Tuesday, September 18, 2012

SRS (supplementary Restraining) & Seat belts

Most vehicles today will feature at least two SRS airbags, a system where in case of an accident, bags of air will deploy for a slower stopping of the body.  In most vehicles, it will feature an airbag in the dash in front of the passenger, and an airbag inside the steering wheel for the driver.  These air bags will deploy when a sensor in the engine bay or the steering wheel column is set off.  Although vehicles feature seatbelts to retrain the body from moving forward into the windscreen, the neck/back will suffer whiplash and cause potential fatality or body paralysis.  (If you've ever been go-carting and crashed head into a wall, the whiplash is very painful.... I heard... not that I have crashed head on to a wall...)

This feature was first introduced in the 1970's by GMC.  These days, cars will come with air bags for rear passengers, side air bags, curtains, and others. They are also featured in other vehicles like motorbikes, and can also be found in seatbelts.   Multiple crash tests have proven that air bags are far safer than having no air bags in a collision crash situation.

The system is controlled to a device similar to an ECU, an ACU (Airbag Control Unit), which I've usually found near the passengers left foot inside the walls of the vehicle.  It is hooked up to a bunch of different types of sensors that sense sudden changes in speed and collapsing in places like the steering wheel column.  The air bag is deployed by a canister of Nitrogen, which basically explodes and releases into the bag/curtain.

It is important that the SRS light comes on during the self check when the key is turned in the ignition barrel. 

Some safety precautions should be taken, as the air bag is powerful enough to potentially knock you unconcious if working on vehicle.  (I've heard stories of the panelbeater getting knocked out at the shop where I used to work).  The SRS system is electronic, so it is important that if working on the steering wheel, dashboard, that you remove the negative terminal on the battery.   

Seat belts

All cars today will have seat belts.  They are safety harnesses in typical road cars, reduces the chances of injury in collisions dramatically.  It is important that during WOF inspections that the seatbelts are clearly inspected and are not damaged in any way.  Any frayed edges, holes, cuts dis-colouration can fail warrants.  The buckles also must be in good condition.  They must work properly and the belt tongue should easily click into the buckle.  Any damage in the buckle will also fail.   Many cars today will have a sensor to indicate if a passenger is not wearing a seat belt.  (I find it really annoying because the smallest weight like less than 1KG will light up the dashboard to indicated that my water bottle is not wearing a seatbelt,  some cars will actually beep if they think that a passenger is sitting in the seat and not wearing a belt. Seriously who weighs less than 1KG?  not even a new born baby fresh out of the vagina weighs less than 1KG.)

Seatbelts will have a tag to indicate if the belt is 'V' (Vehicle) type or a 'W' (webbing) type.  The vehicle type means that if you pull the belt quickly, the belt will lock up and will not pull out.  This feature means that incase of a sudden stop, the seatbelt will hold the driver/passenger's body back from moving forward.  the webbing type features a mechanism inside the retractor, with a ball that rolls around.  As the body slows down, the ball's weight will move forward and stop the seatbelt from pulling out.

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