67 Chapter 4 Fundamentals of Collision Damage
Copyright Goodheart-Willcox Co., Inc.
works. The only variable in this example is the surface
area of impact. The vehicles are the same weight,
they are moving at the same speed, and the targets
do not move or give. In Figure 4-17A, the entire front
of the vehicle sustains damage. The damage does
not extend more than about one foot into the engine
compartment. In Figure 4-17B, there is a smaller
area of impact but the damage extends much farther
into the engine compartment. In a collision, force
concentrated in a small area will tend to cause deeper
damage than force spread out over a larger area.
Vehicle Height
The last collision factor that must be considered
is vehicle height. When the front of a vehicle collides
with a target, it is the front bumper that first contacts
the target. The bumpers on all vehicles are bolted to
the frame or unirails. The frame or unirails are the parts
of the vehicle most resistant to impact.
Ideally, the bumpers of the vehicles involved in a
collision would match in height. This would give the
passengers the most protection. However, bumper
heights are not uniform. See Figure 4-18. A panic stop
caused the front of the blue vehicle to move down and
slide under the rear of the red vehicle.
As another example, consider a pickup truck that
crashes into the side of a small car. The rocker panel of
the car is strong, but the truck’s bumper is higher than
the rocker panel. The truck’s bumper will push the car’s
center pillar and doors inward. This is because the
car’s center pillar and doors are not as strong as the
bumper. In this example, passengers could be injured.
Damage
As discussed in the previous section, there
are several factors that play a part in the amount
of damage that occurs in a crash. In the following
sections, the types of damage that occur in full-frame
and unibody vehicles will be discussed. As you read
these sections, remember that because all parts of the
vehicle are connected, damage in one area can have
an effect on other areas of the vehicle, even an area far
from the point of impact.
Direct and Indirect Damage
Damage that occurs at the point of contact during a
collision is called direct damage. Figure 4-19 shows a
damaged high-crown panel. This damage was caused
by the bumper of another vehicle hitting the molding.
The area of direct damage is small. However, the panel
has collapsed, with buckles extending away from the
A
B
Goodheart-Willcox Publisher
Figure 4-17. A—If the impact force is spread over a
large area, damage is confined to the front 1″ of the ″
vehicle. B—When the impact force is concentrated in
a small area, the damage extends more than 1″ into ″
the engine compartment.
Goodheart-Willcox Publisher
Figure 4-18. This is what happens when bumpers are
not at the same height. The front bumper of the blue
car slid under the rear bumper of the red car. Notice
the hood buckle.