Some interesting (if ugly!) pictures of a blown compressor tank over on
the yesterday's tractor site
http://www.tractorshed.com/cgi-bin/g...uble/r1956.jpg
http://www.tractorshed.com/cgi-bin/g...uble/r1957.jpg
http://www.tractorshed.com/cgi-bin/g...uble/r1959.jpg

If those links don't work try the pictures without text:
http://www.tractorshed.com/gallery/trouble/r1956.jpg
http://www.tractorshed.com/gallery/trouble/r1957.jpg
http://www.tractorshed.com/gallery/trouble/r1959.jpg

A good reminder to drain your tank regularly.

RoyJ wrote:
Some interesting (if ugly!) pictures of a blown compressor tank over
on the yesterday's tractor site
http://www.tractorshed.com/cgi-bin/g...uble/r1956.jpg
http://www.tractorshed.com/cgi-bin/g...uble/r1957.jpg
http://www.tractorshed.com/cgi-bin/g...uble/r1959.jpg

If those links don't work try the pictures without text:
http://www.tractorshed.com/gallery/trouble/r1956.jpg
http://www.tractorshed.com/gallery/trouble/r1957.jpg
http://www.tractorshed.com/gallery/trouble/r1959.jpg

A good reminder to drain your tank regularly.

No over pressure safety valve I take it?

Ken.

--
Volunteer your idle computer time for cancer research
http//www.grid.org/download/gold/download.htm
Return address courtesy of Spammotel http://www.spammotel.com/

"RoyJ" wrote

A good reminder to drain your tank regularly.

I don't see a lot of rust or corrosion. Even looks shiny.

Steve

"Steve B" wrote in message
news:zUccg.27219$QP4.4329@fed1read12...

"RoyJ" wrote

A good reminder to drain your tank regularly.

I don't see a lot of rust or corrosion. Even looks shiny.

Steve


Might just be fatigue cracking. Remember the "convertible" 737 that
Hawaiian Airlines had?

Steve.

"SteveF" wrote in message
. ..

"Steve B" wrote in message
news:zUccg.27219$QP4.4329@fed1read12...

"RoyJ" wrote

A good reminder to drain your tank regularly.

I don't see a lot of rust or corrosion. Even looks shiny.

Steve


Might just be fatigue cracking. Remember the "convertible" 737 that
Hawaiian Airlines had?

Steve.



Correction - Aloha Airlines.

Steve.

I saw a program about that and they mentioned that a large part of the
problem was due to debonding of the adhesive so the rivets took all the
load which wasn't intended. It was mentioned that Boeing tightened
their procedures for the conditions under which the bonding took place
after those early planes were made and Aloha hadn't been carrying out
the checks properly to detect telltales signs of the problem.

Its something I consider when I see people querying about bonding car
panels and what conditions they are done under. Temperature, humidity,
surface prep can have a critical effect.

SteveF wrote:

"Steve B" wrote in message
news:zUccg.27219$QP4.4329@fed1read12...

"RoyJ" wrote

A good reminder to drain your tank regularly.

I don't see a lot of rust or corrosion. Even looks shiny.

Steve


Might just be fatigue cracking. Remember the "convertible" 737 that
Hawaiian Airlines had?

Steve.

I think you missed the text in the first picture "when the regulator
stuck causing the tank to rupture".
This isn't being offered as a case of rust (but you should still drain
the tank).

Steve

RoyJ wrote:

Some interesting (if ugly!) pictures of a blown compressor tank over
on the yesterday's tractor site
http://www.tractorshed.com/cgi-bin/g...uble/r1956.jpg

http://www.tractorshed.com/cgi-bin/g...uble/r1957.jpg

http://www.tractorshed.com/cgi-bin/g...uble/r1959.jpg


If those links don't work try the pictures without text:
http://www.tractorshed.com/gallery/trouble/r1956.jpg
http://www.tractorshed.com/gallery/trouble/r1957.jpg
http://www.tractorshed.com/gallery/trouble/r1959.jpg

A good reminder to drain your tank regularly.

Should be a safety relief valve on the back side of the manifold.

Steve Smith wrote:
I think you missed the text in the first picture "when the regulator
stuck causing the tank to rupture".
This isn't being offered as a case of rust (but you should still drain
the tank).

