An Unexpected Slide

Unexpected events are what separate the men from the boys. This isn’t based on a real event, it IS the real thing. So I’ll tell a little tale:

I was in Lexington, Ne waiting for my trailer at IBP. It was an ugly week, bunch of loads going places I wasn’t. So Kirby, my dispatcher, offered me a long delivery Amarillo that loaded that day. I jumped on it thinking I’d run through Elk City, Ok, where I’d spend some time with a friend and my brother. Wasn’t real thrilled about time off away from home, but it was by far the best option.

So I’m watching the weather as I cool my heels knowing that IBP just might screw this up. (deadline ship was 2 days away!) There’s a winter storm bearing down on Kansas, freezing rain that night with a day of blizzard conditions following that. I was rather used up, and saw them grab my trailer about 18:00, so I sacked out.

Sometime shortly after midnight, I get the CB call that I’m ready to go. Needless to say, I got my rear in gear and was southbound within the half hour. And shortly after finding Kansas, I found the ice. It was pasable, but slow. I found Oklahoma, and wet roads, around daybreak, and very soon the freezing rain had become a light drizzle. So far, so good.

Now it’s an hour and half later, and I’m making tracks, cruise set about 68, there having been no signs of ice on the grass and trees for over an hour.

(yeah, yeah. I’m being long winded cause I’m bored, so just keep reading! )

Now somewhere south of Woodward there’s a set of 45 degree S-curves that are nicely banked and large radius, so there’s no need to slow down. (been through em on a bike at more than the ton.) I roll through the right and I’ve just stabilized the left when:

“BUTT TO BRAIN! BUTT TO BRAIN! WHAT THE *#$& !”

Now if you’ve been at this a while, you know what I’m talking about. The seat of my pants had just informed me of a unexpected and undesirable yaw event. (the rotation axis of my rig had just shifted well forward)

A quick glance left showed no sign of the trailer. Expected, but unpleasant nonetheless. A right glance showed, yes, you guessed it, trailer. LOTS of trailer. And now for our quiz.

One of these is the right choice, the others will have various unpleasant outcomes. So, do you:

A) lightly apply the brake pedal to slow the truck.

B) use the Johnny bar (trailer brakes) to pull the trailer back in line.

C) disengage cruise to allow truck to slow down

D) disengage cruise, maintain neutral throttle (an in-gear coast)

E) accelerate to pull the trailer back in line.

Hhmmmmmmm…………..

‘A’ and ‘B’ would have similar outcomes. Your trailer tires are already sliding, teetering on the edge of adhesion. Any brake application will almost surely lock them up, reducing their friction (a rolling tire has more traction than a sliding tire, even if it’s rolling with a high slip angle.) and, combined with the slowing tractor, send the trailer swinging to the right. Well, swinging until it ends up in the ditch or smacks your cab in a slow jackknife, anyway. 

‘C’ is an iffy choice. As the tractor slows, it’s pushing back against the kingpin. Which would be fine if your trailer was inline. But it’s not, and as you push back, the momentum of the trailer pushes the back-end of the truck forward at the same time it’s also yawing it to the side. Not a good idea! You might get lucky and have enough traction at the tractor to keep it from snapping into a jackknife. But you might not! Do you feel lucky?

‘E’. Well, you know how when you come up on a wreck and the truck and trailer are on their right side, across the road, with the top of the rig facing his former direction of travel. And you wonder, “how’d he do that?” This is how you do that! Nuff said?

Which leaves us with ‘D’. The idea being to minimize the traction you’re requesting from your tires. Some people prefer the ‘push the clutch in and coast’ method, which is basically equivalent to this. Just be careful reengaging that you match RPM or else you might cause another skid, with the tractor this time. I’ve always had a good feel with the throttle and prefer that way. There’s still no guarantee that you won’t further lose control with this technique, but it gives you the best chance of a safe recovery.

And that’s what I did, I kept just enough throttle to keep just the slightest forward pull on the kingpin. Some speed bled off, the trailer slowly came back in line, and away I went! By the way, that is the most stable dynamic state you can have a truck in. It’s how you should always cross an iced-over bridge, the truck may be slowing, but it’s still pulling on the kingpin, which is always more stable than the trailer pushing on the truck.

What was the root cause of the slide? We’ll never know. I was over an hour south of the freezing precip, with no indications of any freezing for over an hour. It’s possible that was a cold spot the night before, or it could have been something spilled on the road; but it really doesn’t matter. The point is you have to be prepared for the unexpected, and just deal with it. The why is just something to occupy your mind later.

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