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32 | BSA 7xxx / 8xxx | Calculation methods
8.
Calculation methods
8.1
Deceleration
Deceleration measures the performance of a brake
system. It is specified as the percentage ratio of
braking force to weight.
Axle deceleration
F
axis
Z =
x 100 %
G
*g
axis
Z
Deceleration in percent
F
Axle brake force
axis
G
Axle load
axis
g
Acceleration due to gravity
Total deceleration
F
+ F
front
rear
Z =
x 100 %
G
*g
total
Z
Deceleration in percent
F
Front axle brake force
front
F
Rear axle brake force
rear
G
Total weight
total
G
Vehicle weight
vehicle
G
Weight of tester
test person
g
Acceleration due to gravity
Parking brake deceleration
F
hand
Z =
x 100 %
, G
total
G
*g
total
Z
Deceleration in percent
F
Brake force of parking brake
hand
G
Total weight
total
G
Vehicle weight
vehicle
G
Weight of tester
test person
g
Acceleration due to gravity
8.2
Out-of-roundness
Maintain a constant pedal force. BSA 7xxx / 8xxx
measures the resulting minimum and maximum brake
force. The out-of-roundness is calculated as follows:
F
- F
max
min
(~) =
x 100 %
F
max
~
Out-of-roundness in percent
F
Maximum brake force
max
F
Minimum brake force
min
|
1 691 806 123
2017-06-23
, G
= G
+ G
total
vehicle
test person
= G
+ G
vehicle
test person
8.3
Brake force difference
The brake force difference is measured at maximum
brake force.
F
- F
DF =
max
min
x 100 %
F
max
Brake force difference in percent
DF
F
Higher left/right wheel brake force value
max
F
Lower left/right wheel brake force value
min
8.4
Extrapolation of brake forces
i
The extrapolation of brake forces is defined in
national regulations.
The gross permissible weight of trucks and trailers may
be several times higher than the curb weight.
Vehicles are generally tested in unladen condition. Due
to the low test weight, the brake forces which can be
generated by the brake system cannot be transmitted
to the test rollers over the full area.
In order to be able to obtain the deceleration of the
fully laden vehicle in such cases, the brake forces of the
individual wheels have to be extrapolated accordingly.
8.4.1
One-point extrapolation
i
In Germany, one-point extrapolation is used to
calculate deceleration in safety tests (SP) as per
sec. 29 of the German Road Traffic Licensing Act
(Straßenverkehrs-Zulassungsordnung - 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 up to the value F
R
The maximum axle brake pressure is p
.
max
.
max
Beissbarth GmbH
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