Steve

RoyJ wrote:

Some interesting (if ugly!) pictures of a blown compressor tank over
on the yesterday's tractor site
http://www.tractorshed.com/cgi-bin/g...uble/r1956.jpg

http://www.tractorshed.com/cgi-bin/g...uble/r1957.jpg

http://www.tractorshed.com/cgi-bin/g...uble/r1959.jpg


If those links don't work try the pictures without text:
http://www.tractorshed.com/gallery/trouble/r1956.jpg
http://www.tractorshed.com/gallery/trouble/r1957.jpg
http://www.tractorshed.com/gallery/trouble/r1959.jpg

A good reminder to drain your tank regularly.

In article ,
"Ken Davey" wrote:

No over pressure safety valve I take it?

Or perhaps more commonly, one there, never checked, corroded into a
non-operating condition?

--
Cats, coffee, chocolate...vices to live by

"I saw a program about that and they mentioned that a large part of the

problem was due to debonding of the adhesive so the rivets took all the

load which wasn't intended. It was mentioned that Boeing tightened
their procedures for the conditions under which the bonding took place
after those early planes were made and Aloha hadn't been carrying out
the checks properly to detect telltales signs of the problem.

Its something I consider when I see people querying about bonding car
panels and what conditions they are done under. Temperature, humidity,
surface prep can have a critical effect. "

Considering Boeing is now building planes that are made of carbon fiber
and LOTS of adhesive, it will be interesting to see what their long
time life span (and maintainance costs) will be.

TMT

"SteveF" wrote in message
. ..

"Steve B" wrote in message
news:zUccg.27219$QP4.4329@fed1read12...

"RoyJ" wrote

A good reminder to drain your tank regularly.

I don't see a lot of rust or corrosion. Even looks shiny.

Steve


Might just be fatigue cracking. Remember the "convertible" 737 that
Hawaiian Airlines had?

Steve.



Steel doesn't suffer from fatigue problems nearly as bad as aluminum.

Stuck regulator or Stuck Pressure Switch?

I'm guessing the switch, the regulator probably worked fine which is
why the piping didn't let go.

H.

My dad was an aeronautical stress analysis so I got some info regarding
these things, He worked for Grumman, Fairchild, Rockwell, Boeing, P & W
etc. I thought the various parts off the airframe had design lives which
they should meet and they could be extended or otherwise from
operational experience. I guess like many things these days you can't
test the product to its actual life cycle or it would be obsolete before
sale but you can try and predict its life. A single item such as
aluminium may not be to arduous but a composite structure I would expect
to be somewhat more difficult. Good thing for computers and hopefully
still people to make sure the answers make sense.

Too_Many_Tools wrote:

"I saw a program about that and they mentioned that a large part of the

problem was due to debonding of the adhesive so the rivets took all the

load which wasn't intended. It was mentioned that Boeing tightened
their procedures for the conditions under which the bonding took place
after those early planes were made and Aloha hadn't been carrying out
the checks properly to detect telltales signs of the problem.

Its something I consider when I see people querying about bonding car
panels and what conditions they are done under. Temperature, humidity,
surface prep can have a critical effect. "

Considering Boeing is now building planes that are made of carbon fiber
and LOTS of adhesive, it will be interesting to see what their long
time life span (and maintainance costs) will be.

TMT

What welding rod should I use to fix this? Will 7018 be good enough?


"RoyJ" wrote in message
nk.net...
Some interesting (if ugly!) pictures of a blown compressor tank over on
the yesterday's tractor site

http://www.tractorshed.com/cgi-bin/g...=http;//www.tr
actorshed.com/gallery/trouble/r1956.jpg

http://www.tractorshed.com/cgi-bin/g...=http;//www.tr
actorshed.com/gallery/trouble/r1957.jpg

http://www.tractorshed.com/cgi-bin/g...=http;//www.tr
actorshed.com/gallery/trouble/r1959.jpg

If those links don't work try the pictures without text:
http://www.tractorshed.com/gallery/trouble/r1956.jpg
http://www.tractorshed.com/gallery/trouble/r1957.jpg
http://www.tractorshed.com/gallery/trouble/r1959.jpg

A good reminder to drain your tank regularly.

