I am going to build a chamber type vacuum sealer.

Unlike the Food-saver Seal-a-Meal machines that pull a weak vacuum, do
not seal really well and use expensive special bags, a chamber style
has an impulse sealer inside the chamber and the product is bagged,
set inside the chamber, and sealed after you have drawn a vacuum.

The reason I am going to build this is that prices for the commercial
models start around $1,500 and you have to repack a whole lot of food
to recoup that kind of money.

I think I have most of the design figured out, but I am unsure how to
fabricate the chamber itself. My first thought was to use a stainless
steel steam table pan, but I am worried that this might crush in under
vacuum, as the thickest one made is only 20 gauge.

My first thought was to make a tubular frame and epoxy some supports
that could then be wired to the frame to give some support to the pan
to prevent it from crushing.

My next thought was to layer a 1/4 inch of fiberglass on the outside
of the steam table pan using epoxy resin.

Then I wondered if the pan was necessary at all or if I could just
mold a fiberglass chamber over a chunk of foam or plywood and end up
with a chamber that would hold up to the pressure and the cycling.

So I figured that before I went to a bunch of work and watched a
failure because it was not quite strong enough, or wasted a whole lot
of money overbuilding, I figured I would run it by you guys for your
thoughts.

Roger Shoaf

RS at work wrote:
I am going to build a chamber type vacuum sealer.

How about decapping an air tank or gas cylinder
and welding flanges to rejoin the end?

Experiment with a paint pot first?

Couple paint pots mouth - to - mouth via a foot
flange containing a central shelf?

--Winston

I have one of the regular ones, cost about $200 new, and it works like a
charm. Are you talking about something a lot bigger?

Steve

In article
,
RS at work wrote:

I am going to build a chamber type vacuum sealer.


Section of pipe. Or two stainless-steel salad or mixing bowls if you
want to grab things form the kitchen. Rather than frig with a weak
shape, start with a strong one.

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

Winston wrote:
RS at work wrote:
I am going to build a chamber type vacuum sealer.

How about decapping an air tank or gas cylinder
and welding flanges to rejoin the end?

Experiment with a paint pot first?

Couple paint pots mouth - to - mouth via a foot
flange containing a central shelf?

--Winston


I am going to need a chamber that is somewhere in the order of 14X14X6
inches. If I went with a chunk of pipe, that would have to be
something like 16" diameter. The down side to this would be cost and
bulk. The more empty space inside the chanber the longer evacuation
time.

Also if I used a 16" inch pipe it would also be difficult to make a
door. The door would have to be hinged and by the time I dod all of
that work, it would get pretty pricy.

Steve B wrote:
I have one of the regular ones, cost about $200 new, and it works like a
charm. Are you talking about something a lot bigger?

Steve

Look at a package of bacon you get from the market. No air bubbles,
no leaks, no freezer burn.

I had one of the food savers and I did't like paying the price for the
bags and I tossed a lot of meat that got freezer burned when the bags
developed a slow leak.

Also if the stuff you are sealing is juicy it sucks the juice out of
the bag and fouls the pump.

On Oct 13, 2:41*pm, RS at work wrote:
I am going to build a chamber type vacuum sealer.

Unlike the Food-saver Seal-a-Meal machines that pull a weak vacuum, do
not seal really well and use expensive special bags, a chamber style
has an impulse sealer inside the chamber and the product is bagged,
set inside the chamber, and sealed after you have drawn a vacuum.

I presume you are aiming for rough vacuum (air pressure is about
30 inches-of-Hg, and you'd be satisfied with 0.5 inches-of-Hg). The
force on the sidewalls, about 15 psi, means that flat-sided
boxes aren't suitable. Usually, one sees a glass bell jar atop
a castiron plate, gravity and a greased rubbery gasket hold the
vacuum,
or aluminum or SS pipe-spools with flanges on the ends for
bolted-compression gasketing or O-rings.

Cylinders and hemispheres (like the bell jar dome) can be made
of light construction, and still be safe. The lid, though, will
require
machined plate or flanges, so a machine shop is called for. One
with welding equipment, preferably.

In article
,
RS at work wrote:

I am going to need a chamber that is somewhere in the order of 14X14X6
inches. If I went with a chunk of pipe, that would have to be
something like 16" diameter. The down side to this would be cost and
bulk. The more empty space inside the chanber the longer evacuation
time.

Also if I used a 16" inch pipe it would also be difficult to make a
door. The door would have to be hinged and by the time I dod all of
that work, it would get pretty pricy.

Trivial to make a door. No hinge required. Take a 6 inch length of 16
inch pipe, weld a plate on the bottom (years of vacuum experience says
1/4" steel plate would probably do nicely, thinner would work if you
domed it a tad) and put a flange (better yet, get 6" with a flange cut
off a pipe at the junkyard) with an o-ring groove (hey - metalworking!)
on top. A crapped out 16" valve body and a blank flange for the bottom
might doing it from stock parts with no cutting. For 16" a 1" Lexan top
(if you want to see what happens) should work - we used 1-1/2 or 2" for
a 24-30" dia unit much like this (a bit bigger) that was primarily used
for vacuum-casting epoxy. The vacuum holds the lid on quite well indeed.
Making it cheaply is a matter of picking the right junkyard (try one
that gets stainless steel scrap from a university), and seeing the right
things in the junk.

If you want the opposite of doing it right, try a 12" port and a sheet
of window glass. Does a heck of a job on a tubomolecular pump running
full speed (it didn't break right away, so the researcher/culprit
actually got the high vac pump running before he filled it with glass
shards.)

If evacuation time is an issue for you at food-sealing pressures, you
need a better pump...

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

"Steve B" wrote in message
...
I have one of the regular ones, cost about $200 new, and it works like a
charm. Are you talking about something a lot bigger?

Steve


You probably have an external vacuum sealer. Seal a meal. The chambers are
over a grand. I have thought of making one also. As too cheap to spring
for a chamber one. Bags are a lot cheaper and you can package tuna in
retort bags for a better product. I was thinking a small stainless sink,
but I like the steam table pan idea better. I was going to weld some studs
on the bottom to attached some stringers or weld some stringers to the
bottom of the sink. Pan sounds better. Then maybe weld a stainless steel
bar top grid for sealing. Have not figured out the lid yet, as I would like
a transparent lid. I have read about someone using a refrigerator
compressor as the vacuum pump. Pulls 28" of mercury, which is what the
better chamber sealers claim.

