Slick roads 101

Just curious if anyone has gone through skid pad training?

 

Yeah..its called hwy 80 in Nebraska in the winter time..last time I went through there in the winter..they don't use sand..and when the calcium chloride freezes at 10 degrees.it gets slicker than synthetic grease.

 

I've been through there too but I'm talking about actual skid pad training where you try to control the truck without rolling it.

 

Never done actual skid pad, but I've played (and learned) a lot in slick, open parking lots. You can do completely controllable bootleg turns in a tractor-trailer combo. And that tandem sliding sideways throws a huge amount of snow!

 

My following comment pertains ONLY to the physics/forces of your trailer/load on the tractor itself. This applies to EVERY jack-knife situation.

Yep Hammer166, I guess, to most, I'm kinda weird in that respect. Since I began driving I never think of it as "the trailer pushing the truck" which to me is a "blob/mass" too general of a viewpoint of the forces on the tractor. Even tho I'm pulling a trailer, I picture my truck as a bobtail with a 1 foot "stub" of a kingpin shaft locked into the fifth wheel jaws, and sticking upward. This allows me to "picture" the controllable or uncontrollable forces that my load (loaded trailer) exerts on my tractor.

Jack-knife 101
To explain further, when you're in any curve or turn, (and this applies especially to the initial millisecond of ALL jack-knife situations), your tractor and trailer are not perfectly straight. The angle between your tractor and trailer might be less than 1°,, or it may be 12° of angle, depending on the curve.

For the purposes of understanding control of the truck, now picture a giant hand pushing on that kingpin "stub" exerting say,, 75,000 lbs force somewhat sideways (say 5° or 10° angle) to the tractor, with the force focused (again, somewhat sideways) over the rear axles. It will try to push the rear axles of the tractor sideways, while your steer tires remain in place, thus the tractor will be pushed to an uncontrollable/undesired angle on the road.

This is also the exact same "physics" used by cops when doing a "PIT" maneuver to send a suspect's vehicle out of control.

I know what many drivers are thinking... You can't have 75,000 lbs force, because my empty trailer plus load weight is only 60,000 lbs, maximum.
What they overlook is INERTIA, which can greatly add to the forces, hence the 75,000 figure. In some situ's it could even be more.

 

In every single car/truck I've ever driven my parents trained me on skids. We use to have a friend (retired detective that taught Emergency Vehicle Driving) that had a huge area that we could dowce with water for training on.

It's SO MUCH FUN and good practice.

 

Most excellent advise and discussion.

Regarding jakes, I don't like to have them on unless I'm on a downgrade. I try to engage them in Low setting with rpm's at about 1100-1200. This might require applying brakes before engaging the jake to the desired speed before turning on the jake. The reason I want low setting at a relatively low rpm is the jake will come in at the lowest power. After engaging I let the rpm's rise and will switch to Medium or even High as necessary. If that particular gear won't hold in Medium without extensive snub braking, then I'll apply brakes to take a lower gear.

If I start to feel the jakes cause a slide (remember, with jakes only your drive axles are braking, which can cause the trailer to push on you) then I immediately turn off the jakes and will coast down the hill to correct the slide and start again by applying light, steady brake pressure to bring the speed down and start by applying jakes again in low setting at a speed where the rpm's will be at about 1200.

Another thought about making decisions whether to park it or keep going, if you REALLY want to park it then stop at a truck stop, go inside, and ask how the conditions are headed west or wherever you intend to go. Invariably you will get truckers chiming in how BAD it is, so bad you'll want to park your rig and assume a fetal position. Rarely does that information translate into reality, the folks already parked at the truck stop don't have first hand knowledge of the conditions and they are all trying to reinforce the correctness of their decision not to run.

 

It's not so much a sideways force, at least in the initial stages, as the trailer is pushing forward, the problem is if that push is offset from the center of gravity, i.e. the truck isn't exactly lined up with the trailer. You can go be bored with a more detailed description here: http://www.thetruckersreport.com/tr...g-dynamics-101-a-post3072202.html#post3072202

 

I'm from northern MN and have been driving on snow and ice my whole life. This is the first winter in a truck. I'm glad someone posted " you have to feel the truck". It's like a sixth sense. I've been in situations where I feel I need more rpms and when to let up on the accelerator. It's like you are one with the truck.

Like other people have stated there are many shades of ice and your truck will react differently to each one. Temp is a major factor and what dot is putting on the surface.

I hope this makes sense as I've been up too long today. Time to hit the bunk

slow and easy wins the race