MK IV rear axle system
The ASFT Mk IV rear-axle is a new generation of surface friction testers based on the highly successful Mk II system. The new design has no connection to the chassis of the host vehicle, and is therefore very stable. This unique solution is generating an unmatched repeatability and reproducibility.

1. The Measuring Computer
This reads signals from the vertical and torque transducers (sensors) which are then converted into digital form and sent to the main computer together with the pulses from the pulse transmitter. The measurement computer also performs automatic tests on the system, which makes any tedious adjustments unnecessary.

2. The Relay Box
Relays and fuses for the measurement system are centralised to a service box which is very easy to reach. Here you also have the new system usage counter.

3. The Rear Axle and Housing
Contains rear wheels, drive shafts, free wheel, primary chain drive and magnet coupled power outlet for the self watering system.

4. The Wheel Down Sensor
In the upper part of the hydraulic cylinder is a magnetic sensor to check the position of the measuring wheel. This to determine whether itís retracted or not. Itís very important that the sensor is protected since this is a critical part of the system. That makes this an ideal position.

5. The Hydraulic System
This unit provides constant pressure for the wheel retraction mechanism and for the vertical load on the measuring wheel. The system consist of a pump, and oil container, two directional valves, and accumulator tank, a hydraulic cylinder, a pressure gauge plus some additional valves and pipes. The hydraulic system together with the very fast measuring computer ensure the speed and accuracy of the Mk IV system.

6. The Hydraulic Cylinder
It is connected to the rear-axle via a ribbed spring, and no to the body. This to avoid transfers of any surface bumps from the host vehicle to the test wheel.

7. The Vertical Load Sensor
This monitors the vertical down pressure created by the hydraulic system, and makes any necessary adjustments to it. It ensures that an absolute constant ground contact pressure is kept.

8. The Water Nozzle
Used to spray a water film on the surface in front of the measuring wheel.

9. T-transducer
The T-transducer senses the force on the chains in the transmission arm. During measurement, there will be a force on these chains due to the slip. The size of the force depends on how much friction there is on the surface that is being measured. The better friction there is on the surface, the more force you get on these chains, which leads to a higher friction value.

10. The Transmission arm
Holds the T-sensor, vertical load sensor, measuring wheel and the hydraulic cylinder.

11. The Pulse Transmitter
This sensor generates 1 pulse per meter (2 pulses for every turn of the wheel) which makes it possible for the computer to measure the travelled distance.