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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

Balancing a fan



 
 
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  #1  
Old May 14th 10, 03:07 PM posted to rec.crafts.metalworking
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Posts: 3,176
Default Balancing a fan

I got so much help on my sprayer, I'm trying again...

Full time investigation and part replacement has me working on this theory
of the problem cause: The squirrel cage fan is out of balance. It is barely
detectable because the fan has a 2" solid steel shaft and some serious
pillow block bearings mounted solid to a beefy frame. At the resonate RPM,
this imbalance feeds on the slack in the drive line. Any system upset causes
the fan to become unstable and it lurches back and forth.

I've called around and not found a place to dynamic balance something like
this. Are there any home brew methods? Or other suggestions? Its built so
solid I don't think I'm looking for a minor imbalance.

Karl



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  #2  
Old May 14th 10, 03:13 PM posted to rec.crafts.metalworking
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Posts: 3,446
Default Balancing a fan

On 5/14/2010 7:07 AM, Karl Townsend wrote:
I got so much help on my sprayer, I'm trying again...

Full time investigation and part replacement has me working on this theory
of the problem cause: The squirrel cage fan is out of balance.


I bet you can whip one of these up in no time!

http://www.youtube.com/watch?v=bBzviKTPMrg

--Winston
  #3  
Old May 14th 10, 03:26 PM posted to rec.crafts.metalworking
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Posts: 10,563
Default Balancing a fan

What comes to mind to me. The fan has to come off the shaft
(might be dificult).

Take a ball berring that's larger than the shaft hole in the
center. Drill a counter sink on the end of a shaft. Put the
ball berring on the end of the shaft, and the fan on the
ball berring. Ends up looking like a crude lamp shade.

That should give you a rough idea which is the heavy side.
Similar to balancing lawn mower blades.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Karl Townsend" wrote in
message
anews.com...
I got so much help on my sprayer, I'm trying again...

Full time investigation and part replacement has me working
on this theory
of the problem cause: The squirrel cage fan is out of
balance. It is barely
detectable because the fan has a 2" solid steel shaft and
some serious
pillow block bearings mounted solid to a beefy frame. At the
resonate RPM,
this imbalance feeds on the slack in the drive line. Any
system upset causes
the fan to become unstable and it lurches back and forth.

I've called around and not found a place to dynamic balance
something like
this. Are there any home brew methods? Or other suggestions?
Its built so
solid I don't think I'm looking for a minor imbalance.

Karl




  #4  
Old May 14th 10, 03:40 PM posted to rec.crafts.metalworking
external usenet poster
 
Posts: 204
Default Balancing a fan

Karl Townsend wrote:
I got so much help on my sprayer, I'm trying again...

Full time investigation and part replacement has me working on this theory
of the problem cause: The squirrel cage fan is out of balance. It is barely
detectable because the fan has a 2" solid steel shaft and some serious
pillow block bearings mounted solid to a beefy frame. At the resonate RPM,
this imbalance feeds on the slack in the drive line. Any system upset causes
the fan to become unstable and it lurches back and forth.

I've called around and not found a place to dynamic balance something like
this. Are there any home brew methods? Or other suggestions? Its built so
solid I don't think I'm looking for a minor imbalance.


Something like this, only bigger?

http://www3.towerhobbies.com/cgi-bin...&I=LXHY61&P=ML

Before you dynamic balance, can you check the static balance? If the
static balance is perfect then I'd doubt that the thing is out of
dynamic balance.

If those bearings aren't as free as free can be then you've got a
problem. How much of a pain is it to take the fan out? Could you use
the "knife edge" with the fan shaft on a couple of angle irons, corner up?

Or: can you take the shaft out, and make an adapter so the thing will go
on a truck tire balancer?

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
  #5  
Old May 14th 10, 04:02 PM posted to rec.crafts.metalworking
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Posts: 6,757
Default Balancing a fan


Karl Townsend wrote:

I got so much help on my sprayer, I'm trying again...

Full time investigation and part replacement has me working on this theory
of the problem cause: The squirrel cage fan is out of balance. It is barely
detectable because the fan has a 2" solid steel shaft and some serious
pillow block bearings mounted solid to a beefy frame. At the resonate RPM,
this imbalance feeds on the slack in the drive line. Any system upset causes
the fan to become unstable and it lurches back and forth.

I've called around and not found a place to dynamic balance something like
this. Are there any home brew methods? Or other suggestions? Its built so
solid I don't think I'm looking for a minor imbalance.

Karl


Remember that any vibration would relate to the rotational speed of the
item out of balance. Can you get your hands on a resonant reed
tachometer? The RRTs are recommended for isolating vehicle driveline
vibrations by identifying the frequency of the vibration so you can
correlate it to which driveline components rotate at that frequency.

