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Old 08-30-2004, 07:03 AM
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whether it matters to you or not, the most logical way to shim a motor is as wayne or rc_square pointed out. why?

because when the motor is energized, the armature is pulled to it's magnetic center. this is the same as where it sits at rest. it isn't pulled very hard to this center, and dyno pulls won't change if you miss the center, but if you are going to shim, do it right. let the motor spin where it won't be pushed up against either bushing unless you give it some extraneous forces (ie, centripetal, gears, impacts, etc.)

there is still some speculation about how large of a gap to leave. if a large gap is beneficial, i suspect it has to do with periodically letting the armature move to a spot were there is fresh comutator contacting the brushes. this is only something that can really occur when the serrations are still present on the brush. or a large gap works better if you miss the gap altogether when shimming tighter.

the above has nothing to do with the position of the brushes on the com. that is dictated by the relative placement of the magents in the can. and where the center of the stack is relative to the comutator. that is the reason every motor will get shimmed differently.
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