I'm helping a noobie pull apart a 12090 outrunner so he can add halls. I thought since I was telling him all of this that it was a good time to post up how I remove motor bells from outrunners and armatures from inrunners so that I can get at the halls or to add them.
If your outrunner has a bell top and your shaft doesn't extend out the bottom of the motor, you will need to remove the bell top so you can pull the armature/bell from the top of the motor. If your outrunner has already been modded, like all of mine are, so the shaft extends out the bottom of the motor, then you can push the shaft and bell off from the bottom of the motor. My Alien Power C80100 is currently in parts on my bench so I can add new halls to the bottom of the stators. I'll post some pictures later of how I pushed off the armature when I do that actual post for adding halls to it.
Follow one of these 2 sets of steps to get the armature/bell off the stators on an outrunner.
Note about pulling motor bells:
The cylinder portion of the bell can be quite difficult to pull off the stator because the magnets are strongly attracted to the stator. They are N35 or stronger so they are going to pull quite hard on the stator. Just about any 80mm stator is going to be strong enough to get away from you and possibly cause magnet damage, but they can be pulled off with muscle strength alone. I strongly recommend NOT doing that. A 120mm stator and magnets is so strong that I recommend NOT using brute strength...NOT EVER. I always use a puller to remove the motor bell and to put it back on.
*** Using a 3 jawed puller to remove the motor bell keeps everything moving slowly and in 100% control. There is virtually no chance of losing control of the motor bell and accidentally damaging the magnets.
1. If your motor shaft does not stick out the bottom of the motor sufficiently to be used to push the bell off the stator, then do this.
a. Remove the bell top from the motor. Outrunners are made where the bell top is a separate part from the cylinder. They are usually held together via small screws and then the two parts of the bell need to be separated at the joint between them. I use an old kitchen knife and tap on the back edge of the knife to wedge it into the crack between the two parts of the bell. Usually it take 5 or 6 spots around the bell to get the top to start seperating from the bottom part that holds the magnets. I then move on to using a screw driver in the gap to widen it further. On my AP 12090, the top is inserted into the bottom by about 1/2", but by about 3/16" it will come off in my hand.
b. if the shaft is still in the motor, push it out down or remove it so it is out of the way of the top of the motor.
c. Remove any screws that hold the skirt bearing to the bell
d. You want to protect the top shaft bearing and the motor windings. The shaft bearings are not designed to take anything other than radial stresses so pushing laterally on the bearing is probably going to do damage. I use a thick washer on top of the bearing to take the load. A piece of plywood or a thick metal disk would work too. The bearing never sees any lateral loading and is protected from damage. A little tape over the tops of the windings keeps them safe from damage.
e. Pullers all have a center screw and 2 or 3 jaws typically. The screw can impact the magnets so I wrap a few layers of tape around it's diameter down by the end of the screw. This provides a cushion between the steel screw and the magnets to help prevent chipping or breaking a magnet.
f. Put the puller jaws around the motor bell. Most larger outrunners have vent holes above the skirt bearing. That's a good place to seat the jaws. The bottom of the bell works to.
g. Tighten the puller screw until it's snug and centered over the top bearing. If the puller jaws won't stay seated around the motor, wrap a few layers of tape tightly around them and the bell.
h. For a typical 80mm stator, I can turn the screw by hand and pull the bell off. For my 12090 and it's 120mm stator, I need light help from a wrench to get the bell moving. If you need more than light pressure on the screw then something is binding up or you forgot to undo something.
I. If your motor has a skirt bearing, it might want to stay in the bottom of the bell and possibly impact the bottoms of the windings. Pry at it as needed to keep it coming out of the bell.
j. Keep turning the puller screw until the magnets clear the stator teeth by about 1/4". At this point, you can probably pull the bell off with your hands easily. I say clear the magnets from the stator because it is possible you might slip or who knows what and if they are not 100% separated, you may impact a magnet on a stator tooth and chip the magnet.
k. Set the motor bell aside where it can't attract metal objects and get to adding halls to your motor. Leave the puller exactly where it is. You will want it there when you put the bell back on the motor.
l. Later reinstalling the bell is the exact opposite process of pulling it off. Use the puller to slowly lower the bell back onto the stators.
