jobstian rim boiling

i see jobst is banging on this one again in the carbon rim thread, all
while criticizing others for not doing their math.

so, if we assume:

no heat losses through conduction, convection or radiation.
100% heat transfer to the rim.
rim - aluminum
rim mass - 500g
aluminum specific heat capacity - 0.9J/g.'C
latent heat of vaporization of water at 100'C - 2260J/g
assume a wet rim can maybe cling 1g of water.
assume he decelerates from 100kph in 100m and weighs 90kg.

now class, for how long will jobst's rim "boil"?

couple things;
if he decelerated from 100kph did he decelerate to 99kph and keep going or
come to a stop.
And if he was going 100kph was he going down hill, I think so... I can't or
never have done 100kph even on a down hill.
the amount of breaking force on a downhill would increase with the grade,
and brake fade would increase with heat.
can it be figured at all without actually testing it.
"jim beam" wrote in message
t...
i see jobst is banging on this one again in the carbon rim thread, all
while criticizing others for not doing their math.

so, if we assume:

no heat losses through conduction, convection or radiation.
100% heat transfer to the rim.
rim - aluminum
rim mass - 500g
aluminum specific heat capacity - 0.9J/g.'C
latent heat of vaporization of water at 100'C - 2260J/g
assume a wet rim can maybe cling 1g of water.
assume he decelerates from 100kph in 100m and weighs 90kg.

now class, for how long will jobst's rim "boil"?

On Jan 24, 8:15*am, jim beam wrote:

so, if we assume:

no heat losses through conduction, convection or radiation.
100% heat transfer to the rim.
rim - aluminum
rim mass - 500g
aluminum specific heat capacity - 0.9J/g.'C
latent heat of vaporization of water at 100'C - 2260J/g
assume a wet rim can maybe cling 1g of water.
assume he decelerates from 100kph in 100m and weighs 90kg.

Assuming bike is 10kg, bike+rider=100kg,
assuming he brakes with both rims (1000g),

100km/h = 27.777... m/s
kinetic energy = 1/2 * 100 * 27.77...^2 = 38580 J
temperature rise = 38580 / (1000 * 0.9) = 42.8°C

which isn't enough to reach the boiling point of water.

But so what. Jobst's example wasn't about
converting his kinetic energy into heat by stopping,
it was about dissipating the energy that comes
from descending (gravitational potential energy).

Really, what was your point?

Tom Ace

In article
,
Tom Ace wrote:

Really, what was your point?

The same point "jim" usually has, which is to discredit himself. Of
course, he's too narcissistic to realize that this is the outcome of the
vast majority of his rants. He's not always wrong (the law of averages
applying) but what usually happens is that he's partially right about
something and he microfocuses on that and then misapplies it
perseveratively.

Anyway, there is some better information out there than one can get from
jim's rants, including measurements. For example:

According to Angel Rodriquez and Carla Black in _The Tandem Book_:

"We have had heat-sensing stickers on our wheels for many years. A
fully loaded tandem making an emergency stop on a steep hill can raise
the rim temperature to 240 degrees Fahrenheit in about twenty seconds.
We have never gotten the rims over 200 degrees in the course of normal
riding, but other tandemists have raised the temperature of their rims
to over 250 degrees on long down hills. Heat sensing stickers are
made by the Markal Company of Chicago."

Joe Riel, a much less histrionic and more rigorous character than "jim,"
posted an analysis at:

http://www.k-online.com/~joer/cycling/rim-heating.pdf

but I got a 404 when trying to find that this morning. Maybe someone
else would have better luck. An excerpt from Joe's article available in
the r.b.t. archives reads:

I've put together a theoretical analysis of the rim temperature rise
during steady state braking. A pdf (40kB) is available at
www.k-online.com/~joer/cycling/rim-heating.pdf.

A few excerpts:

The worst-case velocity (maximum rim temperature) occurs at
Vterm/sqrt(5), where Vterm is the terminal velocity (no braking).

