Page 89 - The Tribology Handbook

AI 4 Spherical bearings

A guide to the selection and performance of ball joints

QPe Straddle or rod end Axial Transverse

Angle 1 10" to f 15" with minimum f25" to f30" 1 IO" to f 15" low angle 125" to
shoulder on central pin, 130" to f 30" high angle
40" with no shoulder on central pin
Main use Linkages and mechanisms Steering rack end connections Steering linkage connections,
suspension and steering articulations
Lubrication Grease Grease Lithium base grease on assembly.
Largest sizes may have provision
for relubrication
Enclosure and Often exposed and resistant to liquids Rubber or plastic bellows, or boot Rubber or plastic seals, or bellows
protection and gases. Rubber gaiters available
(Fig. 14.3)
Materials Inner. Case or through hardened steel, Ball. Case-hardened steel Ball. Case-hardened steel
hardened stainless steel, hardened Bushes. Case or surface hardened Bushes. Case or surface hardened steel,
sintered iron; possibly chromium steel, bronze, plastic or woven bronze, plastic or woven
plated impregnated impregnated
Outer bearing surfaces. Aluminium
bronze, naval bronze, hardened
steel, stainless steel, sintered bronze,
reinforced PTFE
Working Limiting static from 14 MN/m2 to 35 to 50 MN/m2 on maximum or Approximately 15 MN/m2 on plastic,
pressures 280 MN/m2 on projected area measured forces 20 MN/mZ on metal surface
depending on materials. Wear limi- projected areas. Bending stress in
ted on basis of 50 x IO3 cycles of i25 the neck or shank which averages
at 10 cycleslmin from 80MN/mZ to 15 times the bearing pressure limits
180 MN/m2 dependingon materials working load. Fatigue life must
also be considered
Area factors 0.42 to 0.64 with radial loads and 0.25 0.55 large angles 0.7 small angles
0.12 to 0.28 with axial loads

Remarks No provision to take up wear which Spring loaded to minimise rattle Steering and suspension joints spring
probably determines useful life. Use and play loaded to minimise rattle and play
Fig. 14.7 for selection or consult and to provide friction torque. Some
manufacturer plastic bush joints rely on
compression assembly for anti-rattle
and wear compensation

AI 4.4