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"torque wrench" pump/compressor



 
 
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  #31  
Old October 13th 18, 12:56 AM posted to rec.bicycles.tech
AMuzi
external usenet poster
 
Posts: 9,723
Default "torque wrench" pump/compressor

On 10/12/2018 5:54 PM, John B. Slocomb wrote:
On Fri, 12 Oct 2018 10:18:06 -0400, Radey Shouman
wrote:

John B. Slocomb writes:

On Thu, 11 Oct 2018 15:36:04 -0400, Frank Krygowski
wrote:

On 10/11/2018 1:53 PM, Theodore Heise wrote:
On Thu, 11 Oct 2018 09:27:02 -0700 (PDT),
Frank Krygowski wrote:
On Thursday, October 11, 2018 at 5:00:33 AM UTC-4, John B. Slocomb wrote:
On Thu, 11 Oct 2018 08:54:38 +0200, Emanuel Berg
wrote:

Just out of curiosity, is there a "torque wrench" pump or
compressor? I.e., you would screw on the presta valve, set
the gizmo to e.g. 35psi, engage it, and instead of watching
the indicator, automagically at the right level it would
stop?

Most of the gas stations here use an air station that you can
set for your desired pressure and then just plug the hose onto
the tire valve
- there is a little clamp to hold it there. When the tire is
inflated to the specified pressure the inflation stops and a
bell rings.

Since they aren't manufactured here I had assumed that the
rest of the world had them too.

My experience from 50+ years ago says not to rely on those
things, although I suppose they may be different now.

Back then I blew a tire off the rim with one. I suspect the
problem was the volume of each pumping stroke. In a large sized
car tire, the volume surge with each big stroke would be
absorbed and barely raise the pressure. In a low volume bike
tire, it caused an explosion. That's my guess anyway.

I usually inflate using a manual floor pump with a gage. It's
easy enough to stop pumping when the dial reads the desired
temperature.

Don't you mean, when the dial reads the desired foot-pounds?

Oh geez, my mistake!

But: Neither! I stop when it reads the desired PRESSURE!

Around here we use psi = pounds per square inch. Weirdly enough, my
pump's pressure gauge is also graduated in kg/cm^2. I would have used
that as a bad example in my courses, since kg is properly used to
measure mass, not force. And pressure is force per unit area.

(This indicates that the SI system gets misused as much as the U.S. or
Imperial system.)

But isn't "pound" a measurement of mass also :-?


When I was in school, years ago, we were quite strictly made to write
either lb_f (pound force) or lb_m (pound mass), and to include unit
conversions from one to the other using constants g (the nominal force
of graivty at the surface of the Earth) and g_c (a unit conversion factor).

The conversion is:

lb_f = lb_m * g / g_c

In English units g = 32.2 ft/s^2
g_c = 32.2 lb_m ft/s^2 lb_f

but if you didn't include the conversion, you failed.


Question. "Lb_m * g". how can you meaure 1 lb_m without gravety?


In theory, smack it into something at a known velocity in
outer space. Nice weekend project.

Not that metric is any better, in that KPa does not equal Atm:
https://www.chemteam.info/GasLaw/Pre...nversions.html


--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971


Ads
  #32  
Old October 13th 18, 03:16 AM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 6,271
Default "torque wrench" pump/compressor

On 10/12/2018 6:54 PM, John B. Slocomb wrote:
On Fri, 12 Oct 2018 10:18:06 -0400, Radey Shouman
wrote:

John B. Slocomb writes:

On Thu, 11 Oct 2018 15:36:04 -0400, Frank Krygowski
wrote:

On 10/11/2018 1:53 PM, Theodore Heise wrote:
On Thu, 11 Oct 2018 09:27:02 -0700 (PDT),
Frank Krygowski wrote:
On Thursday, October 11, 2018 at 5:00:33 AM UTC-4, John B. Slocomb wrote:
On Thu, 11 Oct 2018 08:54:38 +0200, Emanuel Berg
wrote:

Just out of curiosity, is there a "torque wrench" pump or
compressor? I.e., you would screw on the presta valve, set
the gizmo to e.g. 35psi, engage it, and instead of watching
the indicator, automagically at the right level it would
stop?

