HOW IS THE TORQUE CALCULATED?
If you want to calculate the torque, you must first determine the area of application. This is because a torque appears in many different areas of application and is calculated accordingly in different areas. In industry, for example, the application of torque differs from the application of necessary tensile forces in bolted connections. Nevertheless, the basic calculation remains the same. Let us first consider the fundamentals of torque as a physical factor.
THE LAW OF LEVERAGE AS THE BASIS FOR TORQUE CALCULATION
The basis for calculating the torque is the lever law, which has already been formulated by Archimedes. A lever is used to achieve a large effect at a pivot point with a small force. A distinction can be made between single-arm and two-arm levers. The centre of the lever arm always represents the fulcrum. This is also of decisive importance for the calculation of the torque, as the force is generated at the fulcrum, which is referred to as the torque. Good examples of levers in a wide range of applications include bottle openers, wrenches, pharmacy scales and crowbars. All these devices are levers with a fixed fulcrum and a torque at the fulcrum.
THE IMPORTANT UNITS FOR THE TORQUE
The unit for calculating the force at torque is the Newton metre. 1 Nm is exactly the torque that is applied when 1N force is applied to a body at its individual fulcrum at a lever of one meter in length. The shape sign for the torque is given in Newton meters.
CALCULATE THE ACTUAL TORQUE
If you now want to calculate the torque or also the common torque, both the length of the lever and the force used to move the lever must be related to each other. The following reference points are required for this:
– M as torque in Newton metres
– r as lever arm length in meters
– F as force in Newton
The formula for calculating the torque is therefore: M = r * F
Thus, the individual factors in this formula can be resolved against each other, so that when calculating on the basis of two already known values, the third value can easily be calculated. However, very often several different forces have an effect on the angular momentum of a body. This makes the formula for the calculation much more complex, since the torque must be calculated as the vector sum of all individual torques. This makes the calculation much more complicated and time-consuming, which also includes the comprehensive determination of the basic values. When calculating the torque, the signs must also be taken into account. Because even a torque can be shown. In principle, this is referred to as a positive or negative torque. Counterclockwise rotasion indicates a positive torque. However, counterclockwise rotation is referred to as a negative torque.
TORQUE AND MECHANICAL WORK - AN IMPORTANT DIFFERENTIATION
The two factors torque M and mechanical work W are colloquially very often confused with each other and then converted against each other during the calculation. However, this is not allowed. It is not possible to convert from a torque to a mechanical work. This is important because in mechanical work the force and the displacement are parallel to each other. In the torque calculation, however, the lever law plays a central role, in which force and displacement are perpendicular to each other in the form of the lever arm.
SPECIAL APPLICATIONS AND SPECIAL CASES IN INDUSTRY
Even if the basic calculation possibilities of the torque remain the same across all effects, different factors nevertheless play an important role in the calculation. These factors are particularly important in industrial measurement, where even the smallest deviations and disturbances can have a lasting effect on the measurement results and thus also on the calculations. These torques differ, among other things, in the type of load, in the type of movement and also in the type of effect. Type of stress: The torques in these segments are divided into the bending moment and the torsion moment, i.e. the moments in which a component bends or twists. Type of movement: A distinction is made between yaw, pitch and roll moments. These factors become important when measuring special axes of a rigid body during the corresponding movements. Type of effect: A distinction is made between different types of effect of the torques. Among other things, these also influence the measuring accuracy and the effectiveness of the various calculations. Among other things, a distinction is made between:
- The output torque
- The drive torque
- The starting torque
- The tightening torque
- The tilting moment
- The load torque
- The clamping torque
All these different variants can be calculated with the above formula, but often other forces have an effect on the calculation, which makes it even more difficult.
AUTOMATED SOLUTION FOR TORQUE CALCULATION
Often it is easier not to calculate a torque, but to measure it. Thanks to modern sensors, many tasks can be solved more easily and quickly. The efficiency of the various measuring methods depends not least on the individual workpieces and their detectability. Especially the active and passive
magnetic measuring methods can be used successfully in many areas. This saves the cumbersome calculation process if the systems used are appropriately calibrated and precisely fitted. To check the system, however, a manual calculation is often necessary at the beginning to check the measuring accuracy of the systems and sensors. The easier and faster you can calculate a torque, the more you benefit from it in productive work.
HOW TO MEASURE THE TORQUE?
