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It is very important that
the braketest gives a realistic picture of the dynamic behaviour of the
car as when braking on the road. This can only be accomplished when
testing with the car in movement
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Brakedynamics
are displayed for each wheel and the maximum brakeforce is shown in
figures, including the handbrake. Retardation is calculated. Difference
in brakeforce L/R and F/R is stated. With sideslip plate the side-slip
is measured for front and rear wheels. Pedal force and brake force
amplification is measured with an optional pedal force gauge.
Click
on thumbnail to view the full picture.
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The brakes are the most
important safety equipment on a car. Therefore it is very important
that the braketest gives a realistic picture of the dynamic behaviour
of the car while braking on the road.
It should be remembered that the braking result is dependent not only
on the brakes but also on the equipment “above” the
wheels and the brakes, namely the suspension system, shock absorbers
and the chassis, the weight of which parts are transferred to the road
by means of the wheel struts, wheels and tires. Further-more modern
cars are increasingly equipped with technical support systems designed
to help the driver in critical and unforseen situations by damping or
cor-recting any wrong decisions.
Most cars are fitted with limiter valves or proportional valves which
control the distribution of the brakeforce between the front and rear
wheels in order to avoid blocking of the rearwheels which may result in
skidding. Nowadays an increasing number of cars are also fitted with
ABS-systems and a number of vehicles are constructed with 4-wheel drive.
The mechanical construction of the wheel struts, suspension and
steering gear in modern cars is complicated and designed to optimize
the dynamic behaviour of the car under all driving conditions including
braking. All these relations have to be taken into consideration when
evaluating the safety of a car.
When the brake is activated in a moving car, the weight of the vehicle
is propelled dynamically against the front axle causing the front
brakes to be dominating. It is very important to register this dy-namic
course of the brake force in order to conclude how the car brakes under
realis-tic conditions.
The use of a modern plate-braketester which incorporates measuring of
the dy-namic brake force and weight of each wheel is a natural
consequence of this development. On a plate-braketester the braking
ability of a car can be tested under completely realistic conditions as
the test is made when the car is moving at a speed of 10-15 km/h.
Through modern com-puter technology all forces are measured several
thousand times pr. second thereby ensuring that all details in the
dynamic flow are measured.
The measured results are displayed in colours on a big colour screen
making it easy to observe the dynamic flow of brakeforce and
suspension. On the OPTO-PLUS plate-braketester model 510 the dynamic
brakeforces and the dynamic weight are shown for each wheel
sepa-rately. Limiter- and proportional valves , ABS-systems and
permanent 4-wheel drive systems are functioning realistically as on the
road and can therefore be analysed for correct function.
Time used for such an analyzis is minimal and corresponds roughly to
the time it takes to drive over the plates and brake the car. Therefore
the plates can be installed in a driving lane in the work-shop, either
flush-floor or simply mounted on top of an even floor.
Also in relation to the client who wants his car tested this form of
test is excellent. Car owners today are increas-ingly aware of the
safety aspects of their cars and want to know how they stand in respect
to the condition of their vehicles. The plate-braketester is an
instrument offering a quick analysis of a realistic test where the
results are displayed in an easy comprehensible form in coloured
graph-ics. Terms like steering gear, brakeforces, suspension etc. are
easily understood as is the result of the test without it beeing
necessary to use many explanations. For the workshop this is an
excellent oppor-tunity to offer their customers a service product which
increases their satisfac-tion and at the same time augments the image
of the workshop.
Traditionally a roller-braketester is the most used type of brake
tester whereas a plate-braketester like the OPTO-PLUS 510 is relatively
new, its development having been made possible through ap-plication of
modern PC-based systems with big computing power enabling the test
results to be shown in graphic form and in colours.
A test on a roller-braketester can be understood as “the road
turning “ under the wheels, while the car itself stands
still. According to its nature this kind of test is static and in
reality only the effect of the braking function is tested whereas the
dynamic influence from weightdistribution, limiter-and pro-portional
valves, suspension, wheels and tires are not taken into consideration.
Whether one or the other system is the better is dependent on the
individual needs of the workshop and the required range of tests. Both
systems have their advantages and deficiencies. Modern Plate Tester
design has considerable advantages, making it very useful as a test
instrument.
In the table below a comparison has been made between the 2 systems and
their main characteristics. This picture shows the suspension dynamics
for each wheel. At the same time a dampingfactor is calculated for each
wheel as well as the L/R symmetry. Total weight and testspeed are
indicated.
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Rollertester |
Platetester |
| Measuring
Method |
Static:
The weight distribution is static. Cars normally has 60% of the total
weigh on the front axle and 40% on the rear axle.
Measuring results in analog or digital form. |
Dynamic:
The weight distribution is dynamic. At a normal braking action 80-90%
of the total weight is on the front axle.
The dynamic brakeforces is shown in graphic form for each wheel.
Keyvalues are displayed with figures with diagnostic comments.
The weight of each wheel are measured dynamicly and the suspension
action are displayed in graphic form. The damping for each wheel are
calculated with the symmetry Left /right.
The deceleration is calculated. |
Brake
control
valves |
Proportional valves and
limiter valves out
of action on rear wheels |
Proportional- and limiter
valves functions
as on the road. The function is tested and can be observed on the test
results |
| 4-Wheel
drive |
Vehicles with 4-wheel drive
can only be
tested on special testers with double roller sets.
On a roller tester the pedal force is higher on the rear wheels than on
the front wheels to block thewheels.
The measured brakeforces on the front and rear axle are not related to
the result on the road.
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Braking with 4-wheel drive
function as on
the road. The pedal force is the same for the service brake. The
measured brake forces for front and rear wheels are related to the
results on the road. |
| Spoilers |
Vehicles with spoilers or
low suspension
tend to have problems with a proper contact on a rollertester. |
Functions as on the road. |
| Ovality |
Measured over several
revolutions with
constant pedal force. |
Is measured over a fraction
of a revolution. |
| Testtime |
Test of servicebrake and
handbrake takes 3-5
minutes. |
A complete test can be
performed on 30 sec. |
| Testspeed |
Normally 5 km./h. At this
speed the ABS
system is inactive and in most cases it requires that all 4-wheels
turns. |
Normal test at 8-15 km./h.
Higher speed
possible for test of ABS systems. |
| Installation |
Requires installation in
floor with 3 phase
power.
Can be installed in the driveway |
Installed on top of floor
with 220V power. |
| User
friendly |
Many vehicles are difficult
to test as they
tend to jump off the rollers. |
Everybody can use a plate
tester.
Drive on and brake!
On the monitor all results are displayed in color with graphics with
text and numbers. |
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