Most of the gas stations here use an air station that you can
set for your desired pressure and then just plug the hose onto
the tire valve
- there is a little clamp to hold it there. When the tire is
inflated to the specified pressure the inflation stops and a
bell rings.

Since they aren't manufactured here I had assumed that the
rest of the world had them too.

My experience from 50+ years ago says not to rely on those
things, although I suppose they may be different now.

Back then I blew a tire off the rim with one. I suspect the
problem was the volume of each pumping stroke. In a large sized
car tire, the volume surge with each big stroke would be
absorbed and barely raise the pressure. In a low volume bike
tire, it caused an explosion. That's my guess anyway.

I usually inflate using a manual floor pump with a gage. It's
easy enough to stop pumping when the dial reads the desired
temperature.

Don't you mean, when the dial reads the desired foot-pounds?

Oh geez, my mistake!

But: Neither! I stop when it reads the desired PRESSURE!

Around here we use psi = pounds per square inch. Weirdly enough, my
pump's pressure gauge is also graduated in kg/cm^2. I would have used
that as a bad example in my courses, since kg is properly used to
measure mass, not force. And pressure is force per unit area.

(This indicates that the SI system gets misused as much as the U.S. or
Imperial system.)

But isn't "pound" a measurement of mass also :-?


When I was in school, years ago, we were quite strictly made to write
either lb_f (pound force) or lb_m (pound mass), and to include unit
conversions from one to the other using constants g (the nominal force
of graivty at the surface of the Earth) and g_c (a unit conversion factor).

The conversion is:

lb_f = lb_m * g / g_c

In English units g = 32.2 ft/s^2
g_c = 32.2 lb_m ft/s^2 lb_f

but if you didn't include the conversion, you failed.


Question. "Lb_m * g". how can you meaure 1 lb_m without gravety?


Interestingly, they do that! Or rather, they do it in orbit or in free
fall*, which is effectively the same thing.

On the International Space Station, they attach the mass to a spring
system. The frequency of oscillation allows them to determine the mass.

Here you go: https://www.youtube.com/watch?v=8rt3udip7l4

(* Free fall or stable orbit isn't exactly "without gravity" because
gravity is acting on the object. But since the object is accelerating
freely in response to gravity, it's effectively the same as if the
gravitational force were zero.)

--
- Frank Krygowski
  #33  
Old October 13th 18, 03:21 AM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 6,271
Default "torque wrench" pump/compressor

On 10/12/2018 7:01 PM, John B. Slocomb wrote:
On Fri, 12 Oct 2018 11:08:06 -0400, Frank Krygowski
wrote:

On 10/12/2018 10:18 AM, Radey Shouman wrote:
John B. Slocomb writes:

On Thu, 11 Oct 2018 15:36:04 -0400, Frank Krygowski
wrote:

On 10/11/2018 1:53 PM, Theodore Heise wrote:
On Thu, 11 Oct 2018 09:27:02 -0700 (PDT),
Frank Krygowski wrote:
On Thursday, October 11, 2018 at 5:00:33 AM UTC-4, John B. Slocomb wrote:
On Thu, 11 Oct 2018 08:54:38 +0200, Emanuel Berg
wrote:

Just out of curiosity, is there a "torque wrench" pump or
compressor? I.e., you would screw on the presta valve, set
the gizmo to e.g. 35psi, engage it, and instead of watching
the indicator, automagically at the right level it would
stop?

Most of the gas stations here use an air station that you can
set for your desired pressure and then just plug the hose onto
the tire valve
- there is a little clamp to hold it there. When the tire is
inflated to the specified pressure the inflation stops and a
bell rings.

Since they aren't manufactured here I had assumed that the
rest of the world had them too.

My experience from 50+ years ago says not to rely on those
things, although I suppose they may be different now.

Back then I blew a tire off the rim with one. I suspect the
problem was the volume of each pumping stroke. In a large sized
car tire, the volume surge with each big stroke would be
absorbed and barely raise the pressure. In a low volume bike
tire, it caused an explosion. That's my guess anyway.

I usually inflate using a manual floor pump with a gage. It's
easy enough to stop pumping when the dial reads the desired
temperature.

Don't you mean, when the dial reads the desired foot-pounds?

