I've dug around for quite a while, and although I find all sorts of
"comforting" diagonal data about fall heights, column separation, etc, I
cannot find a stated vacuum rating for ASTM D2729 pipe (4").

I'm getting ready to re-do a poorly-designed vacuum hold-down system for
a ShopSabre 4896 that has only ONE 2" pipe to each half of the table,
even though the pump has a 4" inlet!(duh!)

4" water pipe (sch 20-40-80) is slightly too large to fit in the space
provided, but 4" ASTM-D2729 sewer pipe will fit. We're only talking 11"
of vacuum (or -5.4psi). But I want some margin of safety, and can't find
a figure anywhere.

Anyone know?

Thanks,
Lloyd

On Sun, 15 Feb 2015 15:49:04 -0600, Lloyd E. Sponenburgh wrote:

I've dug around for quite a while, and although I find all sorts of
"comforting" diagonal data about fall heights, column separation, etc, I
cannot find a stated vacuum rating for ASTM D2729 pipe (4").

I'm getting ready to re-do a poorly-designed vacuum hold-down system for
a ShopSabre 4896 that has only ONE 2" pipe to each half of the table,
even though the pump has a 4" inlet!(duh!)

4" water pipe (sch 20-40-80) is slightly too large to fit in the space
provided, but 4" ASTM-D2729 sewer pipe will fit. We're only talking 11"
of vacuum (or -5.4psi). But I want some margin of safety, and can't
find a figure anywhere.

Anyone know?

Thanks,
Lloyd

Lloyd, 2" + 2" = 4". What's your problem?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On Sun, 15 Feb 2015 16:05:03 -0600, Tim Wescott wrote:

On Sun, 15 Feb 2015 15:49:04 -0600, Lloyd E. Sponenburgh wrote:

I've dug around for quite a while, and although I find all sorts of
"comforting" diagonal data about fall heights, column separation, etc,
I cannot find a stated vacuum rating for ASTM D2729 pipe (4").

I'm getting ready to re-do a poorly-designed vacuum hold-down system
for a ShopSabre 4896 that has only ONE 2" pipe to each half of the
table, even though the pump has a 4" inlet!(duh!)

4" water pipe (sch 20-40-80) is slightly too large to fit in the space
provided, but 4" ASTM-D2729 sewer pipe will fit. We're only talking
11"
of vacuum (or -5.4psi). But I want some margin of safety, and can't
find a figure anywhere.

Anyone know?

Thanks,
Lloyd

Lloyd, 2" + 2" = 4". What's your problem?

2 2 inch pipes have an area of 6.28 sq inches.
1 4 inch pipe has an area of 12.56 inches.

Tim Wescott fired this volley in news:cb-
:

Lloyd, 2" + 2" = 4". What's your problem?

Yeah...that's what they thought, too!
Lloyd

unk fired this volley in news:mbr5cj$dpt$1
@speranza.aioe.org:

2 2 inch pipes have an area of 6.28 sq inches.
1 4 inch pipe has an area of 12.56 inches.

Yes, he knew that; hence the smiley on the end!

Lloyd

On Sun, 15 Feb 2015 15:49:04 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

I've dug around for quite a while, and although I find all sorts of
"comforting" diagonal data about fall heights, column separation, etc, I
cannot find a stated vacuum rating for ASTM D2729 pipe (4").

I'm getting ready to re-do a poorly-designed vacuum hold-down system for
a ShopSabre 4896 that has only ONE 2" pipe to each half of the table,
even though the pump has a 4" inlet!(duh!)

4" water pipe (sch 20-40-80) is slightly too large to fit in the space
provided, but 4" ASTM-D2729 sewer pipe will fit. We're only talking 11"
of vacuum (or -5.4psi). But I want some margin of safety, and can't find
a figure anywhere.

Anyone know?

Thanks,
Lloyd

I don't know. d8-)

However, here a few formulas, if you want to trust your calculations.
Start with the fact that 4" ASTM-D2729 sewer pipe has a wall thickness
(min.) of 0.075".

http://www.northamericanpipe.com/pro...-sewer---drain

(click on "product spec")

There's a formula near the top of this page...

http://www.lascofittings.com/pressureratingsofplastics

.... for calculating the internal pressure it will take. Then there is
a table lower on the page that relates max. external pressure to the
max. internal pressure -- for schedule 80 pipe.

