**Related Resources: calculators**

### Trailer Hitch Ball Coupler Size Equations and Calculators

Power Transmission Design and Engineering

**Engineering and Design Applications**

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/s^{2}

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 )