Combined Bearing Loading

[Josh2008]

I have been told that you can use an axial and radial bearing side by side in place of a bearing that is designed for combined loading. Is this good engineering practice? Every time I think about the loading with bearings side by side, each meant for a particular load (radial or axial), I feel like this would not work. Is there any articles or literature that discusses this in detail?

Particularly I was going to use a spherical PLAIN bearing for my loading, but because of the load ratio being (50/50) it is not suitable. From what I have gathered, the axial loading is usually defined as being at most, 25% of the radial loading. For example 4000 lb radial and 1000 lb axial is suitable, however 0 lb radial and 1000 lb axial is not. Maybe because without enough radial load the inner piece would dislocate from the outer piece.

So could you use a spherical plain thrust bearing beside a spherical plain radial bearing?

Thanks,
J

 

[MikeHalloran]

What problem are you trying to solve?



Mike Halloran
Pembroke Pines, FL, USA

 

[Josh2008]

Mike,

I have a loading case that can be simplified as a simply supported beam (supported by 2 bearings, each of which is subjected to combined loading).
Can an axial (thrust) and radial bearing be used side by side in place of a bearings that are designed for combined loading? Is this good engineering practice?

Thanks

 

[MikeHalloran]

Now you will probably get a bunch of advice from good hearted people, based on _their_ conjecture about what you didn't say.

Because you have not even clarified whether you're talking about bridge bearings or shaft bearings, some portion of the advice will be grossly wrong. Good luck figuring that out without a picture.




Mike Halloran
Pembroke Pines, FL, USA

 

[JJPellin]

I agree with MikeHalloran. You may think that the term "spherical plain bearing" is perfectly clear and commonly understood. But, in different engineering disciplines, this could be used for drastically different purposes. My experience is primarily in rotating machinery. I work with radial and thrust bearings all the time. But, I have no idea what you are referring to: ball, roller, hydrodynamic, hydrostatic, magnetic, air, or something else entirely.

Johnny Pellin

 

[Tmoose]

Neglecting the spherical part, I'd say thrust and radial bearings have existed happily side-by-side a few times before.

http://t1.gstatic.com/images?q=tbn:ANd9GcQqpL2rxDI_EootMMhFJ74dHjbwbMPhm45ZS9U_yv9B7kJ3dW-6Qw

 

[caoimhin1]

More info needed.
Bearing type depends on the load. Personally I would stay away from spherical plain unless the loads are extreme.
A typical arrangement where you have two bearings side by side is a cylindrical roller bearing and a ball bearing together...the housing supporting the ball bearing is relieved (or the OD of the ball bearing is smaller) so that it takes only axial load, not radial. The cylindrical takes the radial. But I've rarely encountered this....normally you can find a single ball bearing or spherical roller bearing which will take the combined loading.

 

[caoimhin1]

Here's a diagram of what I mean, its the fifth picture down:

http://www.tec.nsk.com/Handbook.asp...Arrangements/Examples/FixedEndAndFreeEnd.html

 

[electricpete]

5th picture down shows on the “fixed end” a deep groove (Conrad) and a cylindrical roller bearing. Is that what you’re referring to? If so the answer as Tmoose said is yes it can be used.

This figure does not show any spherical roller bearing or any plain bearing.

Here is a spherical roller bearing

http://en.wikipedia.org/wiki/Rolling-element_bearing#Spherical_roller

It is different than a deep groove (Conrad) which is what I guess you might be calling “spherical”. The deep groove does have both axial and radial capability.

A plain bearing is a journal bearing.


=====================================
(2B)+(2B)' ?

 

[dinjin]

Single tapered roller bearing are used all the time in combined loading. Think of all the wheel bearing used in cars.
The url that electricpete supplied shows many of the different combinations of combined bearings. You have not given a specific application that you are trying to solve. Application Engineers at all of the bearing manufacturers would be glad to choose the right bearings for your application.
Even tapered roller bearing have spherical o.d. sockets in double row bearings which allow the shaft to rock and roll. Are you talking about barrel type rollers when you are referring to spherical plain bearing?

 

[Josh2008]

Sorry for the confusion or lack of information. I was trying to keep my question basic and not necessarily applicable to my direct application.

I was searching for an explaination of how or if bearings are used at the same support location of which both support a different type of load (axial and radial).

Attached is a picture.

I understand now that this somewhat common to do, and it works by utilizing a clearance on the axial bearing so that there is no radial loading transferred via the shaft.

I am leaning towards this setup as the loading is complex, and changes throughout the cycle. This way I can size the bearings based on a single directional load, and not have to worry about load ratio's (axial vs radial) flucuating beyond a combined loading bearings limit (eg spherical roller).

Hope that clears some of this up. Any feedback is appreciated.

 

[Josh2008]

From the attached picture, I am talking specifically about spherical plain radial bearing, and a spherical plain thrust bearing.

 

[caoimhin1]

Looks good. Just make sure your loads are high enough to justify needing spherical plain bearings.