My question would be what kind of relationship there is between the
internal versus external pressure tolerance for much thinner pipe.
There probably is some aspect of the Euler buckling formula at work,
but I have no clue about what that would be.

If it were me, I'd build it, stand back, and try it. Crumpling is a
lot better than exploding. g

--
Ed Huntress

Ed Huntress fired this volley in
:


If it were me, I'd build it, stand back, and try it. Crumpling is a
lot better than exploding. g

Yeah.... I'm out to the hardware tomorrow for some end caps and a fitting
to hook my HVAC pump up to it. I figure I'll gradually reduce the
pressure inside until it buckles (or doesn't!G). If it will take -
10psi, I'll be pretty comfortable with it.

It will naturally be stronger in compression (vacuum) than in tension
(pressure).

Lloyd

On Sun, 15 Feb 2015 17:25:19 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Ed Huntress fired this volley in
:


If it were me, I'd build it, stand back, and try it. Crumpling is a
lot better than exploding. g

Yeah.... I'm out to the hardware tomorrow for some end caps and a fitting
to hook my HVAC pump up to it. I figure I'll gradually reduce the
pressure inside until it buckles (or doesn't!G). If it will take -
10psi, I'll be pretty comfortable with it.

It will naturally be stronger in compression (vacuum) than in tension
(pressure).

Except for buckling. It could crumple long before it reaches
compressive yield strength.

Calculating buckling is black magic. When you take a basic statics
course, the instructor sizes you up and decides whether he/she should
even tell you about it, aside from the basic column formula. I took
statics in a technology class (no calculus) rather than an engineering
class, so I never got into it until long after I was out of school.

Be glad we don't have to calculate it.

--
Ed Huntress

On Sun, 15 Feb 2015 16:18:07 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Tim Wescott fired this volley in news:cb-
:

Lloyd, 2" + 2" = 4". What's your problem?

Yeah...that's what they thought, too!
Lloyd

Btw..if anyone needs vacuum pumps/gear

http://www.ebay.com/itm/Used-Edwards...-/131428338951

He has a number of pumps including one thats absolutely brand new..NOS

http://www.ebay.com/itm/New-Unused-E...-/131428334706

There are several others..keep watching if the above is not what you
need..or simply call him

Gunner

"At the core of liberalism is the spoiled child,
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosophy of sniveling brats."
PJ O'Rourke

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 4.170...
I've dug around for quite a while, and although I find all sorts of
"comforting" diagonal data about fall heights, column separation,
etc, I
cannot find a stated vacuum rating for ASTM D2729 pipe (4").

I'm getting ready to re-do a poorly-designed vacuum hold-down system
for
a ShopSabre 4896 that has only ONE 2" pipe to each half of the
table,
even though the pump has a 4" inlet!(duh!)

4" water pipe (sch 20-40-80) is slightly too large to fit in the
space
provided, but 4" ASTM-D2729 sewer pipe will fit. We're only talking
11"
of vacuum (or -5.4psi). But I want some margin of safety, and can't
find
a figure anywhere.

Anyone know?

Thanks,
Lloyd

How about two 3" water pipes? 18 16. Try to avoid sharp corners.

You could cap a piece, pull a good vacuum and drop typical weights for
that site on it, to find its impact resistance which may not be the
same as its collapse rating under uniformly distributed external
pressure, as from ground water.
http://roscoemoss.com/technical-resources/calculators/

-jsw

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 4.170...
Ed Huntress fired this volley in
:


If it were me, I'd build it, stand back, and try it. Crumpling is a
lot better than exploding. g

Yeah.... I'm out to the hardware tomorrow for some end caps and a
fitting
to hook my HVAC pump up to it. I figure I'll gradually reduce the
pressure inside until it buckles (or doesn't!G). If it will
take -
10psi, I'll be pretty comfortable with it.

It will naturally be stronger in compression (vacuum) than in
tension
(pressure).

Lloyd

That depends very much on the wall thickess. A soda bottle can hold
over 100 PSI (200?) but collapses if you put hot water in it and let
it cool.
-jsw

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 4.170...
Ed Huntress fired this volley in
:


If it were me, I'd build it, stand back, and try it. Crumpling is a
lot better than exploding. g

Yeah.... I'm out to the hardware tomorrow for some end caps and a
fitting
to hook my HVAC pump up to it. I figure I'll gradually reduce the
pressure inside until it buckles (or doesn't!G). If it will
take -
10psi, I'll be pretty comfortable with it.

