Potential good news for Mt. Washington access. - Page 12 - Cycling Mob: Road Cycling, Mountain Biking and More

01-09-2005, 10:55 PM

jobst brandt wrote:

> Tom Sherman writes:
>
>> There still needs to be a control for temperature in the static
>> test, since of course compressing air into the tire raises the
>> temperature of the air and casing. However, if the tire is inflated
>> slowly, actual temperature rise will be insignificant.
>
>> In addition to the motion between the tire and rim that Jobst Brandt
>> mentions as possibly affecting blow-off pressure, there is the
>> effect of heating the tire, since the rubber will change properties
>> with temperature.
>
> I don't believe inflating a tire makes enough temperature difference
> to worry about. I have not noticed hot tires from inflation nor even
> a hot hose or brass hose-to-valve coupler (hose chuck). I am aware of
> Silca frame fit pump heads getting hot in the hand while pumping but
> that is a big difference from a floor pump and hose.
>
> I think we are scraping at nits. Besides, who gives a damn how much
> pressure a stationary wheel can hold. We are interested in safely
> riding down steep grades.

Then shouldn't it help to know as much as possible about what factors
affect blowoff? In addition to the static case, you could ride the bike
with increasingly higher pressures, without braking, to test your
hypothesis that motion between the tire and rim is contributory. If
temperature as well as pressure were a factor, perhaps using a different
material for the tire bead would help.

--
Benjamin Lewis

Luke, I'm yer father, eh. Come over to the dark side, you hoser.
-- Dave Thomas, "Strange Brew"

01-09-2005, 10:55 PM

jobst brandt wrote:

> Tom Sherman writes:
>
>> There still needs to be a control for temperature in the static
>> test, since of course compressing air into the tire raises the
>> temperature of the air and casing. However, if the tire is inflated
>> slowly, actual temperature rise will be insignificant.
>
>> In addition to the motion between the tire and rim that Jobst Brandt
>> mentions as possibly affecting blow-off pressure, there is the
>> effect of heating the tire, since the rubber will change properties
>> with temperature.
>
> I don't believe inflating a tire makes enough temperature difference
> to worry about. I have not noticed hot tires from inflation nor even
> a hot hose or brass hose-to-valve coupler (hose chuck). I am aware of
> Silca frame fit pump heads getting hot in the hand while pumping but
> that is a big difference from a floor pump and hose.
>
> I think we are scraping at nits. Besides, who gives a damn how much
> pressure a stationary wheel can hold. We are interested in safely
> riding down steep grades.

Then shouldn't it help to know as much as possible about what factors
affect blowoff? In addition to the static case, you could ride the bike
with increasingly higher pressures, without braking, to test your
hypothesis that motion between the tire and rim is contributory. If
temperature as well as pressure were a factor, perhaps using a different
material for the tire bead would help.

--
Benjamin Lewis

Luke, I'm yer father, eh. Come over to the dark side, you hoser.
-- Dave Thomas, "Strange Brew"

01-09-2005, 10:55 PM

jobst brandt wrote:

> Tom Sherman writes:
>
>> There still needs to be a control for temperature in the static
>> test, since of course compressing air into the tire raises the
>> temperature of the air and casing. However, if the tire is inflated
>> slowly, actual temperature rise will be insignificant.
>
>> In addition to the motion between the tire and rim that Jobst Brandt
>> mentions as possibly affecting blow-off pressure, there is the
>> effect of heating the tire, since the rubber will change properties
>> with temperature.
>
> I don't believe inflating a tire makes enough temperature difference
> to worry about. I have not noticed hot tires from inflation nor even
> a hot hose or brass hose-to-valve coupler (hose chuck). I am aware of
> Silca frame fit pump heads getting hot in the hand while pumping but
> that is a big difference from a floor pump and hose.
>
> I think we are scraping at nits. Besides, who gives a damn how much
> pressure a stationary wheel can hold. We are interested in safely
> riding down steep grades.

