• 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.

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):

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:

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

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:

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.

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.