It will naturally be stronger in compression (vacuum) than in
tension
(pressure).

Lloyd

"Test plugs" don't have to be glued on or cut off and discarded
afterwards. My ISP is slow tonight and not returning images, but I
remember using a type with a garden hose fitting to fill the newly
installed drain plumbing until water ran out the roof stack, to check
for leaks before installing the sinks and toilets.

-jsw

"Jim Wilkins" fired this volley in news:mbrdps$cem
:

"Test plugs" don't have to be glued on or cut off and discarded
afterwards. My ISP is slow tonight and not returning images, but I
remember using a type with a garden hose fitting to fill the newly
installed drain plumbing until water ran out the roof stack, to check
for leaks before installing the sinks and toilets.

I have (literally) a shelf-full of them. But all mine are for
"scheduled" (SDR) pipe. I don't even know if they make them to fit the
thinwalled sewer drain pipe. I'll check. but since I need only make one
test, and because I can selectively save at lease one of the caps by
leaving it on the piece... It won't cost me more than a couple of bucks.

Lloyd

Lloyd E. Sponenburgh wrote:
"Jim Wilkins" fired this volley in
news:mbrdps$cem :

"Test plugs" don't have to be glued on or cut off and discarded
afterwards. My ISP is slow tonight and not returning images, but I
remember using a type with a garden hose fitting to fill the newly
installed drain plumbing until water ran out the roof stack, to check
for leaks before installing the sinks and toilets.

I have (literally) a shelf-full of them. But all mine are for
"scheduled" (SDR) pipe. I don't even know if they make them to fit
the thinwalled sewer drain pipe. I'll check. but since I need only
make one test, and because I can selectively save at lease one of the
caps by leaving it on the piece... It won't cost me more than a
couple of bucks.

Lloyd

They do make bushings to use standard fittings on that thin wall drain pipe
..

--
Snag

On Sun, 15 Feb 2015 22:08:19 +0000, unk wrote:

On Sun, 15 Feb 2015 16:05:03 -0600, Tim Wescott wrote:

On Sun, 15 Feb 2015 15:49:04 -0600, Lloyd E. Sponenburgh wrote:

I've dug around for quite a while, and although I find all sorts of
"comforting" diagonal data about fall heights, column separation, etc,
I cannot find a stated vacuum rating for ASTM D2729 pipe (4").

I'm getting ready to re-do a poorly-designed vacuum hold-down system
for a ShopSabre 4896 that has only ONE 2" pipe to each half of the
table, even though the pump has a 4" inlet!(duh!)

4" water pipe (sch 20-40-80) is slightly too large to fit in the space
provided, but 4" ASTM-D2729 sewer pipe will fit. We're only talking
11"
of vacuum (or -5.4psi). But I want some margin of safety, and can't
find a figure anywhere.

Anyone know?

Thanks,
Lloyd

Lloyd, 2" + 2" = 4". What's your problem?

2 2 inch pipes have an area of 6.28 sq inches.
1 4 inch pipe has an area of 12.56 inches.

Wouldn't the area of a pipe depend on it's length? It seems like a long
pipe would cover a lot more area than a short one.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Tim Wescott wrote:
On Sun, 15 Feb 2015 22:08:19 +0000, unk wrote:

On Sun, 15 Feb 2015 16:05:03 -0600, Tim Wescott wrote:

On Sun, 15 Feb 2015 15:49:04 -0600, Lloyd E. Sponenburgh wrote:

I've dug around for quite a while, and although I find all sorts of
"comforting" diagonal data about fall heights, column separation,
etc, I cannot find a stated vacuum rating for ASTM D2729 pipe (4").

I'm getting ready to re-do a poorly-designed vacuum hold-down
system for a ShopSabre 4896 that has only ONE 2" pipe to each half
of the table, even though the pump has a 4" inlet!(duh!)

4" water pipe (sch 20-40-80) is slightly too large to fit in the
space provided, but 4" ASTM-D2729 sewer pipe will fit. We're only
talking 11"
of vacuum (or -5.4psi). But I want some margin of safety, and
can't find a figure anywhere.

Anyone know?

Thanks,
Lloyd

Lloyd, 2" + 2" = 4". What's your problem?

2 2 inch pipes have an area of 6.28 sq inches.
1 4 inch pipe has an area of 12.56 inches.

Wouldn't the area of a pipe depend on it's length? It seems like a
long pipe would cover a lot more area than a short one.

