SFI — 20.1 Specifications

The Ribtect Chest Protector was tested to the SFI 20.1 Specifications for go-kart chest protectors — effective December 9, 2004.

Tests were performed for:

Ages 5-8 — SFI Spec 20.1/1, size SM1

Ages 9-12 — SFI Spec 20.1/2, size SM2

Proof of compliance for SFI 20.1 requires two measurements from the
6-year-old crash test dummy.

With the chest protector the V*C dropped more than 67% in both tests
to 0.41 m/sec in the first test and to 0.42 m/sec in the second test.
Read on to understand how this helps you...

RIBTECT CHEST PROTECTOR

	Ribtect Chest Protector

	SFI Specifications
	Chest Protector Photos

To measure the velocity of displacement first we need to look at the chest deflection. In the chest of the 6-year-old test dummy torso there is a string potentiometer. This device measures deflection of the chest during the impact. View Figure 1.

Figure 1.
Figure 1 shows the chest deflection verses time for the baseline test and the 2 tests with Ribtect chest protectors.
View Figure 1 Details

Figure 2.
In To calculate velocity of the chest deformation the data from the string potentiometer (Figure 1) is differentiated.
View Figure 2 Details

Looking at figure 2 the baseline data and the two tests run with the Ribtect chest protectors were all below the SFI 20.1 limit of 8.5m/sec velocity of chest deflection. The velocity of the chest displacement maxed out at 4.1 m/sec in the baseline case. With the chest protector the velocity dropped 20% to 3.25 m/sec in the first test and dropped by 15 % to 3.5 m/sec in the second test.

Viscous Criterion (V*C) is a method for predicting the soft tissue injury, which can occur in addition to a blunt force or penetration injury. To calculate the V*C both the chest velocity and chest deflection are used. The equation is shown below.

V*C = DeflectionRatio X ChestVelocity X (ChestDeflection/ChestDepth)

V*C = 1.3 X ChestVeolicy X (ChestDeflection/143mm)

The deflection ration is 1.3 for a 6-year-old torso and the chest depth of a 6 year old is 143 mm. V*C is calculated at each time step and the maximum must be less than 1.0 to pass SFI 20.1. The results from the baseline test and the two tests with the Ribtect chest protectors are graphed below in Figure 3.

Figure 3.
The baseline data exceeds the SFI limit of 1.0 m/sec, the V*C maximum was at 1.28m/sec.
View Figure 3 Details

Looking at Figure 3 the baseline data exceeds the SFI limit of 1.0 m/sec, the V*C maximum was at 1.28m/sec. The two tests run with the Ribtect chest protectors were below the SFI 20.1 limit for V*C.

With the chest protector the V*C dropped more than 67% in both tests to 0.41
m/sec in the first test and to 0.42 m/sec in the second test.

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