On Oct 13, 5:41*pm, RS at work wrote:
I am going to build a chamber type vacuum sealer.

Unlike the Food-saver Seal-a-Meal machines that pull a weak vacuum, do
not seal really well and use expensive special bags, a chamber style
has an impulse sealer inside the chamber and the product is bagged,
set inside the chamber, and sealed after you have drawn a vacuum.
...
Roger Shoaf

What will you use for the self-powered remote control sealer?

jsw

"Winston" wrote in message
...
RS at work wrote:
I am going to build a chamber type vacuum sealer.

How about decapping an air tank or gas cylinder
and welding flanges to rejoin the end?

Experiment with a paint pot first?

Couple paint pots mouth - to - mouth via a foot
flange containing a central shelf?

--Winston

Dumb question guys - why not place the bagged food inside a pressureised
chamber with the mouth of the bag exiting from a gap/slit in the pressure
chamber?

Applying air pressure inside the chamber would force excess air etc from the
bag which could then be sealed.


/--------------------\
/ \
========##BAGofFOOD## ==== air press in.
\ /
\--------------------/

^
^
^
heat
seal
here

Dennis wrote:
wrote in message
...
RS at work wrote:
I am going to build a chamber type vacuum sealer.

How about decapping an air tank or gas cylinder
and welding flanges to rejoin the end?

Experiment with a paint pot first?

Couple paint pots mouth - to - mouth via a foot
flange containing a central shelf?

--Winston

Dumb question guys - why not place the bagged food inside a pressureised
chamber with the mouth of the bag exiting from a gap/slit in the pressure
chamber?

Applying air pressure inside the chamber would force excess air etc from the
bag which could then be sealed.


/--------------------\
/ \
========##BAGofFOOD## ==== air press in.
\ /
\--------------------/

^
^
^
heat
seal
here

Think toothpaste.

Otherwise I like your idea.

--Winston

On Sun, 17 Oct 2010 06:21:07 -0700 (PDT), Jim Wilkins
wrote:

On Oct 13, 5:41*pm, RS at work wrote:
I am going to build a chamber type vacuum sealer.

Unlike the Food-saver Seal-a-Meal machines that pull a weak vacuum, do
not seal really well and use expensive special bags, a chamber style
has an impulse sealer inside the chamber and the product is bagged,
set inside the chamber, and sealed after you have drawn a vacuum.
...
Roger Shoaf

What will you use for the self-powered remote control sealer?

jsw


Im rather courious how they close the bag from outside the vacuum
chamber once they pump out the air?

Gunner


I am the Sword of my Family
and the Shield of my Nation.
If sent, I will crush everything you have built,
burn everything you love,
and kill every one of you.
(Hebrew quote)

On Oct 17, 4:17*pm, Gunner Asch wrote:
On Sun, 17 Oct 2010 06:21:07 -0700 (PDT), Jim Wilkins
wrote:

On Oct 13, 5:41*pm, RS at work wrote:
I am going to build a chamber type vacuum sealer.

Unlike the Food-saver Seal-a-Meal machines that pull a weak vacuum, do
not seal really well and use expensive special bags, a chamber style
has an impulse sealer inside the chamber and the product is bagged,
set inside the chamber, and sealed after you have drawn a vacuum.
...
Roger Shoaf

What will you use for the self-powered remote control sealer?

jsw

Im rather courious how they close the bag from outside the vacuum
chamber once they pump out the air?

Gunner


What do you think is particularly difficult about that? An electically
operated clamp and a resistance heater would do it. These things have
no problem operating in a vacuum. The control and power wires pass
through vacuum-tight connectors - for instance:
http://vacuumguide.net/vacuum_compon...edthroughs.htm
..

Dennis wrote:


Dumb question guys - why not place the bagged food inside a pressureised
chamber with the mouth of the bag exiting from a gap/slit in the pressure
chamber?

Applying air pressure inside the chamber would force excess air etc from the
bag which could then be sealed.


/--------------------\
/ \
========##BAGofFOOD## ==== air press in.
\ /
\--------------------/

^
^
^
heat
seal
here



OK I can answe that. If you were to pressurise the outside of the bag
everything inside the bag would try to escape, including the stuff you
wanted to keep in the bag.

Think about a kid stepping on a packet of ketchup.

Roger Shoaf

Jim Wilkins wrote:


What will you use for the self-powered remote control sealer?


I had several ideas here. My firat idea was to get a standard impulse
bag sealer, put it inside the chamber and just run the power wires
through glands in the sidewall. Once the desired level of vacuum was
drawn the power could be applied to the sealer.

In researching plastic sealing however I found a place that sells
parts and controlers. It seems that the state of the art is to
measure the temp of nichrome sealing element by measuring the current
that is being drawn so you do not over heat or underheat the bag you
want to seal. (The resistance changes as the temp rises)

This seems to be the way to go. but that opinion may change when I
price their controler. Optionally, one could mount the guts from the
off the shelf bag sealer outside the chamber and run the lower
voltage to the seal bar inside.

The bag is sealed between two pieces of silicone foam rubber and
several insulating and teflon strips to hold the melted plastic while
in resolidifies.

One thing for sure is that I am going to try an alternate cross
sectional geometry on the heating element. They sell one that has a
radius top edge to prevent the sealing bar from overheating the edge
of the band like the flat bands are prone to do.

Roger Shoaf

RS at work wrote:

Jim Wilkins wrote:


What will you use for the self-powered remote control sealer?


I had several ideas here. My firat idea was to get a standard impulse
bag sealer, put it inside the chamber and just run the power wires
through glands in the sidewall. Once the desired level of vacuum was
drawn the power could be applied to the sealer.



Glands? Use feedthrough capacitors to prevent all air leaks.


