My 11 year daughter is showing a strong interest in science.
We received a Edmunds catalog with lots of cool stuff in it.

I have always wanted to play with vacuum stuff when I was a kid
and I didn't get much of a chance so I figure now is my chance.

I figure it would be cool try to make a crude light bulb inside
a bell jar and things like that.

I looked at ebay and there are many vacuum pumps FA.

Do I need a two stage pump and how big of a pump do I need?
The killer is these things are heavy and shipping is expensive.

chuck

If you have an air compressor, you can make a venturi pump (I think
that is what it is called) like HF sells. It is simply a block of
aluminum with a T intersection angle drilled into it. The air from the
compressor blows through the straight drilled holes which creates a
vacuum on the remaining leg. I use mine for air conditioner work and it
will pull 29 lbs of vacuum.

"TheAndroid" wrote in message
oups.com...
If you have an air compressor, you can make a venturi pump (I think
that is what it is called) like HF sells. It is simply a block of
aluminum with a T intersection angle drilled into it. The air from the
compressor blows through the straight drilled holes which creates a
vacuum on the remaining leg. I use mine for air conditioner work and it
will pull 29 lbs of vacuum.

Really? With only 14.7lb possible? Did you mean 29" of mercury? G

LLoyd

"TheAndroid" wrote in message
oups.com...
If you have an air compressor, you can make a venturi pump (I think
that is what it is called) like HF sells. It is simply a block of
aluminum with a T intersection angle drilled into it. The air from the
compressor blows through the straight drilled holes which creates a
vacuum on the remaining leg. I use mine for air conditioner work and it
will pull 29 lbs of vacuum.

Or salvage a small AC compressor from an old window unit or water
cooler. You will need the run capacitor. Mount it on some type of base and
insulate everything so it is safe.

Vaughn

Chuck, you don't need a two-stage pump. Any motor driven pump capable
of achieving 1-5-mm Hg of vacuum should do the trick. You don't need to
pump down to the micron region.

An important thing to note is that most lightbulbs are not evacuated --
they contain low pressure argon so that the filament material doesn't
evaporate as it would under a high-vacuum.

For a simple demo experiement using a bell jar, I'd pump the bell jar
down to about 30-mm of Hg, then turn on the current to the filament. It
will start to glow, then as you pump more air out of the jar it will
being to glow brighter and brighter, since less and less of the input
energy is being lost to air molecules. Of course you will need to use a
filament material that is (1) not readily oxidized and (2) has a very
high melting temperature.

This is the principle upon which thermocouple vacuum gauges operate.

For such a simple demonstration, I really don't believe that it would
be beneficial to get into issues like the rarified argon backfill,
unless of course you want a bulb that will burn for hundreds to
thousands of hours.

Harry C.

Or salvage a small AC compressor from an old window unit or water
cooler. You will need the run capacitor. Mount it on some type of base and
insulate everything so it is safe.

But don't they need oil which is usually lost when you cut the lines?

TheAndroid posted:

"The air from the
compressor blows through the straight drilled holes which creates a
vacuum on the remaining leg. I use mine for air conditioner work and it

will pull 29 lbs of vacuum."

One of these devices would be inadequate for Chuck to do the
demonstration he wants. A single-stage air conditioning evaculation
pump would be perfect, or as we did in the old days salvage an old
refrigeration sealed compressor from a junked refrigerator and us it,
after cleanup and flushing out, to provide the vacuum.

Harry C.

On 13 May 2005 16:00:04 GMT, the renowned
(Chuck Sherwood) wrote:

My 11 year daughter is showing a strong interest in science.
We received a Edmunds catalog with lots of cool stuff in it.

I have always wanted to play with vacuum stuff when I was a kid
and I didn't get much of a chance so I figure now is my chance.

I figure it would be cool try to make a crude light bulb inside
a bell jar and things like that.

I looked at ebay and there are many vacuum pumps FA.

Do I need a two stage pump and how big of a pump do I need?
The killer is these things are heavy and shipping is expensive.

chuck

Two stage is necessary to do a lot of interesting stuff. Some of the
really interesting stuff requires a much harder vacuum than you can
get with a mechanical roughing pump, and you have to go to a diffusion
(oil, they used to use mercury) or turbomolecular pump. Suggest you
get ahold of some of the old Scientific American Amateur Scientist
columns (especially from the fifties and sixties) for ideas before you
decide on one. Also check the availability and cost of rebuild kits. I
got a brand new yet ancient (1965?) US government surplus one from a
dealer in PA some years back. Still in the original crate, with two
copies of mil-spec manuals sealed in foil, and with a new/old bottle
of pump oil.


