Nissan Spec-V: Part 5: Adding Plates to the Unibody
8/10/2006
Last week we continued to work on the roll cage, adding more tubes to increase the stiffness of the structure. This week we add plates to tie the cage into the car’s unibody. Most modern chassis are a unibody construction. A unibody gets its strength from the folded sections of sheet metal from which it is stamped. The entire structure, from the outer body panels to the inner panels and rails, contribute to the structural strength. To make sure our cage performs we tie it into the unibody in many places with plates of steel. The plates are dimple die-cut to increase stiffness and reduce weight. The dimples act like ribs to give the metal more resistance to bending.
This big dimpled plate connects the main cage tube down the A-pillar of the chassis to the actual “A” pillar. This greatly increases the strength and rigidity with little weight gain.
This dimple die-cut buttress is actually quite light. It ties the cross-tube of the cage to the shock towers and to the chassis main frame rail. This is also where the the suspension lateral locating links tie into the chassis main frame rail. This provides strength and stiffness to a highly stressed part of the chassis.
A plethora of tubes in the rear part of the chassis provide stiffness in both the bending and torsion planes as well as increase side impact and roll over protection.
Many tubes converge at the highly stressed rear shock mounts. The sheet metal mounting plate at the top of the shock tower was doubled to reinforce this area and give the tubes something strong on which to attach.
This is a rearward view of the shock tower area. The reinforcing gives a lot of strength with minimal weight.
Not only is the chassis now resistant to flex, it also cradles the driver in different triangulated structures of steel.
This plate ties the main hoop of the cage into the chassis B-pillar. By coupling the main part of the cage with the main part of the roof, the overall strength more than doubled while adding only a few ounces of material.
Curiously Nissan left the top of the main front frame rails unconnected to the firewall, losing about 30 percent of the frame rail’s potential stiffness. We added this gusset to fully box the frame rail to the firewall and cowl section of the chassis.
Most sanctioning bodies will not allow any sort of hole in the firewall. We welded up the holes left from removing the heater and air condition with these steel plates.