Reinfoircing motor bell to shaft on outrunners

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ElectricGod
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Reinfoircing motor bell to shaft on outrunners

Post by ElectricGod » Aug 28, 2017 7:26 pm

It is common that outrunners won't have good and reliable power transfer from the bell to the shaft. I like running from the shaft for several reasons.

1. Easy access to a wide variety of motor sprockets that either directly fit or with a small adapter will fit just about any monitor shaft.
2. The top of the bell isn't supported very well. You have a narrow tunnel up the center of the motor that the top bearing sits in.
3. If the bell flexes side to side at all, it is putting a lot of lateral force on the tunnel and the skirt bearing if it exists.
4. Running the shaft out the bottom of the outrunner maximizes shaft support and minimizes lateral loading on the bearings and is the strongest point in the motor.

I've done this to 3 outrunners so far. An Alien Power C80100 and !2090 and a turnigy CA80-160KV as well. The C80100 and 12090 have a bolt on prop adapter so modding them separate from the bell was easy. The Turnigy motor has no separate adapter so I had to pull the bell top off the bell to work it for reinforcement. It is very common that the motor shaft extends up into the prop adapter from the factory. just loosen those 2 tiny set screws and drive the shaft down so it is flush with the top of your cut down prop adapter/reinforcement block. Now most of the shaft extends out the bottom of the motor. You will be pulling the shaft out several times until you get things lined up correctly. Don't bother trying to lock anything together until you are finished and test fitting everything.

I did this over the weekend on my 12090. Some time ago, I took it apart to add halls and wasn't going to put it back together until I had the shaft reinforced. I finally got around to it. The first step was to make a block that would bolt to the bell. The bell has these 6 screws through it that the prop adapter bolts to. I reused them to mount the block to the bell. It now has eight 10-32 set screws all sitting in shallow holes on the shaft to transfer torque from the bell to the shaft instead of the two 4mm set screws it had from the factory. The Factory prop adapter takes a lot of the work out this so reuse it!

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The prop adapter is the perfect part to start from for reinforcing the shaft to bell union. Mine is stainless steel, but the aluminum one that comes with the motor is perfect.

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The reinforcement block has 6 threaded holes around it's flat face that mate to those 6 bolt holes in the bell. It also has 6 threaded holes around the outside diameter for mating to the shaft.

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I neglected to take pictures of the shaft, but it has shallow holes around its end at the same positions as the 6 holes around the perimeter of the block. Set screws thread into the block and seat in the shallow holes in the shaft. One hole goes all the way through the shaft and 2 set screws touch in the middle of the shaft. Also the bell has 2 set screws that protrude into the shaft as well. Hopefully that many cross connect points will be enough to reliably transfer 18kw of power to the shaft. Now that it's all assembled, I'll cut off the extra length of the set screws so that they don't protrude beyond the block.

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Now my shaft extends out the bottom of the motor so that I can eventually run a sprocket off of it. I'm not going to bother adapting the shaft yet until I'm much closer to mounting it on something. The motor is ready to go for power. This is essentially the same thing that I did for my C80100.

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The set screws for the reinforcement block...one rolled away. Notice that 2 set screws have smooth ends on them. I put those screws in my drill press and spun it up. Then I ran a file on them to remove the threads to reduce their diameter to fit into the hole all the way through the shaft. The ends of the set screws bottom out into each other in that through hole in the shaft. The other set screws bottom out into shallow holes in the surface of the shaft.

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Last edited by ElectricGod on Aug 28, 2017 8:08 pm, edited 1 time in total.

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Re: Reinfoircing motor bell to shaft on outrunners

Post by ElectricGod » Aug 28, 2017 7:49 pm

Turnigy CA80-160KV outrunner...

Push the shaft down flush with the top of the shaft adapter. The shaft has shallow holes drilled in it's surface so the set screws can seat in them. The bell has 2 set screws in it and then the prop adapter has 4 more. All 6 set screws are 5mm and seat in a shallow hole in the shaft. When I took this picture obviously the set screws were not in place yet. The allen head screw is what I refer to as one of the "bell set screws".

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Last edited by ElectricGod on Aug 28, 2017 7:58 pm, edited 1 time in total.

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Re: Reinfoircing motor bell to shaft on outrunners

Post by ElectricGod » Aug 28, 2017 7:57 pm

Alien Power C80100 shaft to bell reinforcement...

I pushed the shaft down so that it was flush with the adapter top. I used those four 5mm threaded holes and the cut down factory shaft adapter to make this. Two set screws bottom out in the center of the shaft. The other two in the cut down shaft adapter bottom in shallow holes drilled in the surface of the shaft. Same for the bell set screws which were 4mm and are now 8-32. The 4 set screws in the cut down adapter are 10-32.

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Re: Reinfoircing motor bell to shaft on outrunners

Post by spinningmagnets » Aug 28, 2017 8:12 pm

Excellent work! and thanks for posting this. A few years ago, these large outrunners made a lot of ES members drool thinking about the possibilities, but many RC ESC's died when trying to power these on an ebike. I was told that these motors have a problem with inductance (either have too much inductance, or too little?).

This led to several posters showing how to add optical sensors, or hall sensors onto outrunners, so they could be driven by common ebike controllers. I have to admit, though...the tiny size of RC ESCs is intriguing when it comes to stand-up scooters and ebikes. Isn't there some way to increase the inductance, or reduce it, so RC ESCs are an option?

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Re: Reinfoircing motor bell to shaft on outrunners

Post by ElectricGod » Aug 28, 2017 10:33 pm

spinningmagnets wrote:Excellent work! and thanks for posting this. A few years ago, these large outrunners made a lot of ES members drool thinking about the possibilities, but many RC ESC's died when trying to power these on an ebike. I was told that these motors have a problem with inductance (either have too much inductance, or too little?).