The computed maximum temperature rise for a 200 lb bike/rider on a
10% slope with a terminal velocity of 45mph (a guess), is 100degC,
for continually braking with just one wheel.

100C is hot enough to boil water- and more than hot enough to boil water
at altitude on a mountain descent.

Tim McNamara wrote:
In article
,
Tom Ace wrote:

Really, what was your point?

The same point "jim" usually has, which is to discredit himself. Of
course, he's too narcissistic to realize that this is the outcome of the
vast majority of his rants. He's not always wrong (the law of averages
applying) but what usually happens is that he's partially right about
something and he microfocuses on that and then misapplies it
perseveratively.

Anyway, there is some better information out there than one can get from
jim's rants, including measurements. For example:

According to Angel Rodriquez and Carla Black in _The Tandem Book_:

"We have had heat-sensing stickers on our wheels for many years. A
fully loaded tandem making an emergency stop on a steep hill can raise
the rim temperature to 240 degrees Fahrenheit in about twenty seconds.
We have never gotten the rims over 200 degrees in the course of normal
riding, but other tandemists have raised the temperature of their rims
to over 250 degrees on long down hills. Heat sensing stickers are
made by the Markal Company of Chicago."

oh timmy, you're such a retard, not only do you snip all the relevance
from the previous post, you don't even understand the original post.
perhaps if i repeat the original question, you'll have another go at
understanding it:

"for how long will jobst's rim 'boil'?"

there you go timmy, was that so hard?




Joe Riel, a much less histrionic and more rigorous character than "jim,"
posted an analysis at:

http://www.k-online.com/~joer/cycling/rim-heating.pdf

but I got a 404 when trying to find that this morning. Maybe someone
else would have better luck. An excerpt from Joe's article available in
the r.b.t. archives reads:

I've put together a theoretical analysis of the rim temperature rise
during steady state braking. A pdf (40kB) is available at
www.k-online.com/~joer/cycling/rim-heating.pdf.

A few excerpts:

The worst-case velocity (maximum rim temperature) occurs at
Vterm/sqrt(5), where Vterm is the terminal velocity (no braking).

The computed maximum temperature rise for a 200 lb bike/rider on a
10% slope with a terminal velocity of 45mph (a guess), is 100degC,
for continually braking with just one wheel.

100C is hot enough to boil water- and more than hot enough to boil water
at altitude on a mountain descent.

so timmy, math genius, if you have 500g of rim at 250'F [121'C], how
many grams of water are you going to boil given the heat capacity of
aluminum and the latent heat of vaporization of water?

This post is bordering on absurdity,
A rim spining that fast @ 100kph would throw off the water. There would be
no 1 gram of water on the rim.
A wet rim at rest might hold a gram of water, but
spinning at that rate, very doubtful. But if you assume that
riding through a puddle, that is 100 meters long, and that
for every turn of the rim that causes water to fling off
due to gravity or centrifugal force, that new water is added, that the
additional new water amounts to a gram,
your adding cold water to a rim that is heating up. Additionally, when you
touch the water with the break pads it would break the tension between the
rim and water causing more water to fling off. Or if your traveling
100kph, and riding through a puddle, the tendency of the
water would be to either, fling off the center of the tread on the tire ( we
all have had a wet butt riding in the wet), and no water would get on the
rims, or the tires would
hydroplane above the water causing again no water on the
rims. If perhaps the water were deep enough over the
course of 100 meters to get on the rims, to the amount
of 1 gram, it would affect the breaking significantly due to
forward movement and resistance of the tire passing through the puddle. It
wouldn't be a fair and scientific test,
but on paper it looks correct.

"jim beam" wrote in message
t...
Tim McNamara wrote:
In article
,
Tom Ace wrote:

Really, what was your point?

The same point "jim" usually has, which is to discredit himself. Of
course, he's too narcissistic to realize that this is the outcome of the
vast majority of his rants. He's not always wrong (the law of averages
applying) but what usually happens is that he's partially right about
something and he microfocuses on that and then misapplies it
perseveratively.

