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Silca pump gauge repair how-to



 
 
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  #1  
Old September 1st 16, 06:08 AM posted to rec.bicycles.tech
Tim McNamara
external usenet poster
 
Posts: 6,945
Default Silca pump gauge repair how-to

My 20+ year old Silca Super Pista pump has, for the first time,
malfunctioned and needs repair. A few weeks ago I found a little
machine screw on the floor; not knowin gwhat it was, I put it on my
workbench. Today I discovered my Silca pump gauge wasn't reading
correctly. The needle will not return to zero. Indeed, tapping the
pump on the floor lightly caused the needle to bounce upwards rather
than down and it is now resting against the pin but on the wrong side.
I discovered that the screw I found is one of the two on the back of the
gauge. I can't find repair instructions online readily, so I figured
that someone where would know what to do. The pump seems to work fine
otherwise. Silca sells replacement gauges for $22, if it comes to that,
although I suspect it's a standard gauge that can be obtained elsewhere.
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  #2  
Old September 1st 16, 09:29 AM posted to rec.bicycles.tech
John B.[_6_]
external usenet poster
 
Posts: 2,202
Default Silca pump gauge repair how-to

On Thu, 01 Sep 2016 00:08:31 -0500, Tim McNamara
wrote:

My 20+ year old Silca Super Pista pump has, for the first time,
malfunctioned and needs repair. A few weeks ago I found a little
machine screw on the floor; not knowin gwhat it was, I put it on my
workbench. Today I discovered my Silca pump gauge wasn't reading
correctly. The needle will not return to zero. Indeed, tapping the
pump on the floor lightly caused the needle to bounce upwards rather
than down and it is now resting against the pin but on the wrong side.
I discovered that the screw I found is one of the two on the back of the
gauge. I can't find repair instructions online readily, so I figured
that someone where would know what to do. The pump seems to work fine
otherwise. Silca sells replacement gauges for $22, if it comes to that,
although I suspect it's a standard gauge that can be obtained elsewhere.


My experience with repairing gauges has not been wholly satisfactory
mainly because conventional Bourdon Tube gauges usually have
adjustment devices and without a gauge testing service one never knows
whether the repaired gauge is even close to accurate.

If your pump looks like
https://silca.cc/products/silca-supe...iant=902502277
then physically fitting a new gauge shouldn't be a problem.

Common 0 - 200 psi air gauges are cheap as dirt, perhaps $5.00. But, a
gauge with a certified accuracy, maybe 2.5%, may be a bit costly, say
$22.59 :-)

See:
http://tinyurl.com/h3sh6nd
for more information.

--
cheers,

John B.

  #3  
Old September 1st 16, 01:55 PM posted to rec.bicycles.tech
AMuzi
external usenet poster
 
Posts: 13,447
Default Silca pump gauge repair how-to

On 9/1/2016 12:08 AM, Tim McNamara wrote:
My 20+ year old Silca Super Pista pump has, for the first time,
malfunctioned and needs repair. A few weeks ago I found a little
machine screw on the floor; not knowin gwhat it was, I put it on my
workbench. Today I discovered my Silca pump gauge wasn't reading
correctly. The needle will not return to zero. Indeed, tapping the
pump on the floor lightly caused the needle to bounce upwards rather
than down and it is now resting against the pin but on the wrong side.
I discovered that the screw I found is one of the two on the back of the
gauge. I can't find repair instructions online readily, so I figured
that someone where would know what to do. The pump seems to work fine
otherwise. Silca sells replacement gauges for $22, if it comes to that,
although I suspect it's a standard gauge that can be obtained elsewhere.


Unless it was badly smacked around, replace the screw,
tighten both of them (moderately, you're threading into a
brass block). If needed, lift the needle off and press it
back at the zero position. Try not to bend/move/alter the
bourdon tube[1] or its linkage in any way.

Now is a good time to check/tighten the two screws on the
very bottom as they work loose over years of use. You might
also remove the checkvalve and clear out any crud, a common
service issue on these.

