CHASSIS MODIFICATIONS 2-34 E URO C ARGO E URO 4 - 5 Figure 2.14 shows an example of a lowered supplementary cross member. When this solution is applied to vehicles with a short rear overhang, the external connecting plates must conform to the arrangement described in Figure 2.14. Should the brackets of the underrun bar be modified, following the lowering of the rear cross member, the new version will be equivalent to the original in terms of attachment, strength and stiffness and the positioning of the lights checked for compliance with the standards (local standards where applicable).
2.10.5 Centre Axle Trailers (Rigid Towbar) The use of trailers with centre axles (rigid tow bar trailers with single or tandem axles), with respect to articulated tow bar trailers, entails an increase in bending stress on the rear chassis overhang as well as an increased torsional stress of the rear towing cross member resulting from the vertical static and dynamic loads which the tow bar exerts on the hook (for example when braking or on bumpy roads).
On those vehicles on which the towing of trailers is permissible within the values established for each model by IVECO, the mass that may be towed with the centre axle trailer and the vertical loads on the cross member may be authorised on the basis of the dimensions of the flange located on the vehicle cross member. The value of the maximum (static + dynamic) vertical load transmitted by the trailer to the hook can be determined more accurately through the following ISO formula: Fv = a ⋅ x 2 /l 2 ⋅ C ⋅ 0,6 + S Fv = Max vertical load (static + dynamic) transmitted by the trailer to the tow hook (kN).
a = Vertical acceleration in the drawbar/towing hook coupling area; depending on the rear suspension of the tractor for semitrailer, use the following values: - a = 1.8 m/sec 2 , for vehicles with pneumatic suspension (or equivalent) - a = 2.4 m/sec 2 , for vehicles with other suspension types x = Total length in mms of the loading area of the trailer (m). l = Length of the trailer wheelbase (distance between drawbar towing eye centre and axle centre or trailer axle centre line) in m. C = Total weight of trailer, R, minus the static load applied S (all values expressed in tons). S = Static support load (kN). 0,6 = Deceleration factor.
In addition to this, where the overhang is relatively long, it may be necessary to fit an auxiliary frame with longitudinal runners larger than those normally planned (see Table 2.14). If central axle trailers are to be used, the connection of chassis frame to subframe will be carried out from the rear overhang to the front support on the rear suspension with cleat plates or by strengthening the existing connections with shear-resistant reinforcing (see Figure 2.15). Installing a Towing Device Base - July 2006 Revi - June 2007 Print 603.93.431