# Hub Motor Design in progress



## Bugzuki (Jan 15, 2008)

The Open Source Hub Motor thread has lost activity so, I made a new thread to focus just on the motor design.

Ok, so here is what I have so far.

I decided to go with the integrated hub bearing (just makes sense and there are a ton of variances available).










Here it is in wireframe so you can kind of see the assembly together.









Here is the exploded veiw to show the parts. In this particular model I just guessed at a number of plates and added 50. All of them are not shown in the exploded veiw since that would make it much more spread out and harder to see.










Finally here is the rotor assembly


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## Bugzuki (Jan 15, 2008)

So as you can see I have not started on the stator yet. I might have to resize some things inorder to fit it in, but that is part of designing something.

I did put some holes in the rotor to help lighten it up, but need to know how much mass needs to be around the cage rods. I was planning on just using some copper rods brazed to a ring - that way nobody has to try and cast aluminum into the rotor.

The front plate of the housing might have to be made out of steel in order to get enough strength. The back housing might also. I might end up putting a bearing on the back side of the rotor shaft just to add a little support once some analysis is done.

I will also design some sort of mounting location for a brake caliper. This will most likely be on the motor front housing and the rotor will go on the hub in the standard configuration. 

The Hubs from Timken have a built in ABS sensor (in our project it can also act as a speed sensor. This feature is a great advantage since we will not have to speed time making speed wheels and sensor mounts.

If anyone has any suggestions please send them my way. Right now the outside diameter of the motor housing is at 13.5 inches. And the motor housing is 4.5 inches thick.

Right now the rotor has 36 bars. but that will probably need to be increased due to the diameter of the rotor. I took that number from my Siemens Ranger motor. The stator has 48 coils in that motor.

There is a lot that goes into the motor, so if I have missed anything please let me know. Lets start discussing the specifics on how this motor should actually be designed. I see there are some on here that have a lot more knowledge then me.

Here is a picture of the rotor plate. I was invisioning that people would get them laser cut. It will probably cost around 250 for materials and cutting (that is just a guess).

I have not figured out cooling yet either.


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## Bugzuki (Jan 15, 2008)

I copied those last to posts out of the Open Source Hub Motor Thread.

I would like some input on how:

many poles
how many stator/rotor loops
how wide to make the air gap between stator and rotor
What kind of cooling
Overall dimensions (to get the torque desired)
Stator wire size and number of turns
Anyone have motor design experience.


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## synchro (Aug 16, 2008)

Hi, I just joined and found your site while searching for information on Hub Motors and what it would take to make one. I have contacted both PML FliteLink and BluWav and have gotten the song and dance about being an OEM etc. 

I have extensive design cad experience in structures and electronics packaging, cooling,etc. I would be happy to work on this project since I was trying to figure out how to get this going. I have contacts of people who design high power motor controllers for airplane equipment who may be interested in doing some work as well. 

I was just in Monroe Wa yesterday looking at a friends space workshop space and trying to figure out what to make with all the tools and skills we have aquired.

I think to start, a motor hub for a smaller vehicle (~<600lbs) with 10-15 KW would be good.


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## synchro (Aug 16, 2008)

as far as cooling, i think fins and water are very primative. some sort of phase change method would be optimal. perhaps a heatpipe to dump the heat to another location such that the weight is not in the hub (unsprung)


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## xrotaryguy (Jul 26, 2007)

Aah... this is an AC induction motor right? So you could run high voltage yeah? If you can run high voltage, then you can run lower amperage and cooling is a much smaller issue. Keep the cooling system as simple as possible.

I had assumed that a project like this would be for a ~2,300 lb car. If one starts out with a little motor, then the part needs to be redesigned in order to be useful. Not that a 600 lb car can't be useful, but a hub motor for a regular car would be better. I don't think that designing the one would be any easier than designing the other.

I agree that the front and back sides of the hub should be made of steel. It would be nice if one could get away with gusseting the backside of the motor, but most cars will probably not have a lot of room for that kind of thing.

Have you considered drum brakes? drum brakes are lighter and consume less space. Also, the motor is already in the shape of a drum, so that lends itself to a drum brake. Furthermore, the majority of the braking should be done via regen. The friction brakes should only be there for a parking brake and for added security.


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## 1clue (Jul 21, 2008)

Would it be reasonable to have fewer plates for a small car and more plates for a big one?

The one thing that really bugs me about this project is that it's a one-size-fits-all project. FWIW, I'm more interested in a motor linked to the wheel through a CV joint and axle to get the unsprung weight down.

I also think that a water cooled motor is best, or at least have the option to do that. A water cooled motor could be denser in that you could run magnetic flux and electrical current levels higher and still cool the motor. That makes for less weight, and also makes for possible heater in the winter, especially if the controller is also water cooled.

That said, I'm very much a n00b on motors, I've been immersing myself in some stuff on the net but I have no experience yet.


