CHASSIS MODIFICATIONS 2-27 E UROCARGO Euro 4/5 2.6.3 Towhook for mid-axled trailers Trailer with rigid drawbar - The mobile connection with the towing vehicles is made with a tow device. - The drawbar is not connected with the chassis so that it can freely be moved and therefore can transmit vertical torques. - According to its construction part of its total mass is carried by the towing vehicle. - For the mechanical connection devices suited for centre-axle trailers, the values Dc, S and V defined by the following formulas: Dc = g ⋅ T ⋅ C T + C = (kN) V = a ⋅ X 2 l 2 ⋅ C (kN) D = representative value of the hook class (kN).
It is defined as the theoretical reference force for the horizontal force between the towing vehicle and the trailer; g = acceleration due to gravity (m/s 2 ); T = maximum mass (t) of the towing vehicle; T+S = maximum mass (t) of the towing vehicle including, when necessary, the vertical load of a centre-axle trailer; R = maximum mass (t) of the trailer; S = value of the static vertical load (t) that, under static conditions, is transmitted to the point of connection.
S must be ≤ 0.1 ⋅ R ≤ 1000 kg; C = sum of the maximum axial loads (t) of the centre-axle trailer at maximum load; it is equal to the maximum mass of the centre-axle trailer decreased by the vertical static load (C = R - S); V = value V of the intensity of the theoretical vertical dynamic force; a = equivalent acceleration at the point of connection; depending on the rear suspension of the drawing vehicle, use the following values:
- a = 1.8 m/s 2 for air suspension; - a = 2.4 m/s 2 for other types of suspension; X = length of the load surface (m); l = theoretical length of the drawbar (distance between the centre of the eye of the drawbar and the centreline of the trailer axles ) (m); X 2 / l 2 ≥ 1 if the result is less than one, use the value 1. Computational example of the class of the connection device for full trailers We consider a new vehicle with maximum mass 12 t that has to haul a conventional trailer with maximum mass equal to 8000 kg. From the data 1. T = 12 t 2. R = 8 t we obtain: D = 9.81 · (12 · 8) / (12 + 8) = 47.0 kN Installing a towing device Print 603.93.431 Base - January 2008