Oh geez, my mistake!

But: Neither! I stop when it reads the desired PRESSURE!

Around here we use psi = pounds per square inch. Weirdly enough, my
pump's pressure gauge is also graduated in kg/cm^2. I would have used
that as a bad example in my courses, since kg is properly used to
measure mass, not force. And pressure is force per unit area.

(This indicates that the SI system gets misused as much as the U.S. or
Imperial system.)

But isn't "pound" a measurement of mass also :-?


As I used to explain it to students: Properly speaking, a _force_ is a
push or a pull on an object. Properly speaking, _mass_ is a measure of
the amount of matter in an object. _Weight_ is a particular force, i.e.
the force of gravity on an object.

So in a U.S. grocery if you buy 2.2 pounds of cheese, you're buying the
amount of cheese upon which the earth's gravity exerts a force of two
pounds. It's a roundabout way of specifying the mass you want, but it
works as long as you're just talking cheese, etc.

In a European country, you'd specify you wanted a kilogram of cheese,
which is about 2.2 pounds worth. There, you're directly specifying the
amount of cheese you want.

I think I must have been out of school for too long. How is 1 kilogram
which equates to approximately2.20462262185 pounds a different
measurement than pounds? Aren't they both a measurement of the effect
of gravity on a certain amount of stuff?


First, don't trouble yourself. For ordinary everyday stuff it doesn't
matter.

But at its heart, mass is not the same as weight. For a simple example,
if you took a 1 kg mass to the moon its mass would still be 1 kg. But
its weight would be about 1/6 of what it was on earth. And in the ISS
the observed weight or effective weight of that object would be zero.

Again, if you're just (say) buying cheese on the surface of the earth
the difference doesn't matter. If you don't keep it straight in
calculations involving dynamics - as in "how much tension will be on
this connecting rod?" - you're apt to get answers that are off by a
factor of 32. Or in an SI system country, off by a factor of 9.8 or so.


--
- Frank Krygowski
  #34  
Old October 13th 18, 03:42 AM posted to rec.bicycles.tech
Radey Shouman
external usenet poster
 
Posts: 1,071
Default "torque wrench" pump/compressor

John B. Slocomb writes:

On Fri, 12 Oct 2018 10:18:06 -0400, Radey Shouman
wrote:

John B. Slocomb writes:

On Thu, 11 Oct 2018 15:36:04 -0400, Frank Krygowski
wrote:

On 10/11/2018 1:53 PM, Theodore Heise wrote:
On Thu, 11 Oct 2018 09:27:02 -0700 (PDT),
Frank Krygowski wrote:
On Thursday, October 11, 2018 at 5:00:33 AM UTC-4, John B. Slocomb wrote:
On Thu, 11 Oct 2018 08:54:38 +0200, Emanuel Berg
wrote:

Just out of curiosity, is there a "torque wrench" pump or
compressor? I.e., you would screw on the presta valve, set
the gizmo to e.g. 35psi, engage it, and instead of watching
the indicator, automagically at the right level it would
stop?

Most of the gas stations here use an air station that you can
set for your desired pressure and then just plug the hose onto
the tire valve
- there is a little clamp to hold it there. When the tire is
inflated to the specified pressure the inflation stops and a
bell rings.

Since they aren't manufactured here I had assumed that the
rest of the world had them too.

My experience from 50+ years ago says not to rely on those
things, although I suppose they may be different now.

Back then I blew a tire off the rim with one. I suspect the
problem was the volume of each pumping stroke. In a large sized
car tire, the volume surge with each big stroke would be
absorbed and barely raise the pressure. In a low volume bike
tire, it caused an explosion. That's my guess anyway.

I usually inflate using a manual floor pump with a gage. It's
easy enough to stop pumping when the dial reads the desired
temperature.

Don't you mean, when the dial reads the desired foot-pounds?

Oh geez, my mistake!

But: Neither! I stop when it reads the desired PRESSURE!

Around here we use psi = pounds per square inch. Weirdly enough, my
pump's pressure gauge is also graduated in kg/cm^2. I would have used
that as a bad example in my courses, since kg is properly used to
measure mass, not force. And pressure is force per unit area.

(This indicates that the SI system gets misused as much as the U.S. or
Imperial system.)

