MIL-DTL-24643C
4.7.3.3 Procedure. The two following test shall be performed using not fewer than five specimens. The
specimen shall be tested one at a time for each test. The same specimen shall not be used for more than one test.
a. Springiness. One specimen shall be selected and secured by one end to the mandrel such that it is both in
contact with the curved surface of the mandrel and perpendicular to the mandrel axis. The opposite end of the
specimen shall be attached to the scale, the specimen shall be wrapped circumferentially around the mandrel, by
handling the scale only, for not fewer than four complete turns, while maintaining a specimen tension of not less
than 100 nor more than 125 grams. Care should be taken to pull the scale in such a direction that it accurately
indicates the specimen tension. The specimen shall then be released from the scale and allowed to uncoil. Any
specimen which is kinked at any place other than the attachment points at either end shall be considered an invalid
specimen; the test shall be repeated using a different specimen. This test shall be successfully repeated four more
times (five times total), using a different specimen each time.
b. Toughness. One specimen shall be selected and secured by one end between the rounded, horizontal, and
parallel vise edges, such that not less than 2 inches of the specimen extends vertically above the vise. The scale
shall then be attached to the free end of the specimen and a specimen tension of 100±10 grams shall be established
by handling the scale only. The specimen shall be bent 90+15, -O degrees alternately in both directions
perpendicular to the vise edges, while maintaining the specified vise tension. Not fewer then ten 90 degree bends
shall be made unless the specimen breaks sooner. The bending rate shall not exceed fifty 90 degree bends per
minute. This test shall be repeated four (4) more times (five times total), using different specimens each time.
4.7.3.4 Observation. Either of the following shall constitute specimen failure:
a. Springiness. The o.d. of the coil formed by any of the specimens around the mandrel, as measured at a
middle portion of the specimen, exceeds inch.
Toughness. -y specimen withstands fewer than ten 90-degree bends without breaking.
b.
4.8 Test methods (physical).
4.8.1 Abrasion resistance. Abrasion resistance of insulation coverings and cable jackets shall be determined as
4.8.1.1 Specimens. Specimens shall be as follows:
a. Insulation. Each specimen shall consist of a single insulated conductor (including insulation covering, if
any) of not less than 22 inches in length. Specimens shall be removed from completed cable as follows:
(1) Cables containing 4 or fewer conductors - one conductor shall be removed from each insulated
conductor.
(2) Cables containing more than 4 but fewer than 21 different insulated conductors (a total of 4
specimens).
(3) Cables containing 21 or more conductors - the number of specimens removed shall be equal to the
square root (rounded to the nearest whole number) or the total number of conductors. Each specimen shall be
removed from a different insulated conductor.
b. Cable jacket. One cable jacket test specimen shall be prepared by extruding material onto a 16 AWG
(19/29) conductor. The material shall be manufactured using process conditions as close as possible to those used to
produce the overall cable jacket and shall have an overall cable diameter of 0.119+0.001, - 0.000 inch.
4.8.1.2 Special apparatus. Apparatus shall include the following:
a. Abrading machine - A cylinder, which incorporates 2 abrading elements on its surface, which is motor
driven to rotate about a horizontal axis at 17 plus 3, minus 2 revolutions per minute (rpm) and over which the
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