LOL

"RoyJ" wrote in message
nk.net...
Some interesting (if ugly!) pictures of a blown compressor tank over on
the yesterday's tractor site

http://www.tractorshed.com/cgi-bin/g...=http;//www.tr
actorshed.com/gallery/trouble/r1956.jpg

http://www.tractorshed.com/cgi-bin/g...=http;//www.tr
actorshed.com/gallery/trouble/r1957.jpg

http://www.tractorshed.com/cgi-bin/g...=http;//www.tr
actorshed.com/gallery/trouble/r1959.jpg

If those links don't work try the pictures without text:
http://www.tractorshed.com/gallery/trouble/r1956.jpg
http://www.tractorshed.com/gallery/trouble/r1957.jpg
http://www.tractorshed.com/gallery/trouble/r1959.jpg

A good reminder to drain your tank regularly.

Tony wrote:

What welding rod should I use to fix this? Will 7018 be good enough?

You mean JB Weld won't work?


"RoyJ" wrote in message
nk.net...

Some interesting (if ugly!) pictures of a blown compressor tank over on
the yesterday's tractor site


http://www.tractorshed.com/cgi-bin/g...=http;//www.tr
actorshed.com/gallery/trouble/r1956.jpg

http://www.tractorshed.com/cgi-bin/g...=http;//www.tr
actorshed.com/gallery/trouble/r1957.jpg

http://www.tractorshed.com/cgi-bin/g...=http;//www.tr
actorshed.com/gallery/trouble/r1959.jpg

If those links don't work try the pictures without text:
http://www.tractorshed.com/gallery/trouble/r1956.jpg
http://www.tractorshed.com/gallery/trouble/r1957.jpg
http://www.tractorshed.com/gallery/trouble/r1959.jpg

A good reminder to drain your tank regularly.

On Mon, 22 May 2006 17:44:46 -0700, the renowned Jim Stewart
wrote:

Tony wrote:

What welding rod should I use to fix this? Will 7018 be good enough?

You mean JB Weld won't work?

Heck, the break is on the bottom. Bondo and a fresh coat of paint.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

On Mon, 22 May 2006 17:44:46 -0700, Jim Stewart
wrote:

Tony wrote:

What welding rod should I use to fix this? Will 7018 be good enough?

You mean JB Weld won't work?

JB weld would likely be safer than welding. It'll let go before the
pressure gets high enough to do REAL serious damage.


"RoyJ" wrote in message
nk.net...

Some interesting (if ugly!) pictures of a blown compressor tank over on
the yesterday's tractor site


http://www.tractorshed.com/cgi-bin/g...=http;//www.tr
actorshed.com/gallery/trouble/r1956.jpg

http://www.tractorshed.com/cgi-bin/g...=http;//www.tr
actorshed.com/gallery/trouble/r1957.jpg

http://www.tractorshed.com/cgi-bin/g...=http;//www.tr
actorshed.com/gallery/trouble/r1959.jpg

If those links don't work try the pictures without text:
http://www.tractorshed.com/gallery/trouble/r1956.jpg
http://www.tractorshed.com/gallery/trouble/r1957.jpg
http://www.tractorshed.com/gallery/trouble/r1959.jpg

A good reminder to drain your tank regularly.





*** Posted via a free Usenet account from http://www.teranews.com ***

I agree that corrosion was the culprit, but corrosion of the safety valve
and not the tank. I never understood why they couldn't make a tank with a
weak spot that would blow out first before the entire tank ruptured.
Obviously this is what the spring loaded safety valve is for, but those can
fail (as we've seen). Perhaps during the manufacturing process, have a flat
spot ground or milled near the bottom of the tank (thick enough to withstand
normal pressure, but slightly thinner than the rest of the tank so that this
spot will blow out first).

I have a Bostitch roofing nailer with a "spot" on the cylinder which looks
like a shallow plunge cut from an endmill. If over pressurized (for example
if someone were to connect it to a 2000 psi nitrogen tank), this spot will
blow out rather than the whole cylinder exploding.

wasn't the A300 with the composite vertical stabilizer that separated
when the pilot over=reacted to a wake vortex - all on board died -
that's carbon composite


On 22 May 2006 07:36:41 -0700, "Too_Many_Tools"
wrote:

"I saw a program about that and they mentioned that a large part of the

problem was due to debonding of the adhesive so the rivets took all the

load which wasn't intended. It was mentioned that Boeing tightened
their procedures for the conditions under which the bonding took place
after those early planes were made and Aloha hadn't been carrying out
the checks properly to detect telltales signs of the problem.