But isn't "pound" a measurement of mass also :-?


When I was in school, years ago, we were quite strictly made to write
either lb_f (pound force) or lb_m (pound mass), and to include unit
conversions from one to the other using constants g (the nominal force
of graivty at the surface of the Earth) and g_c (a unit conversion factor).

The conversion is:

lb_f = lb_m * g / g_c

In English units g = 32.2 ft/s^2
g_c = 32.2 lb_m ft/s^2 lb_f

but if you didn't include the conversion, you failed.


Question. "Lb_m * g". how can you meaure 1 lb_m without gravety?


Apply a known force and see how fast it accelerates.

--
  #35  
Old October 13th 18, 03:57 AM posted to rec.bicycles.tech
John B. Slocomb
external usenet poster
 
Posts: 87
Default "torque wrench" pump/compressor

On Fri, 12 Oct 2018 22:16:00 -0400, Frank Krygowski
wrote:

On 10/12/2018 6:54 PM, John B. Slocomb wrote:
On Fri, 12 Oct 2018 10:18:06 -0400, Radey Shouman
wrote:

John B. Slocomb writes:

On Thu, 11 Oct 2018 15:36:04 -0400, Frank Krygowski
wrote:

On 10/11/2018 1:53 PM, Theodore Heise wrote:
On Thu, 11 Oct 2018 09:27:02 -0700 (PDT),
Frank Krygowski wrote:
On Thursday, October 11, 2018 at 5:00:33 AM UTC-4, John B. Slocomb wrote:
On Thu, 11 Oct 2018 08:54:38 +0200, Emanuel Berg
wrote:

Just out of curiosity, is there a "torque wrench" pump or
compressor? I.e., you would screw on the presta valve, set
the gizmo to e.g. 35psi, engage it, and instead of watching
the indicator, automagically at the right level it would
stop?

Most of the gas stations here use an air station that you can
set for your desired pressure and then just plug the hose onto
the tire valve
- there is a little clamp to hold it there. When the tire is
inflated to the specified pressure the inflation stops and a
bell rings.

Since they aren't manufactured here I had assumed that the
rest of the world had them too.

My experience from 50+ years ago says not to rely on those
things, although I suppose they may be different now.

Back then I blew a tire off the rim with one. I suspect the
problem was the volume of each pumping stroke. In a large sized
car tire, the volume surge with each big stroke would be
absorbed and barely raise the pressure. In a low volume bike
tire, it caused an explosion. That's my guess anyway.

I usually inflate using a manual floor pump with a gage. It's
easy enough to stop pumping when the dial reads the desired
temperature.

Don't you mean, when the dial reads the desired foot-pounds?

Oh geez, my mistake!

But: Neither! I stop when it reads the desired PRESSURE!

Around here we use psi = pounds per square inch. Weirdly enough, my
pump's pressure gauge is also graduated in kg/cm^2. I would have used
that as a bad example in my courses, since kg is properly used to
measure mass, not force. And pressure is force per unit area.

(This indicates that the SI system gets misused as much as the U.S. or
Imperial system.)

But isn't "pound" a measurement of mass also :-?

When I was in school, years ago, we were quite strictly made to write
either lb_f (pound force) or lb_m (pound mass), and to include unit
conversions from one to the other using constants g (the nominal force
of graivty at the surface of the Earth) and g_c (a unit conversion factor).

The conversion is:

lb_f = lb_m * g / g_c

In English units g = 32.2 ft/s^2
g_c = 32.2 lb_m ft/s^2 lb_f

but if you didn't include the conversion, you failed.


Question. "Lb_m * g". how can you meaure 1 lb_m without gravety?


Interestingly, they do that! Or rather, they do it in orbit or in free
fall*, which is effectively the same thing.

On the International Space Station, they attach the mass to a spring
system. The frequency of oscillation allows them to determine the mass.

Here you go: https://www.youtube.com/watch?v=8rt3udip7l4

(* Free fall or stable orbit isn't exactly "without gravity" because
gravity is acting on the object. But since the object is accelerating
freely in response to gravity, it's effectively the same as if the
gravitational force were zero.)


