Cooling fans inside Hub motors

[Cowardlyduck]

Hi all,

I've posted about this a few times in other threads, but I think it deserves a thread of it's own as I believe the idea has merit and I plan to try it in the future with my Crystalyte HS4065 once I repair it.

If you take a look at Crystalyte Hx series motors (and many other motors), you will see they have 6 holes in the stator support. These holes measure approx 25mm diameter in the case of my HS4065.

This is a picture of my motor which I'm yet to repair, but will be the platform on which I test this idea.

The idea is to secure 5 of these or similar covering each hole, and plug/seal up the remaining holes.

I would then hook them up to run off the 5V Hall sensor line. Fingers crossed that line can handle the 0.5A needed to run 5 of them together.

I may also add some fly-screen to the intake side cover holes to prevent larger debris getting sucked into the motor.

As far as I can tell, no-one else has done this yet. I can't see why not...am I missing something? I'm keen to be the guinee pig, and give it a try though...these little motors are so cheap anyway.

What do others think?

Cheers

 

[nechaus]

I have done this, Not via halls tho, I did it with a All metal housing fan as well..
I Managed to cook the wires to the fan, The plastic came off and was shorting where i had zip tied it to the stator... so if you go ahead with a fan inside, maybe run good insulation on the fan wiring

If you search, justin from ebikes.ca did heaps of test, I think a better way would be to run fan fins on the inside of the case, You could use aluminium fins and smear heat paste where it contacts the outer case..
however up to you, something is better than nothing..



I can remember pushing a magic pie 2 so hard, I managed to get 20min round trips to the shops and back, Full power there and full power back, I use to dump water on the case and watch the steam come off, eventually the windings looked much the same as your pic, black wire, took a couple of months, spots here and there went black first.

 

[Cowardlyduck]

I have done this, Not via halls tho, I did it with a All metal housing fan as well..

Which fans did you use? Got a link? Any pics?

If you search, justin from ebikes.ca did heaps of test,

Indeed, which is where I also posted this idea a while back, but no-one seemed interested then and I wrote it off due to only being able to find uber expensive RC ducted fans. Now I see these cheap as PC fans I'm keen again.
http://endless-sphere.com/forums/viewtopic.php?f=2&t=48753&start=275#p796868

I can remember pushing a magic pie 2 so hard, I managed to get 20min round trips to the shops and back, Full power there and full power back/quote]
Good to know it might work well then.

The only thing I worry about is noise. Since these are server fans, there is practically no consideration for how much noise they make. It would suck to have great cooling ability, but sound like a small jet engine going down the bike path. :lol:

the windings looked much the same as your pic

Actually that's not from overpower. I spray painted the stator black with a silicone based high temp paint to protect it when I vented my side covers. Seems to have mostly worked. The dirt is just from using it with vented side covers. I figure, if my side covers are already vented and it get's this dirty, whats a bit more air rushing through the stator going to do?
Might suck a leaf or two in, but that's what the fly-screen will be for.

Cheers

 

[Cowardlyduck]

Just bought this one to test if it will run off the hall sensor line and how much air it can push.
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=170759068678

We'll see how it goes.

Cheers

 

[nechaus]

yeah man will be interesting..Nah this was ages ago, I never bothered mucking around with cooling other than holes after that, just went to a bigger motor

Do a smoke test if you get it working..

140 ma current is needed for that fan, I cant remember how much current goes down them, For some reason 40ma comes to mind...
Maybe try a 12 volt fan with external power if that one fails..

 

[full-throttle]

Just bought this one to test if it will run off the hall sensor line..

I wouldn't do it if I were you.. You'll blow the voltage regulator inside the controller.

 

[sn0wchyld]

Ive done it on my norco. Helps a bit, particually if you stop for a minute or two, keeps the air moving through the motor. I used 3 blower fans out of laptops, they move allot of air for their size. I also ran a seperate 5v line from a dcdc converter, as well as wires for a temp sensor

 

[Cowardlyduck]

I wouldn't do it if I were you.. You'll blow the voltage regulator inside the controller.

Glad you chimed in...I had no idea that could happen.
Do you think it would work with just 1 or 2 fans ok? This one is only drawing 0.14A.