We're talking cross section , not volume . Double the diameter and you
quadruple the cross section .

--
Snag

On 02/15/2015 04:08 PM, unk wrote:

Lloyd, 2" + 2" = 4". What's your problem?

2 2 inch pipes have an area of 6.28 sq inches.
1 4 inch pipe has an area of 12.56 inches.


Is that similar to circular mills?
For example, 2 24 gage wires twisted together
will carry the same maximum current as 1 21 gage.



technomaNge
--
Saw a chart somewhere.

"Terry Coombs" fired this volley in
:

They do make bushings to use standard fittings on that thin wall drain
pipe

Yep, and I'm counting on that so as not to throw away the parts of the
ShopSabre plumbing that are (at the least) just adequate.

I plan to later 'plenum' the entire underside of the table, rather than
using a system of collector pipes, and to also 'remote' the pump to just
outside the room, for noise control. (a 20HP regenerative blower makes a
racket!)

That wouldn't work for someone who did smaller work, but everything we do
on the machine is with full 4x8 sheets of stock (yeah, I know, 'famous
last words').

It only breaks into four zones now, so just keeping 3/4 of a sheet of
stock cut into 1/4-sheet pieces would do the 'zoning' as well as the
valve system it has now.

Lloyd

Tim Wescott fired this volley in
:

Wouldn't the area of a pipe depend on it's length? It seems like a long
pipe would cover a lot more area than a short one.

???

technomaNge fired this volley in news:mbrmo8$pa3$1
@dont-email.me:

s that similar to circular mills?
For example, 2 24 gage wires twisted together
will carry the same maximum current as 1 21 gage.

Same concept. Only, ShopSabre used the logic thus:

"If it takes a 12-gauge wire to go 12 feet, then I should be able to run
36 feet with only 36 gauge wire! We'll save LOTS of money!"

Lloyd

On 2/15/2015 5:44 PM, Gunner Asch wrote:
On Sun, 15 Feb 2015 16:18:07 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Tim Wescott fired this volley in news:cb-
:

Lloyd, 2" + 2" = 4". What's your problem?

Yeah...that's what they thought, too!
Lloyd

Btw..if anyone needs vacuum pumps/gear

http://www.ebay.com/itm/Used-Edwards...-/131428338951

He has a number of pumps including one thats absolutely brand new..NOS

http://www.ebay.com/itm/New-Unused-E...-/131428334706

There are several others..keep watching if the above is not what you
need..or simply call him

Gunner


What kills me is there isn't a mention of what level of vacuum it can pull.

Is this a food grade bag sucker ?
Is this a 4'x16' plastic vac table for CNC plastic.....

One has to know the machine and use before spending 1 or 2.5k !

Martin

In article 0,
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:

a ShopSabre 4896 that has only ONE 2" pipe to each half of the table,
even though the pump has a 4" inlet!(duh!)

4" water pipe (sch 20-40-80) is slightly too large to fit in the space
provided, but 4" ASTM-D2729 sewer pipe will fit. We're only talking 11"
of vacuum (or -5.4psi). But I want some margin of safety, and can't find
a figure anywhere.

Two 3" pipes are slightly larger than one 4" pipe, so you could just
make the pipe to each half 3" Sch. 20, 40 or 80 and run to a 4" (via
Tee, Wyes, reducers etc in the smoothest transition manner possible) at
the pump/bower. Should be effective and means not trusting SDR to do too
much, which is usually a good idea.

If committed to using 4" sewer pipe, being a practical git and an old
vacuum hand, I'd rig up a test section and suck it down to 30" to see if
it collapsed or not. Use a regular roughing pump that can just pull that
without a sweat, not your blower/pump which probably can't. Leave it for
a good long while. Barring some sort of kink, defect, etc I would not be
too surprised if it didn't collapse. If it did, I'd pay attention to
when that happened (if during pump-down) and try another piece at an
inch or two less, until it didn't, to get a general idea of where it
usually failed. A trap/screen on the pump input would be wise for this
testing, as might a wire cage around the test pipe in case of shrapnel
leaving.

On the third hand this is the ugly cousin of using PVC for compressed
air; but I guess most of the shrapnel would end up in the pump/blower
if/when it failed.

--
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.

On Sun, 15 Feb 2015 15:49:04 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

I've dug around for quite a while, and although I find all sorts of
"comforting" diagonal data about fall heights, column separation, etc, I
cannot find a stated vacuum rating for ASTM D2729 pipe (4").

