Rolling Resistance

  ↵

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)]