52 replies to this topic

[ckent323]

My Wife's angle gauge is more sensitive than mine.  She has gotten out on two occasions when we were traversing a steep slope.  On one of them I encountered several downed trees around a corner well beyond where I scouted and I had to back out across the slope (way too steep to turn around). She stood in the shade under a tree watching and shaking her head as I backed out  I told her I thought it was great and thrilling experience.  More head shaking.

[Wallowa]

Well I just learned a new word today - hooning

  Hooning.. Oz term for :  "anti-social behavior in a vehicle"....Hmmm, wonder if that included us in the 60's at drive-in movies?  

Edited by Wallowa, 12 January 2022 - 09:19 PM.

[ntsqd]

  Hooning.. Oz term for :  "anti-social behavior in a vehicle"....Hmmm, wonder if that included us in the 60's at drive-in movies?  

Wouldn't that have been more social than anti-social? Maybe I've been doing it wrong.

[Wallowa]

Wouldn't that have been more social than anti-social? Maybe I've been doing it wrong.

 

 

Not certain what activity you are referring to... ...but I was thinking of driving out with the speaker still in the window....

[ckent323]

Hooning is a term for doing burnouts, broadies, driving in a reckless manner.  I first heard the term several years ago here in the states from a friend who had been to Australia..

[ntsqd]

^^^ Practitioners of which are referred to as "hoonigans" from what I gather.

 

So is "hoon" pronounced "who*n"? or "ooh*n"?

 

Not certain what activity you are referring to... ...but I was thinking of driving out with the speaker still in the window....

Clearly I've been doing it wrong.

 

Back on track; If the height  and lateral location of the CG of the combined vehicle were carefully determined then one could fairly easily determine the static tipping angle. It would be the angle at which a line from the CG to the center of Earth would pass to the outside of the downhill tire's contact patch on the ground.

The dynamic tipping angle will be less than the static, but what it actually is will be entirely dependent on the vertical speed with which the downhill tire drops into the hole or the uphill tire hits the bump.

[Wallowa]

^^^ Practitioners of which are referred to as "hoonigans" from what I gather.

 

So is "hoon" pronounced "who*n"? or "ooh*n"?

 

Clearly I've been doing it wrong.

 

Back on track; If the height  and lateral location of the CG of the combined vehicle were carefully determined then one could fairly easily determine the static tipping angle. It would be the angle at which a line from the CG to the center of Earth would pass to the outside of the downhill tire's contact patch on the ground.

The dynamic tipping angle will be less than the static, but what it actually is will be entirely dependent on the vertical speed with which the downhill tire drops into the hole or the uphill tire hits the bump.

 

 

I have been reading with amusement...determination of most vehicle CGs is at best a WAG...let alone the measurements to that CG...factor in the variables of variations in speed over distance, responses of suspension to the changes in surface structure... and friction coef.... and constantly changing slope variances...well, a good masters thesis if not doctoral study..talking dynamic not static tipping point..

 

Good off road veterans can intuit most of this and stay upright...but like predicting avalanches it remains a crap shoot on some tracks...miss a cue or unseen event and over you go...

 

But hey, I could be wrong...

[ntsqd]

Determining CG location isn't terribly difficult, but you do need a scale with good resolution. Weigh F/R and L/R, determine track width and wheel base. Say the rear axle has 60% of the total weight on it. The CG's fore/aft location (X) is 60% of the wheel base. Say that the L/R is evenly split. Then you know that the CG is center on the chassis center-line (Y). Now you've got its X & Y coordinates, just need the Z (height).

 

Now for the hardest part. Weigh fore/aft again, but with the vehicle at the steepest angle F to R that can be managed and measured. Use a plumb-bob to measure the effective wheel base. Use Similar Triangles to find the CG's height.

[Wallowa]

Good article explaining the contribution of mass and gravity to the stability of a vehicle....not bedtime reading, but simplified.

 

http://thecartech.co..._of_Gravity.htm

 

Even after all this if a max lean angle can be calculated the driver must in real time be able to measure and react to that angle..

 

Hence, seat of the pants judgment gained through experience becomes the final determinant of your limit and  when/how to correct before that limit is reached...even the best off road racers roll vehicles...in practice not really a science but more of alchemy...

 

But these are just my opinions...

[ntsqd]

I was tired last night, I meant to include that once you have located the CG it will tell you a lot of things, but still won't tell you exactly how the vehicle will behave in a dynamic situation. As has been pointed out, there are too many other variables involved. Depending on the driver, knowing where the CG is may actually inhibit them from using the vehicle to its full safe potential. Maybe that is fine, and maybe that means that they won't get to see places that others will.

 

The SoP limit is the driver's limit to what they'll accept, can handle, or are willing to deal with, but it may or may not be anywhere close to what the vehicle is capable of. Some drivers always seem to get more out of their vehicle. It isn't that the vehicle is capable of more, it is that the particular driver's limits are more finely tuned to the vehicle. I saw this in person in the Dune Buggy Brigade (see avatar). All of the buggies were built fairly similarly, yet of the 9 of us one driver was always the first to get stuck, the first to break something, and the only one who has suffered a roll-over. He was not an overly macho or full of bravado type of personality.