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## 1clue (Jul 21, 2008)

I made an Open Source thread here:
http://www.diyelectriccar.com/forums/showthread.php/open-source-general-discussion-18993.html

I'll post it in the other thread this one spun off of as well as a few other places where OS discussions have distracted the main topic somewhat. Please post open source comments there which do not directly pertain to this specific project. This is as much for me to stay out of trouble as for anyone else.


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## Bugzuki (Jan 15, 2008)

synchro said:


> Hi, I just joined and found your site while searching for information on Hub Motors and what it would take to make one. I have contacted both PML FliteLink and BluWav and have gotten the song and dance about being an OEM etc.


I got that a bunch also.



synchro said:


> I have extensive design cad experience in structures and electronics packaging, cooling,etc. I would be happy to work on this project since I was trying to figure out how to get this going. I have contacts of people who design high power motor controllers for airplane equipment who may be interested in doing some work as well.


What CAD Package do you use? I have a copy of Pro/Engineer WF3. I would be happy to get some help. I do not have much in the way of machine tools, so if you had that we could save some money on prototypes.



synchro said:


> I was just in Monroe Wa yesterday looking at a friends space workshop space and trying to figure out what to make with all the tools and skills we have aquired.


How often do you make it to Monroe. Kenmore is only like 17 miles away. I work at Philips in Bothell.



synchro said:


> I think to start, a motor hub for a smaller vehicle (~<600lbs) with 10-15 KW would be good.


If we design the motor right we should be able to size it to whatever is needed. I think that it would be most beneficial to size it to a compact size car, so 2500 lbs or so. That way it can be tested. Unless you have a liteweight car. 



synchro said:


> as far as cooling, i think fins and water are very primative. some sort of phase change method would be optimal. perhaps a heatpipe to dump the heat to another location such that the weight is not in the hub (unsprung)


Can you make flexible heatpipes? In order for the motor to be attached to the suspension the cooling would need to be flexible. Personally I like water the best, but it would take some routing. It could probably be routed in the stator using pipe. Needs to be something that can be built by someone in there garage. At least that is how this started. That means that casting/forging is out of the questions for manufacturing processes, unless we can set something up to get a good price.



xrotaryguy said:


> Aah... this is an AC induction motor right? So you could run high voltage yeah? If you can run high voltage, then you can run lower amperage and cooling is a much smaller issue. Keep the cooling system as simple as possible.


Yes, AC induction. High voltage is what I would like. Good thinking about there being less current so probably less heat. But it is still an issue, unless there is enough air movement in the wheel. Testing.



xrotaryguy said:


> I agree that the front and back sides of the hub should be made of steel. It would be nice if one could get away with gusseting the backside of the motor, but most cars will probably not have a lot of room for that kind of thing.


gusseting would be nice except that it would probably entail casting the parts. We could probably make some ribs to be welded on, but that would probably need to be setup for the individual suspension systems.



xrotaryguy said:


> Have you considered drum brakes? drum brakes are lighter and consume less space. Also, the motor is already in the shape of a drum, so that lends itself to a drum brake. Furthermore, the majority of the braking should be done via regen. The friction brakes should only be there for a parking brake and for added security.


I think that it would be a lot easier to implement disk brakes. Trying to make the motor as small as possible would make space for the brake shoes much tighter. Drum brakes are very in efficient and need to be in contact with the drum all the time. Disk pads can be released away from the disk and eliminate contact. If we went with drum brakes the drum would probably be part of the rotor, so if a shoe went bad the rotor would be scored. With disk brakes any rotor and caliper can be fitted to the motor.

Those are my thought, so if you have some ideas as to how Drums or another design would work better, please elaborate.



1clue said:


> Would it be reasonable to have fewer plates for a small car and more plates for a big one?
> 
> The one thing that really bugs me about this project is that it's a one-size-fits-all project. FWIW, I'm more interested in a motor linked to the wheel through a CV joint and axle to get the unsprung weight down.


My goal is to make a motor that can be easily redesigned to fit anyones configuration. That way making the stator and rotor thinner would make less power or the dimensions can be modified to fit a different wheel size. 

For a pure electric vehicle attaching to drive shafts or to the transmission is feasible. But if you wanted to make a hybrid or wanted to use hub motors - hub motors are better. I think once we get a motor working we can change the design to fit different applications. So, don't give up since we might not be exactly where you want. It is not my prefered starting point either, but lots of people want hub motors.



1clue said:


> I also think that a water cooled motor is best, or at least have the option to do that. A water cooled motor could be denser in that you could run magnetic flux and electrical current levels higher and still cool the motor. That makes for less weight, and also makes for possible heater in the winter, especially if the controller is also water cooled.
> 
> That said, I'm very much a n00b on motors, I've been immersing myself in some stuff on the net but I have no experience yet.


I am leaning to water cooled, unless someone can come up with a better idea. If so please share your ideas and I can get them incorporated.

