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Silent Air Compressors


#1

I should have known better than to leave a suggestion in the air like
expecting readers to make their own web search. The article I saw
was some time ago and I had not kept the reference. At the time I
read the article the details checked out with the silent compressor I
had so here goes an attempt to explain it.

The refrigerator compressor is hermetically sealed in an egg shaped
canister so that the Freon refrigerant circulates within the system.
There is a high pressure out tube, which goes to the condenser coils
(under the fridge to evaporate the water in the drip tray) then to
that network of evaporator coils at the back of the fridge. These
two coils dump the heat from compression. The Freon is close to room
temperature by the time it enters the expansion evaporator coils in
the icebox. The energy for expansion extracts the heat from (cools)
the icebox. The low pressure Freon is then returned to the
compressor canister to complete the cycle.

There is another sealed tube with a crimped end next to the power
breaker switch. This is the Freon refill tube.

To recover the refrigerator compressor about all you can do is to cut
off the Freon out and return tubes and unbolt the mountings. A more
Ozone friendly refrigerant may be used now but there are
environmental regulations on the disposal/release of Freon if you
care to look them up. Do not tilt the compressor canister as there is
a pool of motor oil at the bottom. The purpose of this oil is the
same as crankcase oil, to lubricate the compressor motor and help
keep it cool. There will be dissolved refrigerant so replace it with
fresh 10/30W motor oil if you wish.

You have a complete silent compressor now. What then are we paying for
when the same compressor is sold at the art shop?

Well the art quality compressor�s canister�s top cover is not welded
(but is strapped) to the bottom bowl so that one can open the
canister to see what is inside. The mechanism consists of a simple
single cylinder compressor whose crankshaft is integral with the
electric motor shaft. The unit is mounted on rubber grommets
recessed into coiled springs welded to the bottom of the bowl. The
spring suspension and the unit�s total enclosure within the canister
is what gives it its silent operation.

The high pressure out tube is the only part you need to add the
regulator and air connections to. Leave the return tube open and cut
open the crimped refill tube so that your canister can �breath�, that
is draw in air from outside for the compressor.

For anything else go look at the catalogues on silent compressors at
the art shops or dental supplies shops to get ideas. Then go to a
welding or air compressor parts shop where there is a larger
selection of parts and fittings that are a lot cheaper to buy.

Kelvin Mok


#2

I too balked at the price of the “silent” air compressors. I bought
an inexpensive compressor from Wal Mart for $150, and yes, it’s
deafening. So I put it outside my home studio (which is a finished
room walled off from the rest of my pole barn) and run the hose
through the wall. It’s quiet enough, now. It irritates my daughter’s
rabbits a bit, though. Here’s my idea, though. I’m going to build a
small enclosure out of ply-wood and line it with a thick layer of
foam insulation (from the local Home Depot), then install a small
"muffin fan" (which makes no noise to speak of) to keep the enclosure
from getting too hot from the motor. If this works, I’ll do the same
at work (where I have another exceptionally loud contractor’s
compressor). Maybe I won’t though, since it’s right above the boss’s
office and he gets to hear it too. I’ve asked him to get someone to
put it in the basement and run a line, but I suppose that’s not going
to happen soon. . .misery loves company, eh?

David L. Huffman


#3

David, I am sure there is someone online that remembers the Dot Matrix
printers noise plus vibrations, and the baffle boxes that had to be
built to make them user friendly.

Do you think that would help?
Teresa


#4

I think the design is what I’m after, but I’m sure these wouldn’t be
large enough. Even the smallest contractor’s compressor is
comparatively large next to a printer. Those printer enclosure’s are
where I got the idea, though.

David L. Huffman


#5

Be careful in enclosing an air compressor to silence it. They
generate a lot of heat and are designed to have a free flow of air
around the compressor to cool it. If you enclose and insulate it to
reduce the noise you also trap the heat and can start a fire.

Jim


jbin@well.com
James Binnion Metal Arts
4701 San Leandro St #18
Oakland, CA 94601
510-533-5108


#6

For those of you with those noisy air compressors and older
Gravermeisters that make a bunch of noise. A friend of mine I officed
with was doing a lot of engraving and the compressor was really noisy.
The solution we found was to place it in a desk drawer with a small
ventilation fan installed in the back. This cut down on the compressor
overheating and cut down on the noise as well. You might also try
lining whatever box you use with egg grates etc. to kill even more
noise. Noise pollution is just as bad as any other kind. They are
sandblasting a large water tank 1/2 block down the street from my
studio and it has been 3 Months. The noise is low pitched and
penetrating. City fathers Thanks. Frank Goss in hot, humid, and
NOISY Houston.


#7
    I'm going to build a small enclosure out of ply-wood and line it
with a thick layer of foam insulation, then install a small "muffin
fan"  to keep the enclosure from getting too hot from the motor. 

