There's metal content as this will be part of a lathe repower project.

If one were to take two fans, something like square framed heat sink
fans,and stack them one after the other would they act as a 'two stage'
fan, so to speak?

I'm changing my lathe over to a VFD and as the motor will be running at
slower speeds I think extra cooling will be required. There's no 120
VAC on the machine but I can easily get 220 VAC. Yes, I could buy or
scrounge a 220 volt heat sink fan but I'm thinking about wiring two 120
volt fans in series as those are much more common and as long as I was
going to have two I started thinking if stacking them would offer any
advantages.

regards
Paul


--
-----------------------------------------
It's a Linux world....well, it oughta be.
-----------------------------------------

it might work, but little 110 to 220 transformers are really cheap ( a few
dollars each), why not just add a transformer - if this is in the USA, just
pull a neutral to the lathe and you have 110 as well as 220. But I think I
can assure you the VFD won't need extra cooling - if you meant extra cooling
for the motor, I think you will find that 220VAC muffin fans are much
cheaper at surplus stores than 110 ones.


"Paul" wrote in message
. ..
There's metal content as this will be part of a lathe repower project.

If one were to take two fans, something like square framed heat sink
fans,and stack them one after the other would they act as a 'two stage'
fan, so to speak?

I'm changing my lathe over to a VFD and as the motor will be running at
slower speeds I think extra cooling will be required. There's no 120 VAC
on the machine but I can easily get 220 VAC. Yes, I could buy or scrounge
a 220 volt heat sink fan but I'm thinking about wiring two 120 volt fans
in series as those are much more common and as long as I was going to have
two I started thinking if stacking them would offer any advantages.

regards
Paul


--
-----------------------------------------
It's a Linux world....well, it oughta be.
-----------------------------------------



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

"William Noble" wrote in message
.. .
it might work, but little 110 to 220 transformers are really cheap ( a few
dollars each), why not just add a transformer - if this is in the USA,
just pull a neutral to the lathe and you have 110 as well as 220. But I
think I can assure you the VFD won't need extra cooling - if you meant
extra cooling for the motor, I think you will find that 220VAC muffin fans
are much cheaper at surplus stores than 110 ones.


"Paul" wrote in message
. ..
There's metal content as this will be part of a lathe repower project.

If one were to take two fans, something like square framed heat sink
fans,and stack them one after the other would they act as a 'two stage'
fan, so to speak?

I'm changing my lathe over to a VFD and as the motor will be running at
slower speeds I think extra cooling will be required. There's no 120 VAC
on the machine but I can easily get 220 VAC. Yes, I could buy or
scrounge a 220 volt heat sink fan but I'm thinking about wiring two 120
volt fans in series as those are much more common and as long as I was
going to have two I started thinking if stacking them would offer any
advantages.

regards
Paul


--
-----------------------------------------
It's a Linux world....well, it oughta be.
-----------------------------------------



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


As a general rule, fan in series increase the head pressure allowing air to
move through a more restrictive path without loosing a lot of volume CFM.
Usually are better if placed one at inlet and one at outlet, staked the
second fan works in the wake of the first and is not that efficient.

Side by side, in parallel, they produce more volume, more cooling assuming
the air path is not so restricted to reduce the volume.
The fan curve is similar to an electrical generator.
Plugged it provide maximum pressure but no volume and absorbs minimal power.
In free air it uses up all the available energy to increase the air velocity
giving maximum volume but minimal ability to compress the air and push it
trough a restrictive path.
In a real application it works somewhat in the middle of the curve. It
spends some energy to impart kinetic energy to the air and some to compress
the air creating the pressure necessary to overcome the resistance of the
path through the enclosure.

Assuming that two fan in series (electrically) is really the final design, I
would place them side by side blowing on the side of the motor, rather than
stacked coaxially with the motor. The reason being that the air path is very
free and open and you get the fasted air and highest volume.

Mauro

William Noble wrote:
it might work, but little 110 to 220 transformers are really cheap ( a few
dollars each), why not just add a transformer - if this is in the USA, just
pull a neutral to the lathe and you have 110 as well as 220. But I think I
can assure you the VFD won't need extra cooling - if you meant extra cooling
for the motor, I think you will find that 220VAC muffin fans are much
cheaper at surplus stores than 110 ones.


Good idea about the surplus store. The two stacked fans was one of those
ideas one briefly considers while deciding how to do something, I was
just wondering how it would work.

I'm pretty sure the 220 volt fan is how it will go, and it is for motor
cooling, the VFD should be fine on it's own. 120 volts would require a
neutral, as you point out, and that would require allot of work, machine
and circuit is 220 three phase.

--
-----------------------------------------
It's a Linux world....well, it oughta be.
-----------------------------------------

You would save a large amount of time and effort if you buy a 220v
fan. Or you can go with a 12v transformer and a 12v fan, I can give
you a 12v tfansformer, I give 80% probability that I have one.


i

would it be easier to just run a neutral wire back to the panel and use one
of the existing hot leads, and run your fan on 110?


