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TM 10-3930-643-34
GENERAL MAINTENANCE PROCEDURES. (cont)
2-12.
Application of Adhesives. (cont)
b.
Silicone Rubber Adhesive.
Except for the instrument panel which is
sprayed with anti-corrosive varnish, all electrical connections
are
sealed
against moisture with a room temperature vulcanizing silicone rubber
sealant,
MIL-A-46146A, Type 1.
If you must break into this seal for repair work you
must remove the switch involved completely from the machine
and
thoroughly
clean all existing sealant and dirt that may remain on switch.
Replace the
switch if corroded.
The sealant must have a clean surface to adhere to or
there will not be an effective seal.
After switch is cleaned and reassembled
or replaced apply sealant.
Cover the switch and terminals
completely
with
sealant.
Press sealant into and around the terminals
to ensure
complete
coverage.
Sealant will set in 15-30 minutes depending on temperature and
humidity.
c.
Loctite Retaining and Sealing Compounds.
These compounds will resist
solvents, heat, shock and vibration. They provide a positive seal against
leakage and sheer strength resistance to loosening when used in the assembly of
threaded, slipfit or press fitted parts.
Use the grade of Loctite specified.
Once cured these compounds have an operating temperature range of -65 to 300
degrees F (-54 to 149 degrees C), and will resist attack by oils,
chemicals,
hydraulic fluids and solvents.
Do not use Loctite where other retaining means
are provided, such as lock wires, lock washers, lockplates and fasteners.
Do
not substitute grades or usage unless specified.
Do not use Loctite on items
that need frequent servicing, or on brass fittings or plugs, or when operating
temperatures exceed 300 degrees F (149 degrees C) (Example:
Engine
exhaust
systems). Loctite is applied as follows:
(1) Threadlock adhesives.
Loctite MIL-S-46163, Type II, Grade O, a high
strength adhesive for fasteners and Loctite MIL-S-46163, Type I, Grade L, a
high viscosity, high strength adhesive for large bolts and studs,
are
recommended for use on this vehicle.
Primers are not required with thread-
lock adhesives, but if used will speed up the cure and act as a cleaner.
Surface preparation depends on type of metal and purpose of application. In
general, most surfaces must be cleaned thoroughly. Apply Loctite to bolts and
studs by filling full length of thread with one strip in diameters up to 1
inch, two strips 180 degrees apart, on diameters up to 2 inches,
and
three
strips 120 degrees apart, on diameters over 2 inches.
Apply one strip into
tapped holes.
For blind hole applications, apply enough Loctite to fill
the
bottom 2 to 3 threads of engagement, then insert stud.
If engagement length
exceeds one diameter use proportionally more Loctite.
For non-seated studs
(studs that go deeper in hole than required) turn stud one turn deeper than
required.
After bubbling stops, apply a ring of Loctite around stud at top of
hole, then back stud to required height.
Loctite will set in 10 minutes to 2
hours. Temperature and humidity affect drying time.
2-8
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