Holey pipe? Por que?


I'm getting ready to re-do a poorly-designed vacuum hold-down system for
a ShopSabre 4896 that has only ONE 2" pipe to each half of the table,
even though the pump has a 4" inlet!(duh!)

The 4" has 4x the area of a single 2", so you're at the halfway point.
What pump is on there now?


4" water pipe (sch 20-40-80) is slightly too large to fit in the space
provided, but 4" ASTM-D2729 sewer pipe will fit. We're only talking 11"
of vacuum (or -5.4psi). But I want some margin of safety, and can't find
a figure anywhere.

Does the ShopSabre have specs on CFM of flow for those? Measure the
holes, add 'em up, and figure the area at 2 pi r2. Finding data for
figuring vacuum by leakage area ought to be tricky, though.


Anyone know?

What type of spoilboard are you using? One with open holes in it, or
one with rubber ringed vacuum switches which apply vacuum only where
they are depressed? A 1hp 5cfm will do ya for the latter, but you'll
need a big multi-horse for the former. Do these come with a regen
blower? (Real efficient, like a compressed air venturi vacuum pump.

--
A sound mind in a sound body is a short but full description
of a happy state in this world.
-- John Locke

On Sun, 15 Feb 2015 21:10:20 -0600, Lloyd E. Sponenburgh wrote:

Tim Wescott fired this volley in
:

Wouldn't the area of a pipe depend on it's length? It seems like a
long pipe would cover a lot more area than a short one.

???

Well, I lay a one foot piece of pipe on my bench and it fits just fine.
But a 20 foot piece -- heck, it lops over both ends and keeps cloths-
lining me every time I walk by.

(Lloyd, how am I supposed to respond to that unk's response than to say
something off the wall _without_ a smiley face? Honestly.)

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On Sun, 15 Feb 2015 21:15:01 -0600, Lloyd E. Sponenburgh wrote:

technomaNge fired this volley in news:mbrmo8$pa3$1
@dont-email.me:

s that similar to circular mills?
For example, 2 24 gage wires twisted together will carry the same
maximum current as 1 21 gage.

Same concept. Only, ShopSabre used the logic thus:

"If it takes a 12-gauge wire to go 12 feet, then I should be able to run
36 feet with only 36 gauge wire! We'll save LOTS of money!"

There was an engineer involved in there someplace, I know it.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Larry Jaques fired this volley in
:

On Sun, 15 Feb 2015 15:49:04 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

I've dug around for quite a while, and although I find all sorts of
"comforting" diagonal data about fall heights, column separation, etc,
I cannot find a stated vacuum rating for ASTM D2729 pipe (4").

Holey pipe? Por que?
It comes in solid, too.


I'm getting ready to re-do a poorly-designed vacuum hold-down system
for a ShopSabre 4896 that has only ONE 2" pipe to each half of the
table, even though the pump has a 4" inlet!(duh!)

The 4" has 4x the area of a single 2", so you're at the halfway point.
What pump is on there now?

20HP 3-phase regen blower; it'll pull 11" at many, many CFM


4" water pipe (sch 20-40-80) is slightly too large to fit in the space
provided, but 4" ASTM-D2729 sewer pipe will fit. We're only talking
11" of vacuum (or -5.4psi). But I want some margin of safety, and
can't find a figure anywhere.

Does the ShopSabre have specs on CFM of flow for those? Measure the
holes, add 'em up, and figure the area at 2 pi r2. Finding data for
figuring vacuum by leakage area ought to be tricky, though.

You mean, there's a formula for area?
Maybe that's where they screwed up!

1/2" MDF, -0.040" 'deglazed' on both sides, and edge-sealed, all-around.
It's sort of the standard for this kind of machine, doing full-sheet
work.

This stuff must not come over in anything close to the order posted. I
posted all that stuff yestiddy.

I'm pretty competent at vacuum work, too. I just want to know if anyone
has ever seen a vacuum spec for 2729.

Lloyd

Tim Wescott fired this volley in
:

(Lloyd, how am I supposed to respond to that unk's response than to say
something off the wall _without_ a smiley face? Honestly.)

That is what I was referring to about things not coming over in the order
posted. Your response arrived before his inane comment.

LLoyd

Tim Wescott fired this volley in
:

There was an engineer involved in there someplace, I know it.

yep... and to the 'engineer' who suggested I pull 30" and wait to see what
happens.