[1] looks like a brass tortellini with soldered seams.

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


  #4  
Old September 1st 16, 02:50 PM posted to rec.bicycles.tech
JBeattie
external usenet poster
 
Posts: 5,870
Default Silca pump gauge repair how-to

On Thursday, September 1, 2016 at 1:29:29 AM UTC-7, John B. wrote:
On Thu, 01 Sep 2016 00:08:31 -0500, Tim McNamara
wrote:

My 20+ year old Silca Super Pista pump has, for the first time,
malfunctioned and needs repair. A few weeks ago I found a little
machine screw on the floor; not knowin gwhat it was, I put it on my
workbench. Today I discovered my Silca pump gauge wasn't reading
correctly. The needle will not return to zero. Indeed, tapping the
pump on the floor lightly caused the needle to bounce upwards rather
than down and it is now resting against the pin but on the wrong side.
I discovered that the screw I found is one of the two on the back of the
gauge. I can't find repair instructions online readily, so I figured
that someone where would know what to do. The pump seems to work fine
otherwise. Silca sells replacement gauges for $22, if it comes to that,
although I suspect it's a standard gauge that can be obtained elsewhere.


My experience with repairing gauges has not been wholly satisfactory
mainly because conventional Bourdon Tube gauges usually have
adjustment devices and without a gauge testing service one never knows
whether the repaired gauge is even close to accurate.

If your pump looks like
https://silca.cc/products/silca-supe...iant=902502277
then physically fitting a new gauge shouldn't be a problem.

Common 0 - 200 psi air gauges are cheap as dirt, perhaps $5.00. But, a
gauge with a certified accuracy, maybe 2.5%, may be a bit costly, say
$22.59 :-)

See:
http://tinyurl.com/h3sh6nd
for more information.


I've used a variety of cheap replacement gauges, including Serfas and some generics. A model from Grainger used to be recommended back in the day. But . . . $20 is not a ton of money, and it is nice keeping the Silca pumps reasonably OE.

I look forward to hearing if Tim can get the needle reading correctly again. Jobst hypothesized that this problem occurred due to over-pressure when the presta valve stuck shut and air backed up into the pump rather than going into the tire.

-- Jay Beattie


  #5  
Old September 1st 16, 05:17 PM posted to rec.bicycles.tech
Tim McNamara
external usenet poster
 
Posts: 6,945
Default Silca pump gauge repair how-to

On Thu, 01 Sep 2016 07:55:04 -0500, AMuzi wrote:
On 9/1/2016 12:08 AM, Tim McNamara wrote:
My 20+ year old Silca Super Pista pump has, for the first time,
malfunctioned and needs repair. A few weeks ago I found a little
machine screw on the floor; not knowin gwhat it was, I put it on my
workbench. Today I discovered my Silca pump gauge wasn't reading
correctly. The needle will not return to zero. Indeed, tapping the
pump on the floor lightly caused the needle to bounce upwards rather
than down and it is now resting against the pin but on the wrong
side. I discovered that the screw I found is one of the two on the
back of the gauge. I can't find repair instructions online readily,
so I figured that someone where would know what to do. The pump
seems to work fine otherwise. Silca sells replacement gauges for
$22, if it comes to that, although I suspect it's a standard gauge
that can be obtained elsewhere.


Unless it was badly smacked around, replace the screw, tighten both of
them (moderately, you're threading into a brass block). If needed,
lift the needle off and press it back at the zero position. Try not to
bend/move/alter the bourdon tube[1] or its linkage in any way.

Now is a good time to check/tighten the two screws on the very bottom
as they work loose over years of use. You might also remove the
checkvalve and clear out any crud, a common service issue on these.


Well, putting the screw back in was easy. I popped the plastic bezel
off, reset the pointer to rest against the stop, put the bezel back on
and tried pumping up a tire. The pump seems to work fine and to read
fairly accurately. 105 PSI on the Silca gauge corresponded to 102 PSI
on another hand-held gauge that I have. Of course I don't know the
absolute calibration of either and those two gauges have never perfectly
matched anyway; about the same as this.

