Semi hauling Yoplait crashes off I-196

Discussion in 'Trucking Accidents' started by camerabrat, Jul 28, 2011.

  1. Saienga

    Saienga Medium Load Member

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    I did like how, at the end, she said, "You left your gas tank up on the road, so at least we knew you weren't going to catch fire."

    Yes, honey, he left one of his fuel tanks up on the freeway, but the other one he took with him.

    Oh well. My wife still calls it gas, so...
     
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  3. ironpony

    ironpony Road Train Member

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    The engine brake affects the drive wheels on the tractor slowing the vehicle... if the trailer tandems loose traction and start sliding, any side force can cause the trailer to pivot around the fifth wheel causing a jack knife.

    So have I. Just because we've both used them without trouble doesn't mean it can't happen.
    Our lightweight tractors only have ONE fuel tank...
     
  4. otherhalftw

    otherhalftw R.I.P.

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    No, the engine brakes don't effect the drives....they effect a compression within the engine reducing output torque to the drive train. A higher compression making it harder for the pistons to cycle through limiting exhaust gas flow from the chamber.

    Engine brakes (alone) will not cause a jack knife. Engine brakes along with excessive (for the given conditions) braking will cause the drives to break traction and begin a skid. Once this condition exists, the trailer can, through slope of roadway or unbalanced weight of the cargo, or the straight line between tractor and trailer is interrupted, will cause jack knife. Braking alone will cause a jack knife, the engine brakes don't need to be involved.

    Trailer tandems....traction? Since when do trailer axles have anything but rolling resistance? The tandems will come around due to what exactly(?), slope of the roadway while the wheels are turning(?), the force of a side wind pushing the rear of the trailer and not the front and tractor?

    Tandems that have locked up, or have maladjusted brakes causing one side to apply greater brake pressure than the opposite side, will cause the tandem group to find the path of least resistance....or swing out from straight line perspective to the tractor.

    This is why drivers need to learn to apply light pressure to the rig....and in a panic stop, to keep the rig straight and clean. Swerving to avoid is the most common scenario of jack knife events! Breaking the straight perspective, along with excessive braking, brings the trailer around....be it dry, wet, or icy....braking needs to be done properly.
     
    doubledragon5 Thanks this.
  5. THE ROAD VIRUS

    THE ROAD VIRUS Light Load Member

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    as per he manufacturer:

    Slippery Pavement​
    Since the operation of any vehicle under slippery conditions is
    unpredictable, be sure you have plenty of distance when testing service
    brakes or your Jacobs Engine Brake​
    ™.
    The Jacobs Engine Brake will not affect the operation of ABS (Anti-lock
    Braking System) on vehicles so equipped. The ABS systems should
    deactivate the engine brake when wheel slip occurs and traction is lost,
    and will reactivate the engine brake when the ABS system has
    disengaged.
    If the Jacobs Engine Brake is new to you, it is recommended that you do
    not attempt to use it on slippery roads until you have some experience
    with it on dry pavement. When you have that experience, you may use the
    following operation sequence as a guideline.

    Do not use the Jacobs Engine Brake when bobtailing
    or pulling an empty trailer on wet or slippery
    pavement, especially when operating a single drive
    axle vehicle.​
    Slippery Pavement Driving Procedures​
    When driving on wet or icy pavement, start with the master switch in the​
    "​
    Off" position and use the same gear you would normally use under these
    conditions.
    Before activating the engine brake, be sure that you have plenty of
    distance between your vehicle and other vehicles and that traffic
    conditions allow for testing of vehicle braking. Also make sure that the
    vehicle is maintaining traction and stability using the natural retarding of
    the engine alone. If the retarding of the engine alone without the engine
    brake causes any loss of traction, do not attempt to use the engine brake
    until road conditions improve.

    Jacobs Engine Brake
    ™ Operator's Manual 11

    from what I understand from the material is: in slippery conditions, test your jake, if you break traction/lose road grip, SHUT OFF JAKES. Road conditions change. You might be able to engage jakes at first, then as you travel, road conditions worsen, then you lose grip/ break traction. Reaction time is a factor from the time you sense contact loss to the time you flip the off button and hope you caught it in time. It is probably best to just leave them off in slippery conditions, for safety's sake. But to each their own.
     
  6. otherhalftw

    otherhalftw R.I.P.

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    This is Jacobs way of CYA....as I said before in this thread....because of ambulance chasing attorneys, and the sue happy world we live in...all manufacturers must put up any kind of "liability disclosure" they can muster.

    Read it closely....they really don't take a rigid stance on the use or non-use of the Jakes! They do acknowledge that their product is usable in wet/slippery conditions, and offer some "advice" on their recommendations for its use.
     
