I have this gauge:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=250361252136

I put it on a wall to show pressure in my compressor tank (before
filter/regulator).

It works, however, it shows pressure about 25 PSI too low. It is very
easy to see, as the pointer arrow starts rising only some time after
the compressor starts pumping, and stays 25 PSI below the .

25 PSI seems to be a consistent difference regardless of pressure. In
other words, I just need to find some way to turn the arrow to point
to 25 PSI more and it will be accurate.

My obvious question is how are these gauges usually adjusted.
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On Feb 27, 9:51 am, Ignoramus27827 ignoramus27...@NOSPAM.
27827.invalid wrote:
I have this gauge:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=250361252136

I put it on a wall to show pressure in my compressor tank (before
filter/regulator).

It works, however, it shows pressure about 25 PSI too low. It is very
easy to see, as the pointer arrow starts rising only some time after
the compressor starts pumping, and stays 25 PSI below the .

25 PSI seems to be a consistent difference regardless of pressure. In
other words, I just need to find some way to turn the arrow to point
to 25 PSI more and it will be accurate.

My obvious question is how are these gauges usually adjusted.
--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

I have "adjusted" several gauges by dropping them. I can't say that I
would recommend this method.

CarlBoyd

On Feb 27, 9:51 am, Ignoramus27827 ignoramus27...@NOSPAM.
27827.invalid wrote:
My obvious question is how are these gauges usually adjusted.


All of the gauges I've adjusted (deliberately G) have followed the
same pattern.

1) you cannot "calibrate" most bourdon-tube gauges, except at a single
pressure -- that may be why it's 25psi off, or maybe not. The spring
quality of the tube is usually the only spring element, and its
tension is not readily adjustable. IF it has a separate balancing
spring, there may be room for doing some range adjustments.

2) you rotate the hand on the shaft to calibrate it. Sometimes that
involves loosening a hold-down screw that penetrates the hand;
sometimes the hand is held on by friction.

It almost always involves holding the pinion behind the face with some
sort of grasping tool so as not to over-stress the rack assembly.

LLoyd

On 2009-02-27, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
On Feb 27, 9:51 am, Ignoramus27827 ignoramus27...@NOSPAM.
27827.invalid wrote:
My obvious question is how are these gauges usually adjusted.


All of the gauges I've adjusted (deliberately G) have followed the
same pattern.

1) you cannot "calibrate" most bourdon-tube gauges, except at a single
pressure -- that may be why it's 25psi off, or maybe not. The spring
quality of the tube is usually the only spring element, and its
tension is not readily adjustable. IF it has a separate balancing
spring, there may be room for doing some range adjustments.

2) you rotate the hand on the shaft to calibrate it. Sometimes that
involves loosening a hold-down screw that penetrates the hand;
sometimes the hand is held on by friction.

It almost always involves holding the pinion behind the face with some
sort of grasping tool so as not to over-stress the rack assembly.

Lloyd, I just called Ashcroft, and they have someone who knows how to
support old brass gauges. (!)

That guy told me how to do it:

1) Put a little penetrating oil between the arrow hub and the shaft
2) Wait 1 day
3) Pull off the arrow carefully
4) Reinsert it at proper adjustment.

We did talk about linearity. At this point, it does not appear to me
that it has a linearity problem, but I will double check with a
notepad.

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On Fri, 27 Feb 2009 07:02:49 -0800 (PST), Carl
wrote:

On Feb 27, 9:51 am, Ignoramus27827 ignoramus27...@NOSPAM.
27827.invalid wrote:
I have this gauge:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=250361252136

I put it on a wall to show pressure in my compressor tank (before
filter/regulator).

It works, however, it shows pressure about 25 PSI too low. It is very
easy to see, as the pointer arrow starts rising only some time after
the compressor starts pumping, and stays 25 PSI below the .

25 PSI seems to be a consistent difference regardless of pressure. In
other words, I just need to find some way to turn the arrow to point
to 25 PSI more and it will be accurate.

My obvious question is how are these gauges usually adjusted.
--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

I have "adjusted" several gauges by dropping them. I can't say that I
would recommend this method.

CarlBoyd

I've seen a number of gauges with a tiny pinion tool to adjust the
needle, usually on higher end calibration gauges. The pinion has a
pilot which engages a hole in the needle, with the gear engaging a
gear on the retaining nut. I can't make out anything like that on
your gauge, but there does appear to be some sort of nut. The first
thing would be to determine how to get access to the front of the
gauge. Does the bezel screw off?

Pete Keillor

On Feb 27, 9:51*am, Ignoramus27827 ignoramus27...@NOSPAM.
27827.invalid wrote:
I have this gauge:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=250361252136

I put it on a wall to show pressure in my compressor tank (before
filter/regulator).

It works, however, it shows pressure about 25 PSI too low. It is very
easy to see, as the pointer arrow starts rising only some time after
the compressor starts pumping, and stays 25 PSI below the .

25 PSI seems to be a consistent difference regardless of pressure. In
other words, I just need to find some way to turn the arrow to point
to 25 PSI more and it will be accurate.