Ehhh.... I'm reluctant to do that here in Florida. I think I'll stop at
about 29.96".

LLoyd

On Mon, 16 Feb 2015 00:15:52 -0600, Tim Wescott
wrote:

On Sun, 15 Feb 2015 21:15:01 -0600, Lloyd E. Sponenburgh wrote:

technomaNge fired this volley in news:mbrmo8$pa3$1
@dont-email.me:

s that similar to circular mills?
For example, 2 24 gage wires twisted together will carry the same
maximum current as 1 21 gage.

Same concept. Only, ShopSabre used the logic thus:

"If it takes a 12-gauge wire to go 12 feet, then I should be able to run
36 feet with only 36 gauge wire! We'll save LOTS of money!"

There was an engineer involved in there someplace, I know it.

By the book and never in the field before, no doubt.
Engineers, the 2nd Louies of manufacturing!

--
A sound mind in a sound body is a short but full description
of a happy state in this world.
-- John Locke

On Mon, 16 Feb 2015 07:13:33 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Larry Jaques fired this volley in
:

On Sun, 15 Feb 2015 15:49:04 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

I've dug around for quite a while, and although I find all sorts of
"comforting" diagonal data about fall heights, column separation, etc,
I cannot find a stated vacuum rating for ASTM D2729 pipe (4").

Holey pipe? Por que?
It comes in solid, too.


I'm getting ready to re-do a poorly-designed vacuum hold-down system
for a ShopSabre 4896 that has only ONE 2" pipe to each half of the
table, even though the pump has a 4" inlet!(duh!)

The 4" has 4x the area of a single 2", so you're at the halfway point.
What pump is on there now?

20HP 3-phase regen blower; it'll pull 11" at many, many CFM

But what for? Where's the leakage? If you're using holey spoilboard,
have you considered dropping some vinyl over the leaks to bring up the
vacuum?

That thing sounds like an expensive bitch just to run!


4" water pipe (sch 20-40-80) is slightly too large to fit in the space
provided, but 4" ASTM-D2729 sewer pipe will fit. We're only talking
11" of vacuum (or -5.4psi). But I want some margin of safety, and
can't find a figure anywhere.

Does the ShopSabre have specs on CFM of flow for those? Measure the
holes, add 'em up, and figure the area at 2 pi r2. Finding data for
figuring vacuum by leakage area ought to be tricky, though.

You mean, there's a formula for area?
Maybe that's where they screwed up!

g


1/2" MDF, -0.040" 'deglazed' on both sides, and edge-sealed, all-around.
It's sort of the standard for this kind of machine, doing full-sheet
work.

This stuff must not come over in anything close to the order posted. I
posted all that stuff yestiddy.

I've been noticing that. I see stuff today which I didn't yesterday,
but it was posted yesterday. It's fine for people who log on once
every two days, I guess. I'm pleasantly surprised at how well Usenet
does work, though. What a great idea!


I'm pretty competent at vacuum work, too. I just want to know if anyone
has ever seen a vacuum spec for 2729.

Why would there be a vacuum spec for waste pipe (with a mess of holes
in it) which will never see vacuum?

Regular sch 40 will handle a good vacuum, and I've seen numerous
people using it for vac storage. But sewer pipe is thinner, I
believe. I doubt 11" will harm it, though. SWAG

--
A sound mind in a sound body is a short but full description
of a happy state in this world.
-- John Locke

On Mon, 16 Feb 2015 07:37:26 -0800, Larry Jaques wrote:

On Mon, 16 Feb 2015 00:15:52 -0600, Tim Wescott
wrote:

On Sun, 15 Feb 2015 21:15:01 -0600, Lloyd E. Sponenburgh wrote:

technomaNge fired this volley in
news:mbrmo8$pa3$1 @dont-email.me:

s that similar to circular mills?
For example, 2 24 gage wires twisted together will carry the same
maximum current as 1 21 gage.

Same concept. Only, ShopSabre used the logic thus:

"If it takes a 12-gauge wire to go 12 feet, then I should be able to
run 36 feet with only 36 gauge wire! We'll save LOTS of money!"

There was an engineer involved in there someplace, I know it.

By the book and never in the field before, no doubt.
Engineers, the 2nd Louies of manufacturing!

You're being too hard on engineers, because you don't notice when we
succeed in some stunningly creative way. It's just that when we fail,
it's often in some stunningly creative way.

