Sorta silly dc motor question

E

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.
Thanks,
Eric R Snow
 
"Eric R Snow" <etpm@whidbey.com> wrote in message
news:ik2bm05vs4vm524ofa2u1qbmohmlt94iii@4ax.com...
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.
Thanks,
Eric R Snow
Click to expand...
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 =^.^=
 
"Eric R Snow" <etpm@whidbey.com> wrote in message
news:is7bm0te9jopjafikk4iufue4mg8cvftu6@4ax.com...
On Thu, 07 Oct 2004 19:18:26 GMT, "colin"
no.spam.for.me@ntlworld.com> wrote:


"Eric R Snow" <etpm@whidbey.com> wrote in message
news:ik2bm05vs4vm524ofa2u1qbmohmlt94iii@4ax.com...
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.
Thanks,
Eric R Snow

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 =^.^=

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.
Eric
Click to expand...
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 =^.^=
 
On Thu, 07 Oct 2004 19:18:26 GMT, "colin"
<no.spam.for.me@ntlworld.com> wrote:

"Eric R Snow" <etpm@whidbey.com> wrote in message
news:ik2bm05vs4vm524ofa2u1qbmohmlt94iii@4ax.com...
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.
Thanks,
Eric R Snow

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 =^.^=

Thanks, Colin. This motor is so small i think it must have metal
Click to expand...
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.
Eric
 
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