Technical question - trailer emergency brake

Discussion in 'Trucks [ Eighteen Wheelers ]' started by patentlawyer, Jul 6, 2011.

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  1. Jul 6, 2011 #1
    patentlawyer

    patentlawyer Bobtail Member

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    I need some technical assistance from those who know regarding trailer air brake systems. Hopefully someone can quickly answer the following questions:
    1) Typically do trailers have their own dedicated air reservoir tank to supply the brake units?
    2) Is the spring brake valve connected directly to the dedicated air reservoir tank?
    3) When the trailer is disconnected from the tractor, do the spring brakes automatically engage and lock the wheels?

    Can anyone provide a link to some decent 101 level discussion on trailer air brakes and how they operate during various modes of operation?
     
    patentlawyer, Jul 6, 2011
    patentlawyer, Jul 6, 2011
    #1
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  3. Jul 6, 2011 #2
    sidepocket

    sidepocket Light Load Member

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    1) yes... however initially charged and supplied by the trucks compressor.

    2) im not really sure what youre asking... so click here

    3) yes, if it has working spring brakes.
     
    sidepocket, Jul 6, 2011
    sidepocket, Jul 6, 2011
    #2
  4. Jul 6, 2011 #3
    Frenzy

    Frenzy Medium Load Member

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    Frenzy, Jul 6, 2011
    Frenzy, Jul 6, 2011
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  5. Jul 6, 2011 #4
    lovesthedrive

    lovesthedrive R.I.P.

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    All air brakes are supposed to engage when pressure fails. It is a safety feature. Same on trains.

    The air supply actually counteracts a spring in your airbrake cannister and compresses the spring releasing your brakes. When you step on your pedal you are allowing the pressure to bleed off.
     
    lovesthedrive, Jul 6, 2011
    lovesthedrive, Jul 6, 2011
    #4
  7. Jul 6, 2011 #5
    truckbiz

    truckbiz Light Load Member

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    Sorry, doesn't work that way. Although the cannister is one piece, the two lines operate two completely separate systems. You're right one line supplies air to a diaphragm and compresses a large spring to release the "parking brake". The other line supplies air at various pressures for brake application.(service brake)
     
    truckbiz, Jul 6, 2011
    truckbiz, Jul 6, 2011
    #5
    SL3406 and 25(2)+2 Thank this.
  8. Jul 7, 2011 #6
    patentlawyer

    patentlawyer Bobtail Member

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    Thank you all for the input.

    Sidepocket, thank you for the link it was very helpful.

    Does the service reservoir not continue to supply pressurized air to the spring brake valve, thus keeping the spring brake disengaged (at least temporarily until air pressure within the service reservoir depletes) after the trailer is disconnected from the service/emergency air lines from the tractor?
     
    patentlawyer, Jul 7, 2011
    patentlawyer, Jul 7, 2011
    #6
  9. Jul 7, 2011 #7
    lovesthedrive

    lovesthedrive R.I.P.

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    When the driver pulls the button on his dash it drains the system. Otherwise the driver will get a nasty surprise when he goes to remove the glad hand connector between the truck and trailer (red and blue air lines).

    [​IMG]
     
    lovesthedrive, Jul 7, 2011
    lovesthedrive, Jul 7, 2011
    #7
  10. Jul 7, 2011 #8
    patentlawyer

    patentlawyer Bobtail Member

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    lovesthedrive,
    understood and that makes sense. thank you. nothing beats consulting the experts.
     
    patentlawyer, Jul 7, 2011
    patentlawyer, Jul 7, 2011
    #8
  11. Jul 7, 2011 #9
    Pablo-UA

    Pablo-UA Road Train Member

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    No, it is not legal by DOT and EU laws. European trailer park valve differs, there are brake buttons on it. Why trailer park brakes are not directly connected to air tank... see answer to q #2

    If supply (red) air line is disconnected trailer park valve dumps air from park spring brakes, but with some delay and wheels lock in some seconds. So if you pull red button in truck trailer park brakes will apply
     
    Pablo-UA, Jul 7, 2011
    Pablo-UA, Jul 7, 2011
    #9
  12. Jul 7, 2011 #10
    Pablo-UA

    Pablo-UA Road Train Member

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    Pablo-UA, Jul 7, 2011
    Pablo-UA, Jul 7, 2011
    #10
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