Differences Between Bearings

Take a look at this link. It explains the main points in a simple way.

http://www.frostytech.com/articleview.cfm?articleid=193&page=1

Mainly, the difference between rolling element bearings and sleeve bearings is that in sleeve bearings you should not have contact between the moving parts while working, the shaft working on a thin layer of lubricant, so, no contact, no noise, no wear, heat is generated basically by internal atrict in lubricant. It is really efficient where it can be used (all car engines nowadays use sleeve bearings inside).

Of course, it does not solves problems when the speed of the shaft is slow, or the load is too high, or when you cannot assure a good lubrication system with pressurized oil feed. So, spherical or roller bearings must be used. They work essencially the same way, and different from sleeve bearings, as spherical bearings have a point of contact between the spheres and the races to transmit load, while the roller bearings have a line of contact, so, supporting, conceptually, more load under lower speeds.

Those are the very conceptual points of design of them. You'll find over the web a number of different bearing types, like needle bearings (a roller bearing with high speed capability), self aligning bearings, cone shaped roller bearings, thrust bearings, angular contact bearings, self aligning roller bearings... , all for purposes like supporting shaft disalignment, combinations of radial and axial loads, some have special characteristics to allow assembly/disassembly, some are isolated from ambient for work in dirty areas, etc.

Some examples, most of cars here in Brazil rear wheel bearings are of the cone shaped roller bearing, assembled in pairs, to support lateral loads in both directions together with the weight of the vehicle, enclosed in the wheel housing by retainers and lubricated by grease. Front wheels rely on double spherical bearings with combinated loads capability (each assembly of spheres supports load in radial and one axial direction) lubricated in the factory and shielded from ambient, not needing lubrication during assembly. It's more reliable to support more weight from the mechanical assembly, traction, and loads from the wheels turning. They're also substantially more expensive than the rear bearings.

Do a search and have fun. I also suggest NSK home page, www.nsk.com .

Well explained.

Dear Sir,

Thank you very much for the reply. Greatly explained.

Thanks once again.

Regards,

Sleeve bearing:

Hard Polished (Steel)shaft neck called Journal rotates in a (cylindrical Cast Iron, Bronze , powder metal sintered , bamboo/timber axially grained,) sleeve called Bush with a fluid layer in the annular space-a must . Fluid can be gas ,air, water, oils,greases- even graphit or molybdenum sulphide.Can be for Radial,mixed,Thrust loads.

Generally used where space is at a premium and loads are high and impulse shocked.

Read from the classic:Tribology Handbook 3 Vols.---Eds Kragelsky,Alisin-- Mir Publishers

Ball bearing: Factory made , mass produced , Standard dimensioned , standard propertied inner and outer rings(races) separated through hard balls held in a cage to avoid jamming among themselves . Races/Balls made from superior Bearing Steel> C=~1.2%,Cr ~10%,Hardenedground to almost no play. Lubrication by Oil/Grease has non-essential roles to play .

Generally used where space is not at a premium and loads are predictable/steady.

Axial,Mixed,Radial loads are specified predictably. SKF/FAG/other websites tell all.

Spherical Roller is like BallBearings-generally termed Antifriction or Rolling Bearing.

In Spherical the axial strict parallelism needed by Ball Bearings is relaxed to a few Degrees .*************************

Concentricity is of course needed in all type Bearings.

Dear sir,

Thank you very much for the reply. But then how oil bearing and grease bearing are differentiated. And what are the specific application of both.

Regards,

Keyur Shah