--
www.wescottdesign.com

Well, it cost me a double-sawbuck to figure out what I needed to know,
but it leaves me questioning some of the manufacturer's claims.

I took a length of good, clean, and round 2927 pipe (no Larry, no
holes... this is solid pipe), capped both ends, BRACED the ends inside so
they could not initiate a collapse, and stuck in a reefer fitting for my
Robinaire pump... then started gradually pulling it down.

Now, three of the manufacturers of the stuff claimed "ability to
withstand column separation up to five stories high". Working backwards,
a suddenly-separated column of water-borne 'stuff' would initially pull a
vacuum of about 22", before it began to boil and make up the vacuum.

So I felt pretty good about getting through this OK. nahhh.... at about
18", the whole pipe gently folded up into a flat ribbon of PVC, with only
the braced ends staying round. G (kinda neat to watch, even though that
was the expected failure mode)

So, I'm going to have to find room for two runs of 3" Sch-40 under the
table for each of the four table zones. shrug

I'm glad I didn't pipe it first, then find out!

Lloyd

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 4.170...
Well, it cost me a double-sawbuck to figure out what I needed to
know,
but it leaves me questioning some of the manufacturer's claims.

I took a length of good, clean, and round 2927 pipe (no Larry, no
holes... this is solid pipe), capped both ends, BRACED the ends
inside so
they could not initiate a collapse, and stuck in a reefer fitting
for my
Robinaire pump... then started gradually pulling it down.

Now, three of the manufacturers of the stuff claimed "ability to
withstand column separation up to five stories high". Working
backwards,
a suddenly-separated column of water-borne 'stuff' would initially
pull a
vacuum of about 22", before it began to boil and make up the vacuum.

So I felt pretty good about getting through this OK. nahhh.... at
about
18", the whole pipe gently folded up into a flat ribbon of PVC, with
only
the braced ends staying round. G (kinda neat to watch, even though
that
was the expected failure mode)

So, I'm going to have to find room for two runs of 3" Sch-40 under
the
table for each of the four table zones. shrug

I'm glad I didn't pipe it first, then find out!

Lloyd

A buried pipe is supported against bulging out at right angles to
where the collapse begins. Yours wasn't.

"Jim Wilkins" fired this volley in news:mbt9mu$pih$1
@dont-email.me:

A buried pipe is supported against bulging out at right angles to
where the collapse begins. Yours wasn't.

Exactly how does that address "five story high vertical column separation"?

This stuff is not used only buried. It's approved (in some few places) for
vertical vents on DWV systems.

Lloyd

On Mon, 16 Feb 2015 10:32:59 -0600, Tim Wescott
wrote:

On Mon, 16 Feb 2015 07:37:26 -0800, Larry Jaques wrote:

On Mon, 16 Feb 2015 00:15:52 -0600, Tim Wescott
wrote:

On Sun, 15 Feb 2015 21:15:01 -0600, Lloyd E. Sponenburgh wrote:

technomaNge fired this volley in
news:mbrmo8$pa3$1 @dont-email.me:

s that similar to circular mills?
For example, 2 24 gage wires twisted together will carry the same
maximum current as 1 21 gage.

Same concept. Only, ShopSabre used the logic thus:

"If it takes a 12-gauge wire to go 12 feet, then I should be able to
run 36 feet with only 36 gauge wire! We'll save LOTS of money!"

There was an engineer involved in there someplace, I know it.

By the book and never in the field before, no doubt.
Engineers, the 2nd Louies of manufacturing!

You're being too hard on engineers, because you don't notice when we
succeed in some stunningly creative way. It's just that when we fail,
it's often in some stunningly creative way.
And so often is a stupendously stunning creative way!!! Success is
generally so benign in comparison

On Mon, 16 Feb 2015 07:16:00 -0600, Lloyd E. Sponenburgh wrote:

Tim Wescott fired this volley in
:

There was an engineer involved in there someplace, I know it.

yep... and to the 'engineer' who suggested I pull 30" and wait to see
what happens.

Ehhh.... I'm reluctant to do that here in Florida. I think I'll stop at
about 29.96".

