On Sun, 02 Nov 2003 00:31:47 +0000, James Johnson wrote:

Hydrogen is even better yet (better heat transfer coefficient). It is what is
used to cool the 1000 megawatt generators at power plants as air can't carry the
heat from resistance in the windings away fast enough. Just watch out for
flames or sparks. Also hydrogen tends to diffuse through the tire so you have
to replenish it more often.


Having worked in a 1000 MW generating station, I can safely say this is
doggie-donuts. I wouldn't have hydrogen (or any explosive gas) within
100ft of a high-power generator!

Lloyd Sumpter

Lloyd Sumpter wrote:

Having worked in a 1000 MW generating station, I can safely say this is
doggie-donuts. I wouldn't have hydrogen (or any explosive gas) within
100ft of a high-power generator!

Hydrogen cooling is pretty common. He isn't, however, thinking about
just where that heat in a tire is supposed to go.

It's not like there is a heat exchanger to remove the heat from the gas
that was heated by the rubber surrounding that gas to begin with.

Rick

On Sun, 02 Nov 2003 19:48:12 GMT, Rick wrote:

Lloyd Sumpter wrote:

Having worked in a 1000 MW generating station, I can safely say this is
doggie-donuts. I wouldn't have hydrogen (or any explosive gas) within
100ft of a high-power generator!

Hydrogen cooling is pretty common. He isn't, however, thinking about
just where that heat in a tire is supposed to go.

It's not like there is a heat exchanger to remove the heat from the gas
that was heated by the rubber surrounding that gas to begin with.

The wheel. I can see how the heat conductive properties of the gas can
make a difference conducting heat from the tire to the wheel at
different rates. Especially since the rubber itself isn't a good heat
conductor.

Steve

Steven Shelikoff wrote:

The wheel.

The area of the wheel exposed to the gas is so small compared to the
area of the tire producing the heat that I doubt it has much of any
practical value in dissipation of heat above and beyond air flow over
and radiation from the tire itself.

Though it doesn't apply much to boat trailer tires, the heat
conductivity of the gas would work against tire cooling in the case of
race cars and aircraft since it would serve to increase the rate of tire
heating in heavy brake application. Many aircraft tire failures are due
to overheated brakes, heating the wheels to the point of causing the
tires to blow out or burn, not from heat generated by the tires themselves.

Rick

On Mon, 03 Nov 2003 00:20:28 GMT, Rick wrote:

Steven Shelikoff wrote:

The wheel.

The area of the wheel exposed to the gas is so small compared to the
area of the tire producing the heat that I doubt it has much of any
practical value in dissipation of heat above and beyond air flow over
and radiation from the tire itself.

Actually, the area of the wheel exposed to the gas in a race car tire is
pretty large compared to the area of the tire since they are wide and
low profile. A narrow, high profile trailer tire doesn't have very much
wheel exposed to the gas for the amount of tire area producing heat.

Though it doesn't apply much to boat trailer tires, the heat
conductivity of the gas would work against tire cooling in the case of
race cars and aircraft since it would serve to increase the rate of tire
heating in heavy brake application. Many aircraft tire failures are due

Of course it all depends on the type of racing. During most racing like
road racing, twisty corners, etc, heavy braking is applied but for very
short durations. Superspeedway racing, not at all. There's plenty of
cooling air ducted to the brakes and the rest of the suspension
components can also act like a heat sink since they are directly
attached to the brakes and wheel. On the other hand, the tires are
always generating heat whenever the car is moving, and especially in
turns. Heat is the enemy of tire life and whatever can be done to take
away more heat from the tire will help. That being said, I sure
wouldn't want hydrogen in my tires.

to overheated brakes, heating the wheels to the point of causing the
tires to blow out or burn, not from heat generated by the tires themselves.

Slowing a 747 from 180 mph to taxi speed is hardly the same thing as
bleeding off 40 or 50 mph from a super light race car. There's a whole
different set of braking requirements, and aircraft brakes are in many
cases under engineered since they depend so much on engine braking to
slow down.

Steve

Steven Shelikoff, the racing expert wrote:


Actually, the area of the wheel exposed to the gas in a race car tire is
pretty large compared to the area of the tire since they are wide and
low profile.

Not in all types of racing. Actually, in some types, the narrower the
better, less contact area, less friction. Take a salt flat racer, for
instance.



Though it doesn't apply much to boat trailer tires, the heat
conductivity of the gas would work against tire cooling in the case of
race cars and aircraft since it would serve to increase the rate of tire
heating in heavy brake application. Many aircraft tire failures are due

Of course it all depends on the type of racing. During most racing like
road racing, twisty corners, etc, heavy braking is applied but for very
short durations. Superspeedway racing, not at all.

Are you really trying to say that on superspeedways, they don't use
brakes at all? That's pretty stupid. They actually use brakes as
opposed to letting off the throttle, trying to keep the enginer RPM's
up. It takes forever to get those restictor plate engines back up to
speed. They do, however, use completely different brake setups,
smaller rotors, pads. These smaller, thinner rotors will get quite
hot, quite quickly.

