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Lubricate electric engine

  1. Dec 6, 2008 #1
    Is it recommended to lubricate electric engines (i.e. a dc motor)?

    I have an electric engine inside a shaver. The engine has started to make some strange noises (not much but still). Lubrication I have here is ordinary universal bicycle oil. I had a vague concern that maybe my oil would destroy the engine's bearings. Maybe I need some special oil for electric engines? Or maybe electric engines should never be lubricated in that way, maybe the grease coming with the engine when it's made should be enough?
     
    Last edited: Dec 6, 2008
  2. jcsd
  3. Dec 13, 2008 #2
    Also, I've heard that a dc motor could be self lubricating. How is that working?
     
  4. Dec 13, 2008 #3
    IC engine are lubricated because they have pistons rubbing against the cylinderwalls.

    Bearings have already reduced the friction to very low values. They are fed with oil to carry away the heat, carry away dirt etc.

    Electric motors never have any sliding parts, it has only rotary parts.
     
  5. Dec 13, 2008 #4

    FredGarvin

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    So...according to that theory, there is no need to lubricate bearings? Those are rotary.

    A DC motor, will have, at the most, two contacting parts. Those would be the brushes. Some forms are brushless. With small, cheap motors like that you are either looking at end bearings (which are sealed) going bad, or the brushes are going bad. Either way, it's not something to fix. There's nothing to really lubricate. Those cheap motors are not designed to be maintained.

    Are you certain the noise is coming from the motor? If it is something in the mechanism that the motor drives, then perhaps you can clean and lubricate it to fix the problem.
     
  6. Dec 14, 2008 #5

    brewnog

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    Note that the crankshaft/camshaft don't actually run on the bearings; there's a film of oil separating the surfaces. It's only really at rest and under cranking that there is metal/bearing contact, until sufficient oil pressure is achieved to separate the components.
     
  7. Dec 14, 2008 #6

    Danger

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    I seem to vaguely recall that when I was kid, my dad's electric razor had a little hole in the side that said 'add oil here'. I'm not sure what that was about. My clippers are supposed to have the blades lubricated prior to use, but not the motor.
     
  8. Dec 14, 2008 #7
    Isnt that a bit blowing it out of proportions? Ok I used the word never, i shouldn't have. Bad choice of word. Oh, rotary too, it should have been rolling contact.

    Bearings are already anti-friction 'things'(I aint talking about journal bearings). I believe that in rolling contact bearings, main purpose of oil is to carry away the heat & dirt(as far as i have studied & observed). You are the man in business, I am not proposing a theory, just writing what i know.

    of course I wasn't talking about the journal bearings. OP pointed towards rolling contact bearings.
     
  9. Dec 14, 2008 #8
    My Braun came with a small bottle of low viscous and clear oil. Never used it though.
     
  10. Dec 16, 2008 #9
    Most shavers use vibrators as opposed to electric motors in the sense of rotating electric machines. It is doubtful that a vibrator would require lubrication except in the mechanical parts. I would suggest opening the case, blowing it out very well, and looking for any places where there is oscillating mechanical contact. A drop (and only a drop) of oil on oscillating mechanical parts is often quite helpful.
     
  11. Jan 5, 2009 #10
    I've isolated the problem now a bit more. It's not due to the battery, cause I've just installed a new battery. Actually what happens is that when I'm studying just the motor and give som mechanical resistance to the motor axis, some times (once every second minute or so), the axis rotation decreases rapidly, and you here sort of a spinning sound from inside the motor. If I try to hold the axis firmly so that it doesn't rotate at all, then I could still hear this spinning sound from inside the motor for some seconds more until it disappears. It's like the axis become loosen from the other parts of the motor, could that be so?

    Then, if I switch the motor off and on, still holding the axis firmly, there is no spinning sound, and when I loose my grip on the axis, the axis starts rotate normally; if I then try to stop the rotation by again holding the axis firmly until it stops rotate, there is no spinning sound from inside the motor, indicating that the axis isn't loose after all. Confusing...

    But still, a vibrator must be made out of an electric motor, but the rotational motion is transferred to a back and forth one-dimensional motion? Or have I missed something here?

