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Emmy 6250 Round 3  Rate Topic 
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 Posted: Sun Nov 4th, 2018 12:14 pm
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NM Whitney Jr.
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I've been trying to restore a 6250 as a gift for a friend.  There's a long story here I won't bother you with.  The issue now is it develops a rattle after it warms up (i.e. running for about 15 minutes).
What I've ruled out:
- Slop in the spider.  I know these 6250s are notorious for getting loose.
- Blade is balanced.  Spider is spot on and the blades are within 1/16th of an inch of each other on leading and trailing edges (and the tips).
- I've read the neck mount can transmit/amplify rattles so I put a neoprene washer under the head.  This cut the noise by about half.
- Motor reads healthy.  It draws .54 amps and 47 watts after running for one hour.
- Does not appear to be any binding... spin down is 23 seconds.

It does run warmer than my other 6250.  The housing runs about 115*F (my other 6250 runs in the upper 90's).

I can't detect any vertical play in the shaft (not necessarily determinative of shaft wear, I know).  

So I'm at a loss... any advice?  

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 Posted: Sun Nov 4th, 2018 01:56 pm
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David Hoatson
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Does it vibrate/shake?
Try dripping oil down the shaft into the bearings. 

Does it get quiet if you hold it upside down? If you aim it up or down?

Is the shaft in/out play about 1/8”?

Is the cage tight?

You could put the blade on an RC plane prop balancer. 

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 Posted: Sun Nov 4th, 2018 03:38 pm
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George Durbin
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If all the above does not work... Try removing the link arm and see how it does... Then if still noisey remove the gear case... 

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 Posted: Sun Nov 4th, 2018 04:40 pm
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NM Whitney Jr.
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Even with the gear case removed, it rattles once it warms up.

I keep coming back to the front bearing... was hoping, probably in vain, that wouldn’t be the case.

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 Posted: Sun Nov 4th, 2018 06:10 pm
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Charlie Forster
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Might need both bearings replaced, you may have a situation where  one bearing is wore some on the top and the other bearing is wore on the bottom.
Is the armature shaft bent?
a crude way to check for a bent shaft is  put one end in a drill chuck and turn the drill on and observe the other end then switch it 180 degrees and do it again.

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 Posted: Sun Nov 4th, 2018 06:40 pm
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NM Whitney Jr.
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I'm going to give the "drill chuck" to check if the shaft is true a shot...

I've got a 6250 head that I pulled the stator from for this fan (original stator had a buzz that turned into a short). For giggles, I cleaned up the armature shaft and put it in this fan.

No rattle, but I do have a fair bit of vibration now... feels like a phone is on vibrate.

Amps drawn went up to .57 and watts to 48... case temperature dropped to 104*F...

Last edited on Sun Nov 4th, 2018 06:41 pm by NM Whitney Jr.

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 Posted: Sun Nov 4th, 2018 08:12 pm
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Charlie Forster
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A variable speed drill would be  good  just to see how true the other end is  doing.you dont have to turn the drill real fast .
If  you would have a good V block would work  good also or a lathe.
If you have calipers or a   0-1'' MIKE  You can check the  shaft bearing surface and then turn it 1/4 turn and see if the shaft is the same if not the shaft is out of round.
 Some of that model fans  can be a bugger to get the blade off and might have a bent shaft .
  good luck with it.
I have one that the top of the set screw  broke  and the set screw was hard  it was some blue smoke and words to get that one off.

Last edited on Sun Nov 4th, 2018 08:16 pm by Charlie Forster

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 Posted: Mon Nov 5th, 2018 07:20 pm
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NM Whitney Jr.
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Well... I did the drill trick...

The original rotor/shaft had some, peculiarities. The shaft was true, but the rotor part was not. It has a wobble to it and I can barely make out a spot on the very edge of it where it seems to be making contact with the stator.

QUESTION: Is this something that could be filed down to prevent contact without destroying the rotor?

The parts rotor/shaft was perfect to my eye, but it's got a visible vibration once installed.

I've got an I.D. "mike" but it's not small enough to check the interior of the bearings.

I'm going to clean the front housing/bearing from the parts fan and install it... maybe that bearing is in better shape. I'm not crazy about that idea as it seems to be made of a different metal (cast aluminium?) than the cast iron of the original.

I did decide to put the fan aside for a few days... all work and no fan makes Jack a cranky man.

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 Posted: Tue Nov 6th, 2018 01:59 am
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Charlie Forster
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Do you have  somebody near you that has a lathe or a o.d. grinder. and they could true that up for you  easy.
on auto generators and starters  when the get a lot of use and the shaft gets wore on one side  you can   around .010  or so to true it up and make it last a long time.

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