LLoyd

The simple engineering solution to that is to tell Corporate that you need
a round-trip ticket to Death Valley.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

"Tim Wescott" wrote in message
...
On Mon, 16 Feb 2015 07:37:26 -0800, Larry Jaques wrote:

On Mon, 16 Feb 2015 00:15:52 -0600, Tim Wescott
wrote:

On Sun, 15 Feb 2015 21:15:01 -0600, Lloyd E. Sponenburgh wrote:

technomaNge fired this volley in
news:mbrmo8$pa3$1 @dont-email.me:

s that similar to circular mills?
For example, 2 24 gage wires twisted together will carry the
same
maximum current as 1 21 gage.

Same concept. Only, ShopSabre used the logic thus:

"If it takes a 12-gauge wire to go 12 feet, then I should be able
to
run 36 feet with only 36 gauge wire! We'll save LOTS of money!"

There was an engineer involved in there someplace, I know it.

By the book and never in the field before, no doubt.
Engineers, the 2nd Louies of manufacturing!

You're being too hard on engineers, because you don't notice when we
succeed in some stunningly creative way. It's just that when we
fail,
it's often in some stunningly creative way.

--
www.wescottdesign.com

Young engineers tend to an arrogant self-confidence not supported by
their practical experience. As lab manager I had to tactfully show
them that they still had very much to learn, while respecting what
they did know.

For example one of them kept requesting another case of Polaroid film
for the scope camera. When I finally asked why he told me he was
attempting to determine how fast a fuse would blow to protect his
circuit. His schooling hadn't covered real-world device
characteristics, or apparently how to least-squares fit a curve to
noisy data points.

So I gave him a brochure that explained the subtleties of fuse
ratings.
http://www.socfuse.com/products/pdf/P178-P188_E.pdf

-jsw

On Sun, 15 Feb 2015 21:38:49 -0600, Martin Eastburn
wrote:

On 2/15/2015 5:44 PM, Gunner Asch wrote:
On Sun, 15 Feb 2015 16:18:07 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Tim Wescott fired this volley in news:cb-
:

Lloyd, 2" + 2" = 4". What's your problem?

Yeah...that's what they thought, too!
Lloyd

Btw..if anyone needs vacuum pumps/gear

http://www.ebay.com/itm/Used-Edwards...-/131428338951

He has a number of pumps including one thats absolutely brand new..NOS

http://www.ebay.com/itm/New-Unused-E...-/131428334706

There are several others..keep watching if the above is not what you
need..or simply call him

Gunner


What kills me is there isn't a mention of what level of vacuum it can pull.

Is this a food grade bag sucker ?
Is this a 4'x16' plastic vac table for CNC plastic.....

One has to know the machine and use before spending 1 or 2.5k !

Martin

I believe that the model number will tell you , wont it?

They came out of GE Aviation

This might tell you something....

http://www.pchemlabs.com/product.asp?pid=1398

http://mfc.engr.arizona.edu/document...%20Install.pdf

I see that a rebuilt one goes for $9k

Google is your friend...usually ....

Gunner

"At the core of liberalism is the spoiled child,
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosophy of sniveling brats."
PJ O'Rourke

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 4.170...
"Jim Wilkins" fired this volley in
news:mbt9mu$pih$1
@dont-email.me:

A buried pipe is supported against bulging out at right angles to
where the collapse begins. Yours wasn't.

Exactly how does that address "five story high vertical column
separation"?

This stuff is not used only buried. It's approved (in some few
places) for
vertical vents on DWV systems.

Lloyd

How can you pull a five story (50') vacuum?

The rating may be for the overpressure from a five story high water
hammer.
http://en.wikipedia.org/wiki/Water_hammer
Google isn't too helpful.

-jsw

"Jim Wilkins" fired this volley in news:mbtdq5$e3f
:

How can you pull a five story (50') vacuum?

The rating may be for the overpressure from a five story high water
hammer.

You're forming ideas without reading any of the words. "Column
separation"... I've quoted it several times, and you don't seem to 'get
it'.

First, you DON'T pull a "five story vacuum", but you CAN have five
stories of water fall straight down under the force of gravity while the
top of the pipe is stoppered-up somehow.

Then, with just a teensy bit of scientific history under your belt, you'd
be able to determine that the water will drop about 16 feet, essentially
unimpeded, and leaving a vacuum in its wake, until the vacuum holds it up
at 33.9ft... after which the vacuum is relieved fairly rapidly by the
surface of that column's boiling into water vapor to fill the void.

This is junior-high general science class stuff, not the stuff of
"engineering". (well, at least only the most basic underpinnings of
engineering)

Lloyd