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Dumb Question - Air Bags

Discussion in 'Introduce Yourself to the Community' started by flumes, Jan 30, 2008.

  1. flumes

    flumes Junior Member
    Messages: 21

    I just got my plow on the road. 6'9" Fisher on a '97 Wrangler.

    Should I be worried about my air bags going off when I pile snow. Some of the snowbanks are pretty high here and I try to hit them ligh and high. But the odd one sure feels hard.

    Anybody have them go off?

  2. wild bill

    wild bill PlowSite.com Addict
    Messages: 1,239


    depends how hard they are to turn off ,and how hard you ram jam .i only know of one guuy that blew one but he was a real cowboy!!!!!!!!!!!!!
  3. theplowmeister

    theplowmeister 2000 Club Member
    from MA
    Messages: 2,515

    when you hit a snowbank hard enough to wreck the truck the airbag will go off
  4. Crash935

    Crash935 2000 Club Member
    Messages: 2,377

    Yup, if you hit hard enough to set the bags off, your probably going to want them to go off!
  5. toby4492

    toby4492 2000 Club Member
    Messages: 2,513

    Definately going to be in your best interest if they do go off.
  6. flumes

    flumes Junior Member
    Messages: 21

    Thanks guys.

    We had a few days of very mild weather here and then a hard freeze blizzard with a major dump of snow.

    The soft wet snowbanks hardened up real good.

    Like I said, i am brand new to plowing and am trying to figure out the limitations of jeep/plow before I break or hurt something.

    Thanks for the advice.
  7. Plowin in VT

    Plowin in VT Senior Member
    Messages: 233

    Take it nice and slow for the first several storms. It's much better to take extra time per job than to damage your Jeep or your customer's property.

    As far as the airbags go, I believe that I read something a while back that said that there were sensors behind the bumpers, and when they are tripped, the airbags will go off. Since the plow is mounted to the frame, the sensors "should not" be tripped.
  8. Crash935

    Crash935 2000 Club Member
    Messages: 2,377

    Airbag sensors are not located behind the bumper but closer to or in the cab area.
  9. go plow

    go plow Senior Member
    Messages: 322

    i was a autobody tech before i went into landscaping, most air bag sensors are located on the rad.support.
    if they get jogged enough times they can go off, ive seen a plow truck hit a man hole cover, no damage to the truck at all, the the bags blew, still in this case i would want them to go off,and be wearing a seat belt.the impact would be enough to send you into the windshield.
  10. go plow

    go plow Senior Member
    Messages: 322

    if the sensor was near the firewall, by the time they blew, your engine would be on you lap, and the air bags would be useless
  11. SnoFarmer

    SnoFarmer PlowSite Fanatic
    from N,E. MN
    Messages: 7,921

    We have discussed this many times before

    There are no air bag senors in or on the front bumpers..
    (sensors were put in car bumpers and frames but not on trucks)...
    On gmc, chev and some others, I believe they did have a brittle bar built in to the radiator support for the air bags.

    Dodge trucks have there inertia sensor located on the tranny hump in the cab.
    not in the bumper or the frame.

    Air bag wiring is bright yellow wires with a black stripe and will be labeled " Warring air bag" along then too

    Unlike a brittle bar an inertia sensor can go off if you are hit from any direction
    It is like a magnetized ball sitting on a metal golf tee.
    you have to hit to be hit hard enough to knock it off it's perch.

    They will not go off from "normal" plowing.

    They will not go off until you really need them.

    All of you have seen the pics of bent plowframes cracked and bent truck frames and yet not one air bag deployed.
    Last edited: Feb 1, 2008
  12. scottL

    scottL PlowSite.com Addict
    Messages: 1,600

    I believe in the current generation of air bags some have seat sensors for the weight of the occupant. I thought I understood that they will not go off if you do not have your seat belt buckled as the air bag could cause more harm.
  13. zappalawn

    zappalawn Member
    from pgh
    Messages: 56

    i havent worked in a body shop for a few years know so my memory of this stuff is kinda blank but im pretty sure that they wont go off under 25mph i think but all makes models and years are diffrent. i have seen cars come in with airbags sensors crushed were they should have went of but didnt. that turns in to a major pita because the manfactor and other stat and fed dept get involved
  14. SnoFarmer

    SnoFarmer PlowSite Fanatic
    from N,E. MN
    Messages: 7,921

    I learned some thing new.;)
    and had a few q's answered too.

    Automobile airbags
    There have been airbag-like devices for aeroplanes as early as the 1940s, though the first actual example in a production car was the 1981 Mercedes-Benz S-Class.

    The design is conceptually simple—accelerometers trigger the ignition of what is essentially solid rocket propellant to very rapidly inflate a nylon fabric bag, which reduces the deceleration experienced by the passenger as they come to a stop in the crash situation. The bag has small vent holes to allow the propellant gas to be (relatively) slowly expelled from the bag as the occupant pushes against it.

    Initially, most vehicles featured a single airbag, mounted in the steering wheel and protecting the driver of the car (who is the most at risk of injury). During the 1990s, airbags for front seat passengers, then separate side impact airbags placed between the door and occupants, became common. Most jurisdictions now explicitly require at least driver airbags in all cars, or set passenger safety standards that can only be met by their use.

    Statistics show that passengers in cars fitted with airbags have approximately 30% less chance of dying in an accident than in comparable cars without airbags fitted. Despite this, airbags have occasionally caused controversy, as the initial expansion of the bag is in itself a violent event, and if an individual is too close to the airbag when it is initially triggered they can be seriously injured or killed. This was partly due to American airbag designs triggering much more quickly than airbags designed for other countries, to protect occupants not wearing seat belts. Newer airbags trigger slightly less violently; nonetheless, passengers must remain at least 25 centimetres (10") from the bag to avoid injury from the bag in a crash.

