Carrying a Radial and Axial Load 3

[steris]

Hi All,

I have an application where I am hinging a heavy door and to trying to minimize the hinge friction. I started a thread in Mech Eng Design (

http://www.eng-tips.com/viewthread.cfm?qid=331769)

but it seems my question may be more appropriate for this thread. I apologize for the cross post!

My basic question is this: When carrying an axial load and radial load is it better to use two different bearings - one thrust and one radial - or is better to use something like a taper roller or angular contact ball bearing? What are the criteria used in making this determination? This previous thread (

http://www.eng-tips.com/viewthread.cfm?qid=286868)

only somewhat addressed this question.

Any assistance would be greatly appreciated!

Best,
Steris

 

[MikeHalloran]

The usual primary driver is cost.

In your case, I would first look at a tapered roller bearing at one end of the hinge to carry all of the door's weight and half of the moment, and a straight roller bearing to carry the other half of the moment.

ISTR you are also trying to meet a rather tight spec for operating torque. For that, you have to look at the precision class of the bearings, and think of the allowable runout of the bearing elements as being like a ramp that must be climbed by the rolling element. For this exercise, think of the rolling elements as being unwrappped from their actual cylindrical relations onto a plane, so you are then looking at an inclined plane problem. Since no timing limitation was imposed, the inertia of the door is irrelevant to meeting the spec.


Mike Halloran
Pembroke Pines, FL, USA

 

[steris]

Hi Mike,

Thank you so much for your reply!

 

[ApplicationENG]

Steris, you also need to consider two other factors: size and design.

If you were two seperate the functions of a tapered bearing into two seperate bearings, you are taking up much more room, also the cost will most likely be greater.

In terms of design with a tapered bearing, there will be compromises in terms of the loads the bearing can carry. I.E. the thrust is so great that now you have over sized the bearing for the radial loads and now the equipment is overdesigned. by splitting the bearings into components you can design correctly and ccordingly provided you have the money and the space.

 

[avantibngrant]

A little factor to keep in mind is that a deep groove ball bearing can carry up to half of its radial rating in the axial direction. Often very useful for some bearing applications.

Regards

Neil