Hitch / Drawbar eye / calculation

1. Tractor weight – In the absence of the D-value:

The admissible total vehicle combination weight (currently 40 t) minus theadmissible total weight of tractor is the towed load.

2. Vertical load - Static vertical load

Berechnung_Stuetzlast
  • Vertical load from the central axle trailer at the hitch point.
  • The maximum possible static vertical load depends on the size of the hitch andamounts to 10 % of the total weight of the trailer or 1000 kg (which ever isless). Higher values are possible.
  • The static vertical load should be at least 4% of the trailer weight in order toavoid a damaging negative vertical load.
  • The level of the vertical load also depends on the speed.


Central axle trailer (C):

  • Use admissible in principle:
  • Size of the central axle trailer depends on the characteristics of the drawbareye and the tractor unit.

3. D-Value

Berechnung_D-Wert_1
Berechnung_D-Wert_2_02

3. D-value

D-value (not in all hitches)

Theoretical horizontal force between towing vehicle and trailer, comparative mathematical value of forces between two moving masses.
The D-value can only be calculated from the admissible total weight of both masses(towing vehicle and trailer).

Calculation of the D-value in (kN):

Formel_D-Wert_1_111025_01

T: total weight of the towing vehicle in t
R: total weight of the turntable trailer in t
g: gravitational acceleration (9.81 m/s2)
The calculated D-value can be equal to or less than the D-value of the hitch (type plate) or the weakest link in the overall rig.

Where use of the hitch is permitted for the trailer:

Formel_D-Wert_2_111025_01

R1: total weight of the trailer on which the coupling is mounted in t;
R1 ≥ R2

Hitches and drawbar eyes for road traffic which are tested pursuant to the European standard 94/20 also have specialcharacteristic values established for use with the central axle trailer, the Dc-value and the V-value.

4. Towing vehicle and central-axle trailer: The Dc-value and V-value

Berechnung_DC-Wert

    Dc-Wert (valid only in connection with the V-value)

    • Theoretical horizontal force between towing vehicle and trailer, comparative mathematical value of forces between two moving masses
    • The Dc-value can only be calculated from the admissible total weight of both masses (towing vehicle and trailer).

    Calculation of the Dc-value in kN:

      Formel_Dc-Wert_111025_01

      T: total weight of the towing vehicle in t
      C: sum of the axle loads of the central axle trailer in t
      g: gravitational acceleration 9,81 m/s2
      The calculated Dc-value can be equal to or less than the Dc-value of the drawbar eye.

      08_zentachs_anhaenger

        V-Wert (valid only in connection with the Dc-value)

        • Vertical force for central-axle trailer
        • Dependent on the rear axle suspension of the towing vehicle

        Calculation of the V-value in kN:

          a: an equivalent vertical acceleration in the hitch point in m/s2
          a = 1,8 for vehicles with air suspension
          a = 2,4 for vehicles with other suspensions
          I: theoretical drawbar length in meters
          x: length of the loading area in meters
          x²/l²: at least 1,0
          C: sum of the axle loads of the central-axle trailer in t

          For approvals according to ECE R147 applies:

          V (kN) = 1,8 . 1,44 . C

          The calculated V-value can be equal to or less than the V-value of the hitch and of the towing eye.

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