How To Measure Torque?

How To Measure Torque?

According to various sources, torque measurement is crucial in multiple industries and applications, ranging from automotive to industrial machinery. Understanding how to measure torque efficiently ensures the safety, reliability, and performance of mechanical systems.

What is torque?

Torque represents a force that induces rotation around an axis. It can be seen as a twisting force, also known as a rotational force. In physics, if you recall, force is an input affecting the motion of an object over time. The most familiar example of torque can be found in the driveshaft of your vehicle; the torque produced by the motor dictates the level of work the car can perform. Torque is a vector quantity, characterized by both direction and magnitude.

Simply put, torque is the twisting power that acts to rotate or turn various components such as bolts, screws, and wheels. You may often encounter torque measured in SI-derived units \(N m\) (Newton meters) or, in the USA, expressed in foot pounds (\(ft/lbs\)). Converting \(N m\) to \(ft/lbs\) involves dividing the \(N m\) value by 1.356.

Why do we need to measure torque?

Measuring torque is vital for designing, commissioning, and troubleshooting a variety of mechanical systems. The mechanical torque of rotating shafts must often be monitored to ensure compliance with specifications. Precise torque measurements help to guard against potentially harmful excesses that could lead to system failures, making it an essential aspect of predictive maintenance.

What are the main types of torque?

Torque can be classified into two primary categories: rotary torque and reaction torque.

• Rotary torque (also known as rotational or dynamic torque)
• Reaction torque (also known as stationary or static torque)

Rotary (aka rotational or dynamic) torque

This type of torque is seen in objects such as shafts, turbines, and wheels that rotate continuously around an axis.

Reaction (aka stationary or static) torque

Static force applied to an object is termed reaction or stationary torque. For instance, when using a lug wrench on a bolt, the force you apply is considered reaction torque, even if the bolt does not rotate significantly. Measurement occurs in less than one complete revolution in such cases.

How is torque measured?

Torque measurement can be carried out in both direct and indirect ways. When knowing the motor's efficiency and the shaft speed, one can utilize a power meter for an estimation of torque—an indirect measurement approach.

A more dependable option is the direct measurement involving reaction torque sensors or rotary torque sensors. The difference between these methods lies in their application and accuracy.

Reaction (static) torque sensors

These sensors gauge static or non-rotational torque. A prime example would be a torque wrench, which is utilized to ensure an appropriate amount of torque is applied to fasteners such as bolts or nuts. Most torque wrenches feature an audible click to indicate when the desired torque level has been reached. Digital versions offer gauge displays or electronic memory for storing data.

Rotational (dynamic) torque sensors

A rotational torque sensor acts as a transducer that converts rotational torque into measurable output. Common applications for such sensors include motor torque testing, internal combustion engine tests, and measuring torque in driveshafts and turbines.

Indirect methods can be more cost-effective for existing systems, relying on efficiency measures and operational parameters to estimate torque. However, direct torque measurement, often implemented with strain gauges mounted on drive shafts, offers higher accuracy. These sensors detect the minimal twisting of the shaft, which is otherwise imperceptible.

Permanently installed rotary torque measurement systems

In these systems, rotary torque sensors are integrated between the motor and a brake, measuring twisting forces with strain gauges. These sensors often include encoders for precise speed and angle measurement, essential for applications such as dynamometers that require the calculation of power output and motor efficiency.

Temporarily installed rotary torque measurement systems

For non-permanent setups, strain gauges can also be affixed directly to drive shafts. This configuration allows for wireless transmission of data to processing units, making it easy to analyze torque measurements using advanced DAQ systems.

Order analysis applications

Torsional vibrations, which occur due to alternating torques on a rotating shaft, represent a failure source in machinery. Analyzing these vibrations is crucial for diagnosing issues in equipment in automotive, industrial, and power generation contexts.

What is torsional vibration?

Torsional vibration refers to the angular vibrations along a shaft's rotational axis, primarily caused by fluctuating engine power. These angular vibrations lead to variations in rotational speed within a cycle.

What is rotational vibration?

This dynamic aspect of rotational speed can be observed when measuring hi-precision speeds, revealing deviations caused by angular vibrations. Various parameters, including material properties and operating conditions, influence the levels of torsional vibration.

How to measure rotational and torsional vibration

For a brief overview of measuring these important dynamics, a provided video can outline both the foundational theory and practical advantages.

The DewesoftX torsional vibration solution calculates various parameters such as rotational angle, velocity, torsional angle, and frequency during these measurements, which can be conducted in real-time or offline.

Summary

Torque sensors play pivotal roles in numerous applications across diverse sectors. Reactive torque sensors find use in tools like wrenches, while rotary torque sensors are essential for engine tests, dynamometers, and numerous other applications ranging from industrial equipment testing to robotics. The significance of measuring torque spans various fields, with dedicated sensors and DAQ systems facilitating accurate monitoring and analysis.

Torque testing

Torque testing determines how an object reacts during rotation. This rotational force can occur either dynamically at high speeds or statically at lower speeds.

Mecmesin specializes in solutions for static torque measurement. Discover more by visiting our website at Textile Testing.