As for fan balance, if you just take the drive belts off you should be
able to turn the fan by hand to identify any issues. Mark the fan and
spin it by hand a few times and see if it is stopping near the same
orientation each time.
Again, I doubt it's the fan since I expect it's spinning a lot faster
than the 540 RPM PTO and won't have a 9 Hz period if it has an
imbalance. While you have the belts off to hand spin the fan, it would
be good to check both drive and driven pulleys for runout with a dial
indicator.
  #6  
Old May 14th 10, 05:10 PM posted to rec.crafts.metalworking
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Posts: 3,138
Default Balancing a fan

On Fri, 14 May 2010 10:02:20 -0500, "Pete C."
wrote:


Karl Townsend wrote:

I got so much help on my sprayer, I'm trying again...

Full time investigation and part replacement has me working on this theory
of the problem cause: The squirrel cage fan is out of balance. It is barely
detectable because the fan has a 2" solid steel shaft and some serious
pillow block bearings mounted solid to a beefy frame. At the resonate RPM,
this imbalance feeds on the slack in the drive line. Any system upset causes
the fan to become unstable and it lurches back and forth.

I've called around and not found a place to dynamic balance something like
this. Are there any home brew methods? Or other suggestions? Its built so
solid I don't think I'm looking for a minor imbalance.

Karl


Remember that any vibration would relate to the rotational speed of the
item out of balance. Can you get your hands on a resonant reed
tachometer? The RRTs are recommended for isolating vehicle driveline
vibrations by identifying the frequency of the vibration so you can
correlate it to which driveline components rotate at that frequency.

As for fan balance, if you just take the drive belts off you should be
able to turn the fan by hand to identify any issues. Mark the fan and
spin it by hand a few times and see if it is stopping near the same
orientation each time.
Again, I doubt it's the fan since I expect it's spinning a lot faster
than the 540 RPM PTO and won't have a 9 Hz period if it has an
imbalance.


I agree. I also don't see how fan imbalance would generate torque
ripple. I would suspect some aspect of the drive line between PTO and
gearbox: pulley, bent shaft, any couplings or U-joints, etc
  #7  
Old May 14th 10, 05:31 PM posted to rec.crafts.metalworking
external usenet poster
 
Posts: 99
Default Balancing a fan


"Karl Townsend" wrote in message
anews.com...
I got so much help on my sprayer, I'm trying again...

Full time investigation and part replacement has me working on this theory
of the problem cause: The squirrel cage fan is out of balance. It is
barely detectable because the fan has a 2" solid steel shaft and some
serious pillow block bearings mounted solid to a beefy frame. At the
resonate RPM, this imbalance feeds on the slack in the drive line. Any
system upset causes the fan to become unstable and it lurches back and
forth.

I've called around and not found a place to dynamic balance something like
this. Are there any home brew methods? Or other suggestions? Its built so
solid I don't think I'm looking for a minor imbalance.

Karl


From the text Mechanical Vibrations written by Den Hartog: If you have an
out of balance shaft rotating at less than the "Critical Speed" and you
approach that shaft with a pencil or a felt tip pen, the mark will be made
on the "heavy" side. Add wts to the opposite side from the mark. However
if the shaft is rotating at more than the "Critical Speed", your pencil/felt
tip pen will mark the light side and wts must be added to the same side as
the mark. If you are unfortunate enough to have the shaft rotating at the
"Critical Speed" the mark will be made 90 degrees after the heavy side.

This concept has helped me balance helicopter main and tail rotors down by
factors of 4 below the normally acceptable levels. However I do have an
electronic balancer that uses velocimeters to measure the magnitude of the
vibration and a photo sensor to give me the "pencil" mark.
We did have a subscriber to our magazine that balanced his tail rotor using
just a dial indicator and a graphic technique developed by the Russians. I
think that I could make a copy of the article describing that technique
available if you want it.

Stu Fields
Experimental Helo magazine.


  #8  
Old May 14th 10, 05:51 PM posted to rec.crafts.metalworking
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Posts: 3,176
Default Balancing a fan


"Don Foreman" wrote in message
...
On Fri, 14 May 2010 10:02:20 -0500, "Pete C."
wrote:


Karl Townsend wrote:

I got so much help on my sprayer, I'm trying again...

Full time investigation and part replacement has me working on this
theory
of the problem cause: The squirrel cage fan is out of balance. It is
barely
detectable because the fan has a 2" solid steel shaft and some serious
pillow block bearings mounted solid to a beefy frame. At the resonate
RPM,
this imbalance feeds on the slack in the drive line. Any system upset
causes
the fan to become unstable and it lurches back and forth.

I've called around and not found a place to dynamic balance something
like
this. Are there any home brew methods? Or other suggestions? Its built
so
solid I don't think I'm looking for a minor imbalance.

