Effect of Adhesion Limits
See also: Traction (engineering)Adhesion is caused by friction, with maximum tangential force produced by a driving wheel before slipping given by:
- Fmax= coefficient of friction x Weight on wheel
Usually the force needed to start sliding is greater than that needed to continue sliding. The former is concerned with static friction, referred colloquially to as 'stiction', or 'limiting friction', whilst the latter is called 'sliding friction'.
For steel on steel, the coefficient of friction can be as high as 0.78, under the best of conditions (= utopic laboratory condition, on railway realty: 0.35 -0.5 ), whilst under extreme conditions it can fall to as low as 0.05. Thus a 100 tonne locomotive could have a tractive effort of 350 kilonewton, under the ideal conditions (assuming sufficient force can be produced by the engine), falling to a 50 kilonewton under the worst conditions.
Read more about this topic: Rail Adhesion
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