Home Forums Hunting & Shooting Hunter's Campfire When the SHTF - Runaway Semi Down Main Street

Lotta misunderstandings here.

Properly adjusted brakes are a huge deal, but modern trucks can certainly lose
brakes even if they started out adjusted properly. Losing brakes is an affect of getting hot, not too much slack. Unevenly adjusted brakes can accelerate problems due to individual brakes heating faster, then failing. Leaving more burden to the remaining brakes.


Shutting a diesel off does nothing.
The hold back effect of a gas engine is pumping loss.
It's the effort of drawing vacuum, caused by closed throttle plates.
Diesels don't have throttle plates. The throttle directly controls fuel, not air movement.



The brake lever by the steering wheel (looks a bit like an automatic gear selector)
does not "lock everything up". It's simply a hand brake that controls the trailer brakes
only. On straight trucks it controls the drives and any lift axles.
It uses the same air as the foot pedal, in the same way. Except it only actuates the trailer brakes.
Mostly, it's used to lock the trailer axles to slide tandems or 5th wheels.

A lot of company spec trucks don't have them. Guys use them instead of the service brakes. Over taxing the trailer brakes and ruining them.(using them for anything other than sliding stuff is controversial)





As to the brakes locking due to low air?
Pulling the yellow button?

Both are the same thing, one automatic, one driver activated.
Usually, if they automatically deploy, the button pop's out. Sometimes, there is a small psi range where the brakes apply but the button doesn't pop.

That braking system is simple spring powered.
Pushing the yellow button supplies air to an actuator that compresses the springs and
releases the brakes. If the button is pulled or air pressure lost, the actuator disengages and strong springs apply the same brakes normally used.
But not with anything like the power of the air system. A heavy truck rolling at some speed, downhill, is very likely to NOT be stopped by the spring brakes.


Jake brakes can and do fail, not often.
Transmissions can jump out of gear. On old mechanical engines, that usually shut the engine off. Losing the air compressor and power steering. There is no way to get back in gear until the engine is running. If the truck accelerates to a speed higher than
It's governed at, it's impossible to get a gear even if the engine starts.


There are numerous possibilities here, the service glad hand popping off is certainly a possibility.


One thing I will bet the farm on.
It's not one issue.
Accidents are almost never a single failure.

Usually in something like this you will find,
Speed
Brake Maintenance
Brake adjustment
Other mechanical failure
Air loss (maybe tied to other causes, especially maintenence)
Over loaded
To name a few.


By the time DOT is done, they will have a list.



If he was overloaded, the quarry may well be involved.
The one I hauled out of refused to let us leave heavy. Following a wrongful death lawsuit that they were involved in. Selling an extra ton of stone cost them dearly.

Yeah, he could - then he would have been without both brakes AND power steering.