Anyway, there is some better information out there than one can get from
jim's rants, including measurements. For example:

According to Angel Rodriquez and Carla Black in _The Tandem Book_:

"We have had heat-sensing stickers on our wheels for many years. A
fully loaded tandem making an emergency stop on a steep hill can raise
the rim temperature to 240 degrees Fahrenheit in about twenty seconds.
We have never gotten the rims over 200 degrees in the course of normal
riding, but other tandemists have raised the temperature of their rims
to over 250 degrees on long down hills. Heat sensing stickers are
made by the Markal Company of Chicago."

oh timmy, you're such a retard, not only do you snip all the relevance
from the previous post, you don't even understand the original post.
perhaps if i repeat the original question, you'll have another go at
understanding it:

"for how long will jobst's rim 'boil'?"

there you go timmy, was that so hard?




Joe Riel, a much less histrionic and more rigorous character than "jim,"
posted an analysis at:

http://www.k-online.com/~joer/cycling/rim-heating.pdf

but I got a 404 when trying to find that this morning. Maybe someone
else would have better luck. An excerpt from Joe's article available in
the r.b.t. archives reads:

I've put together a theoretical analysis of the rim temperature rise
during steady state braking. A pdf (40kB) is available at
www.k-online.com/~joer/cycling/rim-heating.pdf.

A few excerpts:

The worst-case velocity (maximum rim temperature) occurs at
Vterm/sqrt(5), where Vterm is the terminal velocity (no braking).

The computed maximum temperature rise for a 200 lb bike/rider on a
10% slope with a terminal velocity of 45mph (a guess), is 100degC,
for continually braking with just one wheel.

100C is hot enough to boil water- and more than hot enough to boil water
at altitude on a mountain descent.

so timmy, math genius, if you have 500g of rim at 250'F [121'C], how many
grams of water are you going to boil given the heat capacity of aluminum
and the latent heat of vaporization of water?

In article ,
"g" wrote:

This post is bordering on absurdity,

That's better than usual for "jim." He's usually full-bore into the
absurd by his third post in any thread.

In article ,
jim beam wrote:

Tim McNamara wrote:
In article
,
Tom Ace wrote:

Really, what was your point?

The same point "jim" usually has, which is to discredit himself.
Of course, he's too narcissistic to realize that this is the
outcome of the vast majority of his rants. He's not always wrong
(the law of averages applying) but what usually happens is that
he's partially right about something and he microfocuses on that
and then misapplies it perseveratively.

Anyway, there is some better information out there than one can get
from jim's rants, including measurements. For example:

According to Angel Rodriquez and Carla Black in _The Tandem Book_:

"We have had heat-sensing stickers on our wheels for many years. A
fully loaded tandem making an emergency stop on a steep hill can
raise the rim temperature to 240 degrees Fahrenheit in about twenty
seconds. We have never gotten the rims over 200 degrees in the
course of normal riding, but other tandemists have raised the
temperature of their rims to over 250 degrees on long down hills.
Heat sensing stickers are made by the Markal Company of Chicago."

oh timmy, you're such a retard, not only do you snip all the
relevance from the previous post, you don't even understand the
original post. perhaps if i repeat the original question, you'll have
another go at understanding it:

"for how long will jobst's rim 'boil'?"

there you go timmy, was that so hard?

Oh, dear, "jim," did you miss the part about these being actual
measurements of rim temperatures and not some obfuscational waffling by
an obsessed lunatic cyberstalker?

Joe Riel, a much less histrionic and more rigorous character than
"jim," posted an analysis at:

http://www.k-online.com/~joer/cycling/rim-heating.pdf

but I got a 404 when trying to find that this morning. Maybe
someone else would have better luck. An excerpt from Joe's article
available in the r.b.t. archives reads:

I've put together a theoretical analysis of the rim temperature
rise during steady state braking. A pdf (40kB) is available at
www.k-online.com/~joer/cycling/rim-heating.pdf.

