Old motor frame size = unobtainium.
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  1. #1
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    Default Old motor frame size = unobtainium.

    My old wells index model 40 has a spindle motor made by Master Electric Company in Dayton Ohio. The frame is a 7420 which isn't a frame size I can find the specs on. I am wondering if anyone can tell me the modern cross reference for this size frame? It is a 3ph 1/2 hp motor. I'll be replacing it with a new motor because the bearings sound horrible and I think I have a good 3/4 hp motor I can swap after er a couple of modifications. Oh, the fact that I crashed the fan into the motor windings has absolutely no bearing on my decision to not simply replace the bearings and reuse the motor.
    I'm an idiot. A very pissod off idiot.
    Thanks

    Sent from my Pixel 2 using Tapatalk

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    Quote Originally Posted by challenger View Post
    My old wells index model 40 has a spindle motor made by Master Electric Company in Dayton Ohio. The frame is a 7420 which isn't a frame size I can find the specs on. I am wondering if anyone can tell me the modern cross reference for this size frame? It is a 3ph 1/2 hp motor. I'll be replacing it with a new motor because the bearings sound horrible and I think I have a good 3/4 hp motor I can swap after er a couple of modifications. Oh, the fact that I crashed the fan into the motor windings has absolutely no bearing on my decision to not simply replace the bearings and reuse the motor.
    I'm an idiot. A very pissod off idiot.
    Thanks

    Sent from my Pixel 2 using Tapatalk
    Consider calling wells for a quote on a new motor

    They are really nice people, even though they do this for a living

    They were so reasonable and helpful when I owned my Wells CNC, that when I scrapped it, I gave them whatever parts they wanted [basically the head] and strapped them to a pallet that they paid to have shipped back 'home'

    They no doubt passed it on to some other WElls owner, like you

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    You're right, "7420" is not a standard (even very old) frame size.

    I'm afraid you are going to have to measure a few dimensions. With those dimensions, you can find the closest modern NEMA frame size. To narrow things down, you want a fractional HP (generally two-digit) frame, and the most common examples are 42, 48 and 56, with shaft centerline heights of 2-5/8, 3, and 3-1/2", and shaft diameters of 3/8, 1/2, and 5/8", respectively.

    If you know the shaft centerline height of your 7420 frame, that will help narrow things down a lot. The first two digits of three-digit NEMA frame numbers are 4 times the height in inches. I.e., NEMA frames beginning 28x have a centerline height of 7 inches. Since you can always make a mounting pad/spacer, you should look for frames with your current frame's centerline height, or less.
    Last edited by sfriedberg; 05-15-2018 at 07:23 PM.

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    Dealing with physical objects is so much harder than managing people.

    Damage a person, just call HR for another.

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    Quote Originally Posted by sfriedberg View Post
    You're right, "7420" is not a standard (even very old) frame size.

    I'm afraid you are going to have to measure a few dimensions. With those dimensions, you can find the closest modern NEMA frame size. To narrow things down, you want a fractional HP (generally two-digit) frame, and the most common examples are 42, 48 and 56, with shaft centerline heights of 2-5/8, 3, and 3-1/2", and shaft diameters of 3/8, 1/2, and 5/8", respectively.

    If you know the shaft centerline height of your 7420 frame, that will help narrow things down a lot. The first two digits of three-digit NEMA frame numbers are 4 times the height in inches. I.e., NEMA frames beginning 28x have a centerline height of 7 inches. Since you can always make a mounting pad/spacer, you should look for frames with your current frame's centerline height, or less.
    You are correct.
    I have taken some measurements and compared them to the NEMA charts and this motor is a long way off. Nothing that a bit of mounting plate and pulley sheave modifications won't address.
    For giggles I'll call the local motor rewinding shop to see what the cost to rewind and rebuild the motor will run. Last one I had done was a Baldor 5hp single phase compressor motor. It was $400.00 to rebuild and a new one was more than that so I had them do it. This time I really doubt I'll be inclined to do so.

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    I don’t know a lot about electric motors but I have seen at least one instance where a motor with damaged windings that had special rotor and end bells was salvaged by taking the stator or center section with the windings from another used motor of the same physical size HP. and voltage and putting it together with the rotor and end bells of the burned out motor .
    You might be lucky enough to find a used motor that could donate the stator and put in a new pair of bearings to get you going again .

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    Quote Originally Posted by challenger View Post
    My old wells index model 40 has a spindle motor made by Master Electric Company in Dayton Ohio. The frame is a 7420 which isn't a frame size I can find the specs on. I am wondering if anyone can tell me the modern cross reference for this size frame? It is a 3ph 1/2 hp motor. I'll be replacing it with a new motor because the bearings sound horrible and I think I have a good 3/4 hp motor I can swap after er a couple of modifications. Oh, the fact that I crashed the fan into the motor windings has absolutely no bearing on my decision to not simply replace the bearings and reuse the motor.
    I'm an idiot. A very pissod off idiot.
    Thanks

    Sent from my Pixel 2 using Tapatalk
    .
    .
    many motors if you can manage to get it apart, changing bearings is relatively easy. some motors getting apart can be a challenge, sometimes rusted solid or they used the high strength loctite never made for taking stuff apart

  10. #8
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    This was very easy to get apart and easier to make the fan blades ruin the armature wiring.

    Sent from my Pixel 2 using Tapatalk

  11. #9
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    many a motor i flopped upside down clamped on a hardened steel plate with holes in it to guide a drill bit as i drilled 1/2 a hole or slotted the holes.
    .
    they also sell hardened drill bushings that can be pressed in soft steel to do same thing. and soft steel good enough to guide a hole saw with pilot removed to also cut 1/2 a hole or slot holes
    .
    or use a rotary file in a hand held grinder to slot the holes.
    .
    most millwrights would have any motor even remotely close to size bolted on in less than 10 minutes. sure if motor over 500 lbs might take a extra 5 minutes


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