overpowering the brakes with the engine

harry k wrote:

> On dry pavement, stopped. Lock your brakes. Floor it. Notice all
> that tire smoke that is _NOT_ appearing?

There's a significant difference between static and dynamic friction.

On Oct 13, 11:12*pm, Arif Khokar > wrote:
> harry k wrote:
> > On dry pavement, stopped. *Lock your brakes. *Floor it. *Notice all
> > that tire smoke that is _NOT_ appearing?
>
> There's a significant difference between static and dynamic friction.

I do believe I made that clear in my post.

Harry K

On Oct 14, 10:22*am, harry k > wrote:
> On Oct 13, 11:12*pm, Arif Khokar > wrote:
>
> > harry k wrote:
> > > On dry pavement, stopped. *Lock your brakes. *Floor it. *Notice all
> > > that tire smoke that is _NOT_ appearing?
>
> > There's a significant difference between static and dynamic friction.
>
> I do believe I made that clear in my post.
>
> Harry K

The brakes can hold the rotor from moving against a larger torque than
they can apply against a moving rotor, because static friction is
greater than dynamic (sliding) friction.

So, 'brakes on, car not moving, throttle applied, car does not move'
does not show that the brakes can bring the rotors to a stop against
the engine, even before figuring in that the engine will be making
much more torque higher up in the rev range.


Dave

Dave

On Oct 14, 7:37*am, XR650L_Dave > wrote:
> On Oct 14, 10:22*am, harry k > wrote:
>
> > On Oct 13, 11:12*pm, Arif Khokar > wrote:
>
> > > harry k wrote:
> > > > On dry pavement, stopped. *Lock your brakes. *Floor it. *Notice all
> > > > that tire smoke that is _NOT_ appearing?
>
> > > There's a significant difference between static and dynamic friction.
>
> > I do believe I made that clear in my post.
>
> > Harry K
>
> The brakes can hold the rotor from moving against a larger torque than
> they can apply against a moving rotor, because static friction is
> greater than dynamic (sliding) friction.
>
> So, 'brakes on, car not moving, throttle applied, car does not move'
> does not show that the brakes can bring the rotors to a stop against
> the engine, even before figuring in that the engine will be making
> much more torque higher up in the rev range.
>
> Dave
>
> Dave

You appear to have reading comprhension problems. I pointed out in my
post that it does not account for dynamic forces. You might as well
continue and discuss the fact that at rest thebrakes operate differnt
than when moving. You can ignore the fact I also pointed _that_ out.

Harry K

On Oct 14, 10:55*am, harry k > wrote:
> On Oct 14, 7:37*am, XR650L_Dave > wrote:
>
>
>
> > On Oct 14, 10:22*am, harry k > wrote:
>
> > > On Oct 13, 11:12*pm, Arif Khokar > wrote:
>
> > > > harry k wrote:
> > > > > On dry pavement, stopped. *Lock your brakes. *Floor it. *Notice all
> > > > > that tire smoke that is _NOT_ appearing?
>
> > > > There's a significant difference between static and dynamic friction.

On Oct 14, 8:12*am, XR650L_Dave > wrote:
> On Oct 14, 10:55*am, harry k > wrote:
>
>
>
>
>
> > On Oct 14, 7:37*am, XR650L_Dave > wrote:
>
> > > On Oct 14, 10:22*am, harry k > wrote:
>
> > > > On Oct 13, 11:12*pm, Arif Khokar > wrote:
>
> > > > > harry k wrote:
> > > > > > On dry pavement, stopped. *Lock your brakes. *Floor it. *Notice all
> > > > > > that tire smoke that is _NOT_ appearing?
>
> > > > > There's a significant difference between static and dynamic friction.
>
> > > > I do believe I made that clear in my post.
>
> > > > Harry K
>
> > > The brakes can hold the rotor from moving against a larger torque than
> > > they can apply against a moving rotor, because static friction is
> > > greater than dynamic (sliding) friction.
>
> > > So, 'brakes on, car not moving, throttle applied, car does not move'
> > > does not show that the brakes can bring the rotors to a stop against
> > > the engine, even before figuring in that the engine will be making
> > > much more torque higher up in the rev range.
>
> > > Dave
>
> > > Dave
>
> > You appear to have reading comprhension problems. *I pointed out in my
> > post that it does not account for dynamic forces. *You might as well
> > continue and discuss the fact that at rest thebrakes operate differnt
> > than when moving. *You can ignore the fact I also pointed _that_ out.
>
> > Harry K
>
> Respectfully, your words-
>
> "On dry pavement, stopped. *Lock your brakes. *Floor it. *Notice all
> that tire smoke that is _NOT_ appearing? "
>
> "Granted that changes a few things. *Brakes are not in 'antilock' mode
> and vehicle momentum is not present. *It does, however show that the
> engine (even after shifting down) cannot overpower the brakes. "
>
> You mention ABS and momentum, make no reference to dynamic forces
> (except momentum) or dynamic vs static friction.
>

Errm...momentum is the only dynamic force present in the situation
under discussion.

So just how does brake friction vary between dynamic and static. I am
sure engineers would appreciate the info.

Harry K

> The bald fact is that the brakes being able to *keep* the car from
> moving bears no fruit in a discussion on whether the brakes can *stop*
> the car once moving. (unless, obviously, they can't keep it from
> moving and therefore would have no hope of stopping it).
>
> Dave

So keep on having fun nit picking. I figured mentioning the missing
factors was sufficient. Sorry it didn't suit you.

Harry K

Harry K

On Oct 14, 11:12*pm, Harry K > wrote:

> > Respectfully, your words-
>
> > "On dry pavement, stopped. *Lock your brakes. *Floor it. *Notice all
> > that tire smoke that is _NOT_ appearing? "
>
> > "Granted that changes a few things. *Brakes are not in 'antilock' mode
> > and vehicle momentum is not present. *It does, however show that the
> > engine (even after shifting down) cannot overpower the brakes. "
>
> > You mention ABS and momentum, make no reference to dynamic forces
> > (except momentum) or dynamic vs static friction.
>
> Errm...momentum is the only dynamic force present in the situation
> under discussion.
>
> So just how does brake friction vary between dynamic and static. *I am
> sure engineers would appreciate the info.
>
> Harry K
>
> > The bald fact is that the brakes being able to *keep* the car from
> > moving bears no fruit in a discussion on whether the brakes can *stop*
> > the car once moving. (unless, obviously, they can't keep it from
> > moving and therefore would have no hope of stopping it).
>
> > Dave
>
> So keep on having fun nit picking. *I figured mentioning the missing
> factors was sufficient. *Sorry it didn't suit you.
>
> Harry K
>

If you believe what you said, you are not equipped to go further.


Dave