Its something I consider when I see people querying about bonding car
panels and what conditions they are done under. Temperature, humidity,
surface prep can have a critical effect. "

Considering Boeing is now building planes that are made of carbon fiber
and LOTS of adhesive, it will be interesting to see what their long
time life span (and maintainance costs) will be.

TMT
Bill

www.wbnoble.com

to contact me, do not reply to this message,
instead correct this address and use it

will iam_ b_ No ble at msn daught com

*** Posted via a free Usenet account from http://www.teranews.com ***

On Mon, 22 May 2006 23:51:56 -0500, "AL" wrote:

I agree that corrosion was the culprit, but corrosion of the safety valve
and not the tank. I never understood why they couldn't make a tank with a
weak spot that would blow out first before the entire tank ruptured.
Obviously this is what the spring loaded safety valve is for, but those can
fail (as we've seen). Perhaps during the manufacturing process, have a flat
spot ground or milled near the bottom of the tank (thick enough to withstand
normal pressure, but slightly thinner than the rest of the tank so that this
spot will blow out first).

I have a Bostitch roofing nailer with a "spot" on the cylinder which looks
like a shallow plunge cut from an endmill. If over pressurized (for example
if someone were to connect it to a 2000 psi nitrogen tank), this spot will
blow out rather than the whole cylinder exploding.

I think haveing that FUZE spot on top would be far better than on the
bottom for a number of reasons, not the least being rust..and having
it blow out and launching the compressor into orbit.

Gunner

"If thy pride is sorely vexed when others disparage your offering, be
as lamb's wool is to cold rain and the Gore-tex of Odin's raiment
is to gull**** in the gale, for thy angst shall vex them not at
all. Yea, they shall scorn thee all the more. Rejoice in
sharing what you have to share without expectation of adoration,
knowing that sharing your treasure does not diminish your treasure
but enriches it."

- Onni 1:33

AL wrote:
I agree that corrosion was the culprit, but corrosion of the safety valve
and not the tank. I never understood why they couldn't make a tank with a
weak spot that would blow out first before the entire tank ruptured.
Obviously this is what the spring loaded safety valve is for, but those can
fail (as we've seen). Perhaps during the manufacturing process, have a flat
spot ground or milled near the bottom of the tank (thick enough to withstand
normal pressure, but slightly thinner than the rest of the tank so that this
spot will blow out first).

I have a Bostitch roofing nailer with a "spot" on the cylinder which looks
like a shallow plunge cut from an endmill. If over pressurized (for example
if someone were to connect it to a 2000 psi nitrogen tank), this spot will
blow out rather than the whole cylinder exploding.


You are describing a rupture disk. Install one into a tank threaded opening so
you wouldn't destroy the tank upon failure...

On Mon, 22 May 2006 23:51:56 -0500, "AL" wrote:

I agree that corrosion was the culprit, but corrosion of the safety valve
and not the tank. I never understood why they couldn't make a tank with a
weak spot that would blow out first before the entire tank ruptured.
Obviously this is what the spring loaded safety valve is for, but those can
fail (as we've seen). Perhaps during the manufacturing process, have a flat
spot ground or milled near the bottom of the tank (thick enough to withstand
normal pressure, but slightly thinner than the rest of the tank so that this
spot will blow out first).

I have a Bostitch roofing nailer with a "spot" on the cylinder which looks
like a shallow plunge cut from an endmill. If over pressurized (for example
if someone were to connect it to a 2000 psi nitrogen tank), this spot will
blow out rather than the whole cylinder exploding.

Freon tanks and disposable helium tanks are built this way.

*** Posted via a free Usenet account from http://www.teranews.com ***

Additional comments were posted by the owner:

# Joe Skinner wrote on Monday, May 22, 2006 (PDT):
# the tank was drained, not as often as it should have been and it had a
pop-off valve also but things just didn't work the regulator had a small
copper line running to it and it got gummed up and the pop-off was
rusted fast. the inside of the tank shows alot of rust pitting on the
bottom side of the tank(now both on top and bottom of the third pic).
like i said earlier it seems odd that the tank blew before the pvc lines
but if you are plumbing a shop you plan to spend alot of time in i'd use
piping.

Ecnerwal wrote:
In article ,
"Ken Davey" wrote:


No over pressure safety valve I take it?