2. If your outrunner is like all of mine, then the first thing I do is modify the shaft. I add more support between the bell top and the shaft. I push the shaft down so it's flush with the top of the bell and is protruding out the bottom of the motor. This makes removing the bell later super easy. SO...do this if your outrunners have the shaft protruding out the bottom of the motor.
a. Undo any screws that hold the skirt bearing to the bell.
b. Place the jaws of the puller in the gap between the bell and the motor base.
c. Run the puller screw down until it's snug with the end of the motor shaft.
d. Start turning the screw. For 80mm or smaller motors, hand strength on the screw is probably enough to separate the bell from the stator. For larger motors, you may need light help from a wrench. At no time should you EVER need to crank on that screw with more than light force. If you do, something is binding up or isn't removed yet. That might be a circlip on the shaft or a screw in the skirt bearing.
e. The skirt bearing may want to stay in the bottom of the bell. It is possible it will ride up and impact the bottoms of the windings. Pry at it as needed so it comes out the bottom of the bell.
f. Turn the puller screw until the magnets clear the stators by about 1/4" and then pull it off the rest of the way by hand. You are pushing against the motor shaft which is attached to the bell and pushing the whole thing off as a single unit.
g. Set the bell aside where it can't attract metal objects.
h. Later reinstalling the bell is the exact opposite process of pulling it off. Use the puller to slowly lower the bell back onto the stators.
I use a puller or possibly I put the motor shaft in a bench vice and then pull on the motor can to separate the armature from the stators. Both will work. Most inrunners have fairly large can diameters so you need really large pullers to get around the can and then to push on the motor shaft to slowly eject the armature. If your inrunner has vent holes, they can be used to attach to the motor shell so the puller screw can push on the shaft. Most inrunners have removable end plates that are held on with screws. Sometimes those screws can be partly loosened and the end plate is separated from the motor can enough to get the puller into the gap. Some end plates have threaded holes for mounting the motor. I've used them and made up an aluminum plate that matches those holes and then screwed the plate to the motor. This provided the purchase needed for the puller jaws. Sometimes there are no options like this and then I take the end plates off and put the motor shaft in my bench vice and just pull the armature out. I can't be as methodical with inrunners as I can be with outrunners, but also the chances of magnet damage are less too.
1. 3 jaw pullers are more stable and less likely to fall off or shift than are 2 jaw pullers. I prefer 3 jaw pullers for this reason.
2. They can be found at most automotive parts stores, hardware stores, amazon, ebay, etc.
3. They come in different sizes. I have 3. The smallest one is perfect for 80mm motors. It's a 3" puller. The next one has only 2 jaws and if it had 3 jaws wouldn't fit on my 12090 outrunner. It is categorically a 4" puller. For 120mm motors, get a 5" 3 jaw puller. Anything smaller is going to be too small to get around the motor bell. My big one is 6" and I've only every used it when working on cars.
Other things to consider while you have the motor apart...
1. This is a perfect time to go find sealed ceramic bearings that fit your motor. Don't bother with fully ceramic bearings. They cost a fortune and are only slightly better than bearings with ceramic balls only. All ceramic bearings have about half the internal friction than do all steel bearings that typically come one everything. They are SEALED and probably the bearings that came on your motor are not. Sealed bearings keep dirt and water out. Shielded bearings like your motor has do not and so they will fail prematurely from road grit, water and loss of lubrication.
2. Add a second set of halls.
3. Add a temperature sensor. They are super cheap and can be purchased on ebay, any electronics parts stores or scrounged from your kitchen digital thermometer. I get cheap Chinese digital temperature gauges that I put on my EV's. I get them on ebay for $2-3 each. They include a sensor. I cut off the wire that goes to the sensor long enough to be the same length as my hall wires coming out of the motor. The sensor gets mounted in the windings some place convenient. Use the cheap meter or something else.
4. If it's an outrunner, just about all of them have inadequate support between the bell and the shaft. If you intend running from the shaft and I recommend doing so, then reinforce the shaft to bell union. This is my thread on that subject. viewtopic.php?f=30&t=90264
A few notes about magnets...
1. All magnets including ceramic ones are brittle and chip easily.
2. Neodymium and samarium cobalt magnets are REALY UBER brittle. They chip super easily and break easily too.
3. A chipped magnet will still work, but is less effective than a whole magnet and your motor is a little out of balanced now too.
4. Neodymium is usually coated in nickle or copper. This coating is to protect the magnetic material from corrosion. Neodymium rusts and oxidizes very easily and quickly. I have a small neo I use for testing halls. Some time ago, I decided to peel off the chrome coating. Mys kin oils were enough to immediately corrode the neo material a little. In a motor exposed to weather, rain, whatever, this process would be more significant.
5. Neo magnets are the most commonly used magnet type in BLDC motors. There is a very high chance that 100% of your motors have neo magnets. They are strong and attract ferrous objects with lots of force. When a magnet starts pulling on something. The acceleration is very fast. There is little chance you will stop the metal object from impacting with a magnet. Most likely the magnet will get chipped or broken. Don't let this happen. Keep your motors magnets away from loose metal objects!