While I was at it, I cleaned out the check valve which appeared to have
a couple of cat hairs stuck in it and popped out the plunger to spread
the leather out a smidge as it seemed a little loose in the tube. Pump
seems to be happy now, I have today and tomorow off in advance of Labor
Day weekend and the weather is absolutely freaking gorgeous, so time to
pump up the tires and go for a bike ride!

Thanks!
  #6  
Old September 1st 16, 06:39 PM posted to rec.bicycles.tech
Jeff Liebermann
external usenet poster
 
Posts: 4,018
Default Silca pump gauge repair how-to

On Thu, 01 Sep 2016 15:29:25 +0700, John B.
wrote:

My experience with repairing gauges has not been wholly satisfactory
mainly because conventional Bourdon Tube gauges usually have
adjustment devices and without a gauge testing service one never knows
whether the repaired gauge is even close to accurate.


Adjusting the typical bourdon tube gauge is difficult, but not
impossible. In general, if there's internal damage, it's easier and
better to replace the gauge. If you're lucky and the gauge has a zero
adjust, then just turn the screw and it should return to zero. Most
small diameter gauges, as found on a bicycle pump, lack easily
accessible adjustments.

Checking the calibration is easy, but you will need to have a known
good pressure gauge available. I built a brass manifold with two
Schrader valves, a Schrader to Presta valve adapter, and a 0-100 lb
digital pressure gauge. If you don't want to buy an accurate pressure
gauge, just install another valve stem and use a known good floor
pump. Then, all you do is pump the tire pump to a value that's in
your operating range, and compare readings between the reference gauge
and your floor pump.

However, that's probably overkill. Just take two Schrader valve stems
(see below) and attach them together with a 1/4NPT female to female
coupler. Do NOT insert the valves into the stems. Attach two tire
pumps. Pump up either pump and compare gauge readings.

If you need Presta, use an adapter. If you hate adapters, glue two
Presta valve stems together[1].

I'll post a photo when I find mine, but really, it's quite simple to
build.

Brass manifold or tee from the plumbing section of the hardware store.
http://www.provacusa.com/assets/images/4waymanifold.jpg
https://img4.fastenal.com/productimages/440107-131280.jpg

Two gas line pressure test fittings with Shrader valve stems.
https://www.spudtech.com/images/products/airfill.jpg

Schrader to Presta adapter (required if you have a Presta only pump).
http://www.cantitoeroad.com/Valve-Adapter--Schrader-to-Presta_p_263.html

Accurate gauge:
https://www.google.com/search?q=digital+pressure+gauge+1/4+npt&tbm=isch
If you don't like the astronomical prices, something more modest.
https://www.google.com/search?tbm=isch&q=+pressure+gauge+1%2F4+npt


[1]. Careful with this glue method as it could blow apart at high
pressures. Just be VERY careful with the glue job or maybe build a
brass "cage" for the stems using two brass washers and some careful
soldering.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #7  
Old September 2nd 16, 03:57 AM posted to rec.bicycles.tech
Jeff Liebermann
external usenet poster
 
Posts: 4,018
Default Silca pump gauge repair how-to

On Thu, 01 Sep 2016 10:39:59 -0700, Jeff Liebermann
wrote:

I'll post a photo when I find mine, but really, it's quite simple to
build.


I decided it was easier to build a new bicycle pump pressure gauge
comparator contraption than to remember whom I loaned it to[1]:
http://www.11junk.com/jeffl/pics/bicycles/misc/slides/Bicycle%20pump%20pressure%20gauge.html
Those are 2 Schrader bicycle valves masquerading as gas line pressure
test fitting:
https://www.plumbingsupply.com/testing.html#testgauge
and a generic pressure gauge. All the fittings are 1/4" NPT. However,
the prices were a bit high at the local Ace Hardware store. $10 for
the gauge, $5/ea for the valves, and $8 for the Tee. Ouch.

