ROLLING RESISTANCE

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Introduction:

Rolling resistance or rolling friction or rolling drag, is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface.

Basics of rolling resistance:  

  • due to the deformation of the tire at the tire/road interface
  • tire deformation consumes energy
  • an unequal force is needed  during compression and  elastic recovery
  • Therefore: the normal pressure distribution over the tire/road contact patch is not uniform.
  • the normal force is higher in the leading half of the contact patch than in the trailing half
  • the normal force produces a moment about the axis of rotation of the tire
  • rolling resistance moment:         Mf= Fz.a
  • The driving force fax, applied to the wheel produces a moment to balance the rolling resistance moment.

  • In the actual case of a rolling wheel, both the wheel and the surface will undergo deformations due to their particular elastic characteristics.
  • At the contact points, the wheel flattens out while a small trench is formed in the surface
  • Experiments show: rolling resistance is:
  1. proportional to the tire deformation
  2. Inversely proportional to the radius of the loaded tire.

 

ACCORDING TO THE US STANDARD:

  1. -IF v<50 km/h : f = 0,0165
  2. -IF v>50 km/h : f = 0,0165 [1 00,1.(v –50)]

 

    

 

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