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Sorta silly dc motor question

Discussion in 'Electronic Basics' started by Eric R Snow, Oct 7, 2004.

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  1. Eric R Snow

    Eric R Snow Guest

    I've been fooling around with some tiny vibrating pager motors. These
    motors are .160" dia x .625" long with a .028 dia. x .120 long shaft.
    In MM that would be 4 x 16 with a .7 x 3 shaft. These tiny things are
    rated at 1.3 volts and 65mA. I mounted a relatively large (1.25" x.1")
    brass flywheel on the shaft and am now running it at 4.2 volts at
    270mA. The motor gets hot with the extra work it's doing along with
    the higher volts and amps. As long as the bearings hold up will the
    motor life be about the same if it's mounted in a good heatsink to
    keep it cool? Will the higher voltage and amperage make the brushes
    wear out much faster? I'm looking for ballpark type answers. I know
    that without the complete motor specs it is hard to tell exactly how
    much the life will be shortened.
    Eric R Snow
  2. colin

    colin Guest

    I wouldnt expect to last anywhere near as long, but then not knowing how
    long it would last for normaly this is rather empty information.
    I expect they wernt even rated for continous use at their rated spec anyway.

    It realy depends how over engineered they were to start with, if they have
    long carbon brushes they might last a reasonable time, if the have cheap
    metal strip brushes theyl wear out in no time at al probably.

    the extra heat will probably cuase the bearings to become dry and wear out
    quickly, thats asuming the winding insulation survives the temperature.
    although the case of the motor might be cooled down by a heatsink the inside
    could stil get very high.

    Ive often over driven motors but not by so much, the sort of motors destined
    for use in electric screwdrivers are great, I usualy find the bearings in
    them dont last long enough and have to replace them with miniture ball
    bearing type.

    Colin =^.^=
  3. Eric R Snow

    Eric R Snow Guest

    Thanks, Colin. This motor is so small i think it must have metal
    brushes. Looking closely at the motor using a loupe' it appears that
    there is a long plastic bearing at the weight end. This makes sense
    because that wieght would ruin a regular sleeve bearing pretty fast.
    The bearing is probably delrin or nylon. Both make good, self
    lubricating sleeve bearings.
  4. colin

    colin Guest

    I remember now also ive run some very tiny motors in model servos at higher
    than normal voltage to get more oomph out of them, however they easily burn
    out (insulation failire), but this only hapened when they tried to settle
    past the end stop, adding some overload circuitry solved this problem.

    Colin =^.^=
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