Aluminum Repair - Hummer H1 Service Manual

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10-8 Body

Aluminum Repair

CAUTION: Body repairs should not be made using welding or
heat for forming. Heat will only weaken the material and lead
to further problems.
Material
Aluminum material used for repairs should be of the same al-
loy and temper as the original if possible. In general, 6061-T6
aluminum alloy should be used. Material thickness must be the
same or thicker. This alloy will work well for flat repairs, but is
not well suited to bending because it is quite hard and cracks
easily when bent sharply. When bends must be made, use
softer 6061-T4 aluminum alloy and increase material thickness
by at least 50 percent. As a general rule of thumb, 6061-T4 alu-
minum alloy should be bent with a minimum bend radius of
one to two times material thickness, whereas 6061-T6 alumi-
num alloy requires at least three times material thickness radius
for bends. In all cases, bends should be closely inspected for
cracks. A suitable method for avoiding bending cracks is to ob-
tain angles that are extruded from 6061-T6 aluminum alloy or
use preformed angles for repairs.
Epoxy Adhesive
Where it is necessary to remove parts, note that epoxy adhesive
is used in joints. Use care in parts removal to avoid unneces-
sary distortion. Parts should be separated by peeling action.
Before parts are reassembled, it will be necessary to remove
any remaining cured epoxy from joints so parts will fit together
with good, even contact. Use of epoxy requires special storage
and application procedures which do not lend themselves to
repair. For this reason, epoxy will not be used for repair. To
compensate for the lack of epoxy, additional rivets should be
used when making repairs to existing joints.
Rivet Patterns
1. Rivet patterns are denoted by rivet spacing and rivet edge
distance. Rivet edge distance is the distance from center of
rivet to nearest edge of sheet. Rivet spacing is defined as
the distance from center of rivet to center of adjacent rivet
(Figure 10-1).
2. Required rivet spacing is determined by strength needed in
the joint. A general feel for strength required can be
obtained by inspecting rivet patterns in surrounding areas.
Body repairs made using single rows of rivets should be
performed using rivet spacing not greater than 1.6 in.
(4.1 cm) and not less than 0.625 in. (15.9 mm). Use 1 in.
(25.4 mm) rivet spacing as a general practice for repairs.
Rivet spacing used in original construction may be greater
due to additional strength obtained by using epoxy
adhesive. Do not use rivet edge distances less than 0.375
in. (9.5 mm).
3. High strength joints or large area patterns may require use
of double or multiple rows of rivets to obtain sufficient
strength.
4D
2D
DOUBLE ROW RIVETING PATTERN
3D 3D 3D
2D
TRIPLE OR MULTIPLE ROW RIVETING PATTERN
Figure 10-1:
4. Care must be taken to assure rivet hole patterns are
transferred accurately in cases where a part with no holes
is mated to one which already has rivet holes. Hole
patterns may be transferred using one of the following
patterns:
a. Lay new part in place, and use holes in mating part as
a drill template. This requires the new part to be
underneath the mating part. Care must be taken not to
distort original holes.
b. Use the removed part as a drill template by clamping
the old and new parts together. This requires that parts
rest flat and rivet flange be undistorted.
Joint Design
1. Loads are applied through a joint to fasteners that hold it
together. These loads are applied to fasteners in the form
of shear loads or tension loads. If load is perpendicular to
axis of fasteners, the fasteners are loaded in shear. The
fasteners are loaded in tension when load is along axis of
fastener, causing a pull on each end of fastener.
2. Rivets are designed to be loaded in shear. Do not create
any new joints during repairs which cause rivets to be used
in a tension application. Bolts should be used for tension
applications or substituted for rivets in very high shear
load applications (Figures 10-2 and 10-3).
D = DIAMETER
D
OF RIVET
(PREFERABLY ABOUT
3X THICKNESS OF
THICKER SHEET)
4D
2D
6D
3D
2D
Riveting Patterns
®
6-S10-025