The slewing drive is a gearbox that can safely hold radial and axial loads, as well as transmit a torque for rotating. The rotation can be in a single axis, or in multiple axes together. Slewing drives are made by manufacturing gearing, bearings, seals , housing, motor and other auxiliary components and assembling them into a finished gearbox. 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 on the worm to the number of teeth in the worm wheel or gear. As technology has improved, more slewing drives are using hourglass worm technology, in which the worm is shaped to engage more teeth in the gear. This increased tooth engagement results in greater strength, efficiency and durability.

According to the variable speed transmission form of slewing drive, it can be divided into gear slewing drive and worm gear slewing drive, inheriting the respective characteristics of gear drive and worm gear drive. In terms of bearing capacity, the performance of the worm gear type is better than that of the tooth type, and when the enveloping worm drive is used, its bearing capacity, deformation resistance and transmission rigidity are further improved. However, the worm gear slewing drive is inferior to the gear slewing drive in terms of efficiency. According to the openness of the slewing drive transmission mechanism, the slewing drive can be divided into an open housing slewing drive and a closed slewing drive. Usually, the open structure is mostly used in applications where the environment is too harsh and the maintenance and maintenance cycle is short. The structure is more convenient for the inspection, maintenance and maintenance of the machine parts, and it is also more convenient to replace. On the other hand, where the environmental conditions do not change much and the environmental pollution level is below the medium level, the closed structure can provide a longer maintenance life cycle.

The slewing drive can be used in any occasion that requires full-circle rotation and requires variable speed. When it is necessary to realize the power transmission of larger torque, the transmission of higher precision motion or the selection of the mechanism that requires high compactness and integration. The slewing drives are the best solution. The more common applications are generally the full-circle rotary structure of engineering and construction machinery, as well as solar energy, wind energy and various long-term automatic tracking machinery. Due to the compact structure and short transmission chain, precision slewing drives are easier to achieve and easier to digitize. Therefore, it has many applications in the field of industrial robots.

Spur gears or straight-cut gears are the simplest type of gear. They consist of a cylinder or disk with teeth projecting radially. Viewing the gear at 90 degrees from the shaft length (side on) the tooth faces are straight and aligned parallel to the axis of rotation. Looking down the length of the shaft, a tooth’s cross section is usually not triangular. Instead of being straight (as in a triangle) the sides of the cross section have a curved form (usually involute and less commonly cycloidal) to achieve a constant drive ratio. Spur gears mesh together correctly only if fitted to parallel shafts. No axial thrust is created by the tooth loads. Spur gears are excellent at moderate speeds but tend to be noisy at high speeds. Spur gear can be classified into two pressure angles, 20° being the current industry standard and 14½° being the former (often found in older equipment). Spur gear teeth are manufactured as either involute profile or cycloidal profile. When two gears are in mesh it is possible that an involute portion of one will contact a non-involute portion of the other gear. This phenomenon is known as “interference” and occurs when the number of teeth on the smaller of the two meshing gears is less than a required minimum . Undercutting (cutting the tooth narrower closer to its base) is sometimes used to avoid interference but is usually not suitable because the decreased thickness leaves the tooth weaker at its base. In this situation, corrected gears are used. In corrected gears the cutter rack is shifted upwards or downwards. Spur gears can be classified into two main categories: External and Internal. Gears with teeth on the outside of the cylinder are known as “external gears”. Gears with teeth on the internal side of the cylinder are known as “internal gears”. An external gear can mesh with an external gear or an internal gear. When two external gears mesh together they rotate in the opposite directions. An internal gear can only mesh with an external gear and the gears rotate in the same direction. Due to the close positioning of shafts, internal gear assemblies are more compact than external gear assemblies. The spur gear slewing drive type is the more common one.

Active trackers use motors and gear trains to perform solar tracking. They can use microprocessors and sensors, date and time-based algorithms, or a combination of both to detect the position of the sun. In order to control and manage the movement of these massive structures special slewing drives are designed and rigorously tested. The technologies used to direct the tracker are constantly evolving and recent developments at Google and Eternegy have included the use of wire-ropes and winches to replace some of the more costly and more fragile components. Counter rotating slewing drives sandwiching a fixed angle support can be applied to create a “multi-axis” tracking method which eliminates rotation relative to longitudinal alignment. This method if placed on a column or pillar will generate more electricity than fixed PV and its PV array will never rotate into a parking lot drive lane. It will also allow for maximum solar generation in virtually any parking lot lane/row orientation, including circular or curvilinear. Active two-axis trackers are also used to orient heliostats – movable mirrors that reflect sunlight toward the absorber of a central power station. As each mirror in a large field will have an individual orientation these are controlled programmatically through a central computer system, which also allows the system to be shut down when necessary. Light-sensing trackers typically have two or more photosensors, such as photodiodes, configured differentially so that they output a null when receiving the same light flux. Mechanically, they should be omnidirectional (i.e. flat) and are aimed 90 degrees apart. This will cause the steepest part of their cosine transfer functions to balance at the steepest part, which translates into maximum sensitivity. For more information about controllers see active daylighting. Since the motors consume energy, one wants to use them only as necessary. So instead of a continuous motion, the heliostat is moved in discrete steps. Also, if the light is below some threshold there would not be enough power generated to warrant reorientation. This is also true when there is not enough difference in light level from one direction to another, such as when clouds are passing overhead. Consideration must be made to keep the tracker from wasting energy during cloudy periods. And also there are other solar product spare parts.
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