38
BA053101-en
Roller Resistance Power P-Roll [kW]
The rolling resistance power arises from tire and road
surface deformation as a function of speed:
v
g
m
P
r
Roll
⋅
⋅
⋅
=
m
with e.g.
•
Roll resistance coefficient of the tires
µ
r
=
0.012
•
Vehicle mass
m
=
950 kg
•
Gravitation constant
g
=
9.81 m/s
2
•
Driving speed
v
=
90 km/h
=
25 m/s
the result is:
•
P
Roll
= 0.012 · 950 · 9.81 · 25
=
2.79 kW
Since this value only represents a small fraction of the total Road Load it is entered as a fixed
standard value on our dynamometers: for steel belted radial tires approx. 2.5 kW, for winter tires
approx. 3.75 kW.
Setting of the vehicle mass, the aerodynamic drag power and the rolling resistance power is
absolutely necessary for Road Load simulation and stop watch tests, in order to simulate the
vehicle under the correct Road Loads.
Mass m = Vehicle mass [kg]
This value is needed in order to attain a proportional
traction F via the eddy-current brake from the vehicle
determined acceleration.
[N]
a
m
F
⋅
=
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2.10.2
Torque
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Equation
[U/min]
n
9549
[kW]
P
M
⋅
=
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