Or perhaps more commonly, one there, never checked, corroded into a
non-operating condition?

Agreed, but if someone were standing nearby, the blast might hit them. With
the weak spot at the bottom, the blast would be aimed toward the ground.

"Gunner"
I think haveing that FUZE spot on top would be far better than on the
bottom for a number of reasons, not the least being rust..and having
it blow out and launching the compressor into orbit.

Gunner
Onni 1:33

AL wrote:
Agreed, but if someone were standing nearby, the blast might hit
them. With the weak spot at the bottom, the blast would be aimed
toward the ground.

And this would aim the tank at....?

"Gunner"
I think haveing that FUZE spot on top would be far better than on the
bottom for a number of reasons, not the least being rust..and having
it blow out and launching the compressor into orbit.

Gunner
Onni 1:33

--
Volunteer your idle computer time for cancer research
http//www.grid.org/download/gold/download.htm
Return address courtesy of Spammotel http://www.spammotel.com/

On Tue, 23 May 2006 09:14:43 -0500, "AL" wrote:

Agreed, but if someone were standing nearby, the blast might hit them. With
the weak spot at the bottom, the blast would be aimed toward the ground.

And have the entire compressor hit them. Decisions decisions...
G


"Gunner"
I think haveing that FUZE spot on top would be far better than on the
bottom for a number of reasons, not the least being rust..and having
it blow out and launching the compressor into orbit.

Gunner
Onni 1:33


"If thy pride is sorely vexed when others disparage your offering, be
as lamb's wool is to cold rain and the Gore-tex of Odin's raiment
is to gull**** in the gale, for thy angst shall vex them not at
all. Yea, they shall scorn thee all the more. Rejoice in
sharing what you have to share without expectation of adoration,
knowing that sharing your treasure does not diminish your treasure
but enriches it."

- Onni 1:33

On Tue, 23 May 2006 07:16:55 GMT, Gunner
wrote:

On Mon, 22 May 2006 23:51:56 -0500, "AL" wrote:

I agree that corrosion was the culprit, but corrosion of the safety valve
and not the tank. I never understood why they couldn't make a tank with a
weak spot that would blow out first before the entire tank ruptured.
Obviously this is what the spring loaded safety valve is for, but those can
fail (as we've seen). Perhaps during the manufacturing process, have a flat
spot ground or milled near the bottom of the tank (thick enough to withstand
normal pressure, but slightly thinner than the rest of the tank so that this
spot will blow out first).

I have a Bostitch roofing nailer with a "spot" on the cylinder which looks
like a shallow plunge cut from an endmill. If over pressurized (for example
if someone were to connect it to a 2000 psi nitrogen tank), this spot will
blow out rather than the whole cylinder exploding.

I think haveing that FUZE spot on top would be far better than on the
bottom for a number of reasons, not the least being rust..and having
it blow out and launching the compressor into orbit.

Remember when mother was cooking beets in the pressure cooker and you
forgot to watch the indicator as you had been told, and suddenly there
was a large red spot on the ceiling?
Gerry :-)}
London, Canada

I'm afraid I don't understand why the tank would go airborne. When I open
the drain valve with air still in the tank, my compressor doesn't hit the
ceiling. I'm thinking about a weak spot maybe 0.5 to 1" in diameter, sized
appropriately for the pump.

"Gunner" wrote in message
...
On Tue, 23 May 2006 09:14:43 -0500, "AL" wrote:

Agreed, but if someone were standing nearby, the blast might hit them.
With
the weak spot at the bottom, the blast would be aimed toward the ground.

And have the entire compressor hit them. Decisions decisions...
G


"Gunner"
I think haveing that FUZE spot on top would be far better than on the
bottom for a number of reasons, not the least being rust..and having
it blow out and launching the compressor into orbit.

Gunner
Onni 1:33


"If thy pride is sorely vexed when others disparage your offering, be
as lamb's wool is to cold rain and the Gore-tex of Odin's raiment
is to gull**** in the gale, for thy angst shall vex them not at
all. Yea, they shall scorn thee all the more. Rejoice in
sharing what you have to share without expectation of adoration,
knowing that sharing your treasure does not diminish your treasure
but enriches it."

