1. Bearings
Lubrication
&
Cooling
Roger Bortignon

2. Friction
Friction is:
the resistance opposing any effort to roll or slide one object over another

3. minute imperfections on surface interact
Causes of Friction
minute imperfections on surface interact
adhesion between surfaces causes attraction
deformation or indentation of one object into another

4. Kinds of Friction
1) Fluid friction: is less than solid friction but it exists
2) Static friction: resistance to movement between 2 bodies in contact & at rest
3) Kinetic Friction:
Sliding friction: resistance to continued movement once set in motion
Rolling Friction: one body rolling over another – the least of the 3 frictions

5. Overcoming Friction
Static “Coefficient of Friction” = force to move the object
weight of the object
Kinetic “Coefficient of Friction” = force to keep the object moving

6. Coefficients of Friction
coefficient of friction: The force required to slide an object, divided by the weight of the object
Materials
Static
Kinetic - Sliding
hard steel on hard steel
0.78 (dry)
0.42 (dry)
steel on graphite
0.21 (dry)
0.09 (lubricated)
aluminum on mild steel
0.61 (dry)
0.47 (dry)
glass on glass
0.94 (dry)
0.35 (lubricated)
0.40 (dry)
cast iron on cast iron
1.1 (dry)
0.2 (lubricated)
0.15 (dry)
0.07 (lubricated)
steel on babbitt
0.17 (lubricated)
0.35 (dry)
0.14 (lubricated)
Teflon on steel
0.04
Tire on Pavement
1.7 (approximate)

7. Angle of Repose
angle of repose: the angle at which an object begins to slide
Coefficient of static friction = YZ = Tangent of angle of repose XZ

8. What have we learned so far…
Friction is determined by…
1) force (PSI) pressing materials together
2) coefficient of friction for those 2 materials

9. Bearings Purpose of a bearing: reduce friction
support a load/rotating shaft
radial
axial
Bearing classifications:
friction bearings (aka: plain bearings)
anti-friction bearings

10. 3 types of friction bearings…
Journal bearing: crankshaft, piston pin, camshaft
Guide bearing: valve guide
Thrust bearing: crankshaft end thrust

11. Precision Insert Friction Bearing Essential Characteristics
Embedability: inserts are designed to totally absorb abrasive particles or pass them off completely
Bearing surface heavily embedded with foreign particles. Note bright rings from raised material surrounding largest particles

12. Precision Insert Friction Bearing Essential Characteristics
Conformability: inserts are designed to distribute the load uniformly even when the shaft or bearing bore is out of round.

13. Oil Starvation
Bearing surface streaked and smeared from shaft contact due to breakdown or lack of adequate oil film. Heat discoloration and most severe damage near center.

14. Plain bearing advantages…
small package size
high speed capability
lower cost
easily replaced
can tolerate greater levels of debris in the lubricant

15. 3 types of anti-friction bearings…
1) Tapered roller bearings
tapered rollers are used in heavy radial & thrust loads & typically run at lower speeds.
2) Ball bearings
ball bearings are designed for light to moderate radial loads, limited thrust loads & are better suited for high speeds.
3) Needle bearings 1 2 3 1

16. ball thrust bearings
needle thrust bearings