On Thu, 16 Oct 2008 20:31:56 GMT, "Jerry"
wrote:


"Jeff Liebermann" wrote in message
.. .
On Thu, 16 Oct 2008 17:17:05 GMT, "Jerry"
wrote:

Will the taped end will not leak with 80 PSI air in the conduit?
Jerry KD6JDJ

Well, if it does leak, the sand above the duct tape will dribble down
into the 3/4" conduit creating a rather awkward clean up exercise.
That's why conduit runs usually terminate above the ground, not below.
The trick is to find the conduit end without blowing off the seal.

Hi Jeff
It may be of little interest to the OP, but the sand might have difficulty
leaking back into a conduit with air blowing out of it. In addition, the
air might leak from a small rupture below the oipen end of the conduit.
The OP may have no access to compressed air anyway.

Jerry KD6JDJ

Welcome to rec.radio.amateur.antenna.physics

Ok, let's do the math. Dry sand weighs 100 lb/cubic-foot. There's
about 1 ft of sand above the end of the 3/4" conduit. The weight
action is roughly conical, so the volume of sand involved is (my
guess) about:
100 lbs/ft^3 * 1/3 = 33 lbs of sand.
All that it acting on a 3/4" diameter pipe, with a cross sectional
area of about:
Pi * 0.75" = 2.4 in^2
Therefore, the pressure exerted by the sand is:
33 lbs / 2.4 in^2 = 14 PSI
So, if he can pressurize the pipe to more than 14 PSI, he can lift the
column of sand sufficiently to keep it from dribbling into the pipe.

Of course, it's not that simple. Laminar air flow, pressure gradients
across the conduit, and the effects of the duct tape will ruin my
simplistic guesswork. Worse, the back pressure created by the
immovable column of sand will force some sand particles into the
conduit around the edges with the "reflected" air pressure. In the
middle of the conduit, the air flow is all out of the conduit, but
near the edges, it could easily be the other direction. I'm also
assuming that the sand is a perfect air seal, which it's not. To
prevent all this from happening, the minimum air pressure should be
about twice the 14 PSI, which is easily achievable with an air
compressor, but not a vacuum cleaner.

I'm also trying to imagine how the process will work. I see an air
compressor pumping madly away as the neighbors kids furiously dig
around the resultant sand volcano, as sand rapidly refills the conical
hole. In my never humble opinion, there's no way to prevent sand from
dropping into the conduit if the duct tape seal is broken before
excavating the end of the conduit.

Once the sand is in the conduit, just blowing air through the pipe
isn't going to magically elevate the sand particles 1ft or more in the
air. The air does not have sufficient mass to convey enough momentum
to move the sand particles, much less eject them vertically. For
that, one needs a denser medium, such as water. Shoving a plunger
through might work, but it's equally likely to jam sand particles into
the PVC conduit walls.




--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Thu, 16 Oct 2008 13:57:44 -0700, Jeff Liebermann
wrote:

Worse, the back pressure created by the
immovable column of sand will force some sand particles into the
conduit around the edges with the "reflected" air pressure.

H E R E S Y

Reflected waves do NOT have power in them - or so goes the catechism.

This new and dangerous introduction of a side topic can only lead to
endless debate about the superposition phase properties of sand in
vacua (particel theories inhabiting the crevices in the science of
Equal Librium)

73's
Richard Clark, KB7QHC

On Thu, 16 Oct 2008 14:19:05 -0700, Richard Clark
wrote:

On Thu, 16 Oct 2008 13:57:44 -0700, Jeff Liebermann
wrote:

Worse, the back pressure created by the
immovable column of sand will force some sand particles into the
conduit around the edges with the "reflected" air pressure.

H E R E S Y

Hershey Bar (Chocolate Rules). Besides, following the orthodoxy lacks
entertainment value.

Reflected waves do NOT have power in them - or so goes the catechism.