    Btw, what does this "self-lubricating" mean? That there is nothing to lubricate, or that the motor has some mechanism to automatically lubricate itself?
     
  12. Jan 5, 2009 #11
    A clipper does not require a motor in the sense of a conventional rotating machine. If you look at Den Hartog's Mechanical Vibration, 4th ed., p. 92, you will see a drawing of a one form of an electric clipper that uses an AC coil to drive the blade. While I cannot say with any certainty that your clipper is made like this, I mention it to suggest that there are more possibilities than you seem to be aware of at present. This may help you see some other ways to approach your problem.
     
  13. Jan 5, 2009 #12
    The term "self-lubricating" usually refers to bearings that are oil-impregnated and need no further attention.
     
  14. Jan 5, 2009 #13
    Ah, I found the book with the drawing here on google books. Interesting, the drawing there reminds me of a door bell. But I've checked my motor - it is indeed a rotating axel motor.

    Okey, thanks!

    What about the strange behaviour of my motor...?
     
  15. Jan 6, 2009 #14
    Electrical motor requires lubrication.
    Since your motor is a DC motor, the lubrication process will be different to AC motor.
    Both motor require lubrication on the bearing that support the rotor.
    However, in DC motor, there will have connection between the coiled rotor and the brush.
    At that connection, u have to use high graphite content lubrication oil to keep the electrical conductivity.

    This is due to the different concept of between AC and DC motor.
    AC motor rotate due to the current change of the surounded coil which turn the coil magnet.
    DC motor rotate due to the current change at the rotor coil while the magnet is fixed.
     
  16. Jan 7, 2009 #15
    Thank you for an informative reply! I'll try that.

    Could lack of lubrication be the reason why my motor is spinning?
     
  17. Jan 7, 2009 #16
    sorry, do Spinning means rotating?

    If the motor doesn't rotate well.
    For wearing reason, the most common cause is the bush and the circular commutator of the rotor which connect to the coil. The only thing u can do is to buy new parts if they are available. Otherwise, u can only buy a new motor.

    Another common cause will be the failure of the support bearings. I think buying bearing is more easy than buying those commutators and bushes.

    for your info:
    http://cache.eb.com/eb/image?id=63375&rendTypeId=4
     
  18. Jan 7, 2009 #17
    Sorry, maybe slipping is the word? (What your tyres on your car do when accelerating heavily, driving on ice.) I meant that sometimes when I hold the rotor firmly, there is a spinning sound coming from the motor, although the rotor isn't rotating.

    From an earlier post above:
    I've isolated the problem now a bit more. It's not due to the battery, cause I've just installed a new battery. Actually what happens is that when I'm studying just the motor and give som mechanical resistance to the motor axis, some times (once every second minute or so), the axis rotation decreases rapidly, and you here sort of a spinning sound from inside the motor. If I try to hold the axis firmly so that it doesn't rotate at all, then I could still hear this spinning sound from inside the motor for some seconds more until it disappears. It's like the axis become loosen from the other parts of the motor, could that be so?

    Then, if I switch the motor off and on, still holding the axis firmly, there is no spinning sound, and when I loose my grip on the axis, the axis starts rotate normally; if I then try to stop the rotation by again holding the axis firmly until it stops rotate, there is no spinning sound from inside the motor, indicating that the axis isn't loose after all. Confusing...


    Okey, thank you very much for your help!
     
  19. Jan 7, 2009 #18
    Su Solberg said, "However, in DC motor, there will have connection between the coiled rotor and the brush.
    At that connection, u have to use high graphite content lubrication oil to keep the electrical conductivity."

    Do you mean to say that there is current flow through the bearings? If so, this is a very strange motor design. Current flow through motor bearings is usually carefully avoided because of the damage that it does to bearings. In a DC machine with a commutator, there should be two brushes, so that current flows in at one brush and out at the other brush. There should not be any current flow through the bearings and the idea of using a conductive oil makes no sense at all.
     
  20. Jan 8, 2009 #19
    U better ask someone good in physic.
    I have similar experience but it's in AC motor when the ECS is calling it to rotate at too low RPM and the rotor doesn't rotate /does rotate a bit.

    p.s. beware that so called bush-less DC motor is actually an AC one.
     
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