Calculation methods | BSA 7xxx / 8xxx | 33
1 691 806 123
2017-06-23
|
Beissbarth GmbH
R
The minimum axle brake pressure required to
operate mechanical brake cylinders is p
1
= 0.4 bar.
p [bar]
F [N]
p
max
p
B
F
B
F
max
0
0.4
Fig. 8:
Extrapolation of the measured characteristic curve (thick)
for one-point extrapolation
The characteristic curve (rule of three) permits
calculation of the force F
B
corresponding to the design
pressure p
B
:
p - 0.4 bar
B
p
- 0.4 bar
max
x F
max
F
=
B
8.4.2
Two-point extrapolation
i
In Germany, two-point extrapolation is used to
calculate deceleration in general inspections (HU) as
per sec. 29 of the StVZO.
Extrapolation is based on the following assumptions:
R
Brake force F is a linear function of the pressure p
fed into the brake cylinders (axle brake pressure
Px).
R
The brake force is measured in the range F
1
… F
max
.
R
The axle brake pressure is measured in the range p
1
… p
max
.
p [bar]
F [N]
p
1
p
max
p
B
F
B
F
1
F
max
Fig. 9:
Extrapolation of the measured characteristic curve (thick)
for two-point extrapolation
The slope m of the characteristic curve permits
calculation of the force F
B
corresponding to the design
pressure p
B
:
F
=
B
F
+ m (p - p
); m =
max
B
max
F
- F
max
1
p
- p
max
1
8.4.3
Extrapolated total deceleration
If the extrapolated brake forces F
Bi
for all wheels i are
known, the total deceleration can be calculated as
follows:
F
Bi
G
total
x 100 %
Z =
Z
Extrapolated total deceleration in percent
F
Bi
Extrapolated brake force of the wheel i
G
total
Gross permissible weight of the vehicle
i
With passenger cars the difference between curb
weight and gross permissible weight is generally
negligible. The measured brake forces can be
referenced to the gross permissible weight of the
vehicle without the need for conversion.
en