Then shouldn't it help to know as much as possible about what factors
affect blowoff? In addition to the static case, you could ride the bike
with increasingly higher pressures, without braking, to test your
hypothesis that motion between the tire and rim is contributory. If
temperature as well as pressure were a factor, perhaps using a different
material for the tire bead would help.

--
Benjamin Lewis

Luke, I'm yer father, eh. Come over to the dark side, you hoser.
-- Dave Thomas, "Strange Brew"

01-09-2005, 11:20 PM

"Alfred Ryder" <[Only registered and activated users can see links. ]> writes:

> While we are all offering gratuitous suggestions to the one doing the work,
> let me put in mine.
>
> What about expanding Frank's suggested lab test as follows. Attach a heating
> element to the rim, either bonded to the braking surfaces or inside the rim
> somewhere. The amount of thermal energy put into the wheel would be easy to
> know. Also monitoring the temperature and pressure of the air in the tube,
> temperature of the rim, etc. would be much easier in the lab than on the
> road. Then plot the blow-off point as a function of rim temperature and air
> pressure, both being controllable variables.
>
> Such a lab experiment would not replace the road test. But I agree with
> Frank that it would add information, probably necessary information. (My
> suspicion is that the rim can get very hot for a long time before the tube
> air temperature changes very much.)

Jobst's test should reveal that; he's logging the rim temperature and
air pressure.

Something we [meaning those of us in the peanut gallery] might want
to do is ascertain whether the road test is sufficient to settle the matter.

I believe that three factors have been proposed as directly
contributing to tire blow-off:

1. tire (air) pressure (i.e. increased pressure due to heating),
2. tire movement (i.e. sidewall flexing while rolling under load).
3. tire (cord/rubber) temperature

Jobst is measuring the first while applying the second. No attempt is
being made to measure or independently vary the third factor; however,
we may be able to indirectly determine whether it could be
significant. For example, if during steady state braking, the tire
pressure quickly rises to its final value but the tire doesn't blow
off until significantly later, that would be consistent with (3) being
a factor [because the thermal mass of the tire will delay its
temperature rise].

One reason for measuring the static blowoff pressure is that it serves
as a baseline against which to compare the dynamic blowoff pressure.
As it is, we [the peanut gallery] should be able to determine whether
they are roughly the same by first measuring the static blowoff pressure,
then pumping a tire to slightly below that and just riding around to see
if doing so induces a blowoff. Any takers? Ear-protection is recommended.

Joe

01-09-2005, 11:20 PM

"Alfred Ryder" <[Only registered and activated users can see links. ]> writes:

> While we are all offering gratuitous suggestions to the one doing the work,
> let me put in mine.
>
> What about expanding Frank's suggested lab test as follows. Attach a heating
> element to the rim, either bonded to the braking surfaces or inside the rim
> somewhere. The amount of thermal energy put into the wheel would be easy to
> know. Also monitoring the temperature and pressure of the air in the tube,
> temperature of the rim, etc. would be much easier in the lab than on the
> road. Then plot the blow-off point as a function of rim temperature and air
> pressure, both being controllable variables.
>
> Such a lab experiment would not replace the road test. But I agree with
> Frank that it would add information, probably necessary information. (My
> suspicion is that the rim can get very hot for a long time before the tube
> air temperature changes very much.)

Jobst's test should reveal that; he's logging the rim temperature and
air pressure.

Something we [meaning those of us in the peanut gallery] might want
to do is ascertain whether the road test is sufficient to settle the matter.

I believe that three factors have been proposed as directly
contributing to tire blow-off:

1. tire (air) pressure (i.e. increased pressure due to heating),
2. tire movement (i.e. sidewall flexing while rolling under load).
3. tire (cord/rubber) temperature

Jobst is measuring the first while applying the second. No attempt is
being made to measure or independently vary the third factor; however,
we may be able to indirectly determine whether it could be
significant. For example, if during steady state braking, the tire
pressure quickly rises to its final value but the tire doesn't blow
off until significantly later, that would be consistent with (3) being
a factor [because the thermal mass of the tire will delay its
temperature rise].

