Mixer Problem

Discussion in 'General Electronics Chat' started by R!f@@, Oct 11, 2011.

  1. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    Guys, I need a solution...what are my options..:confused:

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    Last edited: Oct 11, 2011
  2. iONic

    AAC Fanatic!

    Nov 16, 2007
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    Great pics! We don't often see such quality. But UGGH! that motor looks pretty darn ugly.
    What's it from? What's your experience in rebuilding motors?
     
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  3. shortbus

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    Before spending too much time on it you should make sure the windings aren't fried. When a commutator gets that hot, the windings some time melt where they connect to the segments of the commutator. Check for continuity and shorts to the rotor.
     
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  4. SgtWookie

    Expert

    Jul 17, 2007
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    How much room do you have in your trash can?

    Unless that's a REALLY expensive mixer, buying a new one is probably your best option.

    The rotor needs to be re-wound, and there are somewhere between three and eight commutator segments that are burned so badly that they need to be replaced. Usually, you could chuck the thing in a metal turning lathe and dress the commutator so that it's back to serviceable condition. However, that one is so damaged that I doubt if brushes could be made to ride smoothly over it any more; too much material would have to be removed.

    You'd also need a growler and a megger to make certain that the insulation & windings are good after the repair. I'll venture that you have neither of those (I don't either) but they are required to complete the job.

    Unless, of course, you have an electric motor repair shop somewhere in the Maldives, and they will repair the motor for a reasonable price.
     
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  5. R!f@@

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    Pics are taken by a Sony cyber shot..nothing fancy.

    Actually I do not have much experience on Motors. After seeing the commutator somewhat weird I knew something is wrong in the armature.

    Never realized that a winding could be shorted. That is why I showed this to u guys.
    These are heavy duty juice mixers. Two of them. They have simple triac speed control. Problem is something starts to burn with in a few seconds after starting. Sparking suddenly increases and something definitely starts to cook. I can smell it burning. The brushes are really dull.

    I doubt it is worth winding these. I don't think there is any one here who can fix the commutator. Better to buy new ones since these aren't that expensive.

    So..you guys are sure that one winding is indeed shorted, or else the commutator won't melt like that. right ?
     
  6. SgtWookie

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    I'm not certain that it's shorted, but it's certainly a mess. The windings near the commutator on at least one of them look mighty fried. I don't think it would be safe to run them, even if the commutators were cleaned up using a file.

    I didn't realize it was more than one rotor; I thought you had taken a couple of photos from both sides of the same one.
     
  7. THE_RB

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    Considering you are on a "deserted island" ;) , if you know someone local with a metal lathe willing tohave a go, chuck it in the lathe and skim the commutator. It's not much work. There's still a significant chance the winding may be shorted, but it's also possible the commutator just developed a hot spot. If that seems to fix it, then it's worth a little extra effort to "undercut the commutator", i'll let you google that but it can be done pretty easily by hand.

    There's a bit of carbon that needs carefully scraping off between some of those commutator segments too.
     
  8. shortbus

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    That type of damage some times happens when the brushes get worn to bad. They start arcing instead of contacting the commutator and heat things up and it just keep getting worse.
     
  9. dataman19

    Member

    Dec 26, 2009
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    First read this note (*****)
    *** Motors are fixed by putting the commutator into a machine Lathe.
    *** The commutator windings are machined smooth.
    *** The spaces between the copper contacts are then machined to restore
    *** the mandatory 3/32nd of an inch depth.
    ...
    Now for my suggestion:
    ...
    Put the thing in a drill press, put a 2x4 (securely clamped) to the bottom and slowly lower the thing so that it sits centered on the 2x4 and turn on Drill press (be cautious - if it isn't centered it will not stay put).
    ...
    Then take a Bastard File (the broad flat file) and slowly file down the copper until you get it smoothed out. Take care not to file this too small or you won't be able to proceed with step two.
    ...
    Take a hack saw blade and cut one end off (where the teeth are at the end of the blade). Then hold the blade in one hand (wear a glove).
    Slowly dig out the areas between the copper contacts that have been smoothed by the filing and remove all the copper filings.
    ...
    Clean with a contact cleaner and dry with forced air...
    ..
    Buy a new set of brushes (because the old ones were burned by the stalled motor winding).
    ..
    Put the whole thing back together...
    ....
    FYI I spent several years over seas. I took a 1973 V-8 Vega to Germany where I lived and worked for 9 years. Try getting parts for an American Alternator or Starter in Germany in the early 1980's ( Mid 1980's doesn't count - because I started a car parts company to eliminate this problem. If you need American Car parts in Germany now - just call Peter Schuetz at American Car Shop, Bochum, Germany. Peter now owns the American Car Parts Company. I sold it to him in 1989)...
    ..
    We restored and rebuilt a lot of American Alternators and Starters in the Military Hobby shops using this exact procedure. So I absolutely know it works...
    ..
    Dave Mason
    dataman19
     