"Paul" wrote in message
. ..
There's metal content as this will be part of a lathe repower project.

If one were to take two fans, something like square framed heat sink
fans,and stack them one after the other would they act as a 'two stage'
fan, so to speak?

I'm changing my lathe over to a VFD and as the motor will be running at
slower speeds I think extra cooling will be required. There's no 120 VAC
on the machine but I can easily get 220 VAC. Yes, I could buy or scrounge
a 220 volt heat sink fan but I'm thinking about wiring two 120 volt fans
in series as those are much more common and as long as I was going to have
two I started thinking if stacking them would offer any advantages.

regards
Paul


--
-----------------------------------------
It's a Linux world....well, it oughta be.
-----------------------------------------

Fans are designed with curved blades (pitch changes from leading to trailing
edge) so that air flow across the blade is tangential. Putting a second fan
directly behind the first will put faster moving air in contact with the
leading edge, which will not be pitched correctly. It would be like trying
to push a car that is moving as fast as you can walk.

Ignoramus29233 wrote:
You would save a large amount of time and effort if you buy a 220v
fan. Or you can go with a 12v transformer and a 12v fan, I can give
you a 12v tfansformer, I give 80% probability that I have one.


i

Iggy

Thanks for the offer but I know I can find some 120 volt fans laying
around, we're always junking obsolete controls at work. There might
even be some 220 volt available.

Paul


--
-----------------------------------------
It's a Linux world....well, it oughta be.
-----------------------------------------

Leo Lichtman wrote:
Fans are designed with curved blades (pitch changes from leading to trailing
edge) so that air flow across the blade is tangential. Putting a second fan
directly behind the first will put faster moving air in contact with the
leading edge, which will not be pitched correctly. It would be like trying
to push a car that is moving as fast as you can walk.


Leo

I like your analogy, and that's sorta the way I though it might work!

Paul


--
-----------------------------------------
It's a Linux world....well, it oughta be.
-----------------------------------------

On Sat, 15 Sep 2007 12:34:49 -0500, Paul wrote:
Ignoramus29233 wrote:
You would save a large amount of time and effort if you buy a 220v
fan. Or you can go with a 12v transformer and a 12v fan, I can give
you a 12v tfansformer, I give 80% probability that I have one.


i

Iggy

Thanks for the offer but I know I can find some 120 volt fans laying
around, we're always junking obsolete controls at work. There might
even be some 220 volt available.

Your idea to install a fan is a very good one. With a fan, you could
run your motors slowly all day long.

i

Ignoramus29233 wrote:

On Sat, 15 Sep 2007 12:34:49 -0500, Paul wrote:

Ignoramus29233 wrote:

You would save a large amount of time and effort if you buy a 220v
fan. Or you can go with a 12v transformer and a 12v fan, I can give
you a 12v tfansformer, I give 80% probability that I have one.


i

Iggy

Thanks for the offer but I know I can find some 120 volt fans laying
around, we're always junking obsolete controls at work. There might
even be some 220 volt available.


Your idea to install a fan is a very good one. With a fan, you could
run your motors slowly all day long.

i


I would recommend getting a small 220 to 110 transformer that could be
run off the three phase and supply 110 to the fans,lighting and your
dro. This would eliminate having two separate power sources coming to
the machine. Most machines use a step down transformer to get 110.
The only thing is make sure the outlets are fused and that you don't
plug in a toaster or some high current device that would overload the
transformer or get a bigger transformer.


John

According to Paul :
Leo Lichtman wrote:
Fans are designed with curved blades (pitch changes from leading to trailing
edge) so that air flow across the blade is tangential. Putting a second fan
directly behind the first will put faster moving air in contact with the
leading edge, which will not be pitched correctly. It would be like trying
to push a car that is moving as fast as you can walk.

[ ... ]

I like your analogy, and that's sorta the way I though it might work!

Aside from that -- since I gather that you were considering them
to be both in series electrically and in the airflow sense, I see a
possible problem -- even assuming that they are identical fans. The
bearings tend to fail in these over time, and once that happens, one fan
stalls, putting more voltage across the other, and frying its windings.
(And that bit above about the blade curvature might mean that two close
coupled in airflow series would be unbalanced anyway.

Enjoy,
DoN.

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Email: | Voice (all times): (703) 938-4564
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On Sep 14, 10:25 pm, Paul wrote:


If one were to take two fans, something like square framed heat sink
fans,and stack them one after the other... There's no 120
VAC on the machine

220/240 VAC fans are in the $10 to $30 range at www.digikey.com, just
like 120 VAC
ones. No need to buy used/surplus, really. If you need more air
flow, don't
use square 'muffin' fans, but go to a squirrel-cage blower (they have
lower
cubic-feet-per minute CFM ratings, but better performance with
backpressure).