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IW4/IW7 WB/WBV Description
D1 0412BA1-GB04 1
1 Description
1.1 Introduction
The IW4/IW7 WB/WBV (4WD) belong to the group of roller brake testers.
This class includes two different measuring methods to record brake forces:
! the testing of drive torque or
! the testing of drive power.
The former is applied in the MAHA IW4/IW7 WB/WBV (4WD) brake tester. The
IW4/IW7 WB/WBV (4WD) consists of a proven roller set and an open-ended electronic system
based on a processor board with an integral operating system.
The standard test stand may be expanded to a complete test line by using the MAHA
accessories.
1.2 General Information about Brake Testing
To avoid skidding it is important that the brake forces of the individual wheels of one axle are the
same. Just as important is the minimum brake torque for each individual wheel, so that when
braking no vehicle brake is overburdened. Consequently, each wheel is tested individually on the
brake tester.
For measuring the brake force, a static and a dynamic method are available. Using the static
method the force necessary to rotate a wheel which is positioned on a plate, with applied brakes
is determined. The dynamic method is more practice orientated - whereby the wheel is brought
up to a predetermined RPM by the motor driven roller set and then the brakes are applied. A
sensor roller measures the wheel revolutions. A comparison of the drive roller RPM to the
sensor roller RPM determines how large the slippage is. For safety reasons, all MAHA brake
testers automatically interrupt the brake test at a slippage of approximately 30%.
The measurement principle is the same for both methods of testing. The drive motor is
supported in a rotary fashion (motor housing not supported); without any additional support, the
drive shaft and the housing would counter rotate when under load, depending on the force
distribution. The additional support consists of a flexible beam, on which the housing rests. The
steel beam bends corresponding to the torque produced by the motor, which the beam resists.
The torque is zero at the beginning of the static test. With the dynamic test method, the torque is
just high enough to set the drive rollers with the vehicle wheel in motion with the brakes not
applied.
A strain gauge is mounted on the transverse beam which converts the brake force into a usable
electrical value.
For the IW4/IW7 WB/WBV (4WD)) brake tester the dynamic test method is used. This method
ensures the most accurate measurement. There is simply no alternative for 4 wheel drive brake
testing.