Name: friction torque in collar bearings
Uploaded: 2023-09-22T11:49:30.000Z
Duration: 1 min 23 s
Channel: JoVE

Collar bearings are a type of bearing used in machines to support axial loads on rotating shafts, it can have single or multiple collars.
Consider a single collar bearing subjected to an axial load. The area between the external and the internal radius of the collar is the total bearing contact area.
Assuming even support for the bearing, the uniform normal pressure can be expressed as the ratio of force over the bearing area.
Consider an infinitesimal area element on the bearing. The force acting on the differential area can be expressed as a product of the friction coefficient, pressure, and the differential area.
The moment required to cause impending rotation of the shaft is determined from the moment equilibrium equation about the rotational axis.
Next, integration is used to determine the applied moment needed to overcome all the frictional forces.
Finally, by substituting the values of differential force and differential area and integrating the equation over the total bearing area, the moment of the shaft can be estimated.

collar bearings

Collar bearings are essential in various machines designed to support axial loads on rotating shafts. Depending on the specific application and requirements, they can be found with single or multiple collars.
<img alt="Static equilibrium diagram using torque and force vectors; cylindrical rotor; ΣTorque=0, dynamics." src="/files/ftp_upload/14325/14325_Figure_1v3.svg" style="text-align: center; height: 300px;" data-altupdatedat="1761830439000" data-alt="Figure 1">
Consider a single collar bearing subjected to an axial load. The total bearing contact area is the region between the external radius and the internal radius of the collar. When the bearing is assumed to provide even support, the uniform normal pressure can be calculated by dividing the force applied on the collar by the total bearing contact area. This value represents the average pressure distribution across the bearing surface.
To further analyze the forces acting on the collar bearing, consider a small, infinitesimal area element on the bearing surface. The force acting on this infinitesimal area is a product of the friction coefficient, pressure, and differential area. Understanding the relationship between these variables is crucial in calculating the moment required for the shaft to rotate.
The impending rotation of the shaft is determined by analyzing the moment equilibrium equation about the rotational axis. This equation considers all the forces and moments acting on the shaft, including the frictional forces generated by the collar bearing.
<img alt="Static equilibrium equation, moment balance, symbol: M-∫rdF=0." src="/files/ftp_upload/14325/14325_Equation_1v2.svg" style="text-align: center; height: 39px;" data-altupdatedat="1761830439000" data-alt="Equation 1">
By integrating the equation, the applied moment needed to overcome all these frictional forces can be determined, which initiates shaft rotation. Finally, to estimate the moment of the shaft, substitute the differential force and area values into the integrated equation.
<img alt="Static equilibrium formula M in cylindrical coordinates; integral for mechanical analysis." src="/files/ftp_upload/14325/14325_Equation_2v2.svg" style="text-align: center; height: 55px;" data-altupdatedat="1761830439000" data-alt="Equation 2">
Integrating this equation over the total bearing area provides a comprehensive understanding of the forces and moments acting on the collar bearing and the moment required for the shaft to rotate.
<img alt="Static equilibrium formula M=2/3μsP((R2^3−R1^3)/(R2^2−R1^2)); analytical method." src="/files/ftp_upload/14325/14325_Equation_3v2.svg" style="text-align: center; height: 39px;" data-altupdatedat="1761830439000" data-alt="Equation 3">

Collar Bearings

Collar bearings are essential in various machines designed to support axial loads on rotating shafts. Depending on the specific application and ...

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Mechanical Engineering

Unit 1

Friction

KEY TERMS AND CONCEPTS

friction torque in collar bearings

Collar bearings support axial loads on rotating shafts, and their friction helps determine the torque needed to start motion. They are used in many machines and may have a single collar or multiple collars, depending on the application and load needs.

For a single collar bearing under an axial load, the contact area is the ring-shaped region between the external radius and the internal radius of the collar. If the bearing is assumed to support the load evenly, the uniform normal pressure is found by dividing the applied force by this total bearing contact area. This gives the average pressure across the bearing surface.

To study the forces more closely, a small infinitesimal area element is considered on the collar surface. The force on that tiny area equals the friction coefficient times the pressure times the differential area. Using this relationship is important for finding the moment required to rotate the shaft.

The impending rotation of the shaft is found by writing the moment equilibrium equation about the rotational axis. This equation includes the forces and moments on the shaft, along with the frictional forces from the collar bearing. When the equation is integrated over the full bearing area, the applied moment needed to overcome friction and begin rotation can be determined.

Friction Torque in Collar Bearings

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key terms and concepts

Learn how collar bearing contact area, pressure, and friction work together to set the torque needed to start shaft rotation in mechanical systems.

Friction Torque in Collar Bearings | JoVE K12

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mechanical engineering

Friction Torque in Collar Bearings

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