In researching plastic sealing however I found a place that sells
parts and controlers. It seems that the state of the art is to
measure the temp of nichrome sealing element by measuring the current
that is being drawn so you do not over heat or underheat the bag you
want to seal. (The resistance changes as the temp rises)

This seems to be the way to go. but that opinion may change when I
price their controler. Optionally, one could mount the guts from the
off the shelf bag sealer outside the chamber and run the lower
voltage to the seal bar inside.

The bag is sealed between two pieces of silicone foam rubber and
several insulating and teflon strips to hold the melted plastic while
in resolidifies.

One thing for sure is that I am going to try an alternate cross
sectional geometry on the heating element. They sell one that has a
radius top edge to prevent the sealing bar from overheating the edge
of the band like the flat bands are prone to do.

Roger Shoaf


--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

Califbill wrote:


You probably have an external vacuum sealer. Seal a meal. The chambers are
over a grand. I have thought of making one also. As too cheap to spring
for a chamber one. Bags are a lot cheaper and you can package tuna in
retort bags for a better product. I was thinking a small stainless sink,
but I like the steam table pan idea better. I was going to weld some studs
on the bottom to attached some stringers or weld some stringers to the
bottom of the sink. Pan sounds better. Then maybe weld a stainless steel
bar top grid for sealing. Have not figured out the lid yet, as I would like
a transparent lid. I have read about someone using a refrigerator
compressor as the vacuum pump. Pulls 28" of mercury, which is what the
better chamber sealers claim.


As my thoughts have evovled over the past week or so, I am thinking
about using tempered glass for the top and bottom of the chamber and
to use Lexan for the side walls. While lexan is very flexable, my
idea now is to glue on ribs to the sides so as the vacuum wanted to
suck the sidewalls in, the top and bottom of the ribs would be
supported by the edge of the glass top and bottom. Tempered glass is
really tough stuff. As an example think about a pinball machine. I
have seen this 1/4" glass survive people standing on the glass and
slamming down beer bottles etc. In 3/8 or 1/2 you could probably park
a semi on top. Shopping around I found a place that would sell me 14
X 16 X 1/2 tempered glass for about $25

If a full vacuum was pulled on a 14" X 16" panel each square inch
would have about 15 lbs of pressure pushing on it so the total force
against the top would be about 3,360 lbs. and the same for the bottom
for a total of 6,720 on the sidewall, If the sidewall was made of 1/4
inch lexan that would be something like 15 square inchis of lexan
supporting the 6,720 lbs. so that would be a load of 450 lbs. per
square inch so that would definatly support the weight.

For the long side of the side wall, assuming I make this 6 inches high
each long side would have to hold back a force of 1440 lbs. While
that much force would usually cause the side to cave in, by bonding
the ribs to the side If I divided the side wall into 5 segments, that
would give each segment only 288 lbs to support. Piece of cake.

Roger Shoaf

On Mon, 18 Oct 2010 01:14:53 -0400, "Michael A. Terrell"
wrote:


RS at work wrote:

Jim Wilkins wrote:


What will you use for the self-powered remote control sealer?


I had several ideas here. My firat idea was to get a standard impulse
bag sealer, put it inside the chamber and just run the power wires
through glands in the sidewall. Once the desired level of vacuum was
drawn the power could be applied to the sealer.

Im not sure it will be of any use..but Ive a number of Honeywell UDC2000
and UDC 2500 controllers that may be of assitance.

They are temperature/IO controllers for ovens and other heating
applications. Uses a remote termocouple and have a number of outputs
programmable




Glands? Use feedthrough capacitors to prevent all air leaks.


In researching plastic sealing however I found a place that sells
parts and controlers. It seems that the state of the art is to
measure the temp of nichrome sealing element by measuring the current
that is being drawn so you do not over heat or underheat the bag you
want to seal. (The resistance changes as the temp rises)

This seems to be the way to go. but that opinion may change when I
price their controler. Optionally, one could mount the guts from the
off the shelf bag sealer outside the chamber and run the lower
voltage to the seal bar inside.

The bag is sealed between two pieces of silicone foam rubber and
several insulating and teflon strips to hold the melted plastic while
in resolidifies.

One thing for sure is that I am going to try an alternate cross
sectional geometry on the heating element. They sell one that has a
radius top edge to prevent the sealing bar from overheating the edge
of the band like the flat bands are prone to do.

Roger Shoaf


I am the Sword of my Family
and the Shield of my Nation.
If sent, I will crush everything you have built,
burn everything you love,
and kill every one of you.
(Hebrew quote)

RS at work fired this volley in news:45d6e4a8-
:


OK I can answe that. If you were to pressurise the outside of the bag
everything inside the bag would try to escape, including the stuff you
wanted to keep in the bag.

Think about a kid stepping on a packet of ketchup.

Roger Shoaf

Well, Roger, I think, then, that you missed something.

That "kid" is still at work when you pull a vacuum on the bag.

1) the contents will try to escape out the evacuation hole because,
2) the KID weighs 14.7psi at sea level, and he's stomping crap out of
your ketchup.

LLoyd

RS at work wrote:
Jim Wilkins wrote:


What will you use for the self-powered remote control sealer?



I had several ideas here. My firat idea was to get a standard impulse
bag sealer, put it inside the chamber and just run the power wires
through glands in the sidewall. Once the desired level of vacuum was
drawn the power could be applied to the sealer.

In researching plastic sealing however I found a place that sells
parts and controlers. It seems that the state of the art is to
measure the temp of nichrome sealing element by measuring the current
that is being drawn so you do not over heat or underheat the bag you
want to seal. (The resistance changes as the temp rises)


Sounds like the same technique that is used in hot wire anemometers. One
common application of that would be the MAF sensor in many cars. I don't
know if there are any generic controllers that would suit your purpose.

This seems to be the way to go. but that opinion may change when I
price their controler. Optionally, one could mount the guts from the
off the shelf bag sealer outside the chamber and run the lower
voltage to the seal bar inside.

The bag is sealed between two pieces of silicone foam rubber and
several insulating and teflon strips to hold the melted plastic while
in resolidifies.

One thing for sure is that I am going to try an alternate cross
sectional geometry on the heating element. They sell one that has a
radius top edge to prevent the sealing bar from overheating the edge
of the band like the flat bands are prone to do.