This led to several posters showing how to add optical sensors, or hall sensors onto outrunners, so they could be driven by common ebike controllers. I have to admit, though...the tiny size of RC ESCs is intriguing when it comes to stand-up scooters and ebikes. Isn't there some way to increase the inductance, or reduce it, so RC ESCs are an option?
I suppose they can be used. I know you like using those 160 amp castle controllers a good bit. Most RC controllers are very poor at dealing with cogging. Most RC controllers are way too light weight for EV use. They have tiny heat sinks and the mosfets are nearly impossible to replace if needed. I've destroyed a castle ESC trying to use it on an EV. Enough of that! I'll stick with something there's a hope I can actually repair! RC controllers never support FOC or throttle curves or ebrakes or regen or variable regen or ...list anything commonly found in an EV controller. RC controllers pretty much don't have any of those things. They may do batt voltage or current, but that's about it. And they tend to max out at 12S. I've built twice at 12S and both times I went to 16S or 20S after a very short time.

I'm getting a 24 fet controller to run this motor. That won't be enough since it's an 18kw motor. I plan to build a daughter board that is another 24 mosfets...still in the TO-220 package that will only get me to around 12kw. If the controller shell can hold a second daughter board internally, I may add another 24 mosfets to get to 20kw.

My experience with adding halls is that you do better if the hall cable does not pass next to the windings. If you put your halls on top of the motor, then try to run the wires down the central tube if possible. Otherwise, just add them to the bottom of the stators like I have done so it's not a problem. The EMF inside the motor creates a lot of noise on the hall signal wires. I think passing in between 2 sets of windings induces a lot of noise into the hall wires.

Anyway, this thread is about reinforcing motor shaft to bell unions so you can drive from the shaft.

My hall thread is here. Every hall add-on I have done is in this thread.
https://endless-sphere.com/forums/viewt ... 7#p1315587

Outrunners have several advantages and disadvantages vs inrunners. I use both...just depends.

1. Inrunners tend to be closed up so dirt getting into them is not probable. Outrunners are almost always open to the environment.
2. Inrunners tend to weigh a good bit more for the same wattage as an equivalent outrunner. My 18kw outrunner is almost exactly the same size and weight as my 3000 watt HLD inrunner.
3. Inrunners are almost always much more expensive than an equivalent outrunner. just look at any 6000 watt inrunner and compare with any 6000 watt outrunner. The cost is commonly 3:1.
4. Inrunners tend to not need any work on them for EV use. Mount a sprocket and you are done. Outrunners seem to always need as a minimum some shaft work to make them stout enough to drive an EV.
5. Outrunners seem to always use shielded bearings which are open to getting dirt and water in them. It is fairly common for inrunners to have sealed bearings.
5a. Larger outrunners usually have 3 bearings. Two on the shaft and a skirt bearing. This means more friction and a third point of possible failure.
6. Inrunners trap more heat inside them which means a greater chance that the magnets will get too hot. Since outrunners have the magnets on the outside of the stator, they will tend to stay cooler and not fade from heating.
7. Think of a motor armature as a lever. A longer lever requires less force on the long arm to do a fixed amount of work on the short arm. A short arm requires much more force on it to do that same amount of work on the long arm. An inrunner is like a lever where you are applying force on the short arm to do work on the long arm. An outrunner is like applying force on the long arm to do work on the short arm. This essentially means that an outrunner for same amount of wattage applied to the motor should do more work than an equivalent inrunner....just because it is a longer lever.
8. Inrunners tuck up inside frames and other tight spaces with little concern for catching on wires or anything else. An outrunner needs to be clear of nearby objects since it has a spinning bell.
9. This one is up for debate IMHO. Inrunners, since the stators are on the motor can, should dump heat better than outrunners. Outrunners have the stators compactly fit in the middle of the motor. It's my opinion after having several inrunners that they get quite hot. I have to put a blower on them to force air through the motor if I intend to run them hard. Their ability to radiate heat even with added fins on the shell is not as good as an outrunner. Outrunners on the other hand have a built in fan and the stator doesn't seem to get anywhere near as warm.

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Taking apart outrunners and inrunners

Post by ElectricGod » Sep 05, 2017 3:31 pm

I posted this in my halls thread found here...

https://endless-sphere.com/forums/viewt ... 30&t=84112

But since reinforcing the bell to shaft union requires taking your motor apart, I thought it would be good to post it here too. This is essentially a word for word duplicate of my other post.



OUTRUNNERS:

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.

INRUNNERS:
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.

Regarding pullers...
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 balled bearings that fit your motor. Don't bother with fully ceramic bearings. They cost a fortune and have slightly less friction than bearings with ceramic balls only. All ceramic bearings have about half the internal friction of all steel bearings. Bearings with ceramic balls have a little more friction that all ceramics, but still much less than all steel ones. All steel bearings typically come on everything. They work and are cheap, but you pay for it in more friction. Motors commonly come with shielded instead of sealed bearings. Sealed bearings keep dirt and water out and grease in. Shielded bearings like your motor has do not and so they will fail prematurely from road grit, water and loss of lubrication. The seal creates a small amount of friction, but if you use ceramic balls, that still adds up to much less than shielded steel bearings and they will last 4X longer. I use sealed ceramic balled bearings everywhere I can.

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. https://endless-sphere.com/forums/viewt ... 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!

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Re: Reinfoircing motor bell to shaft on outrunners

Post by Ecyclist » Oct 26, 2017 10:43 am

EG, thank you for your posts. They are very helpful. :idea: Once I get 12090 motor from APS I will follow your lead.

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