Future Developments in Hydraulic Orbital Motors - Impro Precision


Future Developments in Hydraulic Orbital Motors

January 18th, 2024

Hydraulic orbital motors are the answer for mobile and industrial applications that need high torque at low speed in a small space. In direct drive applications they save the weight and expense of a gearbox or transmission, they’re also robust, cost-effective and reliable. Technology doesn’t stand still though, and future motors should be even more capable and useful than those available today.

Hydraulic Orbital Motors Today

These motors use a gerotor design to turn fluid flow and pressure into rotary motion. A gerotor looks like a spur gear mounted inside a ring with a matching tooth form on the inside. This lets the spur gear – the rotor – roll around the surface of the ring – the stator.

Motion results from the way the rotor divides the space inside the stator into two chambers. This division comes about by the rotor having one tooth less than the stator, so two opposite rotor teeth are always touching the stator.

Fluid is pumped into one of the chambers under pressure, which pushes the rotor to roll around towards the lower pressure region. Valving on the fluid input ensures this tracks around circumferentially to maintain motion.

The rotor drives an output shaft. The gearing between stator and rotor results in low rotational speed. Fluid pressure plus rotor tooth area generate torque.

The Future for Hydraulic Orbital Motors

Despite their utility across a range of industries, work is underway on improvements. The main areas of focus are:

  • Increased efficiency
  • Size and weight reduction (higher power density)
  • Greater durability
  • Lower noise

Efficiency Improvement

Three areas being targeted are: optimized gear tooth profiles, variable displacement pumps and electronically-controlled valves.

Tooth profiles are the subject of extensive university research. Increasing surface and contact area can enable more torque, while also reducing noise. Materials and surface finish also play a role in reducing friction.

A challenge with the profiles being investigated is how they will be manufactured. Some of the more ambitious forms will be extremely difficult to produce by conventional precision machining techniques. To address this, researchers are exploring the use of additive manufacturing and alternative, moldable materials such as engineering polymers.

Variable displacement pumps reduce energy wastage during motor operation by only running at full output when needed. This can also simplify the hydraulic system. Electronic control offers faster and more precise actuation of both spool and disc valves.

Size and Weight Reduction

Higher efficiency will permit smaller motors, while using polymers rather than high-hardness steel for rotor and stator could reduce weight significantly. Lower mass is always desirable in mobile applications, and higher power density gives engineers more freedom to use hydraulic orbital motors as they need.

If motors can be made small enough it may even open up applications in medical devices and pharmaceutical manufacturing.


The current generation of hydraulic orbital motors has two aspects that require maintenance: seals can wear and leak, and rotor and stator teeth tips will wear. For both these areas, new materials offer the promise of extending service and overhaul/rebuild intervals.


Though not a concern in many mobile and outdoor applications, there are situations where quieter operation is desired. Possible applications in healthcare and life sciences are examples. New gear tooth forms, alternative materials, and improved precision machining techniques should provide ways to lower perceived noise levels.

Low Speed, High Torque Hydraulic Orbital Motors

Impro Fluidtek manufactures a range of hydraulic orbital motors for light, medium, and heavy-duty applications. Incorporating hard-wearing materials and long-lasting seals and with components machined on modern CNC equipment, these provide a combination of reliability, performance and cost-effectiveness. Contact us to discuss your application requirements.


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