Roger Shoaf

Lloyd E. Sponenburgh wrote:
RS at work fired this volley in news:45d6e4a8-
:


OK I can answe that. If you were to pressurise the outside of the bag
everything inside the bag would try to escape, including the stuff you
wanted to keep in the bag.

Think about a kid stepping on a packet of ketchup.

Roger Shoaf

Well, Roger, I think, then, that you missed something.

That "kid" is still at work when you pull a vacuum on the bag.

1) the contents will try to escape out the evacuation hole because,
2) the KID weighs 14.7psi at sea level, and he's stomping crap out of
your ketchup.

LLoyd


I don't think you have thought this out. When you start, the air
pressure on the inside of the bad is the same as it is on the outside
of the bag.

The bag is held shut by a less than hermetic seal, so as the air
pressure in the chamber drops, the air pressure inside the bag drops
also, but unlike the kid stepping on the ketchup packet, there is no
pressure on the other stuff in the bag.

Think of what would happen to a cup of ketchup in a bell jar, as the
air pressure drops, any bubbles in the ketchup would come to the
surface and pop but the ketchup would just sit in the cup, assuming of
course that you didn’t hold the vacuum so long as to vaporize all of
the water.


When a deep level of vacuum has been obtained, there might be space in
the bag, but that space contains no oxygen or a practically zero
oxygen level.

When the bag is then sealed, and air pressure is then reintroduced top
the chamber, now pressure is pushing the stuff inside the bag. Unless
the stuff is like potato chips or other crushable stuff, the air
pressure just holds the plastic against the stuff and prevents the
oxygen in the air from oxidizing and the aerobic bacteria from
growing.

Another cool thing you can do with a chamber sealer is to back fill
the chamber with nitrogen or another inert gas. This is what they do
with potato chips to get an oxygen free packaging.

Roger Shoaf

Gunner Asch wrote:


Im not sure it will be of any use..but Ive a number of Honeywell UDC2000
and UDC 2500 controllers that may be of assitance.

They are temperature/IO controllers for ovens and other heating
applications. Uses a remote termocouple and have a number of outputs
programmable


The problem with using a thermocouple is getting the thremocouple to
react faster than the plastic. A thick freezer bag is only ,004"
thick and it is really easy to over shoot the temp. if you try to use
a thermocouple.

The budget way is to use just time and trial and error. This works if
your timer is consistant and the residual heat is allowed to blead
off. Otherwise it is like making toast, the first slice tends to be a
little lighter than the ones that follow as the toaster is already
hot.

On the other hand, your controller might work if you can use a coil to
measure the amp draw of the heating element, and use that instead of a
voltage of a thermocouple. You might need an additional circuit to
translate the signal so the controler can understand it. When I get
to the control phase of the project I might run this by a electronics
whiz friend of mine.

My suspicion is that you can probably get a good seal using a timed
pulse and trial and error.

Roger Shoaf

On Oct 18, 8:40*am, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
...

Well, Roger, I think, then, that you missed something.

That "kid" is still at work when you pull a vacuum on the bag.

1) the contents will try to escape out the evacuation hole because,
2) the KID weighs 14.7psi at sea level, and he's stomping crap out of
your ketchup.

LLoyd

Not if the whole bag is inside the vacuum chamber.

jsw

In article
,
RS at work wrote:
The bag is held shut by a less than hermetic seal, so as the air
pressure in the chamber drops, the air pressure inside the bag drops
also, but unlike the kid stepping on the ketchup packet, there is no
pressure on the other stuff in the bag.

There is the pressure of any air space in the bag/contents. ie, the
bubbles you mention below...

Think of what would happen to a cup of ketchup in a bell jar, as the
air pressure drops, any bubbles in the ketchup would come to the
surface and pop but the ketchup would just sit in the cup, assuming of
course that you didn¹t hold the vacuum so long as to vaporize all of
the water.

Well, in practice, you have to deal with all the splattered "ketchup" on
the part of the bag you are trying to seal. Yes, I realize that you are
not actually sealing ketchup. But air leaving the food will tend to
bubble or even foam (depending on the food) and those bubbles will break
and splatter any liquid onto the interior of the bag (...and possibly
the exterior, and the chamber, and into the pump if you didn't deign to
avoid that).

The chamber I described before which was used for degassing epoxy had
epoxy splattered over most of the interior, and a good operator needed
to be ready to valve off the pump in a hurry on the initial pumpdown, to
let the bubbles sort themselves out without wasting a lot of epoxy
foaming its way out of the container. Then you'd sit at max vacuum for a
while waiting for the bubbles at the bottom (under the pressure of the
epoxy above them) to grow large enough that they would come to the
surface and pop. A really fancy system would have poured the epoxy under
vacuum (which would get more bubbles out), but that was too much money
on fancy things that would move inside the chamber, at least for our
budget.

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

RS at work fired this volley in news:94d50a8b-
:

I don't think you have thought this out. When you start, the air
pressure on the inside of the bad is the same as it is on the outside
of the bag.

In either scenario.

The bag is held shut by a less than hermetic seal, so as the air
pressure in the chamber drops, the air pressure inside the bag drops
also, but unlike the kid stepping on the ketchup packet, there is no
pressure on the other stuff in the bag.

You're not using a bell jar, you're using a plastic bag. OF COURSE there
is direct pressure (of 14.7psi) on every square inch of food in contact
with the bag. Where do you suspect that force would come from in your
"pressure packed" example, except from a differential between the inside
and outside pressures?


Think of what would happen to a cup of ketchup in a bell jar, as the
air pressure drops, any bubbles in the ketchup would come to the
surface and pop but the ketchup would just sit in the cup, assuming of
course that you didn’t hold the vacuum so long as to vaporize all of
the water.

F'criminy's sake... it's not a bell jar. It's a soft plastic bag! It
conforms to the surface shape of whatever is in it. It applies PRESSURE
to that surface, just as if someone had stepped on it.
..... snipped a bunch of non-sequitor stuff...

Another cool thing you can do with a chamber sealer is to back fill
the chamber with nitrogen or another inert gas. This is what they do
with potato chips to get an oxygen free packaging.