- Onni 1:33

In article , "AL"
wrote:

I'm afraid I don't understand why the tank would go airborne. When I open
the drain valve with air still in the tank, my compressor doesn't hit the
ceiling. I'm thinking about a weak spot maybe 0.5 to 1" in diameter, sized
appropriately for the pump.

What does the assembly weigh and what is the burst pressure? If the
burst pressure is 300 psi and the disk is one inch in diameter, the
thrust at the moment of burst will be (Pi (0.5)^2)(300)= (0.785)(300)=
236 pounds. The impulse (integrated thrust) will be proportional to
tank volume.

Anyway, this thrust is enough to make most compressors move.

Joe Gwinn

What does the assembly weigh and what is the burst pressure? If the
burst pressure is 300 psi and the disk is one inch in diameter, the
thrust at the moment of burst will be (Pi (0.5)^2)(300)= (0.785)(300)=
236 pounds. The impulse (integrated thrust) will be proportional to
tank volume.

Anyway, this thrust is enough to make most compressors move.

Joe Gwinn

Wouldn't that thrust assume you were pushing against a stationary object?
Would it decrease relative to the distance the "hole" was to the floor (or
wall)?

In article oxZcg.1087$No1.766@attbi_s71,
"Dave Lyon" wrote:


What does the assembly weigh and what is the burst pressure? If the
burst pressure is 300 psi and the disk is one inch in diameter, the
thrust at the moment of burst will be (Pi (0.5)^2)(300)= (0.785)(300)=
236 pounds. The impulse (integrated thrust) will be proportional to
tank volume.

Anyway, this thrust is enough to make most compressors move.

Joe Gwinn

Wouldn't that thrust assume you were pushing against a stationary object?
Would it decrease relative to the distance the "hole" was to the floor (or
wall)?

Not quite, the jet stream of pressurized air needs nothing to press
against. Its thrust is independent of anything but the pressure
relationships in the vessel and the nozzle, in this case the tank and
hole. It'd have as much thrust with a vacuum surrounding it. 'tis how
rockets work.

Swoosh!

--
Bring back, Oh bring back
Oh, bring back that old continuity.
Bring back, oh, bring back
Oh, bring back Clerk Maxwell to me.

In article ,
says...
In article oxZcg.1087$No1.766@attbi_s71,
"Dave Lyon" wrote:


What does the assembly weigh and what is the burst pressure? If the
burst pressure is 300 psi and the disk is one inch in diameter, the
thrust at the moment of burst will be (Pi (0.5)^2)(300)= (0.785)(300)=
236 pounds. The impulse (integrated thrust) will be proportional to
tank volume.

Anyway, this thrust is enough to make most compressors move.

Joe Gwinn

Wouldn't that thrust assume you were pushing against a stationary object?
Would it decrease relative to the distance the "hole" was to the floor (or
wall)?

Not quite, the jet stream of pressurized air needs nothing to press
against. Its thrust is independent of anything but the pressure
relationships in the vessel and the nozzle, in this case the tank and
hole. It'd have as much thrust with a vacuum surrounding it. 'tis how
rockets work.


There is a potentially strong surface effect that depends on the
distance to a stationary surface. This surface effect is in addition to
the "rocket" thrust. The rocket thrust is *not* equal to area x
pressure.

Ned Simmons

"John Husvar" wrote in message
...
In article oxZcg.1087$No1.766@attbi_s71,
"Dave Lyon" wrote:


What does the assembly weigh and what is the burst pressure? If the
burst pressure is 300 psi and the disk is one inch in diameter, the
thrust at the moment of burst will be (Pi (0.5)^2)(300)= (0.785)(300)=
236 pounds. The impulse (integrated thrust) will be proportional to
tank volume.

Anyway, this thrust is enough to make most compressors move.

Joe Gwinn

Wouldn't that thrust assume you were pushing against a stationary
object?
Would it decrease relative to the distance the "hole" was to the floor
(or
wall)?

Not quite, the jet stream of pressurized air needs nothing to press
against. Its thrust is independent of anything but the pressure
relationships in the vessel and the nozzle, in this case the tank and
hole. It'd have as much thrust with a vacuum surrounding it. 'tis how
rockets work.

Swoosh!


If there is no benefit from being near the ground for our air compressor
rocket, then why do airplanes and hover crafts have a benefit from ground
effect?

I'm not trying to be a butt, just trying to learn something.

