MIL-DTL-24640C
3.4.9.2 Concentricity. Concentricity shall not be less than 70 percent and shall apply to both the finished wires
and finished cable (see 4.7.1).
3.4.10 Braid armor. The armor shall be applied in the form of a braid. The weave of the braid shall be of
either the "one over - one under" or the "two over - two under" type. The weave shall be such that the wires of a
carrier are laid closely together, flat and parallel. The braid shall be applied with maximum tension possible so as to
prevent loosening and creeping but not to cause broken ends. Splices in the braid strands shall be infrequent,
staggered, and inconspicuous so as not to increase the nominal diameter of the cable or result in rough spots.
Broken ends shall be neatly tucked under the braid so they do not protrude. No greater than 10 end breaks are
allowed in a 50-foot section of cable. This does not include changes in carriers. When a full carrier is changed, the
ends of the carrier shall also be neatly tucked under the braid so they do not protrude. No more than one carrier
changes is allowed within 10 feet of cable. If more than one change is required a length shall be created. The braid
shall remain snug to the cable jacket and not spring away when cut. The selection of the number of wires per carrier
and the number of carriers per braid shall be such as to produce a basket weave to give a minimum of 88 percent
coverage and a braid angle within the limits as specified in table I. The number of wires per carrier shall be not
more than as specified in table II.
TABLE I. Armor braid angle.
Braid angle
Diameter over jacket
Minimum
Maximum
(inches)
(degrees)
(degrees)
0.100 - 0.600
30
60
0.601 - 1.000
35
60
1.001 - 1.500
40
70
TABLE II. Wires per carrier.
Maximum number of ends/carrier
Diameter under braid
One over
Two over
(inches)
One under
Two under
0.100 - 0.400
8
5
0.401 - 0.800
12
10
0.801 - 1.500
16
10
3.4.10.1 Braid angle and coverage. The braid angle and coverage shall be as determined by the following
formulas:
Braid angle = Tan (a) = 2×3.14159 (D+2d)P/C
Percent coverage = 100 (2F-F2)
Where:
F
=
NPd/Sin (a)
a
=
acute angle of braid with axis of cable
d
=
diameter (inch) of individual braid wires
D
=
diameter (inch) of cable under braid
N
=
number of wires per carrier
C
=
number of carriers
P
=
picks per inch of cable length
7
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