One reason for measuring the static blowoff pressure is that it serves
as a baseline against which to compare the dynamic blowoff pressure.
As it is, we [the peanut gallery] should be able to determine whether
they are roughly the same by first measuring the static blowoff pressure,
then pumping a tire to slightly below that and just riding around to see
if doing so induces a blowoff. Any takers? Ear-protection is recommended.

Joe

01-09-2005, 11:20 PM

"Alfred Ryder" <[Only registered and activated users can see links. ]> writes:

> While we are all offering gratuitous suggestions to the one doing the work,
> let me put in mine.
>
> What about expanding Frank's suggested lab test as follows. Attach a heating
> element to the rim, either bonded to the braking surfaces or inside the rim
> somewhere. The amount of thermal energy put into the wheel would be easy to
> know. Also monitoring the temperature and pressure of the air in the tube,
> temperature of the rim, etc. would be much easier in the lab than on the
> road. Then plot the blow-off point as a function of rim temperature and air
> pressure, both being controllable variables.
>
> Such a lab experiment would not replace the road test. But I agree with
> Frank that it would add information, probably necessary information. (My
> suspicion is that the rim can get very hot for a long time before the tube
> air temperature changes very much.)

Jobst's test should reveal that; he's logging the rim temperature and
air pressure.

Something we [meaning those of us in the peanut gallery] might want
to do is ascertain whether the road test is sufficient to settle the matter.

I believe that three factors have been proposed as directly
contributing to tire blow-off:

1. tire (air) pressure (i.e. increased pressure due to heating),
2. tire movement (i.e. sidewall flexing while rolling under load).
3. tire (cord/rubber) temperature

Jobst is measuring the first while applying the second. No attempt is
being made to measure or independently vary the third factor; however,
we may be able to indirectly determine whether it could be
significant. For example, if during steady state braking, the tire
pressure quickly rises to its final value but the tire doesn't blow
off until significantly later, that would be consistent with (3) being
a factor [because the thermal mass of the tire will delay its
temperature rise].

One reason for measuring the static blowoff pressure is that it serves
as a baseline against which to compare the dynamic blowoff pressure.
As it is, we [the peanut gallery] should be able to determine whether
they are roughly the same by first measuring the static blowoff pressure,
then pumping a tire to slightly below that and just riding around to see
if doing so induces a blowoff. Any takers? Ear-protection is recommended.

Joe

01-09-2005, 11:20 PM

"Alfred Ryder" <[Only registered and activated users can see links. ]> writes:

> While we are all offering gratuitous suggestions to the one doing the work,
> let me put in mine.
>
> What about expanding Frank's suggested lab test as follows. Attach a heating
> element to the rim, either bonded to the braking surfaces or inside the rim
> somewhere. The amount of thermal energy put into the wheel would be easy to
> know. Also monitoring the temperature and pressure of the air in the tube,
> temperature of the rim, etc. would be much easier in the lab than on the
> road. Then plot the blow-off point as a function of rim temperature and air
> pressure, both being controllable variables.
>
> Such a lab experiment would not replace the road test. But I agree with
> Frank that it would add information, probably necessary information. (My
> suspicion is that the rim can get very hot for a long time before the tube
> air temperature changes very much.)

Jobst's test should reveal that; he's logging the rim temperature and
air pressure.

Something we [meaning those of us in the peanut gallery] might want
to do is ascertain whether the road test is sufficient to settle the matter.

I believe that three factors have been proposed as directly
contributing to tire blow-off:

1. tire (air) pressure (i.e. increased pressure due to heating),
2. tire movement (i.e. sidewall flexing while rolling under load).
3. tire (cord/rubber) temperature

Jobst is measuring the first while applying the second. No attempt is
being made to measure or independently vary the third factor; however,
we may be able to indirectly determine whether it could be
significant. For example, if during steady state braking, the tire
pressure quickly rises to its final value but the tire doesn't blow
off until significantly later, that would be consistent with (3) being
a factor [because the thermal mass of the tire will delay its
temperature rise].

