Near jacknife in rain

This boils down to one important thing. Regardless of if it is rain, slush or snow. That tire MUST stay in contact with the road. This is why those thread depths are so important. Once that tire loses contact with the pavement the vehicle might as well be on ice. The last 20 or so years my father was alive he would not buy a set of tires even at steep discounts until he inspected the thread patterns. Moving that water away is critical to avoiding a hydroplane.

 

I stopped right there in your speech.

Parallel to the road really only applies while braking or accelerating in a straight line.
How about the force applied in a more perpendicular direction?
As in, turning?
A straight line event does not cause a jackknife. There has to be something getting out of line.

"Centrifugal force in a curve" is another one, which is not really a force. It is the result of inertia.
Centripetal is the force exerted by the tires to keep the vehicle attached to the road while turning.

As it was explained to me about 50 years ago by my (very cute) physics teacher in high school...
If you take a ball that is attached to a string and rotate it, there are two things happening, and the terms are often confused.
Centrifugal and Centripetal motion. Both are often described as a force.
Only one is a force.

It is the same motion with a planet orbiting a star.
Centrifugal motion is the tenancy for an object to remain at the same speed and direction, unless an outside force restricts it. The law of Inertia.
Centripetal force is the energy that holds that object in place.

In the case of a planet orbiting a star, the Centrifugal motion makes it fly outwards while the Centripetal force (gravity) holds it in place. So it goes round and round the more massive object.
In the case of the ball and string, it is the string that is constraining the outward motion.

In the case of a truck and a curve, and tires being the only traction (centripetal) force...

 

And I have not yet met a truck tire that I trust in snow or ice.
The tread is lame and the compound to hard. It slides all over the place.

 

To much speed and to little following distance .
End of story .

 

3 things were none starters for me. Thick heavy fog, Whiteout conditions and ICE. I had no basic issue with driving on snow as long as the DOT were keeping the roads clear. If this become a problem I started looking for a place to stop. There is no load I don't care how important it is that is worth my life. I know most people that think about whiteouts thinks about I 80 and I 90 in the winter. I have seen Whiteouts in Colorado and Kansas. I remember one so bad in Goodland Kansas I got lost walking in the snow trying to find my way to eat. No way was I going to drive in that crap. Jeez that was a long time ago. I was taking a repo back to Denver. Fog is one that can confuse people. Some drivers are not scared to go drive in it. I was caught in some of the southbound backup in THIS pileup. You guessed it, FOG. After that day I made the decision if i did not have good visibility and the (temp dew point spreads) was predicting fog I stayed in. As A pilot I knew how to use the 800 number for weather briefs and got those dew point temps.

 

I almost jackknife last year in the rain...speed and slick tires!!!!

 

Well, you do what you can in the time you have left. If need be that red light does not matter. If it meant a ticket? Ha I'll be happy to pay it it wont be the first time. The trouble is opposing traffic.

When I have problems with the semi, I think of it as juggling balls in the air, all of them need solving. There is always one more ball that wants in and ruin the whole count of solving problems.

 

I was using imprecise terms, yes, because most people do not know enough about physics for me to keep their interest long while using correct terms. I believe the ideas were accurate, and the terms used are layman's terms.

First, I did say, and mean parallel to the road, not to the direction of motion. Parallel motion along the two-dimensional road surface can be forward, back, right, or left.

Second, even when driving in a nearly-straight line, Losing traction while going straight can cause a jackknife if you then lose traction on several other tires. You have a better chance of recovery if you aren't turning, but if you hit a stretch of road where half the roadway is black ice, you can drift into a jackknife. Even if the truck is moving perfectly straight, losing traction on one or more tires can generate forces perpendicular to the direction of travel. Add hills, crowned roads, or wind and it gets more complex.

You are correct that centipedal force is the accurate term. Most people have no idea what centripedal force is. Almost everyone calls it centrifugal force, so I did too.

I think that if you look at what I describe, and think as a layman, it makes sense. I do apologize to the physics-educated out there for incorrect usage of the term centrifugal force.

 

Don't make these forces harder to understand then they have to be. Same with positive G force and negative G force. If you have a heavy object on a string and spinning it centrifugal force is what is acting to keep said object spinning. Centripetal force is what is holding it. Way way to nerdy for these forums.

 

I remember the only thing that straightened me out was to let off the throttle and put it in neutral.Straightened me right out and I tried everything Lol!!!