Torque plays an important role in many applications. It is important to measure this nominal value for smooth operation and maximum efficiency. This is because processes, sequences and components can only be optimally matched to each other by precisely determining the torque. For this reason, it is important to measure the torque so accurately and without the influence of other forces (cross-talk). There are various solutions for this.
HE USE OF TORQUE SENSORS IN INDUSTRY AND OTHER APPLICATIONS
The measurement of different applied torques is extremely important in many areas. This includes not only the industry with its different production plants and production lines, but also motors and motor technology. Electric drives in cars or e-bikes also require precise measurement of the applied torques in order to be able to act effectively and efficiently. In these areas, torque measurement serves primarily as a control variable and must therefore always be able to be determined reliably and without deviations. Of course, a clean and clear torque measurement is of decisive importance for this.
STATIC OR ROTATING: MEASURING TORQUE OVER TIME
At the beginning of the development only a static torque measurement was possible. For this purpose, strain gages were used which made it possible to determine the torque using simple principles. However, the core areas of application for the measurement were found in the so-called rotating shaft train. Accordingly, sensors had to be developed which were able to measure the torque in such a shaft train. Based on these systems and the developments initiated at that time, various systems are now in use which allow the torque to be measured reliably and without difficulty.
FIVE DIFFERENT WAYS TO MEASURE TORQUE
In total, there are currently five different methods for measuring torque. There are other solutions and possibilities, but they are neither usable nor efficient enough for normal use. Most of these solutions only work under perfect laboratory conditions and are therefore not viable for use in industry. So if you want to measure one torque exactly, you should rely on one of the five methods presented.
STRAIN GAUGE: THE CLASSIC OF TORQUE MEASUREMENT
Strain gauges have been in use for a long time and are still used today. However, for a successful measurement an enormously high accuracy during installation and maintenance is necessary. Although the torque can be measured in many areas with the aid of a strain gauge, these systems are not particularly robust against external influences.
OPTOELECTRICAL TORQUE MEASUREMENT
In this form of measurement, various sensors and sensor combinations are used to measure the angle of rotation, the direction of rotation, the speed and the torque. This is important and helpful in many applications, but is also bought by the size of the measuring system. The extremely precise measurement (0.01%) with a robust signal cannot be used in all areas and applications.
MAGNETOELASTIC TORQUE MEASUREMENT
This measuring method is only suitable for so-called ferromagnetic materials, since these special materials permit macroscopic magnetization, which can be checked by the corresponding sensors. By changing the different magnetic states, the torque can also be measured effectively and without interference. However, this method also shows that it cannot be used in all areas. It is always important to adapt the method to the existing conditions.
MEASUREMENT BY SAW METHOD
The term „Surface Acoustic Wave“ refers to a special measuring method. A sensor generates a sound wave which then propagates over the surface of the measuring medium. A change in the torque also changes the propagation and properties of this sound wave. This change can be easily measured and evaluated with the appropriate sensors. The torque can be determined very easily with this method. However, this method is very susceptible to interference and for this reason can only be used to a limited extend in various areas.
PIEZOELECTRIC TORQUE MEASUREMENT
Certain crystals generate a proportional electrical charge under an existing pressure load. This voltage can be converted into an output voltage by an amplifier. This system also works with very small tolerances and is therefore versatile and flexible. However, it is very susceptible to interference and can therefore only be used under certain conditions in the individual application areas.
MEASURE THE TORQUE: CHOOSING THE RIGHT METHOD
It is important that you choose a suitable method for torque measurement that is suitable for the current and desired application and has a low error tolerance. In order to measure the torque reliably, the system must also have as few disturbances as possible. Choosing the right solution is therefore not always easy and, above all, not possible across the board. In principle, magnetoelastic measuring methods have established themselves in many areas, as they can often be used very flexibly. Here again a distinction is made between passive and active measuring methods. In this way, a suitable solution can be quickly and easily developed and used for every area of application.
INTEGRATION OF MEASUREMENT METHODS INTO YOUR OWN DATA PROCESSING SYSTEM
The pure measurement of the torque, however, is not effective in most applications. This is because the data must also be transferred to the corresponding systems. Depending on the measuring method used, amplifiers must be used to transmit the torque and thus make it usable for other systems. Often it is the complete packages that ensure optimum results and enable trouble-free transmission of the measurement results. In such a case, the measurement tolerance can be particularly low and thus stabilize the results.