I'll let you continue to believe that until you see how a continuous
fill/seal line actually works.

In the case of potato chips and nitrogen fill, it has nothing to do with
differential pressures. The "chamber", when it exists at all, is a room,
with no pressure hardware, and no need for it.

LLoyd

Jim Wilkins fired this volley in news:2ce79227-8037-
:

Not if the whole bag is inside the vacuum chamber.

True enough, but that's not the example he offered.
LLoyd

On Oct 18, 4:18*pm, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
Jim Wilkins fired this volley in news:2ce79227-8037-
:

Not if the whole bag is inside the vacuum chamber.

True enough, but that's not the example he offered.
LLoyd

The original proposal:

"I am going to need a chamber that is somewhere in the order of
14X14X6
inches. If I went with a chunk of pipe, that would have to be
something like 16" diameter. The down side to this would be cost and
bulk. The more empty space inside the chanber the longer evacuation
time."

jsw

Jim Wilkins fired this volley in news:b0602d4d-bd61-
:

On Oct 18, 4:18*pm, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
Jim Wilkins fired this volley in news:2ce79227-
8037-
:

Not if the whole bag is inside the vacuum chamber.

True enough, but that's not the example he offered.
LLoyd

The original proposal:

"I am going to need a chamber that is somewhere in the order of
14X14X6
inches. If I went with a chunk of pipe, that would have to be
something like 16" diameter. The down side to this would be cost and
bulk. The more empty space inside the chanber the longer evacuation
time."

jsw


If that's what he originally posted, and IF he intended to do all the
sealing operations within the vacuum in that chamber, then I agree with
what he said.

Not a jot or tiddle of this post showed up on my news reader, and it's
usually reliable in that respect.

LLoyd

On Mon, 18 Oct 2010 17:58:38 -0500, Lloyd E. Sponenburgh wrote:

Not a jot or tiddle of this post showed up on my news reader, and it's
usually reliable in that respect.

Of course I'm familiar with the expression "jot or tittle", but having
never encountered "tiddle" before except in the Monty Python song
where it's meaning doesn't matter, had to look it up. From the 1913
Webster's Revised Unabridged Dictionary, tiddle is a verb that means
"To use with tenderness; to fondle" -- which most news readers
aren't noted for.

http://onlinedictionary.datasegment.com/word/tittle
http://www.cardinalfang.net/songs/bing_tiddle.html
http://onlinedictionary.datasegment.com/word/tiddle

--
jiw

James Waldby fired this volley in news:i9iu1e$7bs$1
@news.eternal-september.org:

From the 1913
Webster's Revised Unabridged Dictionary, tiddle is a verb that means
"To use with tenderness; to fondle" -- which most news readers
aren't noted for.


It's a noun, too:

"A tittle, rather appropriately for a word which sounds like a
combination of tiny and little, is smaller still (than a jot). It refers
to a small stroke or point in writing or printing. In classical Latin
this applied to any accent over a letter, but is now most commonly used
as the name for the dot over the letter 'i'. It is also the name of the
dots on dice."

LLoyd

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley in
. 3.70:




oops... a cite

http://www.phrases.org.uk/meanings/jot-or-tittle.html

On 2010-10-18, Jim Wilkins wrote:
On Oct 18, 4:18*pm, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
Jim Wilkins fired this volley in news:2ce79227-8037-
:

Not if the whole bag is inside the vacuum chamber.

True enough, but that's not the example he offered.
LLoyd

The original proposal:

"I am going to need a chamber that is somewhere in the order of
14X14X6
inches. If I went with a chunk of pipe, that would have to be
something like 16" diameter. The down side to this would be cost and
bulk. The more empty space inside the chanber the longer evacuation
time."

And the more surface area, the greater the force applied by the
atmosphere. Given your 14x14" dimension, that is 196 square inches, and
given an average atmospheric pressure of 14.7 psi that is 2,881 pounds
force which the walls will have to survive.

The 16" pipe would have 201.6 square inches, or 2,955 lbs on the
end plates.

I have my doubts about glued up acrylic (Plexiglas) handling
that.

Good Luck,
DoN.

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DoN. Nichols wrote:
On 2010-10-18, Jim wrote:
On Oct 18, 4:18 pm, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
Jim fired this volley in news:2ce79227-8037-
:

Not if the whole bag is inside the vacuum chamber.

True enough, but that's not the example he offered.
LLoyd

The original proposal:

"I am going to need a chamber that is somewhere in the order of
14X14X6
inches. If I went with a chunk of pipe, that would have to be
something like 16" diameter. The down side to this would be cost and
bulk. The more empty space inside the chanber the longer evacuation
time."

And the more surface area, the greater the force applied by the
atmosphere. Given your 14x14" dimension, that is 196 square inches, and
given an average atmospheric pressure of 14.7 psi that is 2,881 pounds
force which the walls will have to survive.

The 16" pipe would have 201.6 square inches, or 2,955 lbs on the
end plates.

I have my doubts about glued up acrylic (Plexiglas) handling
that.

Good Luck,
DoN.


I dunno. This 24" x 24" x 24" cube looks really neat, though!
http://www.abbess.com/vac/images-chambers/cube-24/24cube-cleardoor/DSCF0010.JPG

--Winston

On 2010-10-20, Winston wrote:
DoN. Nichols wrote:
On 2010-10-18, Jim wrote:

[ ... ]

The original proposal:

"I am going to need a chamber that is somewhere in the order of
14X14X6
inches. If I went with a chunk of pipe, that would have to be
something like 16" diameter. The down side to this would be cost and
bulk. The more empty space inside the chanber the longer evacuation
time."

And the more surface area, the greater the force applied by the
atmosphere. Given your 14x14" dimension, that is 196 square inches, and
given an average atmospheric pressure of 14.7 psi that is 2,881 pounds
force which the walls will have to survive.

The 16" pipe would have 201.6 square inches, or 2,955 lbs on the
end plates.

I have my doubts about glued up acrylic (Plexiglas) handling
that.

