How to determine safe limits for sidehill driving?

[Korben]

IDK if this is common knowledge with you guys and that's why it hasn't come up but just in case. There is a largely mathematical way to find the COG that doesn't involve making the rig stand on end. It involves scales, and leaning the vehicle over with a ramp or jack. Basically you're measuring the change in weight on the scales with the angle change in the rig. Here's a link that has the math and a calculator to do it for you. http://www.longacreracing.com/technical-articles.aspx?item=42586

 

[PIC4GOD]

IDK if this is common knowledge with you guys and that's why it hasn't come up but just in case. There is a largely mathematical way to find the COG that doesn't involve making the rig stand on end. It involves scales, and leaning the vehicle over with a ramp or jack. Basically you're measuring the change in weight on the scales with the angle change in the rig. Here's a link that has the math and a calculator to do it for you. http://www.longacreracing.com/technical-articles.aspx?item=42586

I guess you haven't been following this thread. Your measurements are for static situations only. Tell me how you can apply your formula to the friction of a sideslope while off road along with unknown off camber variations of the terrain. Off road is the farthest situation ftom the lab you can get and requires knowledge of the vehicle and seat of the pants driving.

 

[Korben]

I guess you haven't been following this thread. Your measurements are for static situations only. Tell me how you can apply your formula to the friction of a sideslope while off road along with unknown off camber variations of the terrain. Off road is the farthest situation ftom the lab you can get and requires knowledge of the vehicle and seat of the pants driving.

Well gee I'm so sorry I tried to add a little helpful information.
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I guess you can't read, did I say anything about finding a save angle, no I didn't. I said find the COG. Yes I can read, you "experts" keep referring to the COG like you magically know where it is.

 

[PIC4GOD]

Well gee I'm so sorry I tried to add a little helpful information.
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I guess you can't read, did I say anything about finding a save angle, no I didn't. I said find the COG. Yes I can read, you "experts" keep referring to the COG like you magically know where it is.

Your formula was provided earlier on the thread. I'm not trying to be mean or give you a hard time. Just asking that you read the entire thread before providing input.

 

[Korben]

Your formula was provided earlier on the thread. I'm not trying to be mean or give you a hard time. Just asking that you read the entire thread before providing input.

Where?

OK next time I'll PM you to get permission before I post anything.

 

[PIC4GOD]

BTW, in case anyone didn't know, to correlate the rollover threshold of lateral g-force to angle of tilt, simply take the arcTan aka inverse tan of the angle of tilt.

Example, a sedan that can (theoretically) corner 1.5g before rolling, would have a side slope threshold of: tan^-1(1.5) = 56.3 degrees

A semi tanker than flips at 0.4g have a slope limit of: tan^-1(0.4) = 21.8 degrees

Likewise, if you know a car's COG and track width, you can approximate the theoretical limits by arctan(track width/2/COG). My Vette has a COG of 18" and rear track of 62.5", so:

tan^-1(62.5/2/18) = 60.0 deg or 1.73g

Again, all in theory, assuming infinite friction and flat surface. In reality, aerodynamic downforce and track bank angle can drastically increase that number to over 2.5g.

You misunderstood me.

I didn't say all vehicles are capable of hitting 1.0g performance wise, not even close (I'm a Z06 owner btw, and know what 1g+ feels like).

What I'm saying is, for most STOCK vehicles, including light trucks, IF they can hit 1g (imaginary skidpad with warm slick tires), they can do so without toppling over. LIFTED vehicles can rarely achieve this.

This is just another way of saying they can reach a static 45 degree slope without flipping. Since Tan(45) = 1.0

In other words, traveling a 45 degree side slope and performing a sustained 1.0g turn exerts the same force vector at a vehicle's COG. If this force vector, extended from the COG, does not extend to the outside of the car's track width, the vehicle does not roll.

Where?

OK next time I'll PM you to get permission before I post anything.

Come on man, permission, really. I'm not going to reply to you anymore since you can't respond in an adult way.

 

[Korben]

Also while I'm at it if this is OK with PIC4GOD to post...
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Nowhere in here in this mess of arguing about speed, angle vs. Gs, and COG did I see the single most important piece of advice on side hill driving. ALWAYS be prepared to turn downhill. The split second you feel it going over you turn that wheel as fast as you can in the downhill direction and give it some throttle. This can pull you right out of a rollover and potentially save your life, arm, etc. It doesn't matter if your going to go into a tree, into a gully, whatever, going straight into whatever is downhill from you is safer then rolling over into it.

 

[Korben]

Come on man, permission, really. I'm not going to reply to you anymore since you can't respond in an adult way.

NOT the same thing, it's clear you just don't understand. But I'll give you a hint, notice RoyJ says "if you know a car's COG"
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I'm not trying to be mean or give you a hard time. Just asking that you understand what's being said before providing input.
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I'm not going to reply to you anymore since you can't understand what's going on anyway.

 

[PIC4GOD]

Nowhere in here in this mess of arguing about speed, angle vs. Gs, and COG did I see the single most important piece of advice on side hill driving. ALWAYS be prepared to turn downhill. The split second you feel it going over you turn that wheel as fast as you can in the downhill direction and give it some throttle. This can pull you right out of a rollover and potentially save your life, arm, etc. It doesn't matter if your going to go into a tree, into a gully, whatever, going straight into whatever is downhill from you is safer then rolling over into it.

Now that is a piece of useful information. Thank you Korben!

 

[Sabre]

I thank all who contribute; please, no squabbling. The dynamic nature of the sidehill situation is clear, emphasized nicely by a bunch of you. The COG formula may be less useful in real-world terms, but it would be useful to do this with the truck packed in different configurations, giving a better idea about what all that stuff on the roof is really doing.

 

[pugslyyy]

Probably my least favorite thing. When my butt puckers its too steep. I also have on other method for determining when its too much. When the dog wants out

This. Experience has taught me that the vehicle can take far more than my butt can.

 

[Freebird]

"My daddy can beat your daddy..."
"NO, MY daddy can beat YOUR daddy..."
Ad nausium.

 

[jeep-N-montero]

Without reading the entire thread I will say this, every vehicle has a different height, weight, length, and width that results in a different COG unless you are discussing two vehicles identical in every aspect. So for the most part it is useless for the owner of one vehicle to say a certain slope is safe/unsafe for someone who has a completely different vehicle and/or different level of experience. I have found that most rigs are more capable than the person behind the wheel is willing to find out, not always a bad thing though. For example, there are spots in Moab that I have experience with and can drive through without a spotter, while the guy behind me might be ready to crap himself because it's his first time even though the vehicle itself can handle it.

 

[Stumpalump]

The trick is to go slow enough that you do not bounce. If you do bounce or start to go over then turn down hill. Your natural reaction is to turn up so practice turning down every chance you get.

 

[JackW]

When your six passengers unexpectedly bail out of an 88" open Land Rover on a side hill you're approaching the tip over point - especially when you are counting on the 4 of them on the uphill side to provide a comfortable amount of ballast....

Damn cowards....