| Re: Rim brake heat and clincher blowoff, was Re: Potential goodnews for Mt. Washington access.
Mark and Christine <none@none.net> writes:
> As for friction, you simply do not understand real world
> friction applications if you do not think that friction
> occurs unless the tire is skiding.
We understand the real world quite well, however, that
triple-negative is a bit hard to parse.
Your original (incorrect) point was that the friction of the road
against the tire somehow heated up the air in the tube. It doesn't,
essentially all the heat is generated in the brake/rim interface. The
tire friction is significant only in that without we couldn't generate
the braking friction, however, no significant amount of heat is being
generated at the tire/road interface unless the tire is skidding. And
a skidding tire is not of interest to this discussion (for several
reasons).
> Max heating of a tire
> occurs at the speed just before the tire stops rotating.
That makes no sense. There is no given speed at which a tire stops
rotating. Anyhow, the velocity at which maximum power generation
occurs is not the worst-case for temperature rise under steady-state
braking, one has to consider convection cooling at the rim. A
calculation I did some time ago suggests that the worst-case velocity
is Vterm/sqrt(5), where Vterm is the terminal velocity of the rider.
Joe
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