My obvious question is how are these gauges usually adjusted.
--


Is it possible the gauge is not calibrated in PSI? I have a similar
gauge and it reads in "feet of water"
feet of water * 0.4335 = PSI.
40 feet* 0.4335=17.3 psi 40psi?-17.3psi=22.7psi (approximately 25)

Cool gauge either way.
Good luck,
Andy

--Next time you have a gauge you want to test you might want to
build one of these: http://www.nmpproducts.com/tester.htm
I've found it to be tremendously useful and I take it on 'road
trips' to steam events so's others can check their gauges.

--
"Steamboat Ed" Haas : Politics is a sinkhole for
Hacking the Trailing Edge! : people without hobbies...
www.nmpproducts.com
---Decks a-wash in a sea of words---

"Ignoramus27827" wrote: ( clip) That guy told me how to do it:
clip) 3) Pull off the arrow carefully (clip)
^^^^^^^^^^^^^^^^^^^^
^^^^^^^^^^^^^^^^^^^
There are pullers for this job. If you don't have one, can't find one or
don't want to buy one, you could make it. Attach a couple of hooks to a
nut. Grind down a screw to go in the nut that fits into the hole in the
hand-hub.

On 2009-02-27, Leo Lichtman wrote:

"Ignoramus27827" wrote: ( clip) That guy told me how to do it:
clip) 3) Pull off the arrow carefully (clip)
^^^^^^^^^^^^^^^^^^^^
^^^^^^^^^^^^^^^^^^^
There are pullers for this job. If you don't have one, can't find one or
don't want to buy one, you could make it. Attach a couple of hooks to a
nut. Grind down a screw to go in the nut that fits into the hole in the
hand-hub.

Yes, the guy told me that there are pullers for this. I will make
something along the lines that you suggest. Will weld something during
the TIG class tomorrow.

i


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Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
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"Ignoramus27827" wrote in message
...
I have this gauge:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=250361252136

I put it on a wall to show pressure in my compressor tank (before
filter/regulator).

It works, however, it shows pressure about 25 PSI too low. It is very
easy to see, as the pointer arrow starts rising only some time after
the compressor starts pumping, and stays 25 PSI below the .

25 PSI seems to be a consistent difference regardless of pressure. In
other words, I just need to find some way to turn the arrow to point
to 25 PSI more and it will be accurate.

My obvious question is how are these gauges usually adjusted.
--

Not to discount the other excellent ideas, but often times gauges displaying
this kind of behavior have simply been spiked. When they are, the pinion has
ran off the end of the rack and skipped one or more teeth. It's necessary to
reset the pinion, or you loose reference to any springs in the mechanism.

Carefully see if you can gently wind the pinion to the end of the rack, and
reset it. It might be helpful to pressure the gauge almost to the limit
while you work on it, to avoid unnecessary stress on the components while
you do so.

Can't be certain, but something else you might consider.

On 2009-02-27, Elliot G wrote:

"Ignoramus27827" wrote in message
...
I have this gauge:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=250361252136

I put it on a wall to show pressure in my compressor tank (before
filter/regulator).

It works, however, it shows pressure about 25 PSI too low. It is very
easy to see, as the pointer arrow starts rising only some time after
the compressor starts pumping, and stays 25 PSI below the .

25 PSI seems to be a consistent difference regardless of pressure. In
other words, I just need to find some way to turn the arrow to point
to 25 PSI more and it will be accurate.

My obvious question is how are these gauges usually adjusted.
--

Not to discount the other excellent ideas, but often times gauges displaying
this kind of behavior have simply been spiked.

What do you mean by spiked?

When they are, the pinion has ran off the end of the rack and
skipped one or more teeth. It's necessary to reset the pinion, or
you loose reference to any springs in the mechanism.

Carefully see if you can gently wind the pinion to the end of the rack, and
reset it. It might be helpful to pressure the gauge almost to the limit
while you work on it, to avoid unnecessary stress on the components while
you do so.

Can't be certain, but something else you might consider.

I guess I do not really know how these gauges are build, so I cannot
quite visualize what you say, but I think that I have some idea.

--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
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posting on Usenet.
http://improve-usenet.org/

Spiking is when someone cracks a valve to fast, the inrush of pressure
spins the needle past the pressure limit. It's usually operator error,
equipment error usually takes other things out.

Ignoramus27827 wrote:
On 2009-02-27, Elliot G wrote:
"Ignoramus27827" wrote in message
...
I have this gauge:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=250361252136

I put it on a wall to show pressure in my compressor tank (before
filter/regulator).

It works, however, it shows pressure about 25 PSI too low. It is very
easy to see, as the pointer arrow starts rising only some time after
the compressor starts pumping, and stays 25 PSI below the .

25 PSI seems to be a consistent difference regardless of pressure. In
other words, I just need to find some way to turn the arrow to point
to 25 PSI more and it will be accurate.