[ ... ]

I dunno. This 24" x 24" x 24" cube looks really neat, though!
http://www.abbess.com/vac/images-chambers/cube-24/24cube-cleardoor/DSCF0010.JPG

Yes, it does. But ...

1) It is not *glued* up. There is a single sheet of what looks like
1" thick or better Lexan (not Plexiglas) as the door only.
Lexan is not as brittle as Plexiglas.

2) It is sealed by an O-ring to a flat machined metal surface.

3) The enclosure is welded full length seams on the inside -- and
(I believe) also on the outside.

4) The enclosure is *not* Plexiglas. I don't know the metal
involved. Perhaps stainless steel, perhaps aluminum. If the
latter I would expect metal fatigue over the years as the number
of pressure/vacuum cycles builds up.

5) It appears to be designed to mount in a 19" relay rack. (The
trick is getting that rear crossbar past the front rails. :-)

I kept reading (earlier in the thread) plans for gluing up a box
of Plexiglas -- and *that* I do not trust -- especially in normal
thicknesses.

Enjoy,
DoN.

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On Thu, 21 Oct 2010 02:47:25 +0000, DoN. Nichols wrote:
On 2010-10-20, Winston@BigBrother wrote:
DoN. Nichols wrote:
On 2010-10-18, Jim Wilkins wrote:
....
The original proposal:

"I am going to need a chamber that is somewhere in the order of
14X14X6 inches. If I went with a chunk of pipe, that would have
to be something like 16" diameter. The down side to this would
be cost and bulk. The more empty space inside the chamber
the longer evacuation time."

And the more surface area, the greater the force applied by the
atmosphere. Given your 14x14" dimension, that is 196 square inches,
and given an average atmospheric pressure of 14.7 psi that is 2,881
pounds force which the walls will have to survive.
[snip re 2,955 lbs on end plates of 16" pipe version]
I have my doubts about glued up acrylic (Plexiglas) handling
that.

See comment at end re "glued up" version

....
I dunno. This 24" x 24" x 24" cube looks really neat, though!
http://www.abbess.com/vac/images-chambers/cube-24/24cube-cleardoor/DSCF0010.JPG

Yes, it does. But ...

1) It is not *glued* up. There is a single sheet of what looks like
1" thick or better Lexan (not Plexiglas) as the door only. Lexan is not
as brittle as Plexiglas.

Per http://www.abbess.com/vac/vacuum.html the door is acrylic
rather than polycarbonate. Metal can be aluminum or stainless
steel as buyer prefers.

[snip 2-3-4 re O-ring and metal enclosure]

5) It appears to be designed to mount in a 19" relay rack. (The
trick is getting that rear crossbar past the front rails. :-)

The interior dimensions of the VCC-24 cube in the image are
24" x 24" x 24", so it won't fit into a 19"-on-hole-centers rack.
Also, operating the door latches requires access to the front
left side; see "Standard Latches" picture at middle of
(again) http://www.abbess.com/vac/vacuum.html.

I kept reading (earlier in the thread) plans for gluing up a box
of Plexiglas -- and *that* I do not trust -- especially in normal
thicknesses.

Roger's description wasn't clear -- his mention of bracing ribs
was vague -- but here's my interpretation: He said the top
and bottom would be square plates of 1/2" tempered glass.
These are the faces that would take the 2881 pounds of
pressure you mentioned in earlier post. No glue involved in
bearing that load. The sides would be thicker Lexan
(polycarbonate), "braced by ribs". Presumably two sides
would be braced at their ends against the other two sides,
which are somehow braced apart by "ribs".

I think it would be a better design to rabbet the ends of the
sides so that bracing is symmetric, and to center say
14"x14"x1/4" squares of acrylic on the inside faces of
16"x16"x3/4" glass plates. Pressure on the polycarbonate
sides would be borne by the acrylic, under compression,
with no glue joints in tension. Pressure on the glass sides
would be borne by the polycarbonate sides, again with no
glue in tension.

--
jiw

DoN. Nichols wrote:


Yes, it does. But ...

1) It is not *glued* up. There is a single sheet of what looks like
1" thick or better Lexan (not Plexiglas) as the door only.
Lexan is not as brittle as Plexiglas.

2) It is sealed by an O-ring to a flat machined metal surface.

3) The enclosure is welded full length seams on the inside -- and
(I believe) also on the outside.

4) The enclosure is *not* Plexiglas. I don't know the metal
involved. Perhaps stainless steel, perhaps aluminum. If the
latter I would expect metal fatigue over the years as the number
of pressure/vacuum cycles builds up.

5) It appears to be designed to mount in a 19" relay rack. (The
trick is getting that rear crossbar past the front rails. :-)

I kept reading (earlier in the thread) plans for gluing up a box
of Plexiglas -- and *that* I do not trust -- especially in normal
thicknesses.

Enjoy,
DoN.




DoN,

I appreciate your criticism.

I find that the process of designing something even more satisfying
than building the thing it self. I have set an arbitrary goal of $200
for building this project, which may or may not be doable; nothing is
cast in stone yet.


For the top of the chamber I was originally thinking about some 1”
Lexan, then I priced the stuff, not cheap.

I then asked myself how strong does it have to be? And, is there
something else that can do the job cheaper?


Tempered glass is pretty strong stuff. I have seen a 200# person
stand on the glass of a pinball machine. And that is only 1/4”
thick. In checking a bit, I noted that one glass company shows a guy
jumping up and down on a sheet of 3/8 supported on wood blocks about 5
feet apart. I also noted that people build big aquariums out of glass
and acrylic glued together and supporting holding tons of water.

While I am not sure, I suspect that a clear span of 14” X 16” X 3/8 or
1/2 might support the 3,300 lbs of pressure and still give an
acceptable safety factor. I have a call into the glass company to
check with the engineers that know.

Assuming I will get a satisfactory reply to the glass inquiry, the
plastic sidewall I described admittedly sounds like a failure waiting
to happen, but here is my thinking.

Assume that you have a nice thick chunk of 6” pipe sealed on one end,
and on the open end you have a sheet of Plexiglas and a rubber
gasket. If a vacuum were drawn out of the pipe would a 1/4 sheet of
acrylic have the ability to resist fracture if you got near a full
vacuum? I think it would, as it is about 300 lbs. evenly applied over
about 19 square inches.

