Confused About Forces in Bearings: Getting Reactions in Axial Direction

In summary, the author was confused about the direction of the forces on a bar connected to a spindle. After plugging in some numbers, they determined that the forces shown in Figure A were incorrect and that the directions for the forces shown in Figure B were correct. They also determined that the reaction forces at the bearing would need to be included in the analysis if the analysis is to be complete.
  • #1
Tekneek
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I was confused about this example from a book. After putting in some numbers I got the forces circled in green and blue to be negative. Does this mean the directions for the forces shown is incorrect, and so I should switch the directions before calculating the reaction forces in the bearings (x marked in red).

Also how should i go about getting the reactions in bearing in axial direction (s+p2)? Its pretty simple if I just have one axial reaction force, but with two bearings I am not sure.

Thanks
 
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  • #2
It appears that in B they are only concerted about the reactions on the driving spindle and not any of the components beyond that point. The orientation of the force vectors on that component will always be opposite to those shown in Figure A that represent the forces acting on the bar end connected to the drive spindle.
 
  • #3
JBA said:
It appears that in B they are only concerted about the reactions on the driving spindle and not any of the components beyond that point. The orientation of the force vectors on that component will always be opposite to those shown in Figure A that represent the forces acting on the bar end connected to the drive spindle.
So if I want to calculate the reactions on the bearings should I just keep the negative, not changed the direction of my arrows and proceed with the calculations?
 
  • #4
Yes retain the current forces as shown and treat them as forces on the end of a beam with two supports. At the same time, if you decide to extend your analysis to include the bearings then for a complete analysis you will need to include the forces from the drive pulley/gear on those elements as well.
 
  • #5
JBA said:
Yes retain the current forces as shown and treat them as forces on the end of a beam with two supports. At the same time, if you decide to extend your analysis to include the bearings then for a complete analysis you will need to include the forces from the drive pulley/gear on those elements as well.
So I plugged some numbers into get the forces and also added a force from drive pulley. Does my calculations for the reactions at the bearing look correct? Thanks.
Vao78wn.jpg
 
  • #6
Your bearing reaction directions in the top diagram look correct; but, what does the 94.86 at the left end represent?
 
  • #7
JBA said:
Your bearing reaction directions in the top diagram look correct; but, what does the 94.86 at the left end represent?
94.86 is the force from a pulley. Also, wouldn't the bottom diagram be the one with correction bearing reaction since I got negative values for the reactions (Raz and Rbz) when i solved them?
 
  • #8
The reaction arrow directions for the spindle and the bearing B in the top diagram are correct. Did you use the x load direction at P3 shown in the top diagram or the bottom one? The P3 and all of the other forces shown in the bottom diagram at the tool contact point are tool reactions that are opposite to the reactions on the bar and ultimately on the spindle. If you have done the correct analysis then the horizontal x force at the spindle should be in the same direction as P3 in the top diagram.

PS I suspected that the end load was for the pulley, but I wanted to be sure.
 

Related to Confused About Forces in Bearings: Getting Reactions in Axial Direction

1. What are forces in bearings and why are they important?

Forces in bearings refer to the external loads that act on a bearing, causing it to rotate or move. These forces are important because they can affect the performance and durability of the bearing, and can also impact the overall functioning of the machinery in which the bearing is used.

2. How do I determine the reactions in the axial direction for a bearing?

The reactions in the axial direction for a bearing can be determined by using the principles of statics. This involves analyzing the external loads acting on the bearing, as well as the geometry and design of the bearing, to calculate the reactions in the axial direction.

3. What factors can affect the reactions in the axial direction for a bearing?

There are several factors that can affect the reactions in the axial direction for a bearing, such as the magnitude and direction of external loads, the type and design of the bearing, and the materials used in the bearing. Other factors include the lubrication and temperature of the bearing, as well as any misalignment or uneven loading.

4. How can I ensure that the reactions in the axial direction for a bearing are within acceptable limits?

To ensure that the reactions in the axial direction for a bearing are within acceptable limits, it is important to carefully design and select the bearing for the specific application. This involves considering factors such as load capacity, speed, lubrication, and materials. It is also important to regularly monitor and maintain the bearing to prevent excessive wear and tear.

5. What are some common problems associated with incorrect reactions in the axial direction for bearings?

Incorrect reactions in the axial direction for bearings can lead to various problems, such as premature bearing failure, increased friction and wear, and decreased performance of the machinery. Other potential issues include vibration, noise, and reduced efficiency. It is important to accurately calculate and control the reactions in the axial direction to prevent these problems and ensure optimal bearing performance.

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