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

Chuck, you don't need a two-stage pump. Any motor driven pump capable
of achieving 1-5-mm Hg of vacuum should do the trick. You don't need to
pump down to the micron region.

Will a two stage pump work faster or slower ?

Will I need a higher vacuum for things like neon lights? I assume you
remove most of the air and then inject the gas, so the initial pressure
isn't critical??

An important thing to note is that most lightbulbs are not evacuated --
they contain low pressure argon so that the filament material doesn't
evaporate as it would under a high-vacuum.

Thanks I was wondering about using an inert gas.

Of course you will need to use a
filament material that is (1) not readily oxidized and (2) has a very
high melting temperature.

Will Nichrome wire work reasonably well?

Two stage is necessary to do a lot of interesting stuff. Some of the
really interesting stuff requires a much harder vacuum than you can
get with a mechanical roughing pump, and you have to go to a diffusion
(oil, they used to use mercury) or turbomolecular pump. Suggest you
get ahold of some of the old Scientific American Amateur Scientist

I think they also require a cold trap. I have the amateur scientist
book and CD Rom. I also have a book from lindsey that is much to deep
for my needs.

chuck

Two stage is necessary to do a lot of interesting stuff. Some of the
really interesting stuff requires a much harder vacuum than you can

This pump is close enough I can drive to pick it up. Will it
do the job??

http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7514401181

how about a piece of tungsten??

walt

how about a piece of tungsten??

well I have some tungsten rod for tig welding, but its much to
big. Can you buy tungsten wire or do I have to break a light bulb
to get some?

I had one of those. It'll pull good vacuum, but the CFM is so low it'll
take time to evacuate a moderate sized space.

I upgraded to a brand new robinair pump. A little more money, but worth it.
I use mine for vacuum processing and casting of urethanes, pulling hard
vacuum fast is a good thing. This thing pulls a 12qt bowl down to 29" + in
less than 30 seconds.


"Chuck Sherwood" wrote in message
...

Two stage is necessary to do a lot of interesting stuff. Some of the
really interesting stuff requires a much harder vacuum than you can

This pump is close enough I can drive to pick it up. Will it
do the job??

http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7514401181

In article , Chuck Sherwood says...

Will a two stage pump work faster or slower ?

Two stage pumps will go down to a lower pressure.

Typcially five or ten microns (1 micron = 1 millitor)

A single stage pump might do 40 or 50 microns ultimate
pressure.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

Chuck Sherwood wrote:
Chuck, you don't need a two-stage pump. Any motor driven pump capable
of achieving 1-5-mm Hg of vacuum should do the trick. You don't need to
pump down to the micron region.


Will a two stage pump work faster or slower ?

A two stage pump is usually just two identical pumps on the same shaft
connected in series. It will pump air at exactly the same rate as a
single stage pump of the same displacement (usually pumps are rated in
litres/min or m3/hour) but it will be able to achieve a higher ultimate
vacuum. Naturally if the pump can attain a higher ultimate vacuum, it
will take longer to reach its ultimate vacuum.

Will I need a higher vacuum for things like neon lights? I assume you
remove most of the air and then inject the gas, so the initial
pressure isn't critical??

I think neon signs do require a pretty high vacuum if they are to work
well and stand the test of time, but I'm not certain of this. Perhaps
someone here can confirm? There's also a short article about vacuum
pumps for neon signs here, which suggests that the ultimate vacuum
required is pretty high: http://www.signweb.com/neon/cont/pumpssuckb.htm

You can make a glow discharge tube without neon; just reduce the
pressure of a volume of air and apply a high voltage across it. A single
stage pump should be fine for this. See
http://www.kronjaeger.com/hv/hv/exp/pump/ for more details.

That pump you spotted on eBay looks quite nice. The Welch 1400 is a 25
litre/min two stage pump. It should serve well for small science
experiments. The pump looks in good condition but of course it's hard to
tell without seeing it in person. You might want to ask the seller if he
can test the pump's ultimate vacuum and also tell you what it has been
used for. It does appear to be without a belt guard but I believe these
are available for http://www.duniway.com.