This new and dangerous introduction of a side topic can only lead to
endless debate about the superposition phase properties of sand in
vacua (particel theories inhabiting the crevices in the science of
Equal Librium)

Yeah, but I like playing in the sand. Try this experiment next time
you have an air compressor and nozzle handy. Find a cardboard,
plastic or metal tube at least 3 ft long. A vacuum cleaner extension
pipe will suffice. Plug up the other end with whatever is handy. Blow
air into the center of the tube. Run your fingers around the edges of
the tube and note which way the air is flowing. That's what will
happen if the compressed air is not sufficient to blow 30 lbs of sand
into the air. The air and the sand will flow back into the pipe in
the opposite direction as the compressed air.

73's
Richard Clark, KB7QHC

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Thu, 16 Oct 2008 21:53:20 -0700, Jeff Liebermann
wrote:

Plug up the other end with whatever is handy. Blow
air into the center of the tube. Run your fingers around the edges of
the tube and note which way the air is flowing. That's what will
happen if the compressed air is not sufficient to blow 30 lbs of sand
into the air. The air and the sand will flow back into the pipe in
the opposite direction as the compressed air.

Hi Jeff,

Well, it's been a coon's age since I've seen vacuum cleaners that
would let me attach to their exhaust - so that's out.

As for driving compressed air into a short (or open). I've done that,
but not for sand excavation. Rather, I've used what was commercially
called the "vortex effect" which separates the two air current flows
you allude to above to create a hot stream and a chilled stream of
air. (Elevated or depressed from the average of the inlet
temperature.) I used this for cooling electronics in a paper mill.
Not particularly efficient, but compressed air was available, and the
VorTec nozzle was a quick and easy solution to their NEMA enclosures.

See:
http://www.vortec.com/support_casestudies.php
or
https://secure.vortec.com/store_prod...tID=9&prodID=6

This, and some of my fluidic applications constitute a specialized
niche in alternative logic systems. Notably, they all work off
principles of reflected power that demonstrate palpable examples.

73's
Richard Clark, KB7QHC

Richard Clark wrote:

Well, it's been a coon's age since I've seen vacuum cleaners that
would let me attach to their exhaust - so that's out.

Have you ever heard of a shop vacuum?

Usually only available at highly specialized stores such as Walmart.


--
Jim Pennino

Remove .spam.sux to reply.

On Fri, 17 Oct 2008 06:05:01 GMT, wrote:

Richard Clark wrote:

Well, it's been a coon's age since I've seen vacuum cleaners that
would let me attach to their exhaust - so that's out.

Have you ever heard of a shop vacuum?

Usually only available at highly specialized stores such as Walmart.

Hi Jim,

Unfortunately my shopping nature turns me more towards Fry's and I
certainly have very little interest in yet another vacuum cleaner (if
they offer them). Market forces long (decades) ago convinced me that
Hardware skills were in a declining employment segment in proportion
to software.

There may not be a software solution to this current problem of
locating a buried pipe, but I wouldn't have buried it without some
simple binary marker (it's here!). The analog solutions offered are
inventive, and I do appreciate them however. One or several are
probably far more effective than going to Walmart for a shop-vac (that
would only become a permanent altar attesting to my need to use it in
justification for its expense).

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Fri, 17 Oct 2008 06:05:01 GMT, wrote:

Richard Clark wrote:

Well, it's been a coon's age since I've seen vacuum cleaners that
would let me attach to their exhaust - so that's out.

Have you ever heard of a shop vacuum?

Usually only available at highly specialized stores such as Walmart.

Hi Jim,

Unfortunately my shopping nature turns me more towards Fry's and I
certainly have very little interest in yet another vacuum cleaner (if
they offer them). Market forces long (decades) ago convinced me that
Hardware skills were in a declining employment segment in proportion
to software.

There may not be a software solution to this current problem of
locating a buried pipe, but I wouldn't have buried it without some
simple binary marker (it's here!). The analog solutions offered are
inventive, and I do appreciate them however. One or several are
probably far more effective than going to Walmart for a shop-vac (that
would only become a permanent altar attesting to my need to use it in
justification for its expense).