My obvious question is how are these gauges usually adjusted.
--
Not to discount the other excellent ideas, but often times gauges displaying
this kind of behavior have simply been spiked.

What do you mean by spiked?

When they are, the pinion has ran off the end of the rack and
skipped one or more teeth. It's necessary to reset the pinion, or
you loose reference to any springs in the mechanism.

Carefully see if you can gently wind the pinion to the end of the rack, and
reset it. It might be helpful to pressure the gauge almost to the limit
while you work on it, to avoid unnecessary stress on the components while
you do so.

Can't be certain, but something else you might consider.

I guess I do not really know how these gauges are build, so I cannot
quite visualize what you say, but I think that I have some idea.

On Feb 27, 1:51*pm, Ignoramus27827 ignoramus27...@NOSPAM.
27827.invalid wrote:
On 2009-02-27, Elliot G wrote:





"Ignoramus27827" wrote in message
m...
I have this gauge:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=250361252136

I put it on a wall to show pressure in my compressor tank (before
filter/regulator).

It works, however, it shows pressure about 25 PSI too low. It is very
easy to see, as the pointer arrow starts rising only some time after
the compressor starts pumping, and stays 25 PSI below the .

25 PSI seems to be a consistent difference regardless of pressure. In
other words, I just need to find some way to turn the arrow to point
to 25 PSI more and it will be accurate.

My obvious question is how are these gauges usually adjusted.
--

Not to discount the other excellent ideas, but often times gauges displaying
this kind of behavior have simply been spiked.

What do you mean by spiked?

When they are, the pinion has ran off the end of the rack and
skipped one or more teeth. It's necessary to reset the pinion, or
you loose reference to any springs in the mechanism.

Carefully see if you can gently wind the pinion to the end of the rack, and
reset it. It might be helpful to pressure the gauge almost to the limit
while you work on it, to avoid unnecessary stress on the components while
you do so.

Can't be certain, but something else you might consider.

I guess I do not really know how these gauges are build, so I cannot
quite visualize what you say, but I think that I have some idea.

--
* *Due to extreme spam originating from Google Groups, and their inattention
* * * to spammers, I and many others block all articles originating
* * * *from Google Groups. If you want your postings to be seen by
* * * * *more readers you will need to find a different means of
* * * * * * * * * * * *posting on Usenet.
* * * * * * * * * *http://improve-usenet.org/

I'll guess-

Either gauge has seen a pressure large enough that not only did the
needle reach, it exceeded full-scale,
-or-
the pressure to the gauge didn't exceed the gauge's max pressure, but
the pressure ramped up so quick that once all the bits were moving,
momentum carried the pieces beyond the applied pressure and their
normal range.


Dave

"Ignoramus27827" wrote: What do you mean by spiked?
^^^^^^^^^^^^^^^^^^^^
The bourdon tube has a curved rack at the end, (a part of a gear) which is
meshed to a pinion on the needle shaft, If the gauge is over-pressured, it
is possible for the pinion to rotate past the proper mesh by clicking on the
last tooth of the rack, sort of like a ratchet. It may be that one tooth
produces a 25 psi error--or maybe 2 teeth, or n teeth. This would produce
the kind of "suppressed zero" and constant error you are seeing.

That's probably what Eliot means by "spiked." This is a very good comment.
If you rotate the needle slightly past full scale with your finger you will
start to get clicks. If you do this carefully, one click at a time, you may
be able to reset it without pulling the needle.

"Leo Lichtman" wrote in message
...

"Ignoramus27827" wrote: What do you mean by spiked?
^^^^^^^^^^^^^^^^^^^^
The bourdon tube has a curved rack at the end, (a part of a gear) which is
meshed to a pinion on the needle shaft, If the gauge is over-pressured,
it is possible for the pinion to rotate past the proper mesh by clicking
on the last tooth of the rack, sort of like a ratchet. It may be that one
tooth produces a 25 psi error--or maybe 2 teeth, or n teeth. This would
produce the kind of "suppressed zero" and constant error you are seeing.

That's probably what Eliot means by "spiked." This is a very good
comment. If you rotate the needle slightly past full scale with your
finger you will start to get clicks. If you do this carefully, one click
at a time, you may be able to reset it without pulling the needle.


Exactly.

Iggy, once you have removed the cover it will become clear. By carefully
exercising the gauge, and examine the design, you should be able to tell if
over pressuring the gauge COULD cause this. You can also count the pinion
teeth and compare it to the face, and see if one tooth might cause a 25 psi
error. You can also consider the direction of rotation of the pinion as
pressure increases, and consider of over pressure would cause a plus, or
minus error.

If the answer to these questions are all, YES. Then I would bet that is the
problem. Further, most gauges have a very gentle spring that needs to stay
in sync with it's overall calibration. If this is the problem, and you
correct it by removing and remounting the needle, it could forever affect
accuracy. Also, depending on the gauge and your level of caution, it might
be easier and less risky to reset the pinion as well.

More than anything be EXTREMELY gentle. Bending an of the components can be
instantly fatal. Treat it like a live butterfly.