One reason for measuring the static blowoff pressure is that it serves
as a baseline against which to compare the dynamic blowoff pressure.
As it is, we [the peanut gallery] should be able to determine whether
they are roughly the same by first measuring the static blowoff pressure,
then pumping a tire to slightly below that and just riding around to see
if doing so induces a blowoff. Any takers? Ear-protection is recommended.

Joe

01-10-2005, 05:56 AM

Benjamin Lewis <[Only registered and activated users can see links. ].ca> wrote:

>jobst brandt wrote:

>> I think we are scraping at nits. Besides, who gives a damn how much
>> pressure a stationary wheel can hold. We are interested in safely
>> riding down steep grades.
>
>Then shouldn't it help to know as much as possible about what factors
>affect blowoff? In addition to the static case, you could ride the bike
>with increasingly higher pressures, without braking, to test your
>hypothesis that motion between the tire and rim is contributory. If
>temperature as well as pressure were a factor, perhaps using a different
>material for the tire bead would help.

I think Jobst nailed it on the head. While it might be interesting to
explore all the nuances of this phenomenon, all that really matters is
what the tire does when actually rolling down a steep hill with a
rider on board.

But to add my voice to the chorus of armchair testers, I'd suggest
that it might be interesting to see the effects of using a deep rim on
the rear wheel to see how effective the extra mass is at getting rid
of the heat.

Mark Hickey
Habanero Cycles
[Only registered and activated users can see links. ]
Home of the $695 ti frame

01-10-2005, 05:56 AM

Benjamin Lewis <[Only registered and activated users can see links. ].ca> wrote:

>jobst brandt wrote:

>> I think we are scraping at nits. Besides, who gives a damn how much
>> pressure a stationary wheel can hold. We are interested in safely
>> riding down steep grades.
>
>Then shouldn't it help to know as much as possible about what factors
>affect blowoff? In addition to the static case, you could ride the bike
>with increasingly higher pressures, without braking, to test your
>hypothesis that motion between the tire and rim is contributory. If
>temperature as well as pressure were a factor, perhaps using a different
>material for the tire bead would help.

I think Jobst nailed it on the head. While it might be interesting to
explore all the nuances of this phenomenon, all that really matters is
what the tire does when actually rolling down a steep hill with a
rider on board.

But to add my voice to the chorus of armchair testers, I'd suggest
that it might be interesting to see the effects of using a deep rim on
the rear wheel to see how effective the extra mass is at getting rid
of the heat.

Mark Hickey
Habanero Cycles
[Only registered and activated users can see links. ]
Home of the $695 ti frame

01-10-2005, 05:56 AM

Benjamin Lewis <[Only registered and activated users can see links. ].ca> wrote:

>jobst brandt wrote:

>> I think we are scraping at nits. Besides, who gives a damn how much
>> pressure a stationary wheel can hold. We are interested in safely
>> riding down steep grades.
>
>Then shouldn't it help to know as much as possible about what factors
>affect blowoff? In addition to the static case, you could ride the bike
>with increasingly higher pressures, without braking, to test your
>hypothesis that motion between the tire and rim is contributory. If
>temperature as well as pressure were a factor, perhaps using a different
>material for the tire bead would help.

I think Jobst nailed it on the head. While it might be interesting to
explore all the nuances of this phenomenon, all that really matters is
what the tire does when actually rolling down a steep hill with a
rider on board.

But to add my voice to the chorus of armchair testers, I'd suggest
that it might be interesting to see the effects of using a deep rim on
the rear wheel to see how effective the extra mass is at getting rid
of the heat.

Mark Hickey
Habanero Cycles
[Only registered and activated users can see links. ]
Home of the $695 ti frame