Shop Floor fan question

Discussion in 'General Electronics Chat' started by Gdrumm, Jul 2, 2014.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Someone gave me a shop floor fan that looks like this one.
    No info tag on the motor, but it is a 2 speed.
    It has three blades, but two were damaged and misaligned, and it was running slow.

    I took the motor apart, and didn't see anything other than some rust on the rotor and stator, which I cleaned thoroughly.

    The capacitor looked like one you might see in a ceiling fan, and since the motor does turn, I assume that part is okay.

    I'm pretty sure it's Chinese made; internally it looks sound, no eveidence of burnt wires.

    Would the bent blades, and the rust as mentioned cause it to run slow?

    I haven't reassembled it yet, just bench tested the motor, and it seems to change speeds (I think).

    What other tests could I conduct to see if it's performing properly.
    I have an old RPM gauge, and plan to test that part this weekend.

    Thanks for any insights.

    Gary
     
  2. mlog

    Member

    Feb 11, 2012
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    When the motor is depowered, does the motor rotate freely, i.e. do the blades move easily by hand?
     
  3. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    When the blades where misaligned, there could have been unbalance, wich can have a bad effect on the bearings.
    Is there any backlash on the axe of the motor?

    Bertus
     
  4. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    I currently have the blade assembly removed, and the motor shaft turns freely, by hand.

    When plugged it, it does run, but I haven't checked RPMs yet.

    I'm not sure how to check for the backlash you mentioned.

    I'm also curious about it's horsepower, since it has no markings.

    A similar fan (the one seen in the photo from eBay), is listed as 120 volts, 60hZ, 1.48 amps (low), 1.85 amps (high), Single Phase Motor, Noise Level (dB) 57.

    Does that sounds like a 1/4" hp motor to you?

    If so, might that give me some insights as to how it should perform? (assuming it's the same motor, which I think it is).

    Thanks,
    Gary
     
  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Can you move the axis (up, down, sideways) while not turning the axis?
    If you can the bearing will be damaged.
    This is what I ment with the backlash.
    (the translation may not be correct as english is not my native language, wich is dutch).

    Bertus
     
  6. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    I'll check that this afternoon, and report back.
    I think our slang here would translate "slop in the bearings", and it seemed to me that the bearings were in good shape. But I will confirm.

    Thanks
     
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Give it a good lube, with motor oil, so it flushes out the munge in the bearings. That munge can be really speed critical especially as the bearings/shaft heat up.

    If the munge is real bad you may have to disassemble, but often it will flush out with repeated lubing and running over a couple of days period.
     
  8. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Will check bearings this weekend.
    Wifes BD yesterday, so no time for hobbies.

    Thanks for the ideas.

    Gary
     
  9. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Okay,
    I checked the bearings, and there is no end to end or side to side play.
    They are sealed bearings, so I cannot lube them.
    They don't seem to be running hot.

    I did find a number on the motor, MB-75S4L, and the date of Mfg. was 2008 apparently.

    I checked the RPM's with an old rubber tipped mechnical RPM handheld device.
    At low speed, it read 1163 RPM.
    At high speed it read 1191 RPM.

    Is that what you would call single phasing?

    It does make a change in sound from low to high, as you would expect, but the speed doesn't increase.

    I pressed a wooden stick against the shaft end, while it was running, to simulated a load, but it didn't seem to slow down any.

    Would a bad run capacitor cause it to fail to increase speed?

    Scrap it, or Keep it?

    I priced a 1/4 horse motor, with this type mount, and a cheap one is still well over $100.00

    Any thoughts are appreciated.

    Gary
     
  10. Austin Clark

    Member

    Dec 28, 2011
    409
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    If you have a kill-a-watt meter or something similar (to measure PF, watts, voltage, frequency, etc; coming from your wall socket) use it on the fan to see what the PF and wattage is. Poor PF and/or excessively high wattage could indicate a problem. Check for both High and Low settings. Perhaps there is only a problem with the High setting.
     
  11. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    684
    36
    Update,

    It's all back together, and running great.
    I guess my RMP gauge was slipping or something.

    It runs on high and low speeds, with minimal vibration.

    Looks like I've got me a great garage fan for the Texas summer.

    Thanks for your input.
    Gary
     
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