Seat Belts

1. Seat Belts Prepared by Team Roadrunner: Nathan Durham William C. Moore Benjamin Sargent

2. Newton’s First Law INTRODUCTION HISTORY STATISTICS DESIGN THEORY DESIGN FEATURES FUTURE An Object in motion tends to stay in motion unless acted upon by an out side force. Modern Seat Belts • Prevents occupant from being thrown from vehicle • Applies force to rigid parts of occupants body • Increases stopping time on body by stretching belt • Places occupant in optimal crash position Lap belt 3-Point Belt

3. In 1959, Volvo uses Nils Bohlin’s new three point seat belt system. INTRODUCTION HISTORY STATISTICS DESIGN THEORY DESIGN FEATURES FUTURE History of Seat Belts • 1885 – First safety harness patent • 1956 – Ford offers optional • lap belts • 1959 – Volvo makes first • modern three • point system • 1963 – Volvo makes three point • system standard in US • 1968 – Two point lab belts are • standard in US • 1974 – NHTSA requires Bohlin’s • three point continuous • loop in all new US cars

4. Data from the National Highway Transportation Safety Administration INTRODUCTION HISTORY STATISTICS DESIGN THEORY DESIGN FEATURES FUTURE With 100% seat belt usage, about 340,000 lives would have been saved since 1975!

5. Lives saved per year as a result of seat belt usage. INTRODUCTION HISTORY STATISTICS DESIGN THEORY DESIGN FEATURES FUTURE As more people wear seat belts, more lives are saved each year.

6. The kinetic energy equation represents the energy an occupant has when a vehicles stops. INTRODUCTION HISTORY STATISTICS DESIGN THEORY DESIGN FEATURES FUTURE Including stopping distance: 180 lb person with seat belt (1 ft stopping distance) Stopping from 30 mph experiences 5419 lbs Stopping from 60 mph experiences 21,676 lbs 180 lb person without a seat belt (0.2 ft stopping distance) Stopping from 30 mph experiences 27,096 lbs Stopping from 60 mph experiences 108,384 lbs

7. Retracting Device INTRODUCTION HISTORY STATISTICS DESIGN THEORY DESIGN FEATURES FUTURE Belt webbing is retracted using a spool and a torsional spring

8. Locking Mechanisms • There are two types of locking mechanisms • Mechanisms triggered by vehicle’s movement INTRODUCTION HISTORY STATISTICS DESIGN THEORY DESIGN FEATURES FUTURE During a car crash, the inertia forces the weighted pendulum forward causing the pawl to extend upward. The pawl catches a toothed ratchet gear that is attached to the spool, thus stopping the gear and spool from rotating counter-clockwise.

9. Locking Mechanisms • Mechanisms triggered by belt’s movement INTRODUCTION HISTORY STATISTICS DESIGN THEORY DESIGN FEATURES FUTURE When the spool begins to spin quickly, the weighted clutch lever (centrifugal clutch) is driven outward contacting the cam. The contact with the cam causes a sliding pin to move along a grove pulling the pawl into contact with the ratchet gear. The pawl becomes locked into the gear’s teeth, causing the spool to resist all counter-clockwise rotation.

10. Pretensioner INTRODUCTION HISTORY STATISTICS DESIGN THEORY DESIGN FEATURES FUTURE A pretensioner pulls in on the belt to tighten any slack in the webbing during a crash and moves the passenger in optimal crash position. This mechanism is used in collaboration with one of the previous mentioned methods of locking the spool. Pretensioners can be built around electric motors, solenoids, or pyrotechnics. The most popular pretensioners use pyrotechnics. The figure below shows this type of pretensioner.

11. Future Seat Belt Technology INTRODUCTION HISTORY STATISTICS DESIGN THEORY DESIGN FEATURES FUTURE Inflatable Seat Belt 4 Point Belt Systems • Reduces whipping • Spreads out impact force • Greater restraint on passengers • torso • Spreads out impact force Honeywell “Smart Fiber” Belt • Reduce the impact forces on a passenger

12. INTRODUCTION HISTORY STATISTICS DESIGN THEORY DESIGN FEATURES FUTURE Any Questions?