Orbiting in Harmony: Hydraulic Orbital Motors in Hydraulic Systems - Impro Precision


Orbiting in Harmony: Hydraulic Orbital Motors in Hydraulic Systems

July 4th, 2024

Hydraulic orbital motors turn at low speed while delivering high levels of torque from a compact package. That makes them the preferred choice in a range of mobile applications and a lot of heavy-duty industrial machinery. If you’re exploring their potential use, you need to know what’s involved in putting them to work. This blog explains.

Hydraulic Orbital Motor Basics

Think of a hydraulic motor like a pump operating in reverse: fluid flows in under pressure and creates rotation, rather than rotation creating fluid flow. As with pumps, hydraulic motors take many forms, and choosing which to use requires an understanding of how they work and what the application needs.

A hydraulic orbital motor consists of a gear set and a spool valve inside a housing. Unlike a spur gear pump though, in this design a smaller gear meshes with and rolls around the inside of a larger, fixed gear, (hence the “orbital” part).

The spool valve manages fluid flow to keep the rotor turning, and the gear ratio slows the effective output speed while multiplying torque.

System Integration

As a hydraulic orbital motor is powered by fluid, a complete system needs a number of components, specifically:

  • A pump, sized to meet the flow rate and pressure needs of the motor
  • A fluid reservoir
  • Hydraulic fluid with appropriate characteristics like viscosity and temperature range
  • A flow control valve, to regulate flow rate and hence motor speed
  • A directional control valve – hydraulic orbital motors are bidirectional, but the direction of fluid flow has to be reversed to take advantage of this
  • A pressure relief valve (an essential safety feature)
  • One or more filters to protect the motor from debris
  • Hoses
  • A motor mount and coupling

In addition, though outside the scope of hydraulic system integration, the pump needs a power source. In mobile applications this is either a generator or the engine used to drive the machinery. In a fixed industrial or material handling application an electric motor is an option.

Component Selection

Designing a hydraulic orbital motor system begins with motor selection, which must be matched to the application. The most important characteristics to determine are:

  • Torque
  • Speed
  • Load capacity

These will dictate what pressure and flow rate the pump needs to provide. From here the physical arrangement of pump, motor and reservoir will establish the volume of fluid needed and the size of the reservoir.

Hydraulic fluid is produced in many different types. Viscosity is important for both pump and motor, and this is influenced by operating temperature range. Some applications may need a fire-resistant or environmentally-friendly fluid.

Benefits of Hydraulic Orbital Motors

As the output shaft rotates at low speed and can be reversed, there’s no need for a reduction drive. This saves space and weight, both of which are at a premium in mobile equipment applications. In addition, the simplicity and rugged nature of the design provide tolerance to impacts and rough treatment and ensure high levels of reliability.

Typical Applications

These motors are used extensively in mobile equipment. Scissor lifts and similar aerial work platforms are one class of application, and agricultural and forestry machinery is another. Many skid-steer machinery used in construction and landscaping is built with hydraulic motors at the wheels.

Material handling is another application category for which hydraulic orbital motors are well suited. Long distance conveyors in particular benefit from their torque and durability. Elsewhere, these motors are used in heavy-duty mixing equipment, rolling mills and web-handling applications.

Dependable Rotary Power

When designing or engineering equipment that needs low speed, high torque, rotary motion, a hydraulic orbital motor may be a good choice. It’s important to remember though that these motors must be integrated with ancillary devices like pumps, reservoirs and valves.

Impro Fluidtek manufacturers a wide range of hydraulic orbital motors for light, medium and heavy-duty applications and can advise on integration. Contact us to discuss your need for low speed, high torque rotary motion.


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