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What happens during a frontal impact:
This data is based on
an optimised installation with an upright seating position during dynamic
testing. It simulates a 90° head on collision, utilising a 75 kg [165 lb]
mass dummy, an impact velocity of 50 kph [31 mph] and a stopping distance of
approximately 400 mm [16”] with a maximum deceleration of 30 g [FIA Standard 8854/98
dynamic test requirements]:
·
The
pelvic load, expected to surpass 14 kN [3,100 lb] at each side, will
elongate the lap belt and compress the tissue on the pelvis. The pelvis will
slide forward by 80 to 100 mm [3”-4”]
·
The upper
torso load is expected to surpass 7 kN [1,550 lb] on each strap, will
elongate the shoulder belts, the upper body will roll in, the adjusters will
move up the chest by approximately 200 mm [8”] and forward head trajectory
will be up to 400 mm [16”]
·
The pelvic
movement combined with the shoulder belt forces will load the anti-sub
straps to more than 6 kN [1,320 lb] each in a 5- or 6-point racing harness
and can be intentionally higher in a F‑type model where the anti-sub straps
are routed rearwards.
In more reclined
seating positions, the pelvic load will be reduced to approx. 9 kN
[2,000 lb] since the seat pan, designed as a ramp, will take some of the
load. Therefore it is essential the seat or chassis manufacturer ensure the
seat pan is strong enough not to bend or even collapse under extreme loads.
In any case, seats
are a significant component of the safety system!
What does the discussion of frontal impacts mean to the occupant?
The numbers above seem to be quite high when compared with actual racing
accidents. Fortunately, most racing accidents are not 90° head-on
collisions. Car deformation is greater than the 400 mm [16”], and modern
soft walls also convert impact energy. Therefore, accidents with higher
impact speeds are often less severe than the FIA required test set up.
However, SCHROTH racing harnesses have been tested to speeds and
decelerations surpassing FIA requirements.
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