"Ned Simmons" wrote in message
...
In article ,
says...
In article oxZcg.1087$No1.766@attbi_s71,
"Dave Lyon" wrote:


What does the assembly weigh and what is the burst pressure? If the
burst pressure is 300 psi and the disk is one inch in diameter, the
thrust at the moment of burst will be (Pi (0.5)^2)(300)=
(0.785)(300)=
236 pounds. The impulse (integrated thrust) will be proportional to
tank volume.

Anyway, this thrust is enough to make most compressors move.

Joe Gwinn

Wouldn't that thrust assume you were pushing against a stationary
object?
Would it decrease relative to the distance the "hole" was to the floor
(or
wall)?

Not quite, the jet stream of pressurized air needs nothing to press
against. Its thrust is independent of anything but the pressure
relationships in the vessel and the nozzle, in this case the tank and
hole. It'd have as much thrust with a vacuum surrounding it. 'tis how
rockets work.


There is a potentially strong surface effect that depends on the
distance to a stationary surface. This surface effect is in addition to
the "rocket" thrust. The rocket thrust is *not* equal to area x
pressure.

Ned Simmons


Oh, that computes a little better in my head.

How is the rocket thrust figured?

In article iw_cg.1156$No1.239@attbi_s71,
says...

"Ned Simmons" wrote in message
...
In article ,
says...
In article oxZcg.1087$No1.766@attbi_s71,
"Dave Lyon" wrote:


What does the assembly weigh and what is the burst pressure? If the
burst pressure is 300 psi and the disk is one inch in diameter, the
thrust at the moment of burst will be (Pi (0.5)^2)(300)=
(0.785)(300)=
236 pounds. The impulse (integrated thrust) will be proportional to
tank volume.

Anyway, this thrust is enough to make most compressors move.

Joe Gwinn

Wouldn't that thrust assume you were pushing against a stationary
object?
Would it decrease relative to the distance the "hole" was to the floor
(or
wall)?

Not quite, the jet stream of pressurized air needs nothing to press
against. Its thrust is independent of anything but the pressure
relationships in the vessel and the nozzle, in this case the tank and
hole. It'd have as much thrust with a vacuum surrounding it. 'tis how
rockets work.


There is a potentially strong surface effect that depends on the
distance to a stationary surface. This surface effect is in addition to
the "rocket" thrust. The rocket thrust is *not* equal to area x
pressure.

Ned Simmons


Oh, that computes a little better in my head.

How is the rocket thrust figured?


Now if I could do that I'd truly be a Rocket Scientist g.

If you want to slog thru the numbers this looks like a good start.
http://www.grc.nasa.gov/WWW/K-12/airplane/rktthsum.html

But it doesn't look like there's enough there to do a calculation based
on the pressure behind a nozzle without having data on the flow
characteristics of the specific nozzle. You can probably find data on a
sharp edged orifice (hole in the tank in this case) in a thermodynamics
text or website.

Ned Simmons

In article 0s_cg.1058$1i1.24@attbi_s72,
"Dave Lyon" wrote:

"John Husvar" wrote in message
...
In article oxZcg.1087$No1.766@attbi_s71,
"Dave Lyon" wrote:


What does the assembly weigh and what is the burst pressure? If the
burst pressure is 300 psi and the disk is one inch in diameter, the
thrust at the moment of burst will be (Pi (0.5)^2)(300)= (0.785)(300)=
236 pounds. The impulse (integrated thrust) will be proportional to
tank volume.

Anyway, this thrust is enough to make most compressors move.

Joe Gwinn

Wouldn't that thrust assume you were pushing against a stationary
object?
Would it decrease relative to the distance the "hole" was to the floor
(or
wall)?

Not quite, the jet stream of pressurized air needs nothing to press
against. Its thrust is independent of anything but the pressure
relationships in the vessel and the nozzle, in this case the tank and
hole. It'd have as much thrust with a vacuum surrounding it. 'tis how
rockets work.

Swoosh!


If there is no benefit from being near the ground for our air compressor
rocket, then why do airplanes and hover crafts have a benefit from ground
effect?

I'm not trying to be a butt, just trying to learn something.

Well, our air compressor rocket may gain a little bit of lift from the
air rebounding off the ground toward it, but it won't be much. the one
shown probably got a fair bit from the big flow when the seam parted
though. I doubt the thrust from a burst plate's area would even move it.
For real fun one could try breaking the valve off a full-pressure
compressed gas tank. Those will move quite a bit.