Sorry for such a long post I was busy yesterday.


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## aeroscott (Jan 5, 2008)

Bugzuki said:


> I got that a bunch also.
> 
> 
> 
> ...


some high power dynos use water and oil cooling , one guy said oil cooling was vary hard to get right . helium ( He or H2 have very good thermal conductivity and low drag ) cooling , that is low pressure with inter-cooler circulating like a water system


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## Bugzuki (Jan 15, 2008)

aeroscott said:


> some high power dynos use water and oil cooling , one guy said oil cooling was vary hard to get right . helium ( He or H2 have very good thermal conductivity and low drag ) cooling , that is low pressure with inter-cooler circulating like a water system


Do you pump the helium like you would water, or does it move do to heat (hot air rises cold falls)? Would you have a certain amount of pressure in the system? Since it is helium and not air it would need to be a closed system.


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## 1clue (Jul 21, 2008)

Water cooling is freaky.

It seems to me, from what I've found on the net, that for water cooling they just pump water through the stator. Direct immersion. They say it's a higher drag (it would have to be!) but that electrically the motor should be insulated using the winding varnish anyway, and that the resistance of the electrical parts of the motor is so much lower than the resistance of fresh water that the fresh water makes no difference to the motor.

On the other hand, the controllers might have serious problems with the water. Evidently they can really freak out, but I'm not sure how yet.

I would think that it would be best to have cooling journals in there somehow, and even if the wires are immersed at least the spinning parts should not come in direct contact with the water.

BTW, I posted it on the original thread as well but it seems that the "magnetic gearing" talked about to reduce the RPM on an outrunner motor does not increase torque. Outrunner motors have more torque because they have a bigger diameter, not because of magnetic gearing.


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## Schmism (Aug 16, 2008)

If water cooling your going to need to consider a glycol mix.

Antifreeze or alcohol based (window washer fluid) is likely going to be corrosive to the internal environment of the motor. Unless you develop cooling passages in the motor housing. (but that isnt very DIY fab-able)

As for the motor end plates, you need to decide if the motor is to be an active structural part of the suspension, or simply a bolt on motor that hangs off the backside of a more traditional hub/knuckle design.

The decision above, will have a significant impact of the bearing requirements for the motor.


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## aeroscott (Jan 5, 2008)

Bugzuki said:


> Do you pump the helium like you would water, or does it move do to heat (hot air rises cold falls)? Would you have a certain amount of pressure in the system? Since it is helium and not air it would need to be a closed system.


 yes except a blower is used to pump the low pressure gas through the motor then a heat exchanger like a turbo inter cooler then back through the motor . very low 5 psi or so . 
on water cooling on small motors like ours a jacket is welded to the outside of the motor . some very large motors cool the wire ( stator ) with coolant tubes and the iron core can have tubes too . oil cooling is used by spraying oil in the motor , military jets use this . they have a car size alternator that runs 12000 rpm's and puts out 40 kw . One guy said it was hard to get oil cooling right . it doesn't seam that like that big a deal .


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## Schmism (Aug 16, 2008)

aeroscott said:


> hey have a car size alternator that runs 12000 rpm's and puts out 40 kw . One guy said it was hard to get oil cooling right . it doesn't seam that like that big a deal .


12K rpm is nice as that's roughly the operational rpm of the gas turbine engine, so you just shaft mount it on the front side and your good to go.


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## Action Jackson (Oct 16, 2008)

Bugzuki...any more progress on the motor?


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## Bugzuki (Jan 15, 2008)

Not a lot. I would like to go off of that subaru design that someone posted in the other thread but have not been able to find any large diameter bearings. But, it the system is ridged enough bearings might be unnecessary. The hub bearings might do the trick. That also makes the design much simpler. 

I still have to come up with a way of keeping dirt out from between the rotor and stator. And, since we are now going with a BLDC motor we have to keep metal particles out as well. With the brake rotor right there that might be easier said then done.

I will try to find some time to work on it this weekend. 

About the cooling. If water cooling is used it could be totally isolated from the system and be used to cool a plate that is heated by the electrical components.


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## Hillbilly (Jun 23, 2009)

I've heard that brakes are problematic due to their restricting airflow for cooling, and the metal in the brakes will create eddy currents and absorb your flux. Metal rotors and stators will do this as well. You can try to shield the metal with plastic coatings or rubber, but making things out of composite would be better, just don't know how you can make that strong enough.

I'm not an engineer, and have no practical experience, but I have read a lot about this. If you're going with a three phase induction motor, I think you are only going to have three poles, (someone correct me if I'm wrong) unless you mesh multiple motors into one, which could be done I guess.

I've seen radial flux DC permag motors built, and those can have as many poles as you want to have. The more poles you have, the smoother the power will be.

I was toying with the Idea of having radial and axial arrays of permagnets and coils. More flux in a small space. That may prove to cause eddy current conflicts as well.

Good luck. I hope you get 'er going!


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