It could have been built without the Tee and only one Schrader valve
head. To do that, you could just buy the above gas pipe test kit, and
plug up the pipe hole with a 3/4" NPT plug. However, I want to also
use it to compare two pump gauges, measure the pressure using an
external pressure source, and possibly install a small surge tank in
order to obtain more accurate pressure readings. Those all require
the 2nd fitting.

I previously mumbled something about removing the valves. Don't
bother. The pump head will hold the valve open. Also, my Blackburn
floor pump has a head with requires that the center pin in the head be
pushed inward, or the Presta side of the pump head will leak air.

Testing was easy. I just pushed down on the floor pump while watching
both gauges. There both read identically. Since the volume of this
affair is smaller than the volume of one pump stroke, this test is
rather quick and mostly effortless.

None of this will do anything to repair a broken gauge, but should be
quite adequate for testing any repairs or adjustments.


[1] I just realized that this is the 4th or 5th one of these that
I've built. I gotta learn to stop loaning them to friends.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #8  
Old September 2nd 16, 06:48 AM posted to rec.bicycles.tech
John B.[_6_]
external usenet poster
 
Posts: 2,202
Default Silca pump gauge repair how-to

On Thu, 01 Sep 2016 10:39:59 -0700, Jeff Liebermann
wrote:

On Thu, 01 Sep 2016 15:29:25 +0700, John B.
wrote:

My experience with repairing gauges has not been wholly satisfactory
mainly because conventional Bourdon Tube gauges usually have
adjustment devices and without a gauge testing service one never knows
whether the repaired gauge is even close to accurate.


Adjusting the typical bourdon tube gauge is difficult, but not
impossible. In general, if there's internal damage, it's easier and
better to replace the gauge. If you're lucky and the gauge has a zero
adjust, then just turn the screw and it should return to zero. Most
small diameter gauges, as found on a bicycle pump, lack easily
accessible adjustments.

Checking the calibration is easy, but you will need to have a known
good pressure gauge available. I built a brass manifold with two
Schrader valves, a Schrader to Presta valve adapter, and a 0-100 lb
digital pressure gauge. If you don't want to buy an accurate pressure
gauge, just install another valve stem and use a known good floor
pump. Then, all you do is pump the tire pump to a value that's in
your operating range, and compare readings between the reference gauge
and your floor pump.


But how do you know that the calibration gauge is reading correctly?
Or your digital gauge, for that matter. A proper testing station will
include a dead weight tester to calibrate the calibration gauge(s) :-)


However, that's probably overkill. Just take two Schrader valve stems
(see below) and attach them together with a 1/4NPT female to female
coupler. Do NOT insert the valves into the stems. Attach two tire
pumps. Pump up either pump and compare gauge readings.

If you need Presta, use an adapter. If you hate adapters, glue two
Presta valve stems together[1].

I'll post a photo when I find mine, but really, it's quite simple to
build.

Brass manifold or tee from the plumbing section of the hardware store.
http://www.provacusa.com/assets/images/4waymanifold.jpg
https://img4.fastenal.com/productimages/440107-131280.jpg

Two gas line pressure test fittings with Shrader valve stems.
https://www.spudtech.com/images/products/airfill.jpg

Schrader to Presta adapter (required if you have a Presta only pump).
http://www.cantitoeroad.com/Valve-Adapter--Schrader-to-Presta_p_263.html

Accurate gauge:
https://www.google.com/search?q=digital+pressure+gauge+1/4+npt&tbm=isch
If you don't like the astronomical prices, something more modest.
https://www.google.com/search?tbm=isch&q=+pressure+gauge+1%2F4+npt


[1]. Careful with this glue method as it could blow apart at high
pressures. Just be VERY careful with the glue job or maybe build a
brass "cage" for the stems using two brass washers and some careful
soldering.

--
cheers,

John B.

