4Runner failed me today

[Engineer]

You didn't outright say it, but you do understand that there is no drive line attached to the wheels and there for the treadmill almost becomes a moot point outside of rolling resistance of the tires, assuming they're able to holed themselves together and 2-3 times their Normal speed.

Like I said, just checking because I know you're smart

Were good, just trying to be a smart A$$

EDIT: no we are not good, in my effort to be a smart ass I did assume that the resistance would be significant (obviously knowing there is no drive line attached but not considering the wheels are "free")............tire comment still stands

 

[tigger]

Mechanically coupled tires can approach the net threshold of motion of all 4 tires. Uncoupled tires do not with current brake systems that balance hydraulic pressure and therefore stopping force, not rotational velocity.

The easy example is to take a single axle. (I'm not using units to make this very simple) Let's say for example that the right side has a static friction of 10 and kinetic of 2. The left has static of 5 and kinetic of 1. When you apply a force of 7 to each tire, the left will lose static friction and only provide 1 unit of braking force. The left will provide 7. If the differential is locked the left tire cannot exceed the threshold of motion due to the mechanical coupling with the right tire. It acts as a single system, not two independent systems. So the left will in fact provide 4.5 units of force while the remaining braking force transfers to the right through the axle shafts and the right will provide 9.5 units of stopping force, providing the full 14 units of braking force.

To recap - in open diff scenario you get 8 units of braking friction, in the mechanically coupled axle, you get 14. 14 units of brake force stops faster than 8. Ergo - mechanically coupled drive trains can in many cases stop faster on snow and ice.

On ice, why would the tires have different static friction and kinetic? I am talking about stopping on a sheet of ice where all tires are on it. Not in cases where 2 wheels are on ice and 2 wheels are off. If your tires are locked, I would think you are more likely to slide sideways.

 

[Jetboy]

Ice varies significantly, but generally kinetic friction is somewhere around 10% or less of static friction. On a perfectly uniform ice surface with perfect brakes, it would act similarly in both cases. On a road surface where conditions vary across the surface and along the surface it's unlikely to have similar conditions under each tire. Not unlike offroad where it's very unlikely to have uniform conditions for each tires. The same reason lockers work to go forward will also work to stop.

Another fun ice fact is that icy roads are the most slippery at or near 32*. Icy roads at 10* have as much as 3 times the coefficient of friction with rubber as they do near freezing. At -20*F icy roads actually offer quite good traction. That's one reason that snowy or icy roads in warm areas like California have so many crashes - it's not just the drivers who are not prepared. The roads are actually significantly more slippery than they are on winter day in the north.

Would an airplane take off faster or slower in 4lo with locking differentials on ice on a treadmill?

 

[Quentin]

Didn't they recently model the bumble bee and prove that it did work within modern physics boundaries?

 

[1engineer]

Didn't they recent model the bumble bee and prove that it did work within modern physics boundaries?

Yes, yes they did. There are certain laws you can't break, no matter how hard you try.

 

[blues]

Didn't they recent model the bumble bee and prove that it did work within modern physics boundaries?

I didn't offer it for the "proof" so much as for the fact that the entertaining argument we were treated to put me in mind of it. :nod:

 

[Quentin]

I didn't offer it for the "proof" so much as for the fact that the entertaining argument we were treated to put me in mind of it. :nod:

My response wasn't meant to be inflammatory or contradictory. I just thought I'd read somewhere that it had been modeled.

 

[blues]

My response wasn't meant to be inflammatory or contradictory. I just thought I'd read somewhere that it had been modeled.

:tea: No offense taken...and I'm sure glad that those engineers out there get it right most of the time. Years ago I used to fly on Blackhawks chasing doper aircraft between South FL and Bahamas and I would marvel at the things that the (mostly) former Marine pilots would wring out of those aircraft. (Things which such aircraft with "too many moving parts" were never fully intended to do. olice

 

[77Bronc]

He did say some settings. Put that sucker in 1 on CRAWL mode and you're doing a whopping wind in the face 1 kilometer per hour. Even in position 5 in CRAWL you're only going 3mph.

3W, yes you are correct, I mis read, there are modes where you, yourself can crawl faster than the 4Runner.

What area of LA do you call rural?

77

 

[Raven]

Lol I found that out by reading the manual while taking a shit.

........... and they say that men can't multitask!

 

[Blitzkrieg]

There was this time, back in High School, when I was at band camp....

 

[3wbdriver]

What area of LA do you call rural?

77

Vernon Parish, west of Alexandria. Less than 55,000 people in the entire parish. The largest town (Leesville) numbers less than 10,000 souls. And I live 7 miles out of town. But I do have neighbors on all 4 sides of me and we can converse if we yell loud enough..... :madgrin:

 

[Jhalko]

Vernon Parish, west of Alexandria. Less than 55,000 people in the entire parish. The largest town (Leesville) numbers less than 10,000 souls. And I live 7 miles out of town. But I do have neighbors on all 4 sides of me and we can converse if we yell loud enough..... :madgrin:

Sounds peaceful, I can practically reach out and touch my neighbors houses here...

This thread is pure entertainment... Thanks OP.

 

[77Bronc]

Vernon Parish, west of Alexandria. Less than 55,000 people in the entire parish. The largest town (Leesville) numbers less than 10,000 souls. And I live 7 miles out of town. But I do have neighbors on all 4 sides of me and we can converse if we yell loud enough..... :madgrin:

Been there...my moms from Avoylles Parish, Simmesport. I am in St Tammany Parish

And yes this thread has been fun...

77

 

[jfjehle]

Rural is right, I was station at Fort Polk for some time, right next to Leesville.