A lot of useful information about vacuum pumps is available on this
page, including the specifications of common Welch pumps:

http://repairfaq.ece.drexel.edu/sam/lasercva.htm

I also have a service manual for Edwards pumps which gives a lot of
useful hints about rebuilding, should you need it:

http://www.ruggedmachines.com/docsto...nce_Manual.pdf

Best wishes,

Chris Tidy

you can buy tunsten wi
http://www.ebsstore.com/control/prod...oduct_id=TU-T2
I also found a great article on light bulbs at:
http://science.howstuffworks.com/light-bulb2.htm

I believe bulb manufatcurers use rhenium filiments instead of thoriated
tungsten. I think 2% thoriated wire would work but i'm not an expert.
Good luck, sounds like a fun project!

walt

Chuck Sherwood wrote:
My 11 year daughter is showing a strong interest in science.
We received a Edmunds catalog with lots of cool stuff in it.

I have always wanted to play with vacuum stuff when I was a kid
and I didn't get much of a chance so I figure now is my chance.

By the way I'd recommend a belt driven pump. These are generally much
better made than the direct drive pumps, and should you need a new motor
there are a wide variety of replacements available.

Best wishes,

Chris

Thanks guys. Some excellent info and so FAST!

Chuck Sherwood wrote:
Can you buy tungsten wire or do I have to break a light bulb
to get some?

I have a spool of .002 tungsten wire that you can have some of. The
advantage of .002 is that it will take very little voltage to heat. The
disadvantage is that it'll be hard to handle. "Hard to handle"? Hell,
it's hard to see!

the human hair is 0.001 inch... except on my head, mine is 0.000"
thick.

walt

Christopher Tidy wrote:
Chuck Sherwood wrote:
My 11 year daughter is showing a strong interest in science.
We received a Edmunds catalog with lots of cool stuff in it.

I have always wanted to play with vacuum stuff when I was a kid
and I didn't get much of a chance so I figure now is my chance.

By the way I'd recommend a belt driven pump. These are generally much
better made than the direct drive pumps, and should you need a new motor
there are a wide variety of replacements available.

Best wishes,

Chris


All the broken pumps I've seen were neglected and ruined on the pump side, not the motor. Not using a pump (letting it sit with old oil) seems to be the worst thing you can do to it.

All the broken pumps I've seen were neglected and ruined on the pump side,

What are the important clues to look for when buying a used pump?

Cydrome Leader wrote:
Christopher Tidy wrote:

Chuck Sherwood wrote:

My 11 year daughter is showing a strong interest in science.
We received a Edmunds catalog with lots of cool stuff in it.

I have always wanted to play with vacuum stuff when I was a kid
and I didn't get much of a chance so I figure now is my chance.

By the way I'd recommend a belt driven pump. These are generally much
better made than the direct drive pumps, and should you need a new motor
there are a wide variety of replacements available.

Best wishes,

Chris



All the broken pumps I've seen were neglected and ruined on the pump side, not the motor. Not using a pump (letting it sit with old oil) seems to be the worst thing you can do to it.

Interesting. I got a two stage pump with a burnt out motor free from the
Cavendish Laboratory. Probably the motor had burnt out because of a
faulty oil distributor valve in the pump, which allowed the pump
chambers to fill with oil and stalled the motor. I got the motor rewound
and replaced the pump seals and it's a good pump. I've been lead to
believe that this isn't uncommon on pumps which don't have a thermal
cut-out fitted to the motor. Badly damaged pumps are most likely the
result of water being drawn into the pump (and being allowed to sit,
causing corrosion), or abrasive dirt causing wear.

Chris

FWIW, I bought a vacuum pump from William Noble who posts on this BB
occasionally. I use it for a vacuum chuck I built. I don't know if one of
the pumps he has will meet your needs, but I found William to be a help.
The pump I bought pulls about 25 in and works well. Quiet little thing too.

http://www.wbnoble.com/

Peter

"Chuck Sherwood" wrote in message
...
My 11 year daughter is showing a strong interest in science.
We received a Edmunds catalog with lots of cool stuff in it.

I have always wanted to play with vacuum stuff when I was a kid
and I didn't get much of a chance so I figure now is my chance.

I figure it would be cool try to make a crude light bulb inside
a bell jar and things like that.

I looked at ebay and there are many vacuum pumps FA.

Do I need a two stage pump and how big of a pump do I need?
The killer is these things are heavy and shipping is expensive.

chuck

(Chuck Sherwood) wrote:

My 11 year daughter is showing a strong interest in science.
We received a Edmunds catalog with lots of cool stuff in it.

I have always wanted to play with vacuum stuff when I was a kid
and I didn't get much of a chance so I figure now is my chance.

