SCHASSIS
FRAME
REPAIBS-------------
Perform
the
measuring with accuracy and care.
Suspend
the
plumb-bob from various
corresponding
points on
the
frame, such as indicated by
the
diagonal
lines in Fig. S.2. The plumb-bob should be suspended
slightly above
the
floor.
When
the
plumb-bob comes
to rest, mark
the
floor directly
underneath
It.
The
marks made on
the
floor will
represent
the
various
points of
the
frame
to
be checked diagonally.
Measure
the
diagonal distance
betweenthe
points:
this distance should agree within i in.
or
i In. (6·S mrn,
or
10m
m.), as shown in Fig. S.2.
cross-checked at
the
centre
line on which
the
diagonals-
should also cross, as detailed In
the
chassis dlmensional
drawing, Fig. 5.2. The angle of
the
front
cross-rnernber
should be
r
but
may be given an allowance of ±
f.
Diagonal measurements quickly
determine
which
section of
the
frame is bent.
The
accuracy of side-members Is usually checked
with suitable straight-edges, and squareness of side
rails is checked with straight-edge and square. Twist
Is checked visually against straight-edges [aid
trans-
versely across
the
frame at suitable points.
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i
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ill
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2-0'
Care
must be
taken
to
see
that
any
two
dlagonals
compared
represent
exactly
corresponding
points on
each side of
the
frame.
Upon
the
result of this preliminary investigation a
decision can be
taken
whether
the
frame can be
repaired In position
or
whether
the
frame must be
strtpped
out
completely.
When
repairs
are
under-
taken
with
the
frame in position,
the
damage should be
confined
to
forward of
the
front
engine bulkhead plate.
Damage rearwards of
.the engine bulkhead plate
involves
the
stripping
out
of
the
frame. This also
applies
to
any damage
to
the
rear
end of
the
frame.
Alignment
Checking
the
alignment of
the
bare
frame is a
relatively simple
matter,
especially if
the
frame can be
set
up on a large flat surface or face plate. It Involves
establishing a datum
or
centre
line. from which all
measurements
can be
taken.
Diagonals
are
checked
from suitable fixed locating points, which can be
5.2
Seetion
S.2
STRAIGHTENING
WITH
HEAT
When
the
frame Is heated for straightening,
the
area
affected should be maintained at a
cherry-red
t hro
ughout
th e
enti
re st ralghtening
operat
lon,
When
an acetylene
torch
Is 'used
for
heating. a
"
neutral"
flame should be employed and played
over
the
entire
area
to
be heated until
the
metal has reached
a uniform
cherry-red.
Never
heat
the
metal beyond
a
cherry-red
as it will seriously weaken
the
steel.
It Is good practice
to
check
the
temperature
of
the
heated metal
frequently
with a
dry
pine-stick, while It
is being
worked,
to
maintain it at
the
proper
state
of
ductility and avoid burning. Touchlng a
dry
plne-stlck
to
metal
that
has been heated
to
a
cherry-red
will
cause
the
stick
to
glow and char.
but
not
to
ignite.
The
heated
area of
the
frame should be
protected
from
draughts
to
prevent
sudden cooling of
the
metal.
M.G. Midget. Issue 2 (H & E)
91826-2/55
Wishvilles Classic
Automobile Library
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