Now if you can accept that proposition, think about a 1/4” sheet of
Plexiglas that is 6 “ by 4” and has a 1/4” X 1/2 bonded to each one of
the 4” ends and between and along the 6 inch sides you have two 3/8
thick sides that are 1 inch high and are tee shaped with the top of
the tee being 1/2” high 6 1/2” wide and the bottom being 5 1/2” wide
and bonded to the ends with the tabs sticking out.

What you would have would be a Plexiglas box with 1/2” sidewalls and 4
tabs that are 3/8” X 1/2” X 1/2”.

If you were then to suspend this box on the tabs between two rails and
loaded the box with 360 lbs., would it hold? I think it would.

Now if I haven’t lost you yet, the top and bottom of the chamber are
going to be exerting a total force against the sidewalls of about
6,720 lbs. This will be supported by about 15 square inches of
Plexiglas that is 6 inches high. Would a block of Plexiglas 3 3/4
inches square and 6 inches high support 6,720 lbs.?

As far as the glue joints go, the glue joints should be stronger than
the plastic itself.

If my thinking is off here I would like to know where. The regular
RCMer’s tend to be a bunch that is pretty damn smart, which is why I
tossed the concept out there.

The cost between Plexiglas and Lexan is not much, so I might opt to go
that route, also I might increase the number of side support ribs to
spread out the load a bit more to increase the safety factor, it kind
of depends on the yield I can get from a stock sheet of plastic.

Thanks again for your criticism.

Roger Shoaf

On Oct 21, 6:57*pm, RS at work wrote:
...
Tempered glass is pretty strong stuff. *I have seen a 200# person
stand on the glass of a pinball machine. *And that is only 1/4”
thick. *...
Roger Shoaf

The door glass on these is 5/8" thick:
http://compare.ebay.com/like/2304711...sort=BestMatch

The interior is 8" x 8" x 12" deep, unless caked with old epoxy as
mine was.

jsw

On 2010-10-21, RS at work wrote:


DoN. Nichols wrote:


Yes, it does. But ...

[ ... my post snipped ... ]

DoN,

I appreciate your criticism.

I find that the process of designing something even more satisfying
than building the thing it self. I have set an arbitrary goal of $200
for building this project, which may or may not be doable; nothing is
cast in stone yet.

O.K.


For the top of the chamber I was originally thinking about some 1?
Lexan, then I priced the stuff, not cheap.

:-)

I then asked myself how strong does it have to be? And, is there
something else that can do the job cheaper?


Tempered glass is pretty strong stuff. I have seen a 200# person
stand on the glass of a pinball machine. And that is only 1/4?
thick.

I think that the centers of some of the bumpers are support
columns distributed over the top, so I'm not sure what this proves
without knowing precisely where the weight was applied, and where the
support columns were relative to that.

In checking a bit, I noted that one glass company shows a guy
jumping up and down on a sheet of 3/8 supported on wood blocks about 5
feet apart.

That is somewhat more meaningful.

I also noted that people build big aquariums out of glass
and acrylic glued together and supporting holding tons of water.

We don't know what other support members may be present hidden
from view.

While I am not sure, I suspect that a clear span of 14? X 16? X 3/8 or
1/2 might support the 3,300 lbs of pressure and still give an
acceptable safety factor. I have a call into the glass company to
check with the engineers that know.

O.K. They will certainly err on the conservative side.

Assuming I will get a satisfactory reply to the glass inquiry, the
plastic sidewall I described admittedly sounds like a failure waiting
to happen, but here is my thinking.

Assume that you have a nice thick chunk of 6? pipe sealed on one end,
and on the open end you have a sheet of Plexiglas and a rubber
gasket. If a vacuum were drawn out of the pipe would a 1/4 sheet of
acrylic have the ability to resist fracture if you got near a full
vacuum? I think it would, as it is about 300 lbs. evenly applied over
about 19 square inches.

Hmm ... I don't know the ID of your "6?" (which I presume to be
6 inch) pipe, so calculating from the OD, I come up with 28.27 square
inches, or 145.6 pounds total force.

Now if you can accept that proposition, think about a 1/4? sheet of
Plexiglas that is 6 ? by 4? and has a 1/4? X 1/2 bonded to each one of
the 4? ends and between and along the 6 inch sides you have two 3/8
thick sides that are 1 inch high and are tee shaped with the top of
the tee being 1/2? high 6 1/2? wide and the bottom being 5 1/2? wide
and bonded to the ends with the tabs sticking out.

Again -- I don't trust the bonded principle. There are a lot of
things which can go wrong in the bonding. And -- if you are going to
try solvent bonding over a large area -- expect the solvent to be
trapped in the center areas, weakening them.

And -- add to that the fact that acryllic tends to form cracks
from exposure to oil (from the machine tool which fabricated the parts,
unless you worked with totally clean new tools dipped in acetone to wash
off the oil before cutting. Also -- all clamping surfaces will
similarly need to be cleaned of oil totally.

What you would have would be a Plexiglas box with 1/2? sidewalls and 4
tabs that are 3/8? X 1/2? X 1/2?.

Until I see evidence to the contrary, I am reluctant to consider
two layers of Plexiglas bonded together to be any stronger than the
thicker of the two individual layers.

If you were then to suspend this box on the tabs between two rails and
loaded the box with 360 lbs., would it hold? I think it would.

This looks a lot smaller than what you originally wanted in
volume.

Now if I haven?t lost you yet, the top and bottom of the chamber are
going to be exerting a total force against the sidewalls of about
6,720 lbs. This will be supported by about 15 square inches of
Plexiglas that is 6 inches high. Would a block of Plexiglas 3 3/4
inches square and 6 inches high support 6,720 lbs.?

Maybe -- but consider that the walls are undergong lateral force
which could weaken them. Consider a pipe 20' tall supporting a load
something like 80% of the calculated safe load. Then apply 20% of that
force sideways to the center of the pipe. What would happen?

As far as the glue joints go, the glue joints should be stronger than
the plastic itself.

