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### Trailer Hitch Ball Coupler Size Equations and Calculators

Trailer Hitch Ball Coupler Size Equations and Calculators.

The required trailer coupling size is determined by the D value.

The formula for the D value is as follows:

D = ( G · T · R ) / ( T + R )

Where:

D = D value, in kN,
T = Permissible gross weight of the towing vehicle, in t (Metric Tons),
R = Permissible gross weight of the trailer, in t (Metric Tons),
t = Metric tons,
G = 9.81 m/s2

Example:
Vehicle T31, 19.464 FLC
Permissible gross weight 18000 kg = T = 18 t
Trailer load 22000 kg = R = 22 t

D value:

D = ( 9.81 · 18 · 22 ) / ( 18 + 22 )

D = 97 kN

If the trailer gross weight R and the D value of the coupling device are specified, the permissible gross weight of the towing vehicle T can be determined using the following formula:

T = ( R · D ) / ( ( 9.81 · R ) - D )

If the permissible gross weight of the towing vehicle T and the D value of the coupling device are specified, the maximum permissible trailer load R can be determined using the following formula:

R = ( T · D ) / ( ( 9.81 · R ) - D ) 