Ive done it on my norco. Helps a bit, particually if you stop for a minute or two, keeps the air moving through the motor. I used 3 blower fans out of laptops, they move allot of air for their size. I also ran a seperate 5v line from a dcdc converter, as well as wires for a temp sensor

Hey cool, sounds like I'm not the first then. How did you fit the extra wires? That's my main concern as every time I've pulled the wire side cover off, I've shredded the wire sheaths/heat-shrink and had to baby the cover back on with tones of grease so as to not make it any worse.
I don't have any tools to make the axle groove bigger, so would have to squeeze whatever extra wires I use in with the rest as is...not something I think I could do easily at least. Is there a technique I'm missing?

Cheers

 

[sn0wchyld]

I wouldn't do it if I were you.. You'll blow the voltage regulator inside the controller.

Glad you chimed in...I had no idea that could happen.
Do you think it would work with just 1 or 2 fans ok? This one is only drawing 0.14A.

Ive done it on my norco. Helps a bit, particually if you stop for a minute or two, keeps the air moving through the motor. I used 3 blower fans out of laptops, they move allot of air for their size. I also ran a seperate 5v line from a dcdc converter, as well as wires for a temp sensor

Hey cool, sounds like I'm not the first then. How did you fit the extra wires? That's my main concern as every time I've pulled the wire side cover off, I've shredded the wire sheaths/heat-shrink and had to baby the cover back on with tones of grease so as to not make it any worse.
I don't have any tools to make the axle groove bigger, so would have to squeeze whatever extra wires I use in with the rest as is...not something I think I could do easily at least. Is there a technique I'm missing?

Cheers

I used a dremel clone from hobbyking (about $30-40 delivered) to make the slot just a smidgen bigger. you can pick up a similar one from places like super cheap auto for under $50, with a 2 yr warranty too i think... useful tool to have for more than just ebikes. I also used a small piece of aluminium to protect the wires. you can see pics on my build thread in my sig.

 

[full-throttle]

Do you think it would work with just 1 or 2 fans ok? This one is only drawing 0.14A.

Only??

What are you comparing to? Your friend's uncle's plasma TV?

The 5V regulator inside most controllers is rated to 100mA

 

[Cowardlyduck]

The 5V regulator inside most controllers is rated to 100mA

Well that could still be useful then.
The one I bought might draw too much, but one of these should work.
http://www.ebay.com.au/itm/25mm-10m...ng-Computer-Fluid-Brg-2Pin-099A-/170918645511

Only draw's 0.051A according to the description, or 0.08A according to the photo, but either way, under the 100mA limit.
That is assuming the halls themselves don't draw much power. I wouldn't know...

I realize just one little fan like this wouldn't push much air, but it can't hurt to try and see how much it can help with cooling.

Cheers

 

[full-throttle]

That is assuming the halls themselves don't draw much power. I wouldn't know...

Not just the halls. The 5V is for all the logic, halls, throttle.. etc. Prob 20~50mA.
How much airflow one of these would give you anyway? Is it really worth the risk and time

 

[Cowardlyduck]

That is assuming the halls themselves don't draw much power. I wouldn't know...

Not just the halls. The 5V is for all the logic, halls, throttle.. etc. Prob 20~50mA.
How much airflow one of these would give you anyway? Is it really worth the risk and time

Any addition to airflow is a welcome one, but probably not worth the risk running them off the controller as you say.

As others have reported though, it certainly sounds like it makes a diff running them from another power source. Doing so would also allow greater control over fan speed (noise) and when to turn them on or off.

For those who did this kind of thing previously, did you use DC-DC converters, or a separate power source?

Cheers

 

[amberwolf]

If you only need them to run while the motor is running, you could add a three-phase rectifier to the phase wires inside the motor, and capacitors and a regulator or DC-DC to that.

Then when the voltage to the motor was sufficient, the fans would also run. (or be able to, anyway, depending on whether you ahve a thermal switch on them).

 

[Cowardlyduck]

If you only need them to run while the motor is running, you could add a three-phase rectifier to the phase wires inside the motor, and capacitors and a regulator or DC-DC to that.

Then when the voltage to the motor was sufficient, the fans would also run. (or be able to, anyway, depending on whether you ahve a thermal switch on them).

