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13 - 6
FRAME STRUCTURES
•
I N S P E C T I O N P R O C E D U R E S
INDEX
Page
Dimensions
. 8
General Information
6
Page
Inspection
6
Measurements
7
GENERAL INFORMATION
I m p r o p e r frame a l i g n m e n t is u s u a l l y a r e s u l t o f a n
accident o r vehicle being operated w i t h excessive
loads or w i t h loads n o t positioned i n a reasonably
d i s t r i b u t e d manner.
A distorted frame w i l l affect f r o n t wheel o r rear
axle a l i g n m e n t and cause excessive wear, mechanical
failures i n power t r a i n , w i n d o w glass cracks a n d door
opening
problems. Vehicle
performance, h a n d l i n g
a n d ride q u a l i t y can be i m p a i r e d .
INSPECTION
Before proceeding w i t h frame a l i g n m e n t checks, i n -
spect a l l frame parts for visible damage
such as
cracks, t w i s t s , bends, or other excessive deforma-
tions. Also, riveted, bolted, or welded connections,
looseness o r missing parts.
A l l damaged areas m u s t be repaired or parts r e -
placed as necessary.
HORIZONTAL
OR DIAGONAL
D e t e r m i n e frame deviation f r o m being square b y
t h e f o l l o w i n g procedure:
(1) Select several points along one siderail, prefer-
ably a t crossmember locations.
(2) Transfer these w i t h a p l u m b bob to floor, paper
sheets can be fastened to floor a t these points for bet-
t e r acuracy.
(3) Locate corresponding points on other siderail
and transfer t h e m i n t h e same m a n n e r to t h e floor.
(4) Move t r u c k away a n d measure between a l l
points diagonally a n d p a r a l l e l to siderails, corre-
sponding measurements should n o t differ b y more
t h a n 1/4 inch.
(5) Take measurement across a t f r o n t a n d rear
m a r k s and b y d i v i d i n g distances i n half, indicate t h e
two points o n floor.
(6) Stretch a chalk-line between points 1 a n d 2 i n
F i g . 5 and snap s t r i n g .
(7) Check to see how close centerline is t o diagonal
intersection points A , B , C, D , E, a n d F i n F i g . 5.
(8) M a r k i n g s on floor w i l l now give a n i n d i c a t i o n o f
frame distortion i n p l a i n view.
(9) A n y point on one s i d e r a i l should be w i t h i n 1/8
i n c h ahead or behind corresponding p o i n t on opposite
side.
(10) Frame bow sideways should n o t exceed 1/8
i n c h per 100 inch l e n g t h o f frame.
(11) Overall w i d t h o f frame should n o t v a r y more
t h a n 1/8 inch.
(12) Repeat steps (1) t h r o u g h (11) after s t r a i g h t e n -
i n g frame.
VERTICAL
OR
SIDEVIEW
Determine t w i s t o f frame a n d degree o f siderails
not being p a r a l l e l t o one another as follows:
V e r t i c a l dimensions are measured f r o m a level
floor
to
corresponding
points o n left
a n d r i g h t
siderails. Dimensions should t h e n be plotted to scale
vertical and horizontal on a sheet o f paper and points
connected for each sidemember
separately.
G r a p h
w i l l show t h e relative position of t h e sidemembers.
Points on siderail or for horizontal check are se-
lected a t rear frame crossmembers a n d a n y one o f
these points on one sidemember should be m a x i m u m
1/8 inch above or below corresponding p o i n t o n other
siderail.
D
*
^ — ,
Fig. 5—Alignment
Markings
RN888
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