Seat Belt
Purpose during a crash:
The purpose of a seat belt is to ensure that the passenger does not collide with steering wheel, dashboard, windshield, or leave the vehicle. It also helps the passenger decelerate at a more controlled and slower speed in a crash. Occasionally seat belts cause serious injury in a crash, however they increase the passenger’s chance of survival dramatically, in the front seat it is increased by 50%.
The purpose of a seat belt is to ensure that the passenger does not collide with steering wheel, dashboard, windshield, or leave the vehicle. It also helps the passenger decelerate at a more controlled and slower speed in a crash. Occasionally seat belts cause serious injury in a crash, however they increase the passenger’s chance of survival dramatically, in the front seat it is increased by 50%.
Physics:
During a crash with a stationary object the car stops almost instantly, however the passenger keeps moving forward at a constant velocity until a force stops them (Newton’s first Law). The force could be a steering wheel, dashboard or a windshield if the passenger is not wearing a seatbelt. The table (right) shows the difference in forces acting upon the passenger when they are wearing a seatbelt and not wearing a seatbelt. |
Non-stretch seat belts apply more force to the passenger when the car in a crash. Whereas a stretch seatbelt can increase the passenger’s stopping distance so the average force on the passenger is decreased. Newton’s second law (force equals mass multiplied by acceleration) supports this.
Developments:
1885: Seat belts were invented by English engineer George Cayley in the early 19th century, though Edwars J. Claghorn of New York, was granted the first patent (February 10, 1885) for a safety belt. Claghorn’s patent was for a Safety-Belt for tourists, painters, firemen, etc. who are being raised or lowered, described in the patent as "designed to be applied to the person, and provided with hooks and other attachments for securing the person to a fixed object."
1959: The seat belt has been reviewed, and developed. For example the Volvo introduced the three-point (lap/sash) seat belt in Sweden on the PV544, which is considered to be one of the most important car safety inventions of all time. The three-point seat belt, invented by Swedish engineer Nils Bohlin, secures both the upper and lower body during a crash. In this year the Volvo Amazon and the PV544 became the first cars in the world to have three-point seat belts fitted as standard in the front seat.
1963: Excelsior Motor Company introduces a new type of seat belt that allows the passenger to adjust the seat belt to suit their size when fastening. The inertia reel helps to prevent injury to passenger during rapid braking by locking the seat belt into place.
1970: Australia was the first country to make the fitting of seat belts mandatory in all new passenger vehicles for drivers and front seat passengers.
Modern Seat Belts: Modern Seatbelts include features such as adjustable upper belts to accommodate size, which encourages people to wear them because it is more comfortable. They also have energy management features, for example the seat belt yields during a crash (up to 25cm). This decreases the amount of energy on the passenger’s chest and prevents the stitching in the webbing tearing. The rear center seat has a lap/shoulder belt, which was not previously made and is good for children in booster seats.
1885: Seat belts were invented by English engineer George Cayley in the early 19th century, though Edwars J. Claghorn of New York, was granted the first patent (February 10, 1885) for a safety belt. Claghorn’s patent was for a Safety-Belt for tourists, painters, firemen, etc. who are being raised or lowered, described in the patent as "designed to be applied to the person, and provided with hooks and other attachments for securing the person to a fixed object."
1959: The seat belt has been reviewed, and developed. For example the Volvo introduced the three-point (lap/sash) seat belt in Sweden on the PV544, which is considered to be one of the most important car safety inventions of all time. The three-point seat belt, invented by Swedish engineer Nils Bohlin, secures both the upper and lower body during a crash. In this year the Volvo Amazon and the PV544 became the first cars in the world to have three-point seat belts fitted as standard in the front seat.
1963: Excelsior Motor Company introduces a new type of seat belt that allows the passenger to adjust the seat belt to suit their size when fastening. The inertia reel helps to prevent injury to passenger during rapid braking by locking the seat belt into place.
1970: Australia was the first country to make the fitting of seat belts mandatory in all new passenger vehicles for drivers and front seat passengers.
Modern Seat Belts: Modern Seatbelts include features such as adjustable upper belts to accommodate size, which encourages people to wear them because it is more comfortable. They also have energy management features, for example the seat belt yields during a crash (up to 25cm). This decreases the amount of energy on the passenger’s chest and prevents the stitching in the webbing tearing. The rear center seat has a lap/shoulder belt, which was not previously made and is good for children in booster seats.