G’day; sorry, David, but foam insulation won’t do much more than
keep in the heat built up! The only thing that will cut down noise is
DENSITY. Like concrete; even thick slate or glass works fairly well.
Brick, concrete blocks, etc are more likely to avoid noise getting
out and running amok, together with people in the vicinity… – John
Burgess; @John_Burgess2 of Mapua Nelson NZ


#8

I have been following this thread on compressors for a while. The
most silent, cool, maintenace free, absolutly moisture free, no
electicity to run, non toxic and takes up less than 1 cubic foot of
floor space would be a tank of Nitrogen gas! Be sure to chain it to
the wall. I have been using nitrogen for pressure for years with
excellent results. When you compare the cost of purchase, the
electricity, regular oil changes and the accompanying labor you will
see that bottled Nitrogen is a supperior solution. You can use it to
sand blast, power air tools and inject wax.
John, J.A. Henkel Co.,Inc. Moldmaking, Casting, Finishing


#9

Thank you, John. I didn’t realize that styrofoam wouldn’t insulate
against noise very well. I know in my days in the garage bands, we
used cardboard egg-cartons. Used to be able to buy them by the stack
from the feed store/grainery. I could try those. I quess I could
stack up a wall of cinderblock around it, but I’d figured on
something portable, like a box I could just set down over the little
beast. I think that somewhere I got the idea from seeing those
printer boxes, which were lined with foam. However, the foam was
foam rubber (more dense) and it was configured as a network of
pyramids. . .physically disrupting the sound “wave” much in the way
the egg cartons did. I’m no sound engineer, but if somebody still
makes that stuff, that would probably be enough.

David L. Huffman


#10

Hi John, I used Nitrogen for years and finally broke down and bought a
Silentaire compressor. I have to say that although the Nitrogen was
great pressure wise in the long run the air compressor wins out. Why?
I would go through an entire Nitrogen tank in one session. At $17 per
tank refill that adds up. The time to run to the shop to return the
empty and get another tank. The convenience of having something
available all the time (I work all night long so if I ran out at 3
A.M. I was stuck until the store opened to replace the tank. Forget
trying to replace a tank if it was a weekend or holiday) Also, I would
lease the Nitrogen tank so that expense was about $49 per year. Even
though the air tank takes a little longer to refill to regain the
pressure I’ve learned to space my work around that glitch. The $500
for the air compressor is a bargain compared to what I spent on
Nitrogen tanks. It paid for itself the first month. (new web in
progress) “Listen to the Universe and Dance to the Rhythm of it.”
SES


#11

Dave. I get along with my noisy compressor sitting high atop its
tank,…but then I only use it occasionally so its no big problem. If
I may make a suggestion re the foam rubber thing. You might try using
the “egg crate” foam rubber that is used under a bed pad. You can buy
them at Sears or any furniture/bedding store for about $10. Just a
thought.

Cheers, Don at The Charles Belle Studio where simple elegance IS fine
jewelry!


#12

John, when you say only DENSITY cuts noise I must take exception.
While concrete blocks cut noise they do it by having an interior
composition of sand, pebbles and rock. Did I mention air? It is the
compote of these items in an irregular disposition that cuts the
sound. A cardboard box with the end cut out and pointing away from the
user does just about as good a job. This is because the interior of
cardboard is an accordian shape that bounces the sound outward from
the surfaces. Better yet a cardboard box with composite cardboard egg
cartons glued to the inside on the side facing the user. Foam
pyramids glued to the inside facing side are a wonder as well. The
shape of the F117 stealth airplane is an excellent example of bouncing
"waves" off the surface in such a way that they are not directed in
any particular direction. The same way it becomes invisible is the way
to make sound also “invisible.” Sound, x-rays, radar are all examples
of waves of energy being transmitted. Our goal is to disperse and
absorb that transmission. I have been in a sound room where one walked
on a chicken wire mesh with the floor, the walls and the cieling made
up of 1ft square base foam pyramids. There was no sound whatsoever
bouncing from the interior surfaces. When a person turned away from me
and yelled my name I heard nothing! I have used the trick many times
setting up outdoor events where no electricity was available. We
simply put the generators in large refridgerator cartons with the egg
cartons glued inside. With the open end (open top as well) turned away
from the stadium and the crowd you were not aware they were running at
all.


#13
    Thank you, John.  I didn't realize that styrofoam wouldn't
insulate against noise very well.  I know in my days in the garage
bands, we used cardboard egg-cartons.  

G’day; I was once taken into a couple of anechoic chambers that had
been WW2 concrete ammunition stores. The Govt research folk were
sound experts and had taken them over, and were using them to test
loud speakers and certain sounds for recording. In one the bare
concrete walls had been completely covered in a polyurethane foam
plastic consisting of 2 1/2" pyramids. In the other identical
chamber the walls were covered in papier mache egg cartons. The
concrete chambers were selected because they completely cut out all
outside sound, even passing aeroplanes and helicopters (the walls were
nearly 2 feet thick) and the wall coverings were selected to try and
completely lose all echoes, which both did, only the plastic foam was
a little better. One experienced very strange sort of claustrophobic
sensations on entering the chambers due to the complete lack of
outside sound and internal echoes; the rooms were ‘dead’. But they
told me that the egg cartons wouldn’t cut down sound very much- they
just absorbed a little and stopped sound bouncing back and forth.
They were quite adamant that the only thing to cut out sound was
density.

A suggestion is to make solid boxes from one inch timber - preferably
dense - and cover the inside with egg boxes - one still gets the
papier mache ones here in NZ. Cheers, – John Burgess;
@John_Burgess2 of Mapua Nelson NZ