I want to pick your brains if I may.
I was pulling one of the bosses mates trailers the other day. When connecting the airlines there was an extra connection. It looked the same as the red line but it was slightly thicker in diameter.
Any ideas?
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Must be a VERY old trailer, been that long ago since I ever saw one that I can`t remember what it was called or used for ,but it was definitely for a blue air line,which became obsolete as braking systems modernised.
Lapse of memory in my old age it was the “dead man” operated by a separate lever in the cab,which operated the trailer brake only.Later the handle was combined in the handbrake mechanism
1995 according to the plate.
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In the old…
Days, there were two airline inputs into the trailer, a red line and a slightly larger in diameter blue line. The blue line was for trailer brake only operation with hand device in the cab.
You could coast down steep hills by pulling on the trailer brakes only. In time, this meant that the majority of trailers had virtually no brakes left on them when you picked them up from the docks.
ah the good old days sigh
Could you smell diesel? 
yourhavingalarf:
In the old…Days, there were two airline inputs into the trailer, a red line and a slightly larger in diameter blue line. The blue line was for trailer brake only operation with hand device in the cab.
You could coast down steep hills by pulling on the trailer brakes only. In time, this meant that the majority of trailers had virtually no brakes left on them when you picked them up from the docks.
ah the good old days sigh
Ahh?
Blue line on UK trucks operated trailer brakes as well as unit steer axle I thought. Some exotica such as Volvo and Scania did have a separate lever for trailer brakes only.
That’s my memory at least.?
If you pulled the brake lever halfway up on the MAN I used to drive, it only applied the trailer brakes.
Wheel Nut:
Could you smell diesel?
^^^^^^^^^^^^^^^^^^^
the still current variation is to run the ribena pipe down the existing airline anyway,
means a bit less braking performance,but who cares about that when you have a good pair of super hamptons on the pedal.
Wheel Nut:
Could you smell diesel?
In the transport cafes…
I could smell diesel, Old Holborn, bacon fat and the heady pong of un-washed drivers.
ah the good but smelly old days sigh
…So owner drivers would wear out “someone else’s trailer” whilst preserving their own gears and brake linings… 
I remember the old blue airlines on Leyland Roadtrains years ago… You pulled the squarish trailer brake handle down halfway to “brake the trailer on it’s own”.
No speed limiters back then, and going down Reigate Hill would easily see the combination run away with you a bit… 70mph+
You didn’t want to be stamping on the brakes at the bottom of the hill - or you’d risk your cab being run over by your own loaded trailer! 
yourhavingalarf:
Wheel Nut:
Could you smell diesel?In the transport cafes…
I could smell diesel, Old Holborn, bacon fat and the heady pong of un-washed drivers.
^^^^^^^^^^^^^^^^^^
thatl be the first woooshhh for wheelnut then?ah the good but smelly old days sigh
dieseldog999:
yourhavingalarf:
Wheel Nut:
Could you smell diesel?In the transport cafes…
I could smell diesel, Old Holborn, bacon fat and the heady pong of un-washed drivers.
^^^^^^^^^^^^^^^^^^
thatl be the first woooshhh for wheelnut then?Beat me to it DD!
ah the good but smelly old days sigh
dieseldog999:
yourhavingalarf:
Wheel Nut:
Could you smell diesel?In the transport cafes…
I could smell diesel, Old Holborn, bacon fat and the heady pong of un-washed drivers.
^^^^^^^^^^^^^^^^^^
thatl be the first woooshhh for wheelnut then?Beat me to it DD!
ah the good but smelly old days sigh
Winseer:
…So owner drivers would wear out “someone else’s trailer” whilst preserving their own gears and brake linings…
The Company Jake. 
