D-Value (Articulated Truck/Towed Trailer Coupling)

Grafik eines Lkw — **Calculation formula** The so-called D-value has been defined to determine the load capacity of trailer couplings (D = drawbar).

Red right arrow — **Calculation formula** The so-called D-value has been defined to determine the load capacity of trailer couplings (D = drawbar).

The so-called D-value has been defined to determine the load capacity of trailer couplings (D = drawbar). It applies equally to articulated truck and towed trailer couplings, but is differently calculated. The D-value is stamped into the type plate on a trailer coupling. Its unit is kN. The D-value can be calculated from the permissible total mass of the towing vehicle and trailer. The higher the D‑value, the greater the mass that can be attached to a coupling.

Trailer coupling (D-value)

The D-value for a towing vehicle/ trailer combination is calculated as per the following formula:

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Calculation factors:
g is gravity and = 9,81 m/s²
m_Z is the permissible total mass of the towing vehicle [t]
m_A is the permissible total mass of the trailer [t]

Articulated truck coupling (D-value)

The D-value formula for an articulated truck is:

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Calculation factors:
g is gravity and = 9,81 m/s²
m_Z is the permissible total mass of the towing vehicle [t]
m_A is the permissible total mass of the trailer [t]
S is the permissible vertical load [t]

Example

A towing vehicle with a permissible total mass of
m_Z = 18 t and a trailer with the permissible total mass of von m_A = 14 t are connected to each other by an automatic trailer coupling. What is the minimum D‑value for the trailer coupling?

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A tractor unit with a permissible total mass of
m_Z = 16 t and a maximum vertical load of S = 8 t is pulling a trailer with the permissible total mass m_A= 16 t. What is the minimum D‑value for the articulated coupling?

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