Today I unhooked from a trailer in the usual manner. Detached the pigtail and the glad hands*, lowered the landing gear, started to pull out--and heard the pigtail pop loose. I stopped barely in time to keep from ruining the air lines--or worse.
What saved me?
Two things. First, I always pull out s-l-o-w-l-y. And I usually bear left, so I can see the trailer fittings as soon as possible. Paranoia is sometimes a useful thing to cultivate.
Second, I still had the flashers going from when I was checking the trailer lights. When I noticed the trailer lights flashing even though I wasn't hooked to it anymore, a little warning bell went off softly. When the pigtail popped loose I was ready to hit the brakes quick.
How did I get into this mess in the first place?
Well, I unhooked the lines. Then I went back and hooked them up again. Apparently part of me forgot that I was dropping the trailer instead of picking it up. Just did the next thing without thinking about it.
Because I was thinking about something else. Distraction: it's not just for cell phones anymore.
In this case, I was thinking about the relative impact of sociological, political, psychological, and theological factors in the founding of the Roman Catholic Church. Don't ask. I don't know where that came from either. I'm not even Catholic.
I suspect centerfolds are a more common problem in the industry, anyway...
-----
*I occurs to me I may never have used those terms before. Oh, boy. Well, here goes.
A tractor-trailer is way too heavy to stop easily with the hydraulic brakes cars use. Instead, they use compressed air--at something like 100-150 psi. The truck includes an air compressor and big tanks to store the stuff, and a set of hoses to carry air to the tanks on the trailer.
The connectors that join those air lines to the ones on the trailer work under some peculiar requirements. They have to be strong enough and airtight enough to handle 150+ psi of air pressure. And they have to do it in all kinds of conditions--which include a lot of shaking, yanking, and general abuse. But they can't be TOO strong, or they might end up damaging the truck or the trailer in some odd situation (like I describe above) where the air lines stretch a bit more than they should.
In addition, the connectors have to be easy and quick to connect and disconnect. You might have to do it several times in a day, and if you have to have a wrench and plenty of free time--well, let's just say productivity goes down, and finding a way to cheat might be tempting. And cheating on a safety issue is a Bad Thing.
What the engineers came up with was a widget that uses two rubber washers, squeezed together, to form an airtight seal. The washers are squeezed together by metal housings and sheetmetal flanges that sort of act like cams. You put the "washers" together, then twist the fitting. The flanges engage matching fittings on the other connector and the whole thing is wedged into a tight connection--that will nevertheless pop loose if the stress on the fitting gets too high.
Most of the time. It only messes up the truck or the trailer about one time in ten, maybe. Better than nothing, I guess.
Thing is, the "washers" aren't "on the end" of the hoses--they're at right angles, on those fittings. That's what makes them easy(er) to pull apart if something screws up. When you put them together right, it kind of looks like a pair of robots shaking hands. Thus the nickname "glad hands."
Picture below...
That big thing in the middle is the connector for the power cable--the one that lets the truck power the trailer's electrical system. The cable-and-connector assembly is called a "pigtail." I THINK that's because they were using coiled wire for that job long before they could do it for air lines. And for a cable that big it used big coils--curly like a pig's tail.
There. Done.
1 comment:
You are not forgotten this day, even if it feels like it sometimes.
Merry Christmas - we'll be praying for you.
Post a Comment