newmercman:
[zb] off and grow a pair you purple headed custard spitter
like it
Big Joe:
commonrail:
As long as the unit handbrake is on, connecting the yellow line first before the red will apply the brakes on the trailer whether the trailer h/b is applied or shunt button pushed.
Sorry but that isn’t always true. Some tractors yes - but not all. Some send nothing down the yellow unless the footbrake is applied or the handbrake control held in the secondary position. the trailer park brake should be applied and checked every single coupling and uncoupling.
that is not my quote 
Having now read the full thread and all the posts I am alarmed by the apparent lack of understanding of the trailer brake systems and the message that is being sent across to any potential newby drivers is terrible.
I deliver trailer coupling and uncoupling training as part of DCPC and get a lot of abuse from drivers that have been doing the job for years - fine I soon stop crying. yet ask them to explain to the rest of the class how the brake systems work and they go quiet.
I always start the session by explaining how the brake systems work and generally this gets everyone’s attention as it is genuinely interesting. Once you understand how the brake systems work it becomes quite obvious why you must use the trailer brake in all situations.
When I was learning to drive I was a right ■■■■■■ with the clutch. Couldn’t get the hang of it. When someone explained how the clutch workes - it made sense and I understood what I was doing with that pedal. Isn’t that a similar thing? You need to understand how something works to understand why you need to use it etc
Is there a ‘sticky’ definitive guide to coupling and uncoupling on the forum? I have looked but not found it.
In answer to the origianl post - YES THIS IS HOW PEOPLE GET HURT.
shep532:
I always start the session by explaining how the brake systems work and generally this gets everyone’s attention as it is genuinely interesting. Once you understand how the brake systems work it becomes quite obvious why you must use the trailer brake in all situations.Is there a ‘sticky’ definitive guide to coupling and uncoupling on the forum? I have looked but not found it.
In answer to the origianl post - YES THIS IS HOW PEOPLE GET HURT.
Contained in the posts in this thread is a full description of how the brakes work and how to operate them.
Unfortunately, there is also a large amount of smoke and mirror stuff by people who know better or think that for some reason, someone who doesn’t know something that they do is at fault.
I suspect that even the most definitive guide would be ridiculed by someone who “knows better” because they have never done things properly and have got away with it so far.
There is a perfectly good guide to how to couple and uncouple a semi-trailer here
Unless the HSE don’t know what they are doing either. 
Regards,
Nick
Frankydobo:
Hells bells guys, its obvious listening to this some of you have no idea how the brake system on your vehicles work, which to be honest is frightening. In basic terms the foot pedal or Service brake sends air through the Yellow line to the trailer brakes during normal driving, I’m sure everyone understands that. The handbrake is not just a park brake but also a Secondary brake, pull it slowly on and air will again travel through the Yellow line to trailer brakes, in other words a second braking system which is hand operated incase of failure of the foot brake, it became law back in the Sixties that all vehicles had to have a secondary brake system.When units had the old ratchet mechanical handbrake or similar a separate hand operated air brake was fitted, usually around the left side of the steering wheel, this became known as the ‘Dead Man’ and a third Blue air line was needed to allow air from this to pass to the trailer brakes, the Three line system. When we changed back to the Two line system as used by the continent the secondary brake was incorporated into the hand brake lever. Once the lever is pulled over the notch the hand brake is applied to the unit, air does not continue to the trailer brakes so putting the handbrake on makes no difference to the Yellow line, hence the yellow line does not blow off like the Red when uncoupling the connection.
The Red line as rightly said continually feeds air to the trailer, it needs to do that to keep the brakes released during driving. When the Red line is disconnected you get a small blow off but the self sealing valves in the connection stop any more air escaping. The trailer brakes are held on with air pressure held in the trailer air tank and not spring brake (mechanical pressure) . If this air drains off (mostly overnight) the Spring brake section in the brake chambers overcomes air pressure that is left in the system and applys the brakes mechanically. Put your Red line back on and air pressure releases them again.
Obviously there are various valves in use to do these operations in the correct way and quickly but that is basically how the system works. Now hands up who didn’t know about the Secondary brake system, it could save your life if your foot valve failed so find out about it on your vehicle. Some vehicles may differ slightly in this system depending if Spring brakes are fitted to the front axle and not just the drive and trailer, manufacturers don’t all have the same way of braking on vehicles but they must all have a Secondary system. Hope this helped. Franky.
So if the footbrake on my car goes to the floor do I have to pull the little lever thingy up in the middle to stop or can I just hang my arm out the window and grab hold of a passing telegraph pole 
In the States what we as car drivers refer to as the handbrake or parking brake is called the emergency brake?
I have seen people pulling on that middle leaver to stop the vehicle whilst in motion and perhaps for American automatics then that is a good thing. However for UK vehicles I am not sure how well that would work.
Don’t do that with a Land Rover though. Not sure if they still do but the handbrake certainly used to grip on the drive shaft area rather than just the back wheels.
Also, by pulling up the handbrake on a Defender at motorway speeds will encourage the gearbox to leave its preferred place and abuse the driver such as crushing his legs… Thankfully didn’t happen to me but a friend in the military at the time, and he’s in a wheelchair now and the new squaddie that did it was dismissed…
Saratoga:
In the States what we as car drivers refer to as the handbrake or parking brake is called the emergency brake?I have seen people pulling on that middle leaver to stop the vehicle whilst in motion and perhaps for American automatics then that is a good thing. However for UK vehicles I am not sure how well that would work.
At speed it tends to lock the back wheels, which puts the car into an uncontrollable spin, which frequently ends in a fatal accident that might, or might not, involve innocent people coming the other way.
It’s popular thing for stupid, drunk wives to do while arguing with their similarly stupid, drunk, husbands. For example: mirror.co.uk/news/uk-news/wo … ter-157451
I had a friend who was witness to a similar thing happen in the car in front of him - fortunately it merely threw the car into the field by the road, without killing anyone.
So if the footbrake on my car goes to the floor do I have to pull the little lever thingy up in the middle to stop or can I just hang my arm out the window and grab hold of a passing telegraph pole
No not quite, the Secondary brake in a car is your wife/girlfriend in the passenger seat pushing her right foot into the floor, seems to work as I always stop at Red lights, junctions etc, don’t think I’ll try it without some help from the brake pedal on my side though just incase! 
newmercman:
Now to answer the question you should’ve asked as you seem so upset by my response. I am not having a go at anyone for not knowing how the systems work, what I do find riduculous is that people consider everything to be so dangerous. The post asked isn’t this how people get hurt? Well no it isn’t, you could park a million and one trailers with no parking brake applied and not one single person will get hurtAll this danger around every corner nonsense is just that, nonsense and if you don’t like my opinions then you have two options, one is the foe button, add my name to it and you’ll never see my posts again or two, [zb] off and grow a pair you purple headed custard spitter
^^This^^
100% spot on.