I figure it would be cool try to make a crude light bulb inside
a bell jar and things like that.

I looked at ebay and there are many vacuum pumps FA.

Do I need a two stage pump and how big of a pump do I need?
The killer is these things are heavy and shipping is expensive.

chuck


Take a look at the gast pumps, they seem to be much lighter,
especially the oiless rotary vane ones. Shipping seems to be around
25-40. What you need sort of depends on what you want to do with it
too.
You can get all of the max vac and flow rate information for the gasts
out of their on line info (some times you have to dig a little and
figure out their catalog # systems)
jk

"Greg Deputy" wrote:

I had one of those. It'll pull good vacuum, but the CFM is so low it'll
take time to evacuate a moderate sized space.

I upgraded to a brand new robinair pump. A little more money, but worth it.
I use mine for vacuum processing and casting of urethanes, pulling hard
vacuum fast is a good thing. This thing pulls a 12qt bowl down to 29" + in
less than 30 seconds.

THe only time I tried vacuum with urethane, it started foaming with no
end in sight. How do you do it?

jk

Chrisopher Tidy posted:
"
I think neon signs do require a pretty high vacuum if they are to work
well and stand the test of time, but I'm not certain of this. Perhaps
someone here can confirm? There's also a short article about vacuum
pumps for neon signs here, which suggests that the ultimate vacuum
required is pretty high:
http://www.signweb.com/neon/co=ADnt/pumpssuckb.htm."

Chris, just for the record neon signs do not require a particularly
high vacuum level, and usually just mechanical pumps are required for
their production. Their lifetime is limited by only the outgassing of
their electrodes.

The link that you posted largely addressed secondary oil diffusion
pumps and their ilk, which produce vacuums order beyond anything
required for lighting technology and at a cost orders of magnitude
beyone anything required for this application (as in 10^-6 MM Hg.). In
fact, this is the quality of vacuum required to produce cathod ray
tubes and transmitting tubes, with a little help from something called
a 'getter'.

For the purposed of the original poster, he would be well advised to
salvage a sealed compressor from an old air conditioner or
refrigerator, then convert it to a vacuum source per article that both
appeared in Scientific American and the Amateur Scientist's Handbook.

Harry C.

Weight and shipping cost.

Harry C.

For the purposed of the original poster, he would be well advised to
salvage a sealed compressor from an old air conditioner or
refrigerator, then convert it to a vacuum source per article that both
appeared in Scientific American and the Amateur Scientist's Handbook.

I think its much easier to buy a pump vs make a pump. There
are plenty available. I think the conversions centered around
belt drive AC compressors, which I think are a thing of the past??

On 13 May 2005 16:00:04 GMT, (Chuck Sherwood)
wrote:

My 11 year daughter is showing a strong interest in science.
We received a Edmunds catalog with lots of cool stuff in it.

I have always wanted to play with vacuum stuff when I was a kid
and I didn't get much of a chance so I figure now is my chance.

I figure it would be cool try to make a crude light bulb inside
a bell jar and things like that.

I looked at ebay and there are many vacuum pumps FA.

Do I need a two stage pump and how big of a pump do I need?
The killer is these things are heavy and shipping is expensive.

chuck

A Refrigerator Compressor Vacuum Pump

http://www.sas.org/E-Bulletin/2003-1...esAS/body.html



Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

Yes, yes. Another case of hands working faster than brain.

Chuck Sherwood wrote:
All the broken pumps I've seen were neglected and ruined on the pump side,


What are the important clues to look for when buying a used pump?

Here are a few things to look for. Some of these you can only check if
you can see the pump in person, but that's always a good idea if it's
nearby.

* Check out the general physical condition: does the pump appear to have
been looked after well or is it knocked around and covered with grime
and rust?

* Ask the seller what is has been used for. If it has been used in
industry for neon sign manufacture or air conditioning servicing it will
probably have seen much heavier use that if it was used in a school
science laboratory.

* If the seller has a vacuum gauge available, ask them to measure the
pump's ultimate vacuum.

* Inspect the oil. Is it dirty? Metallic particles in the oil may
indicate heavy pump wear. Vacuum pump oil is usually colourless and
doesn't smell. If it smells it's the wrong kind of oil.

* Unscrew the oil drain and let a few drops run out. Is the oil
contaminated with water?

* Listen to the pump running. These pumps are usually pretty quiet.
Clacking noises may indicate sticking vanes.

