MIL-DTL-10392F
4.5.2 Flexing life test. The finished cords shall be tested for compliance with 3.19. The cord flexing
machine shall contain a rotating actuating arm whose normal zero position is vertical. The arm shall
rotate about a horizontal axis, the outer end traversing a circular arc in a vertical plane. The arm shall
rotate 90º from the zero position to a position 90º from the zero position in the opposite direction, and
then reverse its direction and rotate back to zero position, thus completing a cycle. The arm shall be
rotated at approximately 900 cycles per hour. Two adjustable 0.5 inch (12.70 mm) diameter mandrels
shall be mounted in the machine with their axis perpendicular to the plane of rotation of the actuating arm.
The plane through the axis of the two mandrels shall be horizontal and shall pass through the axis of
rotation of the actuating arm. The mandrels shall be placed so that the axis of rotation lies midway
between the mandrels. A length of cord shall be inserted between the mandrels which shall be so spaced
that there is a slight clearance between the cord and the mandrels. The upper end of the cord shall be
attached to the rotating end of the actuating arm. The lower end of the cord shall be attached to a weight:
One pound for WD-27A/U, two pounds for WT-15A/U, WF-11A/U, WM-59A/U, and a three pound weight
for WM-60A/U, WM-61A/U, WM-62A/U, WM-63A/U, WM-64A/U, WM-69B/U, WM-111A/U and
WM-70B/U. There shall be at least five inches of cord from the plane through the axis of the mandrels to
the point at which the weight is attached to the cord. The weight shall be lightly snubbed to prevent
rotation. The cord shall have all of its conductors connected in series through a relay which will cause the
machine to cease operation if any of the conductors momentarily lose continuity. A bending machine
such as specified in MIL-DTL-13777 is a suitable cord flexing machine for use as indicated. Any other
approved machine which will give equivalent mechanical motion to the cord may be used.
4.5.3 Tin-coating. The tin-coating on the conductor strands and the continuity, adherence and finish
4.5.4 Conductor strand tensile strength and elongation. This test shall be made in accordance with
FED-STD-228, method 3211 (see 3.5.2).
4.5.5 Conductor strand resistance. The conductor strand, prior to stranding into a conductor, shall
be measured for dc resistance in accordance with FED-STD-228, method 6021 (see 3.5.3).
4.5.6 Cord tensile strength. The tensile strength shall be made on a tensile testing machine, power
driven, and preferably of the pendulum type. The test shall be made at the rate of 12 inches (304.80 mm)
per minute. The conductors of the cord may be connected in series to an indicating or signaling device or
automatic stop or both. The arrangement shall be such that an indication will be given when there is a
disruption of electrical continuity due to the breaking of the conductors of the cord under tensile test
(see 3.16).
4.5.7 Dielectric withstanding voltage. Cords shall be tested in accordance with FED-STD-228,
method 6111 except that:
a. The test shall be performed on sample units of finished cords only.
b. The immersion period shall be not less than 6 hours.
c. An alternating potential, as specified in 3.18.1,shall be applied between two terminals, one
being each conductor in turn, and the other being all the remaining conductors tied together in electrical
contact with the water.
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