Karl


Remember that any vibration would relate to the rotational speed of the
item out of balance. Can you get your hands on a resonant reed
tachometer? The RRTs are recommended for isolating vehicle driveline
vibrations by identifying the frequency of the vibration so you can
correlate it to which driveline components rotate at that frequency.

As for fan balance, if you just take the drive belts off you should be
able to turn the fan by hand to identify any issues. Mark the fan and
spin it by hand a few times and see if it is stopping near the same
orientation each time.
Again, I doubt it's the fan since I expect it's spinning a lot faster
than the 540 RPM PTO and won't have a 9 Hz period if it has an
imbalance.


I agree. I also don't see how fan imbalance would generate torque
ripple. I would suspect some aspect of the drive line between PTO and
gearbox: pulley, bent shaft, any couplings or U-joints, etc


Pete and Don, I also agree. I've said it CAN'T be the fan vibration for
years. But I also can't find anything else wrong. And its not for a lack of
trying. I'm about to pop $11,100 and trade it in for a new used one.
Julie's not to keen on that idea, but only because we haven't got the money.


karl



  #9  
Old May 14th 10, 06:36 PM posted to rec.crafts.metalworking
external usenet poster
 
Posts: 6,757
Default Balancing a fan


Karl Townsend wrote:

"Don Foreman" wrote in message
...
On Fri, 14 May 2010 10:02:20 -0500, "Pete C."
wrote:


Karl Townsend wrote:

I got so much help on my sprayer, I'm trying again...

Full time investigation and part replacement has me working on this
theory
of the problem cause: The squirrel cage fan is out of balance. It is
barely
detectable because the fan has a 2" solid steel shaft and some serious
pillow block bearings mounted solid to a beefy frame. At the resonate
RPM,
this imbalance feeds on the slack in the drive line. Any system upset
causes
the fan to become unstable and it lurches back and forth.

I've called around and not found a place to dynamic balance something
like
this. Are there any home brew methods? Or other suggestions? Its built
so
solid I don't think I'm looking for a minor imbalance.

Karl

Remember that any vibration would relate to the rotational speed of the
item out of balance. Can you get your hands on a resonant reed
tachometer? The RRTs are recommended for isolating vehicle driveline
vibrations by identifying the frequency of the vibration so you can
correlate it to which driveline components rotate at that frequency.

As for fan balance, if you just take the drive belts off you should be
able to turn the fan by hand to identify any issues. Mark the fan and
spin it by hand a few times and see if it is stopping near the same
orientation each time.
Again, I doubt it's the fan since I expect it's spinning a lot faster
than the 540 RPM PTO and won't have a 9 Hz period if it has an
imbalance.


I agree. I also don't see how fan imbalance would generate torque
ripple. I would suspect some aspect of the drive line between PTO and
gearbox: pulley, bent shaft, any couplings or U-joints, etc


Pete and Don, I also agree. I've said it CAN'T be the fan vibration for
years. But I also can't find anything else wrong. And its not for a lack of
trying. I'm about to pop $11,100 and trade it in for a new used one.
Julie's not to keen on that idea, but only because we haven't got the money.

karl


Before you go blowing a big wad of money on a new blower, spend a day
checking the things we noted. It should not take that long to check the
fan for imbalance, the pulleys for runout, etc. This isn't that
complicated, it's just an organized process of isolation and
elimination.
  #10  
Old May 14th 10, 07:09 PM posted to rec.crafts.metalworking
external usenet poster
 
Posts: 539
Default Balancing a fan

"Karl Townsend" wrote in message
anews.com...
I got so much help on my sprayer, I'm trying again...

Full time investigation and part replacement has me working on this theory
of the problem cause: The squirrel cage fan is out of balance. It is
barely detectable because the fan has a 2" solid steel shaft and some
serious pillow block bearings mounted solid to a beefy frame. At the
resonate RPM, this imbalance feeds on the slack in the drive line. Any
system upset causes the fan to become unstable and it lurches back and
forth.

I've called around and not found a place to dynamic balance something like
this. Are there any home brew methods? Or other suggestions? Its built so
solid I don't think I'm looking for a minor imbalance.


Fluke makes (made) a hand-held analyzer for dynamic balancing. Proly not
super cheap, but fast, quick, accurate. And proly not as expensive as it
once was. Saw it used, never used it mysef. Field HVAC techs use this.

Might want to ask the assholes on alt.hvac what their experiences are.
And if they have any experience, it's good news, cuz if those assholes can
use one, anyone can.

I googled fluke dynamic balancing, didn't get much, but didn't look long,
either.

Heh, mebbe an auto place, that does dynamic wheel balancing?
--
EA



Karl





 




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