MIL-DTL-68G
D.c. motors.
3.5.4
3.5.4.1 Brushes. Brushes shall be rectangular in shape and shall conform to NEMA-CB1 except that the
brand marking may be omitted. The sides of the brushes shall be smooth and free from saw marks.
3.5.4.2 Brush holders. Brush holders shall be readily accessible for the renewal of brush or spring. The
brush-feeding device shall insure proper brush contact under all conditions of brush and commutator wear. The
brush holder caps shall be so constructed that no live parts are exposed.
3.5.4.3 Commutator. The commutator shall be of sufficient depth to allow turning down to an extent of
0.10 inch reduction in diameter. The insulation between commutator bars shall be undercut.
3.6 Directional adjustment. Unless otherwise specified in the contract or order, the axis revolution shall have
a vertically adjustable range of at least 90 degrees below the horizontal, and a horizontally adjustable range of at
least 90 degrees. It shall be possible to make adjustments by hand while the fan is operating at full speed. The
swivel joints or any other similar means of adjustment shall be firmly constructed, and shall permit being securely
locked by hand.
3.7 Mounting. Fans shall be suitable for operation in the bracket position, that is, with base plate in the
vertical plane. The number and arrangement of the mounting holes shall be as specified in 3.8. The mounting
shall be solid. Grommets or isolation mounts shall not be used. For sheathed quarters onboard ship where
special mounting is required, the details for mounting shall be as specified (see 6.2.1).
3.8
Fan characteristics. Each fan type shall have characteristics as specified in table I.
Table I. Fan characteristics.
Type
Type
Type
Type
Type
Reference
Item
TA12
TD12
SA8
SD8-24
SD8-12
paragraph
Voltage, volts
115V a.c
115V d.c.
115V a.c.
24 d.c.
12 d.c.
4.6.5
±10 volts
±10 volts
±10 volts
Frequency, hertz (Hz)
60
60
Input watts, maximum
67
56
48
40
40
3.11, 4.6.3
Output, pounds
3.13,
thrust, minimum
0.25
0.25
0.23
0.12
0.12
4.6.6
Ratio watts input over
pound thrust, maximum
230
175
180
200
200
3.13
Switch, number of
position
3
3
2
2
2
3.14
Switch, positions
off, low, high
off, low,
off, on
off, on
off, on
3.14
high
Life, hours
5000
5000
5000
5000
5000
3.18
A-weighted sound
54
54
54
54
54
3.10, 4.6.8
pressure level (LA);
decibels (dB)
Weight, pounds,
maximum
15
15
7-1/4
9
9
Dimensions, overall, inch:
10-1/2
10-1/2
10-1/2
Guard diameter, maximum
10-1/2
Height, maximum
10
Depth, maximum
Mounting holes:
Number
3 (min)
3 (min)
4
3 (min)
3 (min)
Size, inches
3/8
3.7
Vertical spacing, inches
1-3/4
Horizontal spacing, inches
2-1/2
4
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