The trailer break was the best thing since sliced bread there is not a lot on here who would remember it or know anything about it
The best one was in the scania cab it was at your fingertips on the dash the 142 and 143 comes to mind
All before this ■■■■ of abs or other crap like it, in it’s time if you had common sense it was as good as anything they have today
Why because you controlled it so I suppose you had to be a real driver then
The new breed would probably ask you now if they seen it on the dash is, what the ■■■■ is that, and when you told them after asking on here loads of times is they would say why the ■■■■ do I need that
There were drivers who had loads of experience who till this day still don’t know what it was, it looked like a handbrake and was only a foot away from the original
hand break
The best way i would describe it is that it was a supertool, brilliant, and gave you full control providing you knew how to use it
the berliet I drove had the lever on the dash, as said ideal for the majority of braking with it especially with trailers off the quayside. and great fun in the snow on a dual carriageway you could pop the trailer out a bit and watch it act like the snow plough, obviously only when nothing was coming the other way.
hotel magnum:
the berliet I drove had the lever on the dash, as said ideal for the majority of braking with it especially with trailers off the quayside. and great fun in the snow on a dual carriageway you could pop the trailer out a bit and watch it act like the snow plough, obviously only when nothing was coming the other way.
Yep indeed, often used it on ice or snow to impress or scare the crap out of annoying cagers.
To OP, the real purpose of the trailer brake was it could be applied in a graduated manner usually using a separate handle to brake the trailer only. This was seen as an important tool to prevent jackknifing prior to the arrival of decent ABS, EBS, proper load sensing systems and so on.
D Dawg, I often pulled those fridges with 5 “air lines” no less.
The extra 2 were only supposed to be used at night time for obvious reasons. Often got a heart attack when I jumped out at lunchtime in Euroland and saw the other two still connected in broad daylight. 
Ribena and return…no limiter… new disc every 8 or 9 hours…and serious dosh… Thems were the days…
Winseer:
No speed limiters back then, and going down Reigate Hill would easily see the combination run away with you a bit… 70mph+
I did 70 on the A14 only 2 days ago 
Blue line is a secondary brake and it was a proper seperate brake system with its own relay valve on the trailer and two air pipes to each brake chamber, one for std air brake and second for secondary brakes, secondary brake were not load sensed so were full bore loaded or empty, this was before spring brake chambers which work differently.
Later on the two trailer brake lines (blue and yellow suzies) went to a valve called a shuttle valve which then sent either air signal to the load sensed relay valve, then they did away with the secindary bit altogether.
The standard air line couplings are called C couplings and the blue line ones were called CA couplings.
Lots of trucks still have a secondary brake except its now built into the handbrake lever and comes on as you pull the lever and goes off just as you pull the know to lock the lever into place.
Some Dafs secondary are tested on brake roller test as are some Mercs, also recall some Scanias as well.
On the some Daf tractors if you apply the park brake then PUSH the knob inwards and pull the lever downwards some more this then releases the trailer brake and checks the tractor park will hold the outfit, why I have no idea!, Dafs being unusual in that they also apply the trailer brakes when the truck park brake is applied.
Trickydick:
Blue line is a secondary brake and it was a proper seperate brake system with its own relay valve on the trailer and two air pipes to each brake chamber, one for std air brake and second for secondary brakes, secondary brake were not load sensed so were full bore loaded or empty, this was before spring brake chambers which work differently.
Later on the two trailer brake lines (blue and yellow suzies) went to a valve called a shuttle valve which then sent either air signal to the load sensed relay valve, then they did away with the secindary bit altogether.
The standard air line couplings are called C couplings and the blue line ones were called CA couplings.Lots of trucks still have a secondary brake except its now built into the handbrake lever and comes on as you pull the lever and goes off just as you pull the know to lock the lever into place.
Some Dafs secondary are tested on brake roller test as are some Mercs, also recall some Scanias as well.On the some Daf tractors if you apply the park brake then PUSH the knob inwards and pull the lever downwards some more this then releases the trailer brake and checks the tractor park will hold the outfit, why I have no idea!, Dafs being unusual in that they also apply the trailer brakes when the truck park brake is applied.
Useful to let off trailer parking brake when raising or lowering trailer height.
(She do jump!)