This -- I don't trust. Especially with the surface area being
solvent glued together. How long would it take the solvent to dry in
the center of the glued surface?

If my thinking is off here I would like to know where. The regular
RCMer?s tend to be a bunch that is pretty damn smart, which is why I
tossed the concept out there.

Well ... I tend to be rather conservative when it comes to
vacuum containers.

And for the tempered glass -- what happens with that if a
scratch is applied to the surface -- especially on the center of the
inside, so it becomes a stress riser.

The cost between Plexiglas and Lexan is not much, so I might opt to go
that route, also I might increase the number of side support ribs to
spread out the load a bit more to increase the safety factor, it kind
of depends on the yield I can get from a stock sheet of plastic.

I would feel more comfortable with Lexan. It is not as brittle
as Plexiglas. (Have you ever used the scribe and bend method of cutting
Plexiglas?)

Thanks again for your criticism.

You're welcome.

Best of luck,
DoN.

--
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Email: | Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---

Just build a reinforced metal top with a small window or two in it. You do
not need to see what is happening except for grins. Could grind a lens on
the end of a plastic slug to see all over the cavity.

"DoN. Nichols" wrote in message
...

On 2010-10-21, RS at work wrote:


DoN. Nichols wrote:


Yes, it does. But ...

[ ... my post snipped ... ]

DoN,

I appreciate your criticism.

I find that the process of designing something even more satisfying
than building the thing it self. I have set an arbitrary goal of $200
for building this project, which may or may not be doable; nothing is
cast in stone yet.

O.K.


For the top of the chamber I was originally thinking about some 1?
Lexan, then I priced the stuff, not cheap.

:-)

I then asked myself how strong does it have to be? And, is there
something else that can do the job cheaper?


Tempered glass is pretty strong stuff. I have seen a 200# person
stand on the glass of a pinball machine. And that is only 1/4?
thick.

I think that the centers of some of the bumpers are support
columns distributed over the top, so I'm not sure what this proves
without knowing precisely where the weight was applied, and where the
support columns were relative to that.

In checking a bit, I noted that one glass company shows a guy
jumping up and down on a sheet of 3/8 supported on wood blocks about 5
feet apart.

That is somewhat more meaningful.

I also noted that people build big aquariums out of glass
and acrylic glued together and supporting holding tons of water.

We don't know what other support members may be present hidden
from view.

While I am not sure, I suspect that a clear span of 14? X 16? X 3/8 or
1/2 might support the 3,300 lbs of pressure and still give an
acceptable safety factor. I have a call into the glass company to
check with the engineers that know.

O.K. They will certainly err on the conservative side.

Assuming I will get a satisfactory reply to the glass inquiry, the
plastic sidewall I described admittedly sounds like a failure waiting
to happen, but here is my thinking.

Assume that you have a nice thick chunk of 6? pipe sealed on one end,
and on the open end you have a sheet of Plexiglas and a rubber
gasket. If a vacuum were drawn out of the pipe would a 1/4 sheet of
acrylic have the ability to resist fracture if you got near a full
vacuum? I think it would, as it is about 300 lbs. evenly applied over
about 19 square inches.

Hmm ... I don't know the ID of your "6?" (which I presume to be
6 inch) pipe, so calculating from the OD, I come up with 28.27 square
inches, or 145.6 pounds total force.

Now if you can accept that proposition, think about a 1/4? sheet of
Plexiglas that is 6 ? by 4? and has a 1/4? X 1/2 bonded to each one of
the 4? ends and between and along the 6 inch sides you have two 3/8
thick sides that are 1 inch high and are tee shaped with the top of
the tee being 1/2? high 6 1/2? wide and the bottom being 5 1/2? wide
and bonded to the ends with the tabs sticking out.

Again -- I don't trust the bonded principle. There are a lot of
things which can go wrong in the bonding. And -- if you are going to
try solvent bonding over a large area -- expect the solvent to be
trapped in the center areas, weakening them.

And -- add to that the fact that acryllic tends to form cracks
from exposure to oil (from the machine tool which fabricated the parts,
unless you worked with totally clean new tools dipped in acetone to wash
off the oil before cutting. Also -- all clamping surfaces will
similarly need to be cleaned of oil totally.

What you would have would be a Plexiglas box with 1/2? sidewalls and 4
tabs that are 3/8? X 1/2? X 1/2?.

Until I see evidence to the contrary, I am reluctant to consider
two layers of Plexiglas bonded together to be any stronger than the
thicker of the two individual layers.

If you were then to suspend this box on the tabs between two rails and
loaded the box with 360 lbs., would it hold? I think it would.

This looks a lot smaller than what you originally wanted in
volume.

Now if I haven?t lost you yet, the top and bottom of the chamber are
going to be exerting a total force against the sidewalls of about
6,720 lbs. This will be supported by about 15 square inches of
Plexiglas that is 6 inches high. Would a block of Plexiglas 3 3/4
inches square and 6 inches high support 6,720 lbs.?

Maybe -- but consider that the walls are undergong lateral force
which could weaken them. Consider a pipe 20' tall supporting a load
something like 80% of the calculated safe load. Then apply 20% of that
force sideways to the center of the pipe. What would happen?

As far as the glue joints go, the glue joints should be stronger than
the plastic itself.

This -- I don't trust. Especially with the surface area being
solvent glued together. How long would it take the solvent to dry in
the center of the glued surface?

If my thinking is off here I would like to know where. The regular
RCMer?s tend to be a bunch that is pretty damn smart, which is why I
tossed the concept out there.

Well ... I tend to be rather conservative when it comes to
vacuum containers.

And for the tempered glass -- what happens with that if a
scratch is applied to the surface -- especially on the center of the
inside, so it becomes a stress riser.

The cost between Plexiglas and Lexan is not much, so I might opt to go
that route, also I might increase the number of side support ribs to
spread out the load a bit more to increase the safety factor, it kind
of depends on the yield I can get from a stock sheet of plastic.

I would feel more comfortable with Lexan. It is not as brittle
as Plexiglas. (Have you ever used the scribe and bend method of cutting
Plexiglas?)

Thanks again for your criticism.

You're welcome.

Best of luck,
DoN.

--
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Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. |
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