FED-STD-228A
Method 2051.1
18 APRIL 2014
FLEXIBILITY, EXTENSILE AND RETRACTILE CORD
1. SCOPE
1.1 This method is intended for use in determining the characteristics of retractile cord.
2. SPECIMEN
2.1 The specimen should consist of a 6-inch length of finished retractile cord.
3. APPARATUS
3.1 The apparatus shall be as follows:
3.1.1 A suitable testing machine that will extend and retract the cord at a fixed rate.
3.1.2 Weights of 6, 8, and 10 ounces.
3.1.3 Cold chamber, such as a refrigerator or other equipment, capable of maintaining the required
temperature within ± 1°C (2°F).
4. PROCEDURE
4.1 Prior to meeting any extensile and retractile tests, the cord shall first be conditioned by extending the
coiled portion 6 to 5 times its retracted length, allowing it to retract freely each time. The cord shall be
capable of returning to its original continguous position when laid on a horizontal surface.
4.2 The resistance of the conductor shall be measured and recorded in accordance with method 6021.
The cord shall then be clamped in a suitable testing machine and extended to 4 times its retracted length
for 5,000 cycles at a rate of not less than 18 nor more than 40 cycles per minute. The cord shall be
capable of returning to at least 20 percent of its original retracted length within one hour after completion
of the cycling. The resistance of the conductor shall be remeasured and the change in the resistance
shall not exceed 10 percent of its original resistance.
4.3 The cord shall then be positioned vertically and a load of 6 ounces for single-conductor cord, 8
ounces for two-conductor core, and 10 ounces for three- or four-conductor cord shall be applied to the
end. The finished cord shall have a minimum extended length of 2-1/2 times its retracted length.
4.4 The cord shall then be suspended vertically and extended to 5 times its retracted length and
immediately released. The cord shall return to within 10 percent of its original length within 5 minutes.
4.5 The cord shall then be extended between two adjustable clamps fastened to a vertical support so
that the coiled portion of the cord is stretched to 250 percent of its original retracted length for a period of
48 hours. After 48 hours, the cord shall be released from its extended position and freed from restraint by
tapping on a horizontal surface and laid at rest. Thirty minutes after being placed at rest on the horizontal
surface, the cord shall return to not more than 115 percent of its original retracted length within 30
minutes.
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