CFR

CFR

572.17—Neck.

(a) (1) The neck for use with the head assembly described in § 572.16(a)(1) consists of the assembly designated as SA 103C 020 on drawing No. SA 103C 001, conforms to each item specified on drawing No. SA 103C 002(B), sheet 9.

(2) The neck for use with the head assembly described in § 572.16(a)(2) consists of the assembly designated as SA 103C 020 on drawing No. SA 103C 001, and conforms to each item specified on drawing No. SA 103C 002, sheet 9.

(b) When the head-neck assembly is tested in accordance with paragraph (c) of this section, the head shall rotate in reference to the pendulum's longitudinal centerline a total of 84 degrees ± 8 degrees about its center of gravity, rotating to the extent specified in the following table at each indicated point in time, measured from impact, with the chordal displacement measured at its center of gravity. The chordal displacement at time T is defined as the straight line distance between (1) the position relative to the pendulum arm of the head center of gravity at time zero, and (2) the position relative to the pendulum arm of the head center of gravity at time T as illustrated by figure 3. The peak resultant acceleration recorded at the location of the accelerometers mounted in the headform in accordance with § 572.21(b) shall not exceed 30g. The pendulum shall not reverse direction until the head's center of gravity returns to the original zero time position relative to the pendulum arm.

Rotation (degrees)	Time (ms) ±(2 .08T)	Chordal displacement (inches ±0.8)
0	0	0
30	21	2.2
60	36	4.3
Maximum	62	5.8
60	91	4.3
30	108	2.2
0	123	0

(c) Test procedure. (1) Mount the head and neck on a rigid pendulum as specified in Figure 4, so that the head's midsagittal plane is vertical and coincides with the plane of motion of the pendulum's longitudinal centerline. Mount the neck directly to the pendulum as shown in Figure 15.

(2) Release the pendulum and allow it to fall freely from a height such that the velocity at impact is 17.00 ±1.0 feet per second (fps), measured at the center of the accelerometer specified in figure 4.

(3) Decelerate the pendulum to a stop with an acceleration-time pulse described as follows:

(i) Establish 5g and 20g levels on the a-t curve.

(ii) Establish t1 at the point where the a-t curve first crosses the 5g level, t2 at the point where the rising a-t curve first crosses the 20g level, t3 at the point where the decaying a-t curve last crosses the 20g level, and t4 at the point where the decaying a-t curve first crosses the 5g level.

(iii) t2 -t1, shall be not more than 4 milliseconds.

(iv) t3 -t2, shall be not less than 18 and not more than 21 milliseconds.

(v) t4 -t3, shall be not more than 5 milliseconds.

(vi) The average deceleration between t2 and t3 shall be not less than 20g and not more then 34g.

(4) Allow the neck to flex without contact of the head or neck with any object other than the pendulum arm.

(5) Allow a time period of at least 1 hour between successive tests of the head and neck.

[44 FR 76530, Dec. 27, 1979; 45 FR 43353, June 26, 1980, as amended at 55 FR 30468, July 26, 1990]