Ah, I understand. So what you are really talking about is an object
falling without any resistance of the air... cause there ain't none
and feathers fall as fast as lumps of lead :-)

--

Cheers,

John B.
  #36  
Old October 13th 18, 04:02 AM posted to rec.bicycles.tech
John B. Slocomb
external usenet poster
 
Posts: 87
Default "torque wrench" pump/compressor

On Fri, 12 Oct 2018 22:21:58 -0400, Frank Krygowski
wrote:

On 10/12/2018 7:01 PM, John B. Slocomb wrote:
On Fri, 12 Oct 2018 11:08:06 -0400, Frank Krygowski
wrote:

On 10/12/2018 10:18 AM, Radey Shouman wrote:
John B. Slocomb writes:

On Thu, 11 Oct 2018 15:36:04 -0400, Frank Krygowski
wrote:

On 10/11/2018 1:53 PM, Theodore Heise wrote:
On Thu, 11 Oct 2018 09:27:02 -0700 (PDT),
Frank Krygowski wrote:
On Thursday, October 11, 2018 at 5:00:33 AM UTC-4, John B. Slocomb wrote:
On Thu, 11 Oct 2018 08:54:38 +0200, Emanuel Berg
wrote:

Just out of curiosity, is there a "torque wrench" pump or
compressor? I.e., you would screw on the presta valve, set
the gizmo to e.g. 35psi, engage it, and instead of watching
the indicator, automagically at the right level it would
stop?

Most of the gas stations here use an air station that you can
set for your desired pressure and then just plug the hose onto
the tire valve
- there is a little clamp to hold it there. When the tire is
inflated to the specified pressure the inflation stops and a
bell rings.

Since they aren't manufactured here I had assumed that the
rest of the world had them too.

My experience from 50+ years ago says not to rely on those
things, although I suppose they may be different now.

Back then I blew a tire off the rim with one. I suspect the
problem was the volume of each pumping stroke. In a large sized
car tire, the volume surge with each big stroke would be
absorbed and barely raise the pressure. In a low volume bike
tire, it caused an explosion. That's my guess anyway.

I usually inflate using a manual floor pump with a gage. It's
easy enough to stop pumping when the dial reads the desired
temperature.

Don't you mean, when the dial reads the desired foot-pounds?

Oh geez, my mistake!

But: Neither! I stop when it reads the desired PRESSURE!

Around here we use psi = pounds per square inch. Weirdly enough, my
pump's pressure gauge is also graduated in kg/cm^2. I would have used
that as a bad example in my courses, since kg is properly used to
measure mass, not force. And pressure is force per unit area.

(This indicates that the SI system gets misused as much as the U.S. or
Imperial system.)

But isn't "pound" a measurement of mass also :-?

As I used to explain it to students: Properly speaking, a _force_ is a
push or a pull on an object. Properly speaking, _mass_ is a measure of
the amount of matter in an object. _Weight_ is a particular force, i.e.
the force of gravity on an object.

So in a U.S. grocery if you buy 2.2 pounds of cheese, you're buying the
amount of cheese upon which the earth's gravity exerts a force of two
pounds. It's a roundabout way of specifying the mass you want, but it
works as long as you're just talking cheese, etc.

In a European country, you'd specify you wanted a kilogram of cheese,
which is about 2.2 pounds worth. There, you're directly specifying the
amount of cheese you want.

I think I must have been out of school for too long. How is 1 kilogram
which equates to approximately2.20462262185 pounds a different
measurement than pounds? Aren't they both a measurement of the effect
of gravity on a certain amount of stuff?


First, don't trouble yourself. For ordinary everyday stuff it doesn't
matter.

But at its heart, mass is not the same as weight. For a simple example,
if you took a 1 kg mass to the moon its mass would still be 1 kg. But
its weight would be about 1/6 of what it was on earth. And in the ISS
the observed weight or effective weight of that object would be zero.

Again, if you're just (say) buying cheese on the surface of the earth
the difference doesn't matter. If you don't keep it straight in
calculations involving dynamics - as in "how much tension will be on
this connecting rod?" - you're apt to get answers that are off by a
factor of 32. Or in an SI system country, off by a factor of 9.8 or so.


O.K. mass would be a factor in the acceleration of an object when a
force is applied to it.

--

Cheers,

John B.
 




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