Self-made air cleaner noise?

[Phil Thien]

Have you run the motor without the squirrel connected?

No. But I did use divining rods designed to locate a noisy motor. They were able to detect this one.

Just kidding, I did run the motor by itself. It vibrates a bit. More so than the 1/4-HP motor on my furnace blower. I've come to the conclusions that: (1) The blower itself amplifies the noise. (2) The box further amplifies it.

[Greg Peterson]

What OS is the motor running? You know if it was running Linux or Mac OS X you wouldn't have this problem. Have you tried rebooting it? Have the latest drivers?

[Larry Edgerton]

Phil

Mine is quiet, and it is hung on threaded rod.

I did however wire on of the fans wrong, and it worked, but it sounded like you discribe. This is why I don't do wiring. I made my OMGA run backwards too! I consulted a shaman and he got me going right then......

[Tim Janssen]

I think you have bad motor, and since it only hums when power is applied to the motor I suspect the field laminations might be loose. I'm assuming that the hum is a 60 or 120 cycle hum? Open the motor up and see if you can find anything unusual.
Good luck.

Tim

[David Hostetler]

Phil,

For what it's worth, I didn't build mine, but rather bought it. I did cobble together one prior to buying my Grizzly, but had too many problems with bad motors... (long story...) On the one I was able to get to work, somewhat passably, it hummed like crazy like a harmonic vibration with the box. As an experiment, I laid down a heavy piece of rubber sheeting on the bottom inside of the box, and the hum went away... Maybe some sort of vibration damping material is in order for yours? (FWIW, I gave up on the DIY approach after too many locked up bearings on pull out motors / squirrel cages... I guess people around here don't replace A/C units until they are gasping their last breath...)

[Phil Thien]

I think you have bad motor, and since it only hums when power is applied to the motor I suspect the field laminations might be loose. I'm assuming that the hum is a 60 or 120 cycle hum? Open the motor up and see if you can find anything unusual.
Good luck.

Tim

I think you're right. I think I have a bad motor. The frequency does seem to be right at about 120-Hz.

I guess I didn't get such a good deal after all.

[Phil Thien]

Phil,

but had too many problems with bad motors...

I was able to compare the noise with a frequency generator and I'd say I'm hearing 120-Hz. I think I have a bad motor, too.

Oh well, back to the drawing board.

A gable fan made its way to my door. I have a feeling any level of filtering will kill the airflow. But no cost, so worth playing around with it.

[Alan Schaffter]

Phil,

I suspect you may have some sort of magnetic resonance caused by improper wiring, windings, or loose stator iron(s). Or it could be the magnetic pull is off center somehow and when that is combined with a bad bearing(s), causing the rotor to wobble only when the power is applied. Make sure the motor housing bolts are tight and there is no play in the sleeve bearings. If that doesn't work, open up the motor and make sure the stator irons and windings are fixed and can't vibrate. Here is a link to an excellent tutorial with photos of what's inside a multi-speed squirrel cage fan. You can bypass the flame about trolls at the beginning (it is also an interesting read on its own merits since we've seen some of that here lately) and start at "Show 'n Tell" .

Good luck!

[Ryan Hellmer]

I wonder if you're overloading the motor. Does it get pretty warm after running for some time? The reason I ask is that those blowers are designed to run with a certain amount of static pressure, relieving them of that makes the fan move LOTS more air increasing the load on the motor substantially and perhaps leading to additional noise/vibration (this is particularly true with low pressure forward curve squirell cages). Have you tried limiting air flow by blocking part of the inlet/outlet? You may find that helps.

Ryan

[Phil Thien]

Thanks Alan, I'll look into the link and see if there is a way to silence this motor.

Ryan, the motor is rated for 3.75A (I think). When I run it on the lowest speed and have the filters in place, I'm drawing about 3.6A. I have tried blocking-off some of the inlet with a piece of hardboard and dropped to 3A. The amplitude dropped a little bit, but the noise was still there.

I did run the motor in free-air. It vibrates. I think I have to disassemble it and look for the cause.

[Alan Schaffter]

Thanks Alan, I'll look into the link and see if there is a way to silence this motor.

Ryan, the motor is rated for 3.75A (I think). When I run it on the lowest speed and have the filters in place, I'm drawing about 3.6A. I have tried blocking-off some of the inlet with a piece of hardboard and dropped to 3A. The amplitude dropped a little bit, but the noise was still there.

I did run the motor in free-air. It vibrates. I think I have to disassemble it and look for the cause.

One quote from my link above (bold and red added by me):

"You can also see how the “end turns” of the windings are laced tightly with lacing twine. This holds the windings in place and keeps them from vibrating, creating hum."

[Larry Edgerton]

I wonder if you're overloading the motor. Does it get pretty warm after running for some time? The reason I ask is that those blowers are designed to run with a certain amount of static pressure, relieving them of that makes the fan move LOTS more air increasing the load on the motor substantially and perhaps leading to additional noise/vibration (this is particularly true with low pressure forward curve squirell cages). Have you tried limiting air flow by blocking part of the inlet/outlet? You may find that helps.


Ryan

I have 8 20"x25"filters on mine and it does not vibrate. Of course mine is an octagon, which is a collection of pyramids when you think about it, so I am collecting all of that positive energy which is probably why mine runs so smooth.

Genius! Shear Genius!

Sometimes I just amaze even myself.......

Larry