There's plenty of
cooling air ducted to the brakes and the rest of the suspension
components can also act like a heat sink since they are directly
attached to the brakes and wheel. On the other hand, the tires are
always generating heat whenever the car is moving, and especially in
turns. Heat is the enemy of tire life and whatever can be done to take
away more heat from the tire will help. That being said, I sure
wouldn't want hydrogen in my tires.

Now that I can agree with.

"basskisser" wrote in message
om...

They actually use brakes as
opposed to letting off the throttle, trying to keep the enginer RPM's
up. It takes forever to get those restictor plate engines back up to
speed.

Can you explain that statement?

Unless your referring to the go karts you rent at the amusment center I
don't understand how you can maintain engine RPMs and slow the car down.

Automatic transmission?? Hmmmm..... Seen it on off road cars, I wasn't
aware of it being very common on any sort of track or pavement vehicles.

Without some sort of a slip clutch or torque converter, the engine RPM is
going to be directly related to the velocity of the car.

Rod

On 3 Nov 2003 05:02:04 -0800, (basskisser) wrote:

Steven Shelikoff, the racing expert wrote:


Actually, the area of the wheel exposed to the gas in a race car tire is
pretty large compared to the area of the tire since they are wide and
low profile.

Not in all types of racing. Actually, in some types, the narrower the
better, less contact area, less friction. Take a salt flat racer, for
instance.

Yeah, and bicycle racing.

Though it doesn't apply much to boat trailer tires, the heat
conductivity of the gas would work against tire cooling in the case of
race cars and aircraft since it would serve to increase the rate of tire
heating in heavy brake application. Many aircraft tire failures are due

Of course it all depends on the type of racing. During most racing like
road racing, twisty corners, etc, heavy braking is applied but for very
short durations. Superspeedway racing, not at all.

Are you really trying to say that on superspeedways, they don't use
brakes at all? That's pretty stupid. They actually use brakes as
opposed to letting off the throttle, trying to keep the enginer RPM's
up. It takes forever to get those restictor plate engines back up to
speed. They do, however, use completely different brake setups,
smaller rotors, pads. These smaller, thinner rotors will get quite
hot, quite quickly.

Sorry to dissapoint you but at NASCAR restrictor plate races like at
Talladega and Daytona, the driver will almost without exception have
the gas pedal to the floor and not touch the brakes all day. They even
tape up the brake vents for more downforce since there's little need to
cool the brakes. When they actually do need the brakes, like to stop in
their pit, they are so bad that they often lock up and skid. That's why
you see drivers overshoot their pit more often on the restrictor plate
races, because the brakes are so touchy. It's done that way to save
unsprung weight and lower friction.

That's the exact opposite from short track and road course races where
they use the brakes so much that they need blowers to cool the them
since the vents don't provide enough cooling. They use a beefy braking
setup for those races since they have twice the power available so
there's much more to overcome braking losses, and they really need the
brakes.

Steve

Steven Shelikoff wrote:

aircraft brakes are in many cases under engineered since they
depend so much on engine braking to slow down.

Incorrect. The brakes on transport category aircraft are certified to
stop the aircraft on the runway remaining after a rejected takeoff at
the highest speed it would still be on the ground (V1) without using
thrust reversers. Thrust reversers provide little braking at high speeds
anyway.

Rick

On Mon, 03 Nov 2003 17:11:20 GMT, Rick wrote:

Steven Shelikoff wrote:

aircraft brakes are in many cases under engineered since they
depend so much on engine braking to slow down.

Incorrect. The brakes on transport category aircraft are certified to
stop the aircraft on the runway remaining after a rejected takeoff at
the highest speed it would still be on the ground (V1) without using
thrust reversers. Thrust reversers provide little braking at high speeds
anyway.

Yeah, right. But not over and over and if that does happen, i.e.,
stopping the plane with the remaining runway after an aborted takeoff,
you're almost guaranteed a brake fire. No matter how the brakes are
certified, if a heavy gets up to takeoff speed on most runways, aborts
and only has the brakes to stop it, chances are it's gonna go off the
end of the runway.

And I'm not sure where you get the idea that thrust reversers provide
little braking at high speeds. They way they work, they really *only*
provide braking at high speed and very little at low speed. They are
the vast majority of braking at landing speed.

While a jet thrust reverser can be used to back up the plane, very
little thrust is actually "reversed". Mostly, it's just diverted into
an unuseful direction, like up and down or outward, and very slightly
forward for backing up. They slow the plane mostly by engine drag, not
by reversing the thrust forward. And engine drag is greater at higher
speeds. In fact, most of the accidents involving thrust reversers occur
when they are inadvertantly or uncommanded deployed in flight, causing
massive drag on the deployed side and throwing the plane out of control.

Steve