72 Section 1 Introduction to Collision Repair
Copyright Goodheart-Willcox Co., Inc.
Figure 4-29 shows portions of a frame that has
sidesway on both C-shaped frame rails. The impact
point was the same as that shown in Figure 4-27.
Notice the buckles on the flanges of the rail that was
directly damaged, Figure 4-29A. The rail that was
indirectly damaged appears to have suffered more
damage. The flanges of the indirectly damaged
rail were stretched to the breaking point. See
Figure 4-29B. Note that the engine cross member
acted as a pivot point.
If the impact is not on a cross member the colli-
sion force will not be transferred as readily to the
nonimpact frame rail. The cross members may act
as pivot points. The wheelbase may shorten on
the impact side. If enough inertia is involved, the
vehicle may take on the shape of a banana. See
Figure 4-30.
Rear Impact
The results of a rear impact are similar to those
caused by a front impact. With enough impact force,
the frame will distort up or down in the arched areas.
Buckling may be found in the arched areas or at the
cross members. Figure 4-31 shows a truck that was
rear ended. One side of the vehicle is higher than
normal. The arched area of the frame rail on the
impact side has been shortened by mash damage.
The mashed rail holds the ends of the leaf spring
closer together. This shorter spring length causes a
greater-than-normal arch in the spring. The overly
arched spring causes the impact side of the vehicle
to sit higher off the ground. Mash is most likely to
occur in an arched area of a frame. This type of
damage is not often found on pickup trucks that have
a straight frame rather than an arched frame in the
bed area.
Goodheart-Willcox Publisher
Figure 4-28. The impact force will be transferred from the right frame rail, through the cross member, and to the
left frame rail. Both rails have moved.
Goodheart-Willcox Publisher
Figure 4-29. A—In this view, the impact force would be
moving toward you. This directly damaged C-shaped
frame collapsed in this way from the lateral force. B—In
this view of the opposite frame rail, the impact force
would be moving away from you. The indirectly damaged
C-shaped frame rail stretched from the lateral force.
I
mpac
t
forc
e
A
B