Appreciate your input Amberwolf.
That would be a better and easier option for powering the fans, but sounds rather complex for a noob like me.
What would happen if I wired up several higher voltage fans (i.e. 24V) in series directly to 2 of the phases? Would I have to match the voltage of all the fans in series to the battery pack voltage?
Would they then pulse on and off when the phase turned on and off?

Cheers

 

[Cowardlyduck]

Actually, never mind that. What about running a 3pin fan from the phases?

http://www.ebay.com.au/itm/PC-Fan-F...t=LH_DefaultDomain_3&var=&hash=item20c7210544

6 of these fans in series would be 72V. Would that work?

Cheers

 

[amberwolf]

A 3 pin fan is not a 3phase ac fan, it simply has a speedo output on one pin, and dc input to power it on the other two.

You can't run the fans off the phases directly, becuase polarity will change on the phases as the motor spins. I'd guess that applying reverse polarity across many of these fans will damage or destroy their electronics. (I know that will happen with at least some that I've dealt with, cuz I've seen them wired backwards in computer cases people brought to the tech shop for repair when i did that sort of things years back...but some of them seemed to be protected against reverse polarity, and survived anyway).

tha'ts why you would need to use a 3phase rectifier at the very least, to create DC out of the AC on the phases, and to get the fans to run properly you'd also need capacitors across the output of the rectifier to turn the DC pulses into flatter DC.

A regulator would be needed to convert the variable voltage that could be very high down to something the fans can tolerate.

If you run the fans in series, then they will only wokr at all when the voltage is very high, high enough to get the voltage to each fan that it needs to run.

So to get them to keep cooling the motor you have to run them in parallel and provide some regulated voltage they can handle.

Anyway, that's just one "easy" way to get power to the fans without adding any wires.


Another way is to disconnect the hall 5V wire from the controller, and isntead use a separate battery-voltage-to-5V DC-DC converter that can handle the current your fans need as well as that of the halls inside the motor. That DC-DC stays outside the motor, wherever is conveneint for it on the bike. Then just power hte fans off the hall power wires.

 

[Cowardlyduck]

A 3 pin fan is not a 3phase ac fan, it simply has a speedo output on one pin, and dc input to power it on the other two.

Thanks for explaining. Does it make a difference that they say this on the ebay page?
"Please note: The third pin on the 3 pin powered fans does not control fan speed"
I'm not sure what it's for though.

Another way is to disconnect the hall 5V wire from the controller, and isntead use a separate battery-voltage-to-5V DC-DC converter that can handle the current your fans need as well as that of the halls inside the motor. That DC-DC stays outside the motor, wherever is conveneint for it on the bike. Then just power hte fans off the hall power wires.

I like this idea. So the controller wouldn't care where the 5V is coming from for the halls, just that they are active or not?
If that could work, it's probably the best option yet, as I already have a 12V DC-DC for my front light that could probably handle the fans.

Cheers

 

[Punx0r]

It's got to be easier to just run two extra strands of thin wire in to power the fans? You could use magnet wire if you want something really thin...

 

[amberwolf]

A 3 pin fan is not a 3phase ac fan, it simply has a speedo output on one pin, and dc input to power it on the other two.

Thanks for explaining. Does it make a difference that they say this on the ebay page?
"Please note: The third pin on the 3 pin powered fans does not control fan speed"
I'm not sure what it's for though.

See the part I highlighted in my original statement.

(edit (added): also the third pin may not do anything at all or even be connected, but the ones I've worked with almost always it is what I highlighted)

I like this idea. So the controller wouldn't care where the 5V is coming from for the halls, just that they are active or not?
If that could work, it's probably the best option yet, as I already have a 12V DC-DC for my front light that could probably handle the fans.

Sure...but you need a 5V DC-DC for the halls, not 12V. So you have to add a 5V DC-DC to run the fans if you want to run them off the hall power wires.

If you are going to run the fans off the 12V DC-DC then you must add a new wire for the +12v thru the axle wire bundle to reach the fans. You *might* be able to use the hall ground wire, as long as the fans don't introduce noise on the ground line that causes false hall signals.

If you wanna run the fans off the hall power wires using your 12V DC-DC, and not run a new wire, then you must add a 5V regulator (and probably some capacitors) inside the motor, between the incoming 12V at the fans and the hall power wires to the halls themselves.