  #9  
Old September 2nd 16, 05:05 PM posted to rec.bicycles.tech
Jeff Liebermann
external usenet poster
 
Posts: 4,018
Default Silca pump gauge repair how-to

On Fri, 02 Sep 2016 12:48:18 +0700, John B.
wrote:

But how do you know that the calibration gauge is reading correctly?
Or your digital gauge, for that matter. A proper testing station will
include a dead weight tester to calibrate the calibration gauge(s) :-)


Use The Force(tm) Luke!

It's actually quite easy. I drag myself over to the local
multiversity, prostate myself before the keeper of the calibration
lab, beg forgiveness for previous equipment damage, issue the required
bribe, and calibrate the indicated reading of my gauge against one of
their dead weight pressure tester:
https://www.google.com/search?q=pressure+calibrator&tbm=isch
I discovered that some of my cheap gauges exhibit some hysteresis
making calibration more difficult:
https://www.dwyer-inst.com/articles/industry/powderbulk/understanding-pressure-sensor-accuracy/understanding-pressure-sensor-accuracy.cfm
My piezo digital gauge doesn't have the problem.

Once I have a calibrated gauge, the rest of my gauges and pumps are
calibrate against it, usually just at key reference points, which
coincide with my favorite pressure settings for my various tires.

Hint: Don't use an automotive oil pressure gauge or sensor. They do
work and are very rugged, but they have horrible accuracy and
linearity problems. They also respond very slowly to changes in
pressure.

I wonder if the LBS could use this as a draw for the local cyclists.
Free bicycle pump gauge calibration. Bring in the pump, we supply the
equipment, and you do all the work. I suspect a fair number of pump
gauges have problems.
https://www.google.com/search?q=bicycle+pump+pressure+calibration

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #10  
Old September 3rd 16, 01:32 AM posted to rec.bicycles.tech
John B.[_6_]
external usenet poster
 
Posts: 2,202
Default Silca pump gauge repair how-to

On Fri, 02 Sep 2016 09:05:14 -0700, Jeff Liebermann
wrote:

On Fri, 02 Sep 2016 12:48:18 +0700, John B.
wrote:

But how do you know that the calibration gauge is reading correctly?
Or your digital gauge, for that matter. A proper testing station will
include a dead weight tester to calibrate the calibration gauge(s) :-)


Use The Force(tm) Luke!

It's actually quite easy. I drag myself over to the local
multiversity, prostate myself before the keeper of the calibration
lab, beg forgiveness for previous equipment damage, issue the required
bribe, and calibrate the indicated reading of my gauge against one of
their dead weight pressure tester:
https://www.google.com/search?q=pressure+calibrator&tbm=isch
I discovered that some of my cheap gauges exhibit some hysteresis
making calibration more difficult:
https://www.dwyer-inst.com/articles/industry/powderbulk/understanding-pressure-sensor-accuracy/understanding-pressure-sensor-accuracy.cfm
My piezo digital gauge doesn't have the problem.

Once I have a calibrated gauge, the rest of my gauges and pumps are
calibrate against it, usually just at key reference points, which
coincide with my favorite pressure settings for my various tires.

Hint: Don't use an automotive oil pressure gauge or sensor. They do
work and are very rugged, but they have horrible accuracy and
linearity problems. They also respond very slowly to changes in
pressure.

I wonder if the LBS could use this as a draw for the local cyclists.
Free bicycle pump gauge calibration. Bring in the pump, we supply the
equipment, and you do all the work. I suspect a fair number of pump
gauges have problems.
https://www.google.com/search?q=bicycle+pump+pressure+calibration


:-)
My experience is that most of the small cheap gauges do have errors,
but I would also guess that the average cyclists doesn't actually
care. My guess is that the average guy pumps the tires up to a number
between the big number and the little number embossed on the tire wall
and rides away contented.

At least, even here, there was sufficient discussion when the subject
came up to show, I believe that even the elite riders really aren't
really that knowledgeable about the effects of tire pressure.

But having said that, snake bite flats aside, what is the actual
importance of tire pressure? What will be the actual (not calculated)
difference in time for a, say 10 mile TT, with 10 psi more or less
pressure in the tires?
--
cheers,

John B.

 




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