Calculating radial and axial loads for a tapered roller bearing

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Discussion Overview

The discussion focuses on calculating radial and axial loads for a tapered roller bearing used in a differential system. Participants explore the relationship between input torque and the resulting forces on the bearing, as well as the factors influencing these calculations, including bearing positioning and design parameters.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents an initial calculation for radial force using torque and bore radius, but acknowledges the need for axial force calculations.
  • Another participant emphasizes the importance of the pitch radius of the pinion and the positioning of bearings in determining axial forces.
  • There is a suggestion that the profile and offset of the hypoid pinion and crown wheel are necessary to resolve axial forces accurately.
  • One participant notes that pinion bearing selection is often based on experience rather than strict calculations, indicating that radial and axial thrust may not be the primary factors in selection.
  • A later reply mentions the need for a 3D position and direction vector to solve for forces on the bearings due to input shaft torque.
  • Participants share links to resources that may provide additional information, although access may be limited due to paywalls.

Areas of Agreement / Disagreement

Participants express varying views on the importance of different parameters in calculating forces on the tapered roller bearing, with no consensus reached on a specific method or approach for determining axial forces.

Contextual Notes

Participants highlight the dependence on specific bearing configurations and design parameters, as well as the potential limitations of the initial calculations presented.

voyager14
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Hi

I'm analyzing a tapered roller bearing as part of a differential. I know the shaft is providing input torque of 333.5 N-m @ 4000RPM, and I know the bore size of the bearing, 30mm. I need to find the radial and axial forces given that torque, so I can move on to finding C10, L10, rated load, and lifetime.

I've tried:
1. Diving torque by bore radius (which I realized is tangential force, which is different)
2. Using
Fr = m(ω)2r
where
ω = (RPM/60)2π
this got me
Fr = 1052N or 1.052kN

I don't know if that's correct, and I could also use help with the axial force.
Thank you.
 
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If the tapered roller bearing is one of two on the input shaft to the pinion, then the pitch radius of the pinion, and the position of the two bearings will be important.

If the tapered roller bearing is one of the two that supports the differential assembly in the carrier, (axial with the axle shafts), then the pitch radius of the crown wheel will be important.

You will need to know the profile and the offset of the hypoid pinion and crown to resolve the axial forces.
 
Baluncore said:
If the tapered roller bearing is one of two on the input shaft to the pinion, then the pitch radius of the pinion, and the position of the two bearings will be important.

If the tapered roller bearing is one of the two that supports the differential assembly in the carrier, (axial with the axle shafts), then the pitch radius of the crown wheel will be important.

You will need to know the profile and the offset of the hypoid pinion and crown to resolve the axial forces.

Thank you. It is one of the bearings on the input shaft to the pinion. Are there any resources you know of to help walk me through this?
 
voyager14 said:
Are there any resources you know of to help walk me through this?
I don't know of a reference, but will take a look.

Pinion bearing selection is not normally a computed parameter, it has evolved through experience. If it fails, differential manufacturers will use the next bearing up, if it never fails, try the next smaller bearing.

Radial and axial thrust may not be the critical selection parameters. The pinion bearings are always pre-loaded against each other, in order to hold the pinion in a well defined position relative to the crown wheel.

If you know the 3D position and direction vector, normal to the pinion contact area on the crown, you should be able to solve the vector problem to find the forces on the two bearings due to the input shaft torque.
 

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