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8.17:

Bearings: Problem Solving

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Mechanical Engineering
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JoVE Core Mechanical Engineering
Bearings: Problem Solving

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Consider a double-collar bearing with a hole radius of 20 millimeters, experiencing an axial force of five kilonewtons. Collar A, with a radius of 40 millimeters, carries 75 percent of the force, while collar B, with a radius of 30 millimeters, carries 25 percent; both collars distribute pressure uniformly. Calculate the maximum frictional moment the bearing can resist, given a static friction coefficient of 0.3 for both collars. Recall the expression for the required maximum frictional moment. By rearranging and substituting the values of the forces supported by both collars, the maximum frictional moment can be determined. Next, modify the configuration by exerting an axial force of 15 kilonewtons on the bearing. Determine the minimum torque required to overcome the friction. Using the frictional moment equation and substituting the values, the moment for both collars caused by the frictional forces can be determined. By equating the sum of moments about the z-axis to zero and substituting the known values, the required minimum torque can be determined.

8.17:

Bearings: Problem Solving

Understanding the calculations and concepts related to double-collar bearings is essential for engineers and designers to optimize the performance of these components in various applications. By analyzing the bearing under different conditions, one can ensure that it can withstand the forces and moments experienced during operation. This knowledge enables better decision-making when designing and selecting bearings for specific purposes and configurations. Consider a double-collar bearing with specific dimensions and an axial force applied to it.

Figure 1

To find the maximum frictional moment that the double-collar bearing can withstand, the following expression can be used:

Equation 1

The maximum frictional moment can be calculated by rearranging the expression and substituting the values of the forces supported by both collars.

Consider a scenario where the applied axial force on the double-collar bearing increases. To determine the minimum torque needed to overcome the friction, first calculate the moment for both collars caused by the frictional forces using the frictional moment equations and substituting the values.

Equation 2

Equation 3

Next, equate the sum of moments about the z-axis to zero and substitute the known values. The required minimum torque to overcome the friction in the modified configuration can be evaluated.

Equation 4

Suggested Reading

  1. Hibbeler, R.C. (2016). Engineering Mechanics ‒ Statics and Dynamics. Hoboken, New Jersey: Pearson Prentice Hall. Pp 454.