Airplanes are said to be in ground effect when their altitude above the
ground is less than their wingspan. There is a slightly increased lift,
but it's relatively small and not terribly significant to a plane's
flight characteristics. If you've felt the slightly mushy springy
feeling as a plane takes off or lands, that's ground effect.

I feel it more on landing because all the laundry's hanging out;
trailing flaps, sometimes leading flaps, landing gear, etc. Hell, one of
the flights I was on recently, the pilot deployed the spoilers during
the descent. Sure as hell felt that! Plane went from feeling like a
slightly bumpy roller coaster to feeling like a Maytag on Spin with bad
bearings and an unbalanced load. (and I was stuck inside, riding the
agitator

Ground Effects Machines like Hovercraft operate best when they have a
skirt where the pressure can build and support the hull. That kind of
ground effect isn't really much related to aircraft ground effect. Some
designs without skirts were tried, but the ground effect was much
reduced and wasn't too reliable.

Real rockets are out of any possibility of reacting to ground effect so
fast that it's doubtful anyone can notice it. But they don't need the
atmosphere to "push against." They just use the force the exhaust
pressure and mass exert on the top of the combustion chamber.

The old balloon thing would work as well in space as down here.

Now for something really scary: Every launch, the astronauts are riding
with the lowest bidder. (and with the guy who said the rocket's OK to
launch, who they hope hadn't had tee many martoonies at lunch.

Recent events have shown that might not be a valid assumption.

--
Bring back, Oh bring back
Oh, bring back that old continuity.
Bring back, oh, bring back
Oh, bring back Clerk Maxwell to me.

In article ,
Ned Simmons wrote:

In article ,
says...
In article oxZcg.1087$No1.766@attbi_s71,
"Dave Lyon" wrote:


What does the assembly weigh and what is the burst pressure? If the
burst pressure is 300 psi and the disk is one inch in diameter, the
thrust at the moment of burst will be (Pi (0.5)^2)(300)= (0.785)(300)=
236 pounds. The impulse (integrated thrust) will be proportional to
tank volume.

Anyway, this thrust is enough to make most compressors move.

Joe Gwinn

Wouldn't that thrust assume you were pushing against a stationary object?
Would it decrease relative to the distance the "hole" was to the floor (or
wall)?

Not quite, the jet stream of pressurized air needs nothing to press
against. Its thrust is independent of anything but the pressure
relationships in the vessel and the nozzle, in this case the tank and
hole. It'd have as much thrust with a vacuum surrounding it. 'tis how
rockets work.


There is a potentially strong surface effect that depends on the
distance to a stationary surface. This surface effect is in addition to
the "rocket" thrust. The rocket thrust is *not* equal to area x
pressure.


I'd think any surface effect would be pretty short-lived, but I'm
certainly _not_ a Rocket Scientist, except sometimes as a hobby when my
kids were younger.

--
Bring back, Oh bring back
Oh, bring back that old continuity.
Bring back, oh, bring back
Oh, bring back Clerk Maxwell to me.

Dave Lyon wrote:
How is the rocket thrust figured?

IIRC, it's basically conservation of momentum: the exiting mass times
its velocity is conserved by the containers mass times its velocity in
the opposite direction. Calculitically, of course - rates of change
very much involved.

In this case, the mass of the exiting air is very small, but the
velocity is high, so who knows. My guess is a rupture plug's blowing
would not lift the compressor. This is not inconsistent with the OP's
case mainly because the plug's relief pressure would be a lot less than
the failure pressure of the tank. For example, a propane tank's
observed rupture (failure) pressure is in excess of 1200 psi, and it's
operational pressure is about that of a compressor. Kind of hard to
believe that the compressor's motor/pump has enough oomph to get the
pressure that high, but what do I know.

Bob

In article ,
says...
In article ,
Ned Simmons wrote:



There is a potentially strong surface effect that depends on the
distance to a stationary surface. This surface effect is in addition to
the "rocket" thrust. The rocket thrust is *not* equal to area x
pressure.


I'd think any surface effect would be pretty short-lived, but I'm
certainly _not_ a Rocket Scientist, except sometimes as a hobby when my
kids were younger.



Yes, I'm sure it drops very quickly with increasing distance.

Ned Simmons