Trinity Highway INGAL SS180 M, Assembly Manual

Page: 14 / 65

trinityhighway.com 13 Revision A November 2019
3) Underride Assembly
With the truck at its actual driving weight and parked on a level surface, measure the distance from
the ground to the bottom of the truck frame. A distance of 711mm ± 25 mm is required. Spacer
Tubes may be added to the bottom of the frame to achieve this height (p. 14, Figure 10).
Note: The truck’s springs may settle with the weight of the TMA, sometimes as much
as 50 mm. Adjust the height to compensate for anticipated settling.
Measure distance from the back end of the frame forward to the rear-most leaf spring hanger. Look
for any obstruction on the bottom of the frame that may interfere with the Socket Receiver. A
minimum of 305 mm is required (Underride Assembly drawing on
p. 60 ).
It is important to check for obstructions before mounting the socket receivers. Position the Socket
Receiver at the rear
end of the frame so that the 76 x 387 mm flat bar is along the outside of the
frame member and the Socket Receiver Assembly is flush with the end of frame. If spacers are
required, weld them to the Socket Receiver and lap the Spacer Splices (pieces of 10 x 51 x 103
mm flat bar) across the Socket Receiver and Spacer at the rear most location (
p. 47 ). The top of
the Socket Receiver shall be 711mm ± 25 mm from the level ground for proper system height ( p.
14, Figure 10).
Important: Welding must be performed by professional or certified welder.
All welds must be then primed and painted.
Australian chassis modification regulations may differ to that explained in this manual. It is always
recommend that you follow your local design rules when modifying the vehicle's chassis and
installing any TMA. Ensure that the vehicle and any modifications carried out meet the compliance
requirements for your region.
To provide addition strength to the rear of the chassis, it is recommend that the Underride Socket
Receivers have the flat mounting bar removed, then weld the Underride Socket Receivers to a large
16mm thick steel fishplate (similar as shown below in figure 8). Remember to position holes in the
fishplates for the pins to pass through the socket receiver. Then bolt the fishplates to the chassis and
if possible, also the tray sub frames. Once bolted on, install an extra cross-brace on the inside
between each Underride Socket Receiver. This will provide a rigid rear mount assembly (without
welding to the chassis), while allowing the removal and replacement of the receivers if damaged in
a TMA impact.