  7. ironpony

    ironpony Road Train Member

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    Well... you certainly do make me think about this a bit more than I usually do! The problem isn't that the trailer tandems break loose, but what happens with the drives. As the truck decellerates the engine braking is providing a force vector opposite the motion of the truck... you can consider the velocity vector of the entire truck and the deceleration vector acting around the center of gravity of the combined vehicle... I'd think that would be located somewhere behind the 5th wheel in all load conditions. As long as everything is stuck to the ground, all your acceleration and decelleration forces act in a straight line, and the truck keeps on truckin' down the road.

    Now we're talking about two different conditions here... one with the tires rolling, and one with the tires sliding - once a tire starts sliding, the coefficient of friction changes drastically, and that alters the force on that tire from the surface its on.

    If anything causes the drive tires to break loose from the surface and start sliding, you have a condition where the trailer shoving forward onto the tractor can cause the combination to start to pivot around the fifth wheel... since the center of gravity isn't located there, it will cause a torque around the physical connection between the two parts of the vehicle. Same with a strong wind... any good side force should be capable of causing that torque. The pressure on the ground from the tires counteracts any side force normally, keeping things moving down the road.

    As long as you don't have the tractor pushing back on the fifth wheel the stack goes forward even with a tire sliding for whatever reason... but you'll probably feel it in the seat of your pants though. If the the tractor is pushing backwards from the jake brake, then the difference in the normal force on the side with the tire sliding vs the side with the tire rotating can cause enough torque around the center of gravity of the vehicle to get the fifth wheel out of alignment with the velocity vector at the center of gravity. At that point the decelleration force from the jake brake is pushing against the fifth wheel/kingpin pivot point, and the trailer center of gravity (not located there) will cause a torque around the fifth wheel/kingpin pivot - and that will cause a jack knife condition.

    ...anyway, that's how I see the forces acting.

    Ah... if y'all want to risk your Otter testing this theory, have at it! Personally, I think I'll stick with judicious non-use of jakes on slippery surfaces, and go with the side of me that figures pushing your luck on ice, snow-pack or a lot of water on a road with a 80,000 lb vehicle and other folks lives on the line will eventually lead you to a velocity vector counter to a proposition that includes continued employment in the truckin' industry!
     
    Last edited: Aug 4, 2011
  8. otherhalftw

    otherhalftw R.I.P.

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    Nice oration!

    Now...you and I would have to order a pot of coffee for discussions over the table....a cup would not suffice! But we would have to agree to pause every once in a while for a chance to hear what the other was actually saying!!!!! LOL:biggrin_25514:
     
  9. ironpony

    ironpony Road Train Member

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    In this situation... I don't think the jakes alone started the accident in the OP. My guess is something else caused him to apply a lot of braking force - maybe another vehicle doing something stupid (Nah?? You think those chowder-heads in 4-wheelers would do somethin' stupid in front of a semi???) - or he was going too fast for conditions in those curves - probably the case considering the end result. A lot of braking, jakes on to contribute to the mess, enough water to start some hydroplaning, one of those unfortunate velocity vector combinations... and the guy chose the "bushes" as a way out to avoid mushing some 4-wheelers into goo.

    Any of us could get caught up in a situation like that... but since there's a big "PRIME" on the side of the trailer, its obvious that the driver was a sub-normal mental midget being goaded on by an evil trucking company. At least that's what the supertruckers would have us think. Its illustrative that when something goes wrong driving one of these things that quite often we have the choice of an accident, or going off the road to avoid the accident. So you have to ask yourself, when things get stacked up against you, what are you going to do???

    A while back there was a semi driver who avoided an accident on one of the toll bridges in Baltimore... 18-or-so-year-old kid driving drunk from a privileged, wealthy family cuts off the semi. The driver goes off of the bridge to avoid the accident. Now if it had said "PRIME" on the side of the trailer, you'd have everyone assuming that the driver was an idiot, second guessing his actions, and making ridiculous claims about his abilities. In this case, the driver was a 20-something year industry veteran, and I believe in his own rig. They delayed testing the kid for alcohol for HOURS (probably the attorneys had a hand in that) to get her blood-alcohol content down because of the family connections - in order to blame the truck driver for the accident. The industry was calling him a "hero" for not mushing the kid into goo. Go figure.
     
    Last edited: Aug 4, 2011
  10. 123456

    123456 Road Train Member

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    Just 1 off the wall question.........


    Is it really better to swerve to miss a vehicle, which causes loss of control.

    Or NOT swerve, and retain most or some control..................
     
  11. ironpony

    ironpony Road Train Member

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    And if by not swerving, you are unavoidably going to crash into a minivan full of kids?

    ...ummm don't the safety guys call that "counter steering?"
     
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