DC motor magnets

I think it depends on the material the magnets are made of.

Some magnet materials need the "magnetic circuit" to be unbroken once they are magnetized. Motors with such magnets either have the magnets magnetized after assembly, or they are magnetized with some sort of "keeper" which is later replaced by the armature. If you take apart one of these motors without replacing the armature with a keeper of similar size (so the air gap doesn't get larger), the magnets will lose strength permanently. I've even seen stepper motors with a label on them saying "disassembly will change operating characteristics".

On the other hand, apparently some rare earth magnets don't care.

Dave

Generally, if the magnets are black, then they are ceramic magnets and the armature can be removed safely. If the magnets are silver then they are alnico and removing the armature will weaken the magnets. Usually, you will see ceramic magnets. Some of the newer motors have nickle or chrome plated magnets. These are rare earth magnets and the armature can be removed from this type of motor too. Steppers usually will be ruined if the armature is removed. All these examples are just generally correct. Since I don't have your motor in hand I can't tell if taking it apart will ruin it. Take my advice with a grain of salr. ERS

Many Chevies, all Saturns, many Fords and many Mopars would beg to differ with you. A VERY SIGNIFICANT portion of todays automobiles have Permanent Magnet Starters.

The DC PM motors I've been seeing have the magnets glued into the case shell, and they look like compressed ferrite core material (dark grey, almost black).

These are 1 to 2 HP treadmill type, and industrial-rated DC gearhead motors that I have in my project motors inventory.

I wouldn't want to remove the magnets, but it may be necessary to remove an armature to recut the commutator and/or replace bearings.

I wondered if pulling the armature out (and then reinstalling it) would cause any demagnetization as a result of distorting the concentrated magnetic lines (trying to avoid the word "field" there).

Thanks WB

Some starter motors are PM motors, maybe most of the ones in new cars. I picked up one from a dumpster recently. The motor is good but the solenoid seems to be shorted.

Dan