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Motor help (Possible death)


Greg Calmly

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Good day everyone. As a box fan collector of 24, I have never heard a fan do such a thing.

I have an early 70's manning bowman 20524, and I was running it overnight last night on low. At 4:00 AM I was woken up by a very low-pitched deep hum. I honestly thought it was like a helicopter over my house or something. Eventually I knew it was the fan. The hum would pulse in and out like every 5 seconds. Keep in mind this fan had ran overnight before so its not the length of runtime.

I also heard a mild buzz from the bottom of the motor.

I pulled out my kilo-watt meter and its drawing the same power from the previous day.

1.47 A , 102 W , 60Hz

For anyone who wants to know about the motor, here you go.

It buzzed 2 other times. Was varnished both times and has stopped. Now its buzzing again quietly.

Motor has new thrustwashers, has been cleaned of old oil and everything and has an amazing spin-down.

All windings are a shiny bright copper color and no burns. And temp of the motor at the time of the humming seemed normal.

 

I am very worried this might be a sign of death soon, but I would love to hear a remedy or something I can do for my little manning bowman.

Thanks ❤️

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THOSE FANS WHEN I WAS YOUNGER WERE ONES I COULD CURB RESCURE AND PRETTY MUCH BE ASSURED THE MOTOR BURNED OUT (SMELLED, BLACK) SO THAT YOU HAD TO VARNISH IT TWICE BEFORE IS NOT NECESSARILY A SURPRISE AS THEY ALWAYS HAD A BORDERLINE BUZZ OR TONE TO THEM WHEN TURNING ON( TO MY EAR.) NOW THE "DEEP" HUM THAT WOULD GO IN AND OUT, WAS THERE ANY DISCERNABLE DIFFERENCE IN PERFORMANCE? DID THE BLADE SLOW DOWN? DID YOU CHECK THE BLADE SET SCREW TO MAKE SURE IT ISNT LOOSE? CHECK THE BLADE FOR A CRACK IN A WING? YOU COULD BE GETING A "FLEX NOISE. TRY IT WITH NO BLADE AT ALL AND SEE IF THE SOUND IS STILL THERE . THE ARMATURE ON THE SHAFT TOO MIGHT BE COMING LOOSE? ALSO THE BUSHINGS ARE PRESSED IN TO THE END OF EACH MOTOR CAP, IS ONE STARTING TO SPIN INSIDE THE MOTOR CAP?. THEY ARE PRETTY SIMPLE MOTORS. MAYBE YOUR DEEP SOUND ISNT THE WINDINGS BUT SOMETHING DIFFERENT 

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To answer your question-

I agree these fans always buzz and its really annoying. (update: The buzzing isnt there anymore? It seems maybe only if it runs awhile it happens.)

During the hum, it seems the fan was running slower (not by much) compared to when I went to bed. It makes no hum without the blades. There are no cracks or any visible damage or anything to be concerned about in the motor. Blades were very tight. Motor with its bolts are tight aswell. I also checked tension to make sure they are even and not too tight or too loose. 

My theory, the blades are giving off the hum. I mean this hum was loud. It was also less imminent when you were in a seperate room or behind the fan which is why I think the blades are amplifying the sound.

I just dont know what a hum means. Is it a sign of death? Weakness? Can it be resolved? 

Thanks for the reply

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try a different set of blades ...i have a GE box fan on the panel and as it goes through wind up there is a flex that makes some rpms louder than others also i had a frigid box fan on low speed at just made a grinding  grating noise through the metal structure and oiling washers etc never made a bit of difference...BUT take the fan handle at 12 o clock and turn the whole fan so the handle  to 3 or 9 o clock and run the fan standing on one of its sides...voila  not a peep the noise came from the motor as i switched it to another fan and sure enough still there 

the fact that your fans slows when it makes the deep hum is a concern as internally something might now be changing with the heat as it runs longer and intermitantly  cycles in and out of a weak point and might ultimately just quit. 

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I have no other blades I can try. The only other one with with a half size shaft is my eskimo which is the same blades.

The fan kinda just whined louder on its side but no hum yet. I think when the motor gets hot it starts humming.

Is there any fix for the hum? I once thought there was no fix for a buzz until I learned about varnish.

heres a video

 

 

 

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  • 3 weeks later...

UPDATE:

All stuff aside, I just temperature tested the motor, and after running for 1 hour and 15 minutes it peaked 142 degrees F

Normally 140 is about as high as the limit should be. This means if I ran it overnight I easily would've hit 150.

(Other fans in my collection hit around 125 F which is pretty tame.)

 

So now we know this motor is overheating, and that is the cause of the hum. Is there any possible repair for this?

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THOSE FAN MOTORS ALWAYS RAN HOT.... BERSTED HAD HOT MOTORS IN THEIR DESK FANS AND OTHERS... THEY HAD SORT OF A BUZZ TO THEM  ASWE DISCUSSED, BUT ARE YOU GETTING A HUM SOUND THAT IS JUST ON CERTAIN SPEEDS?  I HAVE FORGOTTEN ALL THE ISSUES WE DISCUSSED HMMMM I JUST REMEMBERED THE MOTOR HUMS AND SLOWS.  THIS MIGHT SOUND DUMB BUT I WONDER IF YOU HAVE A SWITCH THAT HAS A POOR INTERNAL GUMMED UP CONTACT? YOU CAN TRY A DIFFERENT SWITCH... IT IS POSSIBLE THAT AT TIMES THE CONTACT IS TEMPORARILY POOR THEN BETTER, THEN BACK TO POOR OR ONE OF THE LEADS FROM THE MOTOR GOING IN TO IT IS CORRODED ETC AND IT ISNT RUNNING WELL LIKE IT SHOULD 

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The switch is incased with a plastic covering and when I restored the fan there was no dirt to be seen. It seemed fine.

Im just mainly curious if theres a way to manage the heat coming into the fan because I believe thats the source of the issue.

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  • 2 weeks later...

I have the same fan (mine is a robins egg blue color) and I think your fan sounds like it might need some new shims in the motor (they are usually phenolic washers of some sort) which my fan was noisy like yours as well until I replaced those washers inside the motor and then the motor quieted down significantly.

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Im not sure what they are. I know the fan needed a new thrust washer, which I had done and it took care of some knocking noises but the hum was way after.

The hum was loud and deep pulsing and happens when the motor gets hot. My other fans average around 125 degrees F (when ran overnight)

When I tested the manning bowman, after an hour and 15 minutes the motor peaked 143 F which is way hotter than the others.

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  • 2 months later...

I know these older box fans like this (especially the ones made by the Bersted Company) do tend to get very hot because they are shaded pole motors, but I'm not sure about your fan's situation. I've not actually checked the temperature of my fan like this because I really don't have any sort of temperature measurement device that can tell me what the temperature is on my fan motors (I can't afford to spend $400 on a Flir.)

Edited by Levi Mevis
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On 7/27/2023 at 10:58 AM, Levi Mevis said:

I know these older box fans like this (especially the ones made by the Bersted Company) do tend to get very hot because they are shaded pole motors, but I'm not sure about your fan's situation. I've not actually checked the temperature of my fan like this because I really don't have any sort of temperature measurement device that can tell me what the temperature is on my fan motors (I can't afford to spend $400 on a Flir.)

Harbor freight has laser thermometers real cheap.

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