How To Choose An Orbital Hydraulic Motor: A Comprehensive Guide

When selecting an orbital hydraulic motor, there are several critical factors to consider, including performance, quality, reliability, and cost. Making the wrong choice can lead to numerous issues down the line. Before selecting the motor model, let's first understand the basic principles of the orbital motor.

Basic Principles of Orbital Hydraulic Motors

The orbital hydraulic motor (also known as a Gerotor motor) has a development history spanning several decades. In fact, the first orbital motor produced by Eaton was introduced over 65 years ago. Shortly afterward, the company developed the Geroler motor to meet market demand and improve performance and reliability.

Both orbital motors and Geroler motors use the same rolling track principle. This design gives them a very high power density and compact structure. The star wheel of the orbital motor has six teeth and seven lobes, forming spaces that make up the pressure chambers. When hydraulic oil is injected into these chambers, a high-pressure zone forms on one side, and a low-pressure zone on the other, generating a pressure differential that drives the star wheel to rotate along its track. One complete rotation of the star wheel typically requires 6-8 orbital movements, depending on the geometric design of the star wheel and outer ring.

In addition to the traditional orbital motor principle, the Geroler motor replaces the lobed structure with rollers. This modification reduces friction loss, improves low-speed performance, and extends the motor's lifespan.

Orbital Hydraulic Motor Overview

Orbital hydraulic motors and Geroler motors have a torque output range of 10-50,000 inch-pounds, with maximum speeds reaching 2,000 RPM. Their simple, compact design makes them ideal for use in both mobile equipment and industrial applications. With their exceptional power density, they are particularly suitable for agricultural machinery, material handling equipment, and construction machinery.

Technical Parameters Range

• Torque Output: 10-50,000 inch-pounds

• Max Speed: Up to 2,000 RPM

• Applications: Agricultural machinery, material handling, construction equipment

How to Calculate the Correct Motor Size

The speed and torque requirements of the application determine the motor size, which in turn determines the required displacement (the amount of oil the motor requires per rotation). The following basic formulas can be used for initial calculations:

• Theoretical Torque (inch-lbs) = Displacement (in³/rev) × Pressure Differential (psi) / (2π)

• Theoretical Speed (RPM) = Flow Rate (GPM) × 231 / Displacement (in³/rev)

Five Key Considerations for Motor Selection

1. Performance Evaluation

• Request long-term test data on mechanical efficiency and volumetric efficiency from the supplier. Be cautious of products that only showcase short-term peak performance.

• Industry standards for testing performance parameters are often not unified. Ensure that the test conditions are fully detailed and reliable.

2. Quality Control

• Review the manufacturer’s history of quality stability and consistency.

• Pay attention to the star wheel grinding process, as poor processes can cause performance fluctuations.

• Verify the materials used, ensuring they meet industry standards and do not include subpar materials or substandard heat treatment/forming/grinding processes.

• Compare warranty terms to understand the protection provided.

3. Reliability Verification

• Reliability is the temporal embodiment of quality. Choose products with a proven track record in long-term applications and case studies.

4. Technical Support

• Evaluate whether you require CAD modeling support or customized solutions. These services can significantly enhance the competitiveness of your equipment.

• Distinguish between suppliers offering individual parts and those offering complete system solutions.

5. Cost Analysis

• The cost is an aggregate indicator, and low prices often mean compromises in performance, quality, or reliability.

• Be cautious of "universal" product strategies, and ensure the selected motor is perfectly matched to the actual operating conditions of your equipment.

Conclusion

By systematically considering these five dimensions—performance, quality, reliability, technical support, and cost—along with precise engineering calculations, you can effectively choose a hydraulic drive solution that meets both your current needs and provides long-term reliability.