73's
Richard Clark, KB7QHC

Everyone needs a shop vac, especially a wet and dry one.

Unless you really like spending a long time mopping floors.


--
Jim Pennino

Remove .spam.sux to reply.

On Thu, 16 Oct 2008 22:26:10 -0700, Richard Clark
wrote:

Well, it's been a coon's age since I've seen vacuum cleaners that
would let me attach to their exhaust - so that's out.

The problem with vacuum cleaners is that they all suck. I have an
ancient Electrolux and a Shop Vac that both have usable exhaust ports.
I also have a Hoover upright and a Hoover cannister in the office that
do not. Y'er right that it's a vanishing breed.

However, you re-read what I scribbled, you might notice that I
suggested that one use the air compressor to pressurize the 3/4" PVC
pipe. That's because the average vacuum cleaner can barely generate
more than a few PSI. They also leak badly. If you're trying to lift
a column of sand or demonstrate backpressure, it's much easier with a
proper air compressor.

As for driving compressed air into a short (or open). I've done that,
but not for sand excavation.

I have. The clumsy backhoe operator (me) once dropped a load of dirt
on top of the steel 3" conduit end during construction. I'm also the
idiot that forgot to shove a protective rag into the conduit end. I
spent the next two days trying to figure out how to get the dirt out
of the pipe. I eventually fabricated a cylinder shaped rubber plug
with an eyebolt down the center, dumped some water into the conduit,
and dragged the plug through the pipe with a winch. It took about 5
passes for the water to come out clear. I then pumped out the
remaining water, dragged a sponge through the pipe a few dozen times,
and then let evaporation do the final cleanup. Compressed air was
attempted just for fun, but it was obvious that it wasn't going to
lift the dirt out of the pipe.

Rather, I've used what was commercially
called the "vortex effect" which separates the two air current flows
you allude to above to create a hot stream and a chilled stream of
air. (Elevated or depressed from the average of the inlet
temperature.) I used this for cooling electronics in a paper mill.
Not particularly efficient, but compressed air was available, and the
VorTec nozzle was a quick and easy solution to their NEMA enclosures.

See:
http://www.vortec.com/support_casestudies.php
or
https://secure.vortec.com/store_prod...tID=9&prodID=6

Nice. I built several out of the original Amateur Scientist book
(which I still have on my bookshelf) in the early 1960's. It worked
amazingly well. Much later, I built one out of PVC pipe, which
melted. Now I know why they're made out of metal. Never mind the
inefficiency. It's the noise they make that drives me nuts. At one
point, we had 4 of them in series, with 4 assorted air compressors
pumping about 4 SCFM into each, and got it down to about -100C. We
started with a group of about 10 lab students, and ended up with a
crowd of about 100 nosey students wondering why someone was trying to
operate a jet engine on campus.

This, and some of my fluidic applications constitute a specialized
niche in alternative logic systems. Notably, they all work off
principles of reflected power that demonstrate palpable examples.

I'll pass. I don't believe in logic any more. Everything can be
explained in terms of politics, psychology, and conspriacies. Logic
is obsolete.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Fri, 17 Oct 2008 06:02:04 -0700, Jeff Liebermann
wrote:

However, you re-read what I scribbled, you might notice that I
suggested that one use the air compressor to pressurize the 3/4" PVC
pipe.

Hi Jeff,

I was responding to the broad assortment of methods which included
what was the closest option for me of a vacuum cleaner.

That's because the average vacuum cleaner can barely generate
more than a few PSI. They also leak badly. If you're trying to lift
a column of sand or demonstrate backpressure, it's much easier with a
proper air compressor.

No doubt and no argument. At one point in my career, I found myself
with a dead weight tester, calibrating a pressure gauge to 10,000 PSI
when the coupling line spit sending a fine spray of pressurized oil
past my face. Took me half an hour to shake off the thought of it
hitting me square.

As for driving compressed air into a short (or open). I've done that,
but not for sand excavation.