It seems from what Harry says that you should be fine with a mechanical
pump for making neon signs, although you will need to be able to
manufacture and seal the glassware. Perhaps Harry could confirm if a
single stage pump is adequate or if a two stage pump is required?

Hope this helps

Chris

The urethane mixes I work with contain around 80% solids, so foaming isnt
usuallly a problem. It will be if humidity is high or any of the
ingredients arent nice and dry, though.


"jk" wrote in message
...
"Greg Deputy" wrote:

I had one of those. It'll pull good vacuum, but the CFM is so low it'll
take time to evacuate a moderate sized space.

I upgraded to a brand new robinair pump. A little more money, but worth
it.
I use mine for vacuum processing and casting of urethanes, pulling hard
vacuum fast is a good thing. This thing pulls a 12qt bowl down to 29" +
in
less than 30 seconds.

THe only time I tried vacuum with urethane, it started foaming with no
end in sight. How do you do it?

jk

On 13 May 2005 19:58:34 GMT, the inscrutable
(Chuck Sherwood) spake:


For the purposed of the original poster, he would be well advised to
salvage a sealed compressor from an old air conditioner or
refrigerator, then convert it to a vacuum source per article that both
appeared in Scientific American and the Amateur Scientist's Handbook.

I think its much easier to buy a pump vs make a pump. There
are plenty available. I think the conversions centered around
belt drive AC compressors, which I think are a thing of the past??

Old refrigerator pumps work well for many things and can be had free
around most parts of the country. I see a couple free every week in
the local paper, and the town has just 23k people. One of these days
I'll go get one, pull the pump, and salvage whatever else I can, like
the sheetmetal.

Here are two decent home-made solutions:

http://www.joewoodworker.com/veneering/welcome.htm
http://www.paragoncode.com/shop/vacuum_pump/


------
We're born hungry, wet, 'n naked, and it gets worse from there.
- http://diversify.com Website Application Programming -

Or salvage a small AC compressor from an old window unit or water
cooler. You will need the run capacitor. Mount it on some type of base
and
insulate everything so it is safe.

Vaughn




Or an old refridgerator. I have one that I use for vacuum bleeding brakes.
Pulls a very good suction.
Lane

Ignoramus633 wrote:
Is it possible to use a regular compressor as a vacuum pump? After
all, both do the same, pump air out of some place and into another
place.

Yes but the dead space above the piston (ie, the part of the cylinder
which isn't swept) limits the ultimate vacuum quite badly. Oil-sealed
rotary vane pumps don't suffer from this limitation; their ultimate
vacuum is usually limited by the vapour pressure of the oil.

Chris

On 13 May 2005 10:45:09 -0700, jim rozen
wrote:

In article , Chuck Sherwood says...

Will a two stage pump work faster or slower ?

Two stage pumps will go down to a lower pressure.

Typcially five or ten microns (1 micron = 1 millitor)

A single stage pump might do 40 or 50 microns ultimate
pressure.

Related question: what does "gas ballast" mean in the context of
vacuum pumps, and what is it for?

"Chuck Sherwood" wrote in message
...
| My 11 year daughter is showing a strong interest in science.
| We received a Edmunds catalog with lots of cool stuff in it.
|
| I have always wanted to play with vacuum stuff when I was a kid
| and I didn't get much of a chance so I figure now is my chance.
|
| I figure it would be cool try to make a crude light bulb inside
| a bell jar and things like that.
|
| I looked at ebay and there are many vacuum pumps FA.
|
| Do I need a two stage pump and how big of a pump do I need?
| The killer is these things are heavy and shipping is expensive.
|
| chuck

I guess it ought to be asked if you have an idea of what kind of volume,
flow, and vacuum level you intend to work with? Light vacuum, up to about
29 inches of water or more and great volume and flow is available from your
household vacuum cleaner. Find surplus vacuum blowers and you can get to 90
inches of water. With a large volume system you first empty it with a high
volume pulp like the mentioned blowers then you close that system, switching
to a slower pump. HF sells one or two, one being an air operated one that
is for A/C systems. No vacuum draw is given, but I assume the A/C guys know
what it should be. Above that, then you start looking at lab pumps.
Available in all sizes, flows, and costs, so you need to quantify what your
needs/desires are first.

Chuck Sherwood wrote:

All the broken pumps I've seen were neglected and ruined on the pump side,



What are the important clues to look for when buying a used pump?


If you turn the pump over by hand, one in good condition makes a
distinctive sluurping noise. Of course, if you haven't heard it, this
may not help.

Steve