Clever person needed

[rodp]

Probably need a theoretical physicist for this one.
Been mulling this question over for months now, and still come up with the same answer.

On an Argo you shouldn't hold a steering brake on to make a sweeping turn, but rather go round a curve in a series of "jerks", IE, brake on, brake off, brake on , etc, etc.
What I fail to understand is the physics of this, as in. Given a known curve, at a known speed and a known weight it takes the same amount of energy to steer round it no matter if you "curve" round it or go in a series of "jerks". The energy absorbed by the inside brakes is converted to heat, and this is a given amount relative to speed and radius.
Therefore, if you go round in a series of jerks the amount of heat generated by bringing one side to a frequent halt should equal the amount generated by feathering the brakes .

So gents, any thoughts on this, has anyone actually tested this with a thermometer?

Feel free to blow my theories out of the water, always more than willing to listen to someone better educated (it's how you learn)

[Old Tucker]

You may be right as the same amount of heat is generated to make the same turn. But the Big difference is in short jerks you bring the rotor to a stop. in doing so no heat is generated as the rotor is stopped as you are turning. What heat is generated is for a shorter period of time.
That what I think so. Let me know if I am wrong. I am willing to learn something new today.

[shot410ga]

If one had high end brakes as in Abrams Tank that would be true.

[rodp]

You may be right as the same amount of heat is generated to make the same turn. But the Big difference is in short jerks you bring the rotor to a stop. in doing so no heat is generated as the rotor is stopped as you are turning. What heat is generated is for a shorter period of time.
That what I think so. Let me know if I am wrong. I am willing to learn something new today.

That did cross my mind but theoretically it takes a given amount of energy to turn an Argo around a given radius, whether that be a little amount for a long time, as in feathering the brakes, or a greater amount for a shorter time as in a series of jerks. Either way that given amount of energy will generate a given amount of heat.

[rodp]

If one had high end brakes as in Abrams Tank that would be true.

I'm thinking my Land Rover Discovery may struggle to tow one of those to events.

[frenchconxion]

Rod, you need to put a toyota engine in it then! :-)

[Old Tucker]

Over all the heat generated may be the same but the time the rotor is exposed to the heat is far less. the rotor has less time to absorb the heat, as to a long braking period. Its like putting your hand on to a hot object, If you hold your hand on it you will get burnt. But if you just touch it quickly your skin does not get a chance to absorb the heat even though the object is the same temp.
Now where does that extra heat go? I think some hot headed politicians find it and use it to make some of their stupid laws.
No really, the heat is only on the surface of the rotor and pad and then is dispersed into the air more quickly.
Yes the newer trans. generate less heat in the brakes because they divert that energy ( torque )to the other side drive wheels.

[JohnF]

... Given a known curve, at a known speed and a known weight it takes the same amount of energy to steer round it no matter if you "curve" round it or go in a series of "jerks". ...

This is not true.

[Rock Doctor]

I "feather" my brakes around corners all the time, works fine. Much less "Shock" loading on the drivetrain, and makes for a more comfortable ride. Of course there are times when i want to make hard corners, but in that case, I just apply brakes firmly, but not Jerking, to stop the tires on the inside of the turn.
Trans Gearing and Clutch Setup plays a big roll in being able to do this though.

RD

[Old Tucker]

I "feather" my brakes around corners all the time, works fine. Much less "Shock" loading on the drivetrain, and makes for a more comfortable ride. Of course there are times when i want to make hard corners, but in that case, I just apply brakes firmly, but not Jerking, to stop the tires on the inside of the turn.
Trans Gearing and Clutch Setup plays a big roll in being able to do this though.

RD

Thats the way I drive to And Ive not had a problem. Its a lot smother and easer on all parts involved including your own body parts

[rodp]

This is not true.

Can you explain why not please, in simple terms. Surely if you want to deviate from a straight line it's going to take a given amount of force regardless of whether you feather or jerk ?

[rodp]

I "feather" my brakes around corners all the time, works fine. Much less "Shock" loading on the drivetrain, and makes for a more comfortable ride. Of course there are times when i want to make hard corners, but in that case, I just apply brakes firmly, but not Jerking, to stop the tires on the inside of the turn.
Trans Gearing and Clutch Setup plays a big roll in being able to do this though.


RD

And me, I just didn't want to be the first to own up to it If they overheat you need a bigger blower

[JohnF]

Surely if you want to deviate from a straight line it's going to take a given amount of force regardless of whether you feather or jerk ?

"Given amount of force" isn't a very exact statement (and I really don't know what to say to it). My argument is that it isn't the "same amount of force" or better "same amount of energy consumed" (or power).

Can you explain why not please, in simple terms.

Sure, it is because the force required to overcome the dynamic coefficient of friction is less than the force required to overcome the static coefficient of friction. Think of it like this, in the feathered turn you have to apply enough force to hold your tires in a curve (because they will try very hard to stay static to the surface) whereas the jerky turn applies enough force to break-out of the static coefficient and make the tires dynamic to the surface consuming less net energy to change the direction of the vehicle. Sure, the feathered turn skids too, but at some limit of twist.

Hmm, I don't know if that made sense.

Feathered turn - more twist less skid; jerky turn - more skid less twist. ???

[rodp]

"Given amount of force" isn't a very exact statement (and I really don't know what to say to it). My argument is that it isn't the "same amount of force" or better "same amount of energy consumed" (or power).



Sure, it is because the force required to overcome the dynamic coefficient of friction is less than the force required to overcome the static coefficient of friction. Think of it like this, in the feathered turn you have to apply enough force to hold your tires in a curve (because they will try very hard to stay static to the surface) whereas the jerky turn applies enough force to break-out of the static coefficient and make the tires dynamic to the surface consuming less net energy to change the direction of the vehicle. Sure, the feathered turn skids too, but at some limit of twist.

Hmm, I don't know if that made sense.

Feathered turn - more twist less skid; jerky turn - more skid less twist. ???

But wouldn't the force required to break out of the static coefficient be so great it would equal the much smaller force required to feather ?

Bearing in mind we're not talking paved surfaces here where once friction is broken the tyre just slides. We're more than likely talking trail or mud where a build up against the tyre wall would happen, a sort of constant force against the tyre.

Sorry for not explaining this at first.

[JohnF]

But wouldn't the force required to break out of the static coefficient be so great it would equal the much smaller force required to feather ?

That's a good question. The force required to break the static coefficient has to be great enough to twist the tires AND get the tires sliding, so, the force you apply at the moment you break the static coefficient will be greater than at any time in a constant twist (feathered) turn.

But, the net energy consumed to accomplish the turn will be less.

Remember, you said:

"... Given a known curve, at a known speed and a known weight it takes the same amount of energy to steer round it no matter if you "curve" round it or go in a series of "jerks". ..."

Bearing in mind we're not talking paved surfaces here where once friction is broken the tyre just slides.

Why not? All surfaces act the same, they just have different coefficients.

We're more than likely talking trail or mud where a build up against the tyre wall would happen, a sort of constant force against the tyre.

So, in this case you are artificially increasing the static forces between the tire and the surface. At its limit (the tires never skid) the only way to accomplish a turn will be to deform the tires to drive around the turn.