MIL-DTL-13777K
3.6.5 Cable separator. The separator shall be applied over the assembled conductors or the overall shield if
required. The separator shall consist of dry, soft, cotton braid, fungus treated and conforming to the test
specified in 4.7.1. The size of the cotton shall be 26/2 and the percent coverage shall not be less than 80
percent when computed by the following formula:
2
K = (2F - F ) x 100
F = NPd/Sin a
a = Tan (2š(D +2d) P/C)
-1
Where:
F=
Fill or space factor
K=
Percent coverage
N=
Number of strands per carrier
P=
Picks per inch of wire length
d=
Diameter of individual shield strands in inches
a=
Angle of braid with axis of cable
D=
Diameter of wire under the shield in inches
C=
Number of carriers
3.7 Sheath. Over the cable core, there shall be extruded a well centered sheath. The minimum thickness at
any cross section shall be not less than 90 percent of the average wall thickness at the cross section. The
minimum sheath thickness shall not be less than that specified in the applicable specification sheet. When two
layers are specified, the outer layer shall constitute at least 50 percent of the total thickness.
3.7.1 Reinforcement. Where two layers are specified in the applicable specification sheet, a reinforcement
shall be provided between the two layers consisting of two serves of 16-2/3 fungus resistant cabled cotton,
served in reverse, 7 ends per inch of cable, or equivalent rayon or polyamide tire core may be substituted for
the seine twine serves.
3.7.2 Physical properties.
3.7.2.1 Unaged sheath. Single and double layer sheaths shall consist of a polychloroprene compound (virgin
material) having the characteristics listed in table IV.
TABLE IV. Physical characteristics for unaged sheath.
Property
Value
Tear strength (lb/in.), min.
20
Tension set (inch), max
.375
Ultimate elongation ( 2 inches to break), minimum
2-8
Tensile strength (psi), minimum
1800
3.7.2.2 Accelerated aging. When treated in accordance with 4.8.2.2, the sheath shall meet the requirements in
table V.
TABLE V. Accelerated aging sheath requirements.
Property
Value
Ultimate elongation (2 inch to break), minimum
2-7
Tensile strength (psi), minimum
1600
3.7.2.3 Resistance to oil. When tested in accordance with 4.8.3.1.6, the tensile strength and the ultimate
elongation of the sheath shall not depreciate more than 40%.
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