General Information:

• For a perfect connection between chassis and attachment, for all attachments a subframe or a floor panel assembly (taking over the function of the subframe) is required (except for self-supporting attachments and subframes as a base group).


• The subframe side rails should lie flatly and following the chassis profile on the upper belts of the chassis frame.


• The following applies to LT 46 models (twin tyres):
  In the area of the rear axle, the chassis-frame side rails are inwardly offset. The subframe side rails need not follow this offset but can be executed continuously straight. Wooden fillets between chassis-frame side rail and subframe side rail are not permitted. A bracket attachment, via subframe cross members, is required in the area of the rear axle.
  
  
• Subframe cross members are to be arranged above the chassis-frame cross members.
  
  
• For the side rails, use bevelled u-beams or standard u-beams that are generally used for the construction of vehicles (no rolled steel sections). Box sections are also permitted.
  
  
• The side rails dimensions result from the moment of resistance (Wx) required for attachment and chassis. See diagram 3.3.2. The specified moments of resistance and section/beam dimensions refer to frame side rails that are evenly loaded on both sides.

If several attachments are to be assembled on a chassis (e. g. flatbed and loading tailboard), the greater value of the specified moments of resistance must be taken as a basis for defining the subframe.

Subframe for reinforcing the side bars in the front-end area of the vehicle: For example, when lifting platforms are operated, the entire vehicle may be lifted by 4 hydraulic supports, so that the wheels no longer touch the ground. Due to the high weight of the front end of the vehicle, inadmissibly high tensions appear in the chassis side rails in the area of the front support. For this reason, it is mandatory to reinforce the chassis frame if this application is planned. This requires to lead the subframe through the back of the cab to a location under the seat box. It has to be attached with a supplementary bracket and a bolted connection. An execution recommendation can be requested at Volkswagen AG, department NV-VS.

This subframe execution does not permit to install an additional battery (PR-Nr.8FR).

Material Qualities for Prescribed Steel Subframes:
The subframe with bracket attachment (force-locking) is to be implemented as St 12.03 or St 37-2.

The profile transition at the front ends of the side rails should be gradually realised.

If it is required to implement very high side rails or if low total heights of the chassis are to be implemented, the u-beam - at locked-force connections - must meet the following specifications:

• It must be closed as a box
• It must be nested into each other
• It must be nested

As a result, the moment of resistance and the torsional stiffness are increased. Make sure that the transition between closed side rail and open u-beam is properly executed.

Determine the mounting method depending on the chassis type, attachment and according to the operation purpose of the vehicle. Attach the subframe on the fixing brackets (which are available as standard) of the chassis frame. Use shackle attachments if additional attachment points are required. Define the number of attachments in such a way that is it ensured that the braking and lateral forces are properly absorbed.

The correct attachment is decisive for:

• Road behaviour and the operational safety of the vehicle.
• Operational life of chassis frame and attachment.

If locked-force connection are used, the side rails must be attached length and crosswise.

If pre-assembled subframes are used, constructional tolerances of the chassis frame width (max. + 6/-3 mm) are to be considered. Compensate for manufacturing related frame bending (max. 6 mm) by using supports.

Locked-force connection, bracket attachment

• A movement of the subframe side rail in relation to the chassis side rail is possible with restrictions.
• Perform rigidity strength calculations for each individual side rail.
• Divide up the bending moment according to the moments of inertia.