AR42.25-W-0020-01A | Check braking characteristics of tractor vehicle | ||
| Test sheet on the braking characteristics of tractor vehicles and trailers, form |
1 Apply pressure graduations (pm) to the coupling head for brake according to the test sheet and enter the brake cylinder pressures (p1, p2) and brake forces (F1 to F4) achieved for each wheel in the test sheet. Note the locking limit.
Use the form "Test sheet on the braking characteristics of tractor vehicles and trailers" Only use values below the locking limit. Perform the pressure graduation in an ascending manner and check at the highest possible pressure, releasing the service brake again continuously.
-----------------------------------------------------------------------------------------
2 Add the brake forces (F1 to F4) of the individual axles together and enter the sum of brake forces (FM) of the tractor vehicle, referenced to the individual pressure graduations (pm), in the test sheet.
3 Calculate braking ratio (z) for each pressure graduation (pm).
Total of brake forces (FM)
z = 100 (%)
permissible gross vehicle weight (GM)
-----------------------------------------------------------------------------------------
Example of brake application (z) of tractor vehicle:
Sum of brake forces (FM) with pm 2.0 bar = 2790 daN
permissible gross vehicle weight (GM) = 18,000 kg
2790
z = 100 (%) = 15.5 %
18.000
At a pressure of 1 bar at the coupling head for brake, braking effect must already be showing at the wheel.
Example of brake forces calculated:
Coupling head for brake Total
pm (bar) FM (daN) z (%)
0,0 460 2,6
0,5 460 2,6
1,0 780 4,3
1,5 1800 10,0
2,0 2790 15,5
2,5 3590 19,9
3,0 4500 25,0
4,0 6220 34,6
5,0 7400 41,1
6,5 9200 51,1
>8.5
W42.00-1027-81
4 Transfer the calculated braking values (z) for each pressure graduation (pm) from the test sheet to the EC braking rate band. Connecting the points will result in a curve, which is the braking curve (braking characteristics) of the tractor vehicle.
If the braking curve is outside the EC braking rate band or if too high response pressures are found, a complaint must be raised about the brake. The brake system of the tractor vehicle must then be checked and faults or any signs of wear found must be eliminated. Changes to the brake system are only permissible in consultation with the automotive manufacturer.
1 Braking curve of the tractor vehicle
U EC braking rate band of loaded tractor unit