

, which would later evolve into the worm drive. This mechanism was also used by Leonardo da Vinci

Leonardo da Vinci

Leonardo di ser Piero da Vinci was an Italian Renaissance polymath: painter, sculptor, architect, musician, scientist, mathematician, engineer, inventor, anatomist, geologist, cartographer, botanist and writer whose genius, perhaps more than that of any other figure, epitomized the Renaissance...

 as a component in many of his designs for machines. It can also be found in the notebooks of Francesco di Giorgio

Francesco di Giorgio

Francesco di Giorgio Martini was an Italian painter of the Sienese School and a sculptor, as well as being, in Nikolaus Pevsner's terms, "one of the most interesting later Quattrocento architects'" and a visionary architectural theorist; as a military engineer he executed architectural designs and...

 of Siena

Siena

Siena is a city in Tuscany, Italy. It is the capital of the province of Siena.The historic centre of Siena has been declared by UNESCO a World Heritage Site. It is one of the nation's most visited tourist attractions, with over 163,000 international arrivals in 2008...

. Many slewing drive concepts found prominence with the emergence of larger scale construction and engineering in the height of the Greek and Roman Empires.

Technology

Slewing drives function with standard worm technology, in which the worm on the horizontal shaft acts as the driver for the gear. The rotation of the horizontal screw turns a gear about an axis perpendicular to the screw axis. This combination reduces the speed of the driven member and also multiplies its torque; increasing it proportionally as the speed decreases. The speed ratio of shafts depends upon the relation of the number of threads

Screw thread

A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread...

 on the worm to the number of teeth in the worm wheel or gear

Gear

A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine....

.

As technology has improved, more and more slewing drives are now functioning with hourglass worm technology which functions much in the same way as a traditional worm with one big exception: a traditional worm touches just one tooth at a time while an hourglass engages up to 11 teeth at one time. This increased tooth engagement results in far greater strength and efficiency.

Performance Characteristics

Because of their multiple uses, slewing drives come in a variety of model sizes, performance ranges and mounting characteristics. The drives are perfect for applications that require both load holding and rotational torque from the same gear box. They can also be made with dual axes of rotation, (turning axes at the same time) or with dual drives on the same axis, (two worm threads driving the same ring gear in one axis).

Materials

The specifications for drives and gears varies depending on the material the gear is composed of. However, a majority of the drives and gears commonly used are composed of steel and phosphor bronze. According to an extensive series of tests by the Hamilton Gear & Machine Co., chill-cast nickel-phosphor bronze ranked first in resistance to wear and deformation. Number two on the list was SAE No. 65 bronze

SAE International

SAE International is an organization for engineering professionals in the aerospace, automotive, and commercial vehicle industries. The Society is a standards development organization for the engineering of powered vehicles of all kinds, including cars, trucks, boats, aircraft, and others.SAE...

. For bronze gears a good casting should have the following minimum physical characteristics:

Physical Characteristics

Ultimate Strength	Yield Point
30,000 lbs/psi	12,000 lbs/psi

Applications

There are many applications in which the slewing drive can be utilized, primarily because it is perfect for applications that require both load-holding power and rotational torque strength.

Typical slewing drive applications include but are not limited to:

Applications
Solar Trackers Solar tracker A solar tracker is a generic term used to describe devices that orient various payloads toward the sun. Payloads can be photovoltaic panels, reflectors, lenses or other optical devices....
Wind Turbines Wind turbine design Wind turbine design is the process of defining the form and specifications of a wind turbine to extract energy from the wind. A wind turbine installation consists of the necessary systems needed to capture the wind's energy, point the turbine into the wind, convert mechanical rotation into...
Man Lifts Cherry picker A cherry picker , is a type of aerial work platform that consists of a platform or bucket at the end of a hydraulic lifting system.- Design :...
Hydraulic Machinery Hydraulic machinery Hydraulic machines are machinery and tools that use liquid fluid power to do simple work. Heavy equipment is a common example.In this type of machine, hydraulic fluid is transmitted throughout the machine to various hydraulic motors and hydraulic cylinders and which becomes pressurised according to...
Telescopic Handlers Telescopic handler A telescopic handler, or telehandler, is a machine widely used in agriculture and industry. It is similar in appearance and function to a forklift but is more a crane than forklift, with the increased versatility of a single telescopic boom that can extend forwards and upwards from the vehicle...
Digger Derricks Drilling rig A drilling rig is a machine which creates holes or shafts in the ground. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person...
Lifts Forklift truck A forklift is a powered industrial truck used to lift and transport materials. The modern forklift was developed in the 1920s by various companies including the transmission manufacturing company Clark and the hoist company Yale & Towne Manufacturing...
Cranes Crane (machine) A crane is a type of machine, generally equipped with a hoist, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of...
Drilling equipment Drilling rig A drilling rig is a machine which creates holes or shafts in the ground. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person...
Military Equipment