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  1. #1
    i_r_machinist is offline Titanium
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    Default 5 hp 230v motor rebuild or replace?

    My air compressor motor went out in an impressive blaze (literally) of glory. Is it worth taking this thing to the electric motor shop? I've never had a motor re-wind. This thing is about $250 at TSC.
    Thanks
    i_r_

  2. #2
    MwTech Inc is offline Stainless
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    buy new......lots to chose from........cheap China to Baldor.

  3. #3
    MBensema is offline Hot Rolled
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    Motors that small are throw away at my plant, a decent rewind will probably cost you twice that if not more.

  4. #4
    wippin' boy is offline Diamond
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    Default

    agreed
    5 hp is usualy below the rebuild threashold unless your talking a "special"

  5. #5
    i_r_machinist is offline Titanium
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    Default

    Thanks,
    i_r_

  6. #6
    rons is offline Stainless
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    Get a used 5hp 3 phase motor and replace the bearings.
    motor should cost 50-100 dollars. bearings should cost 40 dollars.

    or

    Switch to a 5hp single phase if you were thinking about it.

  7. #7
    Pattnmaker is offline Hot Rolled
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    Funny I am going through the same thing right now. My compressor motor is in getting repaired right now, however mine only needs a new centrifical switch, the stator machined and new bearings. That is still $400, while I could buy a new 5 hp motor cheaper the standard shaft size is 5/8 and my motor has a 3/4" shaft. My motor rewind shop tells me they have replaced motors like that and then had problems with the shaft bending. I called a local compressor repair place to ask them whether I should be buying a new motor from them they recommended the $400 repair at the motor rewind shop.

  8. #8
    i_r_machinist is offline Titanium
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    This is off of a Ingersol Rand 80 ga. compressor. 3/4" or 7/8" shaft. It was a direct short between the rotor and stator, thus the impressive blaze of glory. I can see melted copper.
    All TSC had was the 5/8" shaft and I actually thought about getting one, but after the shaft bending comment, I'll stick with the bigger size.
    I'm going to hunt around on the net to see what I can find.
    i_r_

  9. #9
    L Vanice is online now Diamond
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    What 5 HP motor has a 5/8 shaft (56 frame)? Looking at real 5 HP general purpose motors by Baldor, I only see 7/8, 1-1/8 and largerr shafts, whether they are single or three phase, whatever the RPM.

    I think a 5/8 shaft indicates an exagerated HP rating, as is seen on some cheap compressors. That sort of motor would not be suitable to run a real 5 HP compressor pump.

    Larry
    Last edited by L Vanice; 09-09-2010 at 09:41 AM.

  10. #10
    Pattnmaker is offline Hot Rolled
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    Quote Originally Posted by L Vanice View Post
    What 5 HP motor has a 5/8 shaft (56 frame)? Looking at real 5 HP general purpose motors by Baldor, I only see 7/8 and 1-1/8 shafts, whether they are single or three phase.

    I think a 5/8 shaft indicates an exagerated HP rating, as is seen on some cheap compressors. That sort of motor would not be suitable to run a real 5 HP compressor pump.

    Larry
    Are the motors you are looking at 1725 rpm or 3450? Higher rpm motors often have a smaller frame and shaft size.

  11. #11
    MBensema is offline Hot Rolled
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    3/4" is an odd ball size for a NEMA motor, are you sure it is inch and not metric? 3/4" is almost exactly 19mm, which would be an IEC 80 size frame. Measure the mounting holes of the motor and see which frame size it matches most closely with. The following link has a listing of the dimentions for both IEC and NEMA motors.

    http://baldor.com/pdf/501_Catalog/BackCover.pdf

  12. #12
    L Vanice is online now Diamond
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    Quote Originally Posted by MBensema View Post
    3/4" is an odd ball size for a NEMA motor, are you sure it is inch and not metric? 3/4" is almost exactly 19mm, which would be an IEC 80 size frame. Measure the mounting holes of the motor and see which frame size it matches most closely with. The following link has a listing of the dimentions for both IEC and NEMA motors.

    http://baldor.com/pdf/501_Catalog/BackCover.pdf

    There are three NEMA frames with 3/4 shafts (145, 203 and 204), probably based upon old standards. Hardinge used motors with 3/4 shafts in the 1935-1960 time frame. Note the frames with 1 inch shafts, too, probably same reason.

    NEMA Motor Size Chart

    Larry

  13. #13
    MBensema is offline Hot Rolled
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    Quote Originally Posted by L Vanice View Post
    There are three NEMA frames with 3/4 shafts (145, 203 and 204), probably based upon old standards. Hardinge used motors with 3/4 shafts in the 1935-1960 time frame. Note the frames with 1 inch shafts, too, probably same reason.

    NEMA Motor Size Chart

    Larry
    Like I said, odd ball sizes The 143/145 in your chart is a short shaft, not very common and the 203 and 204 are over 50 years old and obsolete.

  14. #14
    i_r_machinist is offline Titanium
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    Been doing some reading. It seems like the Emerson motors on the t-30 I-R compressors are a piece of junk.
    Baldor runs about $550 for a 5hp. fla21.5, continuous duty, 7/8"shaft, 3450 rpm, 56hzframe, motor.
    Leeson at Northern Tool is about $325. Haven't read up on them yet.

    still on the hunt
    i_r_

  15. #15
    3t3d is offline Titanium
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    OK, From the BTDT section I can tell that a "5 Horsepower" compressor motor is really "5 Whorespower".
    Secondly, you don't really need a 3400 RPM motor.
    Get yourself an 1740 RPM 3 Horsepower motor, and use a bigger pulley on it.
    You will be many miles ahead!

    I had the same "5 Horsepower" motor on a compressor, you could cook eggs on it, it was wasting SO much power. Most of the electricity it used was wasted heating the air in the shop. I got a three horse motor, 1740 RPM and got about an 8" pulley for it. The compressor runs a little bit slower, but MUCH cooler. And the I burned out the first compressor head, the second one is running cool and strong for years at the very slightly reduced speed.
    The 3 HSP motor runs cool to the touch. So I KNOW it is not wasting all the expensive electricity turning it into wasted heat.

    You could go up to about a 10" pulley on the motor, and get to the original speed of the compressor, but I would recommend a little bit slower, and longer.
    Measure the original diameter of the pulley for the calculations.

  16. #16
    i_r_machinist is offline Titanium
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    After reading all the reviews on the Emerson motors, I might try a Baldor 3hp. I would want to stick with the "cont." duty rating as I use air mist for my mill and not flood coolant.
    Thanks
    i_r_

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