    Smoking a pipe in a seat protected with an airbag should be avoided: if it inflates and hits the pipe while it is in the mouth this may well be deadly.

    Automobile airbags are supplemental restraints, and operate best when the occupant is also using a seat belt. Air bags supplement the safety belt by reducing the chance that the occupant's head and upper body will strike some part of the vehicle's interior. They also help reduce the risk of serious injury by distributing crash forces more evenly across the occupant's body.

    Airbag design
    The air bag system consists of three basic parts-an air bag module, crash sensors and a diagnostic unit. Some systems may also have an on/off switch, which allows the air bag to be deactivated.

    The air bag module contains both an inflator unit and the lightweight fabric air bag. The driver air bag module is located in the steering wheel hub, and the passenger air bag module is located in the instrument panel. When fully inflated, the driver air bag is approximately the diameter of a large beach ball. The passenger air bag can be two to three times larger since the distance between the right-front passenger and the instrument panel is much greater than the distance between the driver and the steering wheel.

    The crash sensors are located either in the front of the vehicle and/or in the passenger compartment. Vehicles can have one or more crash sensors. The sensors are typically activated by forces generated in significant frontal or near-frontal crashes. Sensors measure deceleration, which is the rate at which the vehicle slows down. Because of this, the vehicle speed at which the sensors activate the air bag varies with the nature of the crash. Air bags are not designed to activate during sudden braking or while driving on rough or uneven pavement. In fact, the maximum deceleration generated in the severest braking is only a small fraction of that necessary to activate the air bag system.

    The diagnostic unit monitors the readiness of the air bag system. The unit is activated when the vehicle's ignition is turned on. If the unit identifies a problem, a warning light alerts the driver to take the vehicle to an authorized service department for examination of the air bag system. Most diagnostic units contain a device that stores enough electrical energy to deploy the air bag if the vehicle's battery is destroyed very early in a crash sequence.

    Some vehicles without rear seats, such as pick-up trucks and convertibles, or with rear seats too small to accommodate rear-facing child restraints, have manual ON/OFF switches for the passenger air bag installed at the factory. ON/OFF switches for driver or passenger air bags may also be installed by qualified service personnel at the request of owners who meet government-specified criteria and who receive government permission.

    Triggering conditions
    Air bags are typically designed to deploy in frontal and near-frontal collisions, which are comparable to hitting a solid barrier at approximately 8 to 14 miles per hour (mi/h) (13-22.5 km/h). Roughly speaking, a 14 mi/h barrier collision is equivalent to striking a parked car of similar size across the full front of each vehicle at about 28 mi/h. This is because the parked car absorbs some of the energy of the crash, and is pushed by the striking vehicle. Unlike crash tests into barriers, real-world crashes typically occur at angles, and the crash forces usually are not evenly distributed across the front of the vehicle. Consequently, the relative speed between a striking and struck vehicle required to deploy the air bag in a real-world crash can be much higher than an equivalent barrier crash.

    Because air bag sensors measure deceleration, vehicle speed and damage are not good indicators of whether or not an air bag should have deployed. Occasionally, air bags can deploy due to the vehicle's undercarriage violently striking a low object protruding above the roadway surface. Despite the lack of visible front-end damage, high deceleration forces may occur in this type of crash, resulting in the deployment of the air bag.

    Most air bags are designed to automatically deploy in the event of a vehicle fire when temperatures reach 300 to 400 degrees Fahrenheit (150-200°C). This safety feature helps to ensure that such temperatures do not cause an explosion of the inflator unit within the air bag module.

    Today, airbag trigerring algorithms are becoming more and more complex. They try to remove risks of useless deployments (for example, at low speed, no shocks should trigger the airbag to help reduce damage to the car interior in conditions where the seat belt will be a convenient-enough safety device) and to adapt the deployment speed to the crash conditions. The algorithms are considered as very valuable intellectual property.

    Front air bags are not designed to deploy in side impact, rear impact or rollover crashes. Since air bags deploy only once and deflate quickly after the initial impact, they will not be beneficial during a subsequent collision. Safety belts help reduce the risk of injury in many types of crashes. They help to properly position occupants to maximize the air bag's benefits and they help restrain occupants during the initial and any following collisions. So, it is extremely important that safety belts always be worn, even in air bag-equipped vehicles.
  15. toby4492

    toby4492 2000 Club Member
    Messages: 2,513

    Great information. Thanks for sharing.
  16. MrBigStuff

    MrBigStuff Senior Member
    from Boston
    Messages: 140

    Most of the SRS systems today also use a two stage deployment strategy to account for people who may not be wearing a seatbelt. The bags deploy slower and with less force if you are unbelted. This helps to reduce injuries caused by the passenger sliding into the full force of the deploying bag.

    Manufacturers seem reluctant to disclose the trip speed for their systems. Probably because it is deceleration that matters most but they do have a minimum speed at which they will not deploy. There is a tolerance for gauge accuracy built into the figure. Then plow manufacturers apply their own "fudge factor" which reduces it even more and they end up making a statement like "keep it below 10mph to insure the bags will not deploy during snow plowing operations".

    FLASHMAN Member
    Messages: 78

    Wow... I can't even imagine plowing fast enough to make my airbags go off if I were to hit something... I plow in low gear between 5-10 MPH.
  18. camconcrete

    camconcrete Senior Member
    Messages: 199

    heard that, its bad enough when you hit a curb island you forget about, let alone hit a snow bank hard enough for the airbags to deploy, besides I'm paid by the hour so I take my good ol time