This is a Permanent Magnet Gearhead Motor,
often called a PM Gearmotor, or DC Gearmotor. They are PM Motors with a
gearbox built onto their front. The gearbox is often a different shape,
or slightly larger than the rest of the motor. Gear-reduction in the
motor increases the torque, and decreases the speed of the motor. This
makes them highly suitable to kinetic art making. The motor part of a
PM Gearmotor has the same characteristics as a normal PM Motor, as
illustrated in Kinetic Display Object #1.
This motor shaft turns rather slowly, but its torque is great enough
that it cannot be stopped with fingers. The fact that the lamp
brightness does not change significantly in the two images above shows
that the attempt to stop the motor by grabbing its shaft does not
result in a significant increase in current.
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PM Gearmotors are very expensive when
purchased new, but several surplus suppliers are good sources. Some of
them are H&R, C&H Sales, All Electronics, Marlin P. Jones &
Assoc., and others. See the sources
page for
possible vendors.
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