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  10. R!f@@

    Thread Starter AAC Fanatic!

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    good options...one problem though.

    Need to find a drill press or a lath.
    Will get back to you if I get my hands on one.
    This thing is cheap.
    But I will give the methods a go to see if it works for future cases.
     
  11. Ron H

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    Apr 14, 2005
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    Is this a cause or an effect? Whichever, it needs to be straightened before power is reapplied.

    EDIT: I suppose I just stated the obvious.
     
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  12. vrainom

    Member

    Sep 8, 2011
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    The coil ends in the last pic look charred badly from arching.

    And this is the kind of damage you see in a commutator when the coils have cut wires either in the coil themselves or the ends going to the segments, so just rectifying it in a lathe will not be enough. Another way to know is from the green arch the brushes make when it's powered.

    [​IMG]

    Plus: you see the commutator charred all the way to the bottom in the next pic, and the segment falling off? That makes it useless.
    [​IMG]

    PS: Just one last thought, IF: 1 - The windings are not shorted, 2 - The winding ends are all in place and 3 - you happen to have a similar commutator from another armature (size and number of segments) you can try to replace it. It's a delicate work but it's doable.
     
    Last edited: Oct 12, 2011
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  13. THE_RB

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    The commutator is quite serviceable.

    The big issue is whether the armature is shorted (as others and myself have said).
     
  14. vrainom

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    Sep 8, 2011
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    I do this for a living, so I'm pretty sure it's not.
     
  15. THE_RB

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    So did I. ;)

    Please keep in mind the OP is in the Maldives islands and what might be worth servicing in a remote situation can be a different thing to what a pro workshop in a big city considers servicable.

    I agree totally with you that if a new armature was easily available the idea of servicing that one is pretty silly. :)
     
  16. R!f@@

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    I got me a small lath..
    so thought of first trying to use a Bastard on it..er! bastard file that is...

    One q?
    What is a bastard file....is it the roughness
     
  17. shortbus

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    While a file will work, it's not going to make the commutator surface completely round. If you have the lathe why not just use a cutting tool? A file would be OK to just touch-up, but this is really really bad. Don't forget to under-cut the "Mica". They don't use mica anymore but its the insulating material between the segments. If you don't under-cut it it will cause sparking and wear-out of the brushes. You are putting new brushes in, right?
     
  18. R!f@@

    Thread Starter AAC Fanatic!

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    New brushes definitely.
    By lath I meant a small one..not the fancy type...

    Where does undercut mica come in?
     
  19. vrainom

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    Sep 8, 2011
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    @THE_RB I'm all for rewinding an armature or replacing a commutator (I rebuild armatures and fields for a living), but I don't consider pasting back a bar a safe and long lasting solution, if the bar gets a bit out of place it will start arching badly again (blue sparks). Besides the commutator is carbonized below that bar which I'm sure has made the material conductive, all that material would have to be removed taking away structural integrity from the commutator.

    Anyway I'm gonna keep an eye on this and see how it develops, maybe I'll learn something new.

    @R!f@@: I'm not trying to put you down but I'm pretty sure just lathing the armature is not gonna do it. Please wear safety googles when you power the motor, I know a guy who lost an eye to a flying bar.
     
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  20. shortbus

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