Trailer disconnect switch.

You will want to ensure at whatever cost that landing gear is down and functional. So that if the 5th wheel did let go or fail, the trailer wont fall 4 feet. THUMP...

My milk tanker has no spring brakes. Too old to have any at all. No landing gear either. If you looked closely at the picture I uploaded quite some time ago you will see nothing back there.

One time the 5th wheel got loose while it was empty. And due to the small slope in the field it started to back away from the tractor ready to fall into the ground. With glass (Melted formed Silica) lined tanks you do not want that.

So I started chasing the trailer. I managed to rehook it.

Peals of laughter from the office permanently branded me as a non professional that day. It was one of those turnings where I started looking for other employment. There is nothing to be gained to continue to work there when your credibility has been destroyed.

I know farm work is difficult and humor less but when a little slapstick gets into my life and botches the situation badly, I do not require a audience...

Get a small bungee for your trolley, tie it down next time you go hooking or unhooking etc.

 

Don’t get any fifth wheel grease on your airlines, pants and your hands .

And to satisfy my curiosity, the next time you hook up to a trailer that has no air in the tanks try using that switch to see if you can move it immediately rather than wait for the tanks to fill

 

Even when you are disconnecting an old trailer with no spring brakes, the brakes lock upwhen you dump the emergency line and it will hold the trailer there, just like spring brakes, the air will eventually bleed off and release the brakes. You will need to hook up and charge them before you hook back up to it.
I highly doubt that any modern truck has a valve specifically designed to use for pre 79 trailers.

Log trailers and pipe dollys do not have spring brakes, but has a valve to push to release the brakes after you unhook, it makes it much easier to load back up on the truck if the tires will roll.

Funny story about an old trailer without spring brakes.
It used to be common to haul dozers on short flatbeds. We would remove the landing gear and drop the nose of the trailer to the ground. You then ran the dozer all the way to the back, to raise the front of the trailer back to fifth wheel height, set the brakes on the dozer and get the truck under it, then position the dozer to where it needed to be. Once you had done this enough times, you knew exactly how much track to hang over the back of the trailer to get the exact height, so you didn't have to keep climbing back and forth.
One time my cousin had unloaded the dozer on a pretty good hill, the brakes held properly on the trailer while he unloaded, but after a couple of days working the dozer, they had bled off. When he loaded it and raised the front of the trailer off the ground, he got a high speed dozer ride down the hill. lol

 

Why I posted that link about spring brake priority. I bet that’s what it’s actually for but it should still work for the old trailers even if it wasn’t intended

 

It may, I would have to go back in time and look at how the old systems works, just shooting air through the emergency line only holds the brakes until it gets enough pressure to release. I know on my log trailer it will hold them for a few seconds when I charge them, if I want the trailer to stay put I charge them and have to pull the trailer brake down, by the time the emergency line gets enough air to release them, the service line will hold. I don't think it would be a good idea to depend on that valve to hold it until you hooked up.

 

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