 

[z50king]

I have a thought on airflow. If you only have one fan in one hole, you are just going to push hot air around the hub. Vent holes are too small for that fan to blow directly through. I think you will need a fan in each hole, pointing to the same side of the hub to get any air moving into and out of the hub via vent holes on both sides.

Those small fans thay you posted pictures of move almost zero air. They will burn up before you get any good air flow rates for cooling a hub motor

 

[Cowardlyduck]

I have a thought on airflow. If you only have one fan in one hole, you are just going to push hot air around the hub. Vent holes are too small for that fan to blow directly through. I think you will need a fan in each hole, pointing to the same side of the hub to get any air moving into and out of the hub via vent holes on both sides.

Those small fans thay you posted pictures of move almost zero air. They will burn up before you get any good air flow rates for cooling a hub motor

I'm planning on using multiple fans, probably around 5 anyway.
Since most of these fans can run on 5 or 12 volts I plan on making them switchable for: low noise, low cooling or high noise, high cooling.

More to come on this...I'm in the process of reparing my motor currently...once it's up and running again, I will attempt this mod.

Cheers

 

[Cowardlyduck]

I finally managed to make some significant progress on this mod.

The pics should tell the story enough.

I used a 2 part epoxy to secure the fans, and wires, and hall sensors, and temp sensor. It's not the strongest epoxy in the world, and it does soften a bit with heat...so fingers crossed the cooling fans do there job enough.

Spinning up the motor for the first time it has a bad squeak once a revolution, so I'll have crack it back open to sort that out.

I'm using some side covers that were previously vented for cooling so they have rather large holes also around the axle as well as the perimeter. For now I've just covered the holes around the axle with gaffa (Guerrilla) tape, but I have a feeling it won't stay very long.
Does anyone have a suggestion for covering over these holes more permanently?

Air flow seems good...with the fans running at 12-15V I can feel a steady stream of air flowing out the perimeter of one side. I think the key was partly in the fans I bought.
The age old saying holds true...you get what you pay for. I initially bought 6 of these, thinking all fans are made the same.
http://www.ebay.com.au/itm/321348661838

Alas, they are not all made the same...and these fans are terrible. You can barely feel any air coming off them...even at 15V.

So I forked out and bought these.
http://www.ebay.com.au/itm/170764022133

These were much better, and a single fan blows a noticeable amount...even at 6V. When cranked up to 15V and running 6 in parallel, they appear to definitely have some potential.

More to come on this...I have plans for controlling the fan noise vs cooling with a variable voltage DC-DC converter.

Cheers

 

[madin88]

good job. i also have think of this kind of hubmotor cooling.
my thoughts:
what you want is some fast airflow through the stator tooth with the windings, and/or between the magnet-stator airgap.
imho this will give you best cooling performance. to get such kind of airflow, you have to keep the motor closed at one side. at the other sidecover drill some big holes near the axle (fresh air intake) and many small holes at a diameter as big as possible (hot air outlet).
to prevent the air from mainly only circulating inside the motor, you could install some kind of airduct (some piece of a plastic pipe) with very small gap between it and the drilled sidecover.
can you follow me? what do you say to this idea?

 

[Cowardlyduck]

good job. i also have think of this kind of hubmotor cooling.
my thoughts:
what you want is some fast airflow through the stator tooth with the windings, and/or between the magnet-stator airgap.
imho this will give you best cooling performance. to get such kind of airflow, you have to keep the motor closed at one side. at the other sidecover drill some big holes near the axle (fresh air intake) and many small holes at a diameter as big as possible (hot air outlet).
to prevent the air from mainly only circulating inside the motor, you could install some kind of airduct (some piece of a plastic pipe) with very small gap between it and the drilled sidecover.
can you follow me? what do you say to this idea?

Thanks!
I originally did my side covers exactly like that...minus the airduct. It does help, but not as much as I think these fans will. I mean, I still managed to short the motor (I think from heat) even with the side covers vented like that. Many others have done the same, and some have even done the airducts/vanes idea...just search the forum.

The issue I have now is I no longer want the holes near the axle for the fans to be effective...how to seal them up?
I might just cut up some plastic from an ice cream container etc, paint it black, and epoxy it in the holes.

Cheers