A few excerpts:

The worst-case velocity (maximum rim temperature) occurs at
Vterm/sqrt(5), where Vterm is the terminal velocity (no braking).

The computed maximum temperature rise for a 200 lb bike/rider on a
10% slope with a terminal velocity of 45mph (a guess), is 100degC,
for continually braking with just one wheel.

100C is hot enough to boil water- and more than hot enough to boil
water at altitude on a mountain descent.

so timmy, math genius, if you have 500g of rim at 250'F [121'C], how
many grams of water are you going to boil given the heat capacity of
aluminum and the latent heat of vaporization of water?

Enough to make a hissing sound, which is all that was reported.

Tim McNamara wrote:
In article ,
jim beam wrote:

Tim McNamara wrote:
In article
,
Tom Ace wrote:

Really, what was your point?
The same point "jim" usually has, which is to discredit himself.
Of course, he's too narcissistic to realize that this is the
outcome of the vast majority of his rants. He's not always wrong
(the law of averages applying) but what usually happens is that
he's partially right about something and he microfocuses on that
and then misapplies it perseveratively.

Anyway, there is some better information out there than one can get
from jim's rants, including measurements. For example:

According to Angel Rodriquez and Carla Black in _The Tandem Book_:

"We have had heat-sensing stickers on our wheels for many years. A
fully loaded tandem making an emergency stop on a steep hill can
raise the rim temperature to 240 degrees Fahrenheit in about twenty
seconds. We have never gotten the rims over 200 degrees in the
course of normal riding, but other tandemists have raised the
temperature of their rims to over 250 degrees on long down hills.
Heat sensing stickers are made by the Markal Company of Chicago."
oh timmy, you're such a retard, not only do you snip all the
relevance from the previous post, you don't even understand the
original post. perhaps if i repeat the original question, you'll have
another go at understanding it:

"for how long will jobst's rim 'boil'?"

there you go timmy, was that so hard?

Oh, dear, "jim," did you miss the part about these being actual
measurements of rim temperatures and not some obfuscational waffling by
an obsessed lunatic cyberstalker?

oh timmy, did you read the part about heat capacities and latent heat of
vaporization? you need 2260J to vaporize a gram of water. aluminum can
only give up, assuming 100% transfer, only 0.9J per gram per degree. is
the picture becoming clearer yet, retard?



Joe Riel, a much less histrionic and more rigorous character than
"jim," posted an analysis at:

http://www.k-online.com/~joer/cycling/rim-heating.pdf

but I got a 404 when trying to find that this morning. Maybe
someone else would have better luck. An excerpt from Joe's article
available in the r.b.t. archives reads:

I've put together a theoretical analysis of the rim temperature
rise during steady state braking. A pdf (40kB) is available at
www.k-online.com/~joer/cycling/rim-heating.pdf.

A few excerpts:

The worst-case velocity (maximum rim temperature) occurs at
Vterm/sqrt(5), where Vterm is the terminal velocity (no braking).

The computed maximum temperature rise for a 200 lb bike/rider on a
10% slope with a terminal velocity of 45mph (a guess), is 100degC,
for continually braking with just one wheel.
100C is hot enough to boil water- and more than hot enough to boil
water at altitude on a mountain descent.
so timmy, math genius, if you have 500g of rim at 250'F [121'C], how
many grams of water are you going to boil given the heat capacity of
aluminum and the latent heat of vaporization of water?

Enough to make a hissing sound, which is all that was reported.

and you're enough of a retard to believe that! like the rim is fully
sealed except the valve hole!!! like the rim has sufficient heat
capacity to continue boiling some undefined quantity of water long
enough for jobst to stop and notice!

timmy, you're a living embodiment of the mehrabian rule and proof of why
jobst constantly succeeds in bamboozling the proles.

Tim McNamara wrote:
In article ,
"g" wrote:

This post is bordering on absurdity,

That's better than usual for "jim." He's usually full-bore into the
absurd by his third post in any thread.

translation: "i'm too retarded to follow what's being said".