Automotive Calculating radial and axial loads for a tapered roller bearing

AI Thread Summary
The discussion focuses on calculating radial and axial loads for a tapered roller bearing in a differential system, specifically with an input torque of 333.5 N-m at 4000 RPM. The user initially attempts to derive the radial force using torque and bore radius but realizes the need for a more accurate approach, emphasizing the importance of the bearing's position and pitch radius. It is noted that pinion bearing selection often relies on experience rather than strict calculations, with pre-loading being crucial for maintaining pinion alignment. The conversation also highlights the necessity of understanding the 3D position and direction vector of the pinion contact area to accurately resolve forces on the bearings. Resources for further guidance on this topic are suggested, though some may require payment.
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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