How Seatbelts Work Introduction According to NHTSA seatbelts save 13,000 lives in US each year 7,000 US car accident fatalities could have been avoided if victims had been wearing belts Seatbelts reduce the risk of death for a front seat car occupant by about 50 percent Seatbelts Seatbelt – spreads the crash forces across stronger parts of the body to minimize injury. Consists of lap belt and a shoulder belt Belts extend across the pelvis, rib cage and shoulder. Force is not concentrated in a small area, so injury is reduced. Crashworthiness Crumple zones – front and rear of the car that collapse relatively easily Car seatbelts have the ability to extend and retract You can lean forward easily, belt stays fairly taut In a collision, belt tightens up and holds you in place Seat Belt Retractors Retractor mechanism A spiraled spring rotates the spool to keep the seatbelt webbing taut 1) Centrifugal clutch triggered by belt movement Centrifugal clutch. When the spool rotates quickly, centrifugal force drives the weighted end of a pivoting lever outward. The lever pushes a cam connected to a pawl. The pawl moves into the spinning ratchet gear stopping the belt.