I have. The clumsy backhoe operator (me) once dropped a load of dirt
on top of the steel 3" conduit end during construction. I'm also the
idiot that forgot to shove a protective rag into the conduit end. I
spent the next two days trying to figure out how to get the dirt out
of the pipe. I eventually fabricated a cylinder shaped rubber plug
with an eyebolt down the center, dumped some water into the conduit,
and dragged the plug through the pipe with a winch. It took about 5
passes for the water to come out clear. I then pumped out the
remaining water, dragged a sponge through the pipe a few dozen times,
and then let evaporation do the final cleanup. Compressed air was
attempted just for fun, but it was obvious that it wasn't going to
lift the dirt out of the pipe.

I've done that too. For a summer of my youth (when dinosaurs ruled
the earth) I would plunge down a manhole with a tethered ball. I'd
plug it into the downhill side, clamber out, and fill the manhole with
water. Then go to the next manhole, clamber down and dig out all the
muck that had been plunged ahead of the tether ball. Repeat for
weeks.

Substituting one central phrase of "Apocalypse Now":
"The aroma of it all! The AROMA of it all!"

I'll pass. I don't believe in logic any more. Everything can be
explained in terms of politics, psychology, and conspriacies. Logic
is obsolete.

Last night I went to a reception for Joseph Stiglitz where he
mentioned being a liberal too much (he was apologizing to the group at
that point) and I drew him aside to comment that he had no need to
explain his bias as this was the first time in our political history
when we had two candidates BOTH running against the administration AND
the Republican Party. We laughed at that logic.

73's
Richard Clark, KB7QHC

On Fri, 17 Oct 2008 09:19:00 -0700, Richard Clark
wrote:

At one point in my career, I found myself
with a dead weight tester, calibrating a pressure gauge to 10,000 PSI
when the coupling line spit sending a fine spray of pressurized oil
past my face. Took me half an hour to shake off the thought of it
hitting me square.

Ouch. At that pressure, the first few drops of oil will give you an
instant tattoo. An acquaintance recently had that happen to him. He's
now recovering from the skin grafts and laser ablative cleanup.

The closest I came to that was getting a hydraulic fluid shower while
riding as an operator inside a Rose Float (in about 1968). The floats
animation was run by a pony engine and hydraulic pumps. The coupling
directly over me started to leak. After 2 hours in the float
lumbering through Pasadena, I arrived thoroughly soaked.
http://802.11junk.com/jeffl/pics/jeffl/slides/RoseFloat01.html
That's me testing the chair position (which was arc welded in place so
it had to be perfect). My feet are resting on top of the electrical
animation switching panel.

For a summer of my youth (when dinosaurs ruled
the earth) I would plunge down a manhole with a tethered ball. I'd
plug it into the downhill side, clamber out, and fill the manhole with
water. Then go to the next manhole, clamber down and dig out all the
muck that had been plunged ahead of the tether ball. Repeat for
weeks.

Well, I missed such fun when I was younger. I worked for the same
monopoly. While you were playing in the muck, I was "re-enforcing"
100 pair bundles and working in the battery room.

Substituting one central phrase of "Apocalypse Now":
"The aroma of it all! The AROMA of it all!"

These days, the installers doing FTTS (Fiber Through the Sewers) have
all the fun. Instead of summer interns, the dirty work is done by a
robot which installs a SAM (sewer access module):
http://www.kate-pmo.ch/pages/en/fast.html
Despite the robotics and improved handling, the packets delivered
still seem to smell of effluvia.

... as this was the first time in our political history
when we had two candidates BOTH running against the administration AND
the Republican Party. We laughed at that logic.

Chuckle. Very true. Worse, the "real" agendas of both parties are
almost identical. I noticed that both parties are also against the
status quo (which is generally considered awful). That makes me
wonder just what they are in favor of actually doing. I would prefer
they do absolutely nothing and let the economy fix itself, but that's
too much to hope for. Let the lesser evil win in Nov and never mind
trying to decode their logic.

I should feel guilty for encouraging this off topic discussion,
complete with topic drift, but I don't.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558