Cooling fans inside Hub motors

[Cowardlyduck]

Hey that's awesome Offroader. It's great to see more people trying this now. The more people that attempt it, the more kinks will get ironed out and the better this approach will be.

cowardlyduck, was the fan noise very noticeable while riding or just noticeable if stopped? Was the fan noise annoying in anyway?

With the 12V fans I used it depends on the voltage I set them to with my DC-DC converter.
<10V - Barely noticeable (but still effective)
10V-13V - Noticeable at quiet times, and a little by others if they listen for it.
13V-15V - Always noticeable, slightly annoying. Passers by hear it but don't comment.
15V-18V+ - Annoying, loud! Pedestrians turn before you pass them.

I tend to ride around bike paths etc with them at between 10-14V. When flogging it off road, I crank them up to 15V+. That's why I did it with the DC-DC converter, as I knew it would be noisy and don't like sounding like a jet taking off when just cruising down the bike path. :lol:

I am trying to determine what fan configuration to use in my cromotor.

I can fit up to 30mm fans in my cromotor, and have room for 6 of them.

I will use one slot for a high speed blower, but I want to fill some of the other spots with fans to have some options when driving.

I may use some quiet 30mm fans for when I want silent operation but want some airflow going.

What fan configurations would you recommend?

Thanks

The high speed blower sounds like a good idea, but could add complexity if you want to be able to turn it on/off separately. You'll have to run separate wires for both options then. If you can fit the extra wires/switches etc, and the added complexity doesn't deter you, then I say go for it...you might even want to use 2 blowers, with 4 fans.

If possible see if you can mount bigger fans also. The only reason I used 25mm fans was because that's the size of the holes already in the Crystalyte HS series motors. Bigger fans push more air with less noise, so they are always a preference if possible.

Cheers

 

[Offroader]

cowardlyduck, thanks for the response. I woke up this morning with some ideas.

Maybe the blower and other fans may not be the best idea. The power of that blower may pull air through the other fans even when they are turned on when using an air duct.

I was also thinking, maybe it would be best to use only a couple of those blowers. I have to find out how much control of speed you have with them. For example, if I wanted to just run them silently and still blow some air, will that be possible? This way you have the best of both worlds, low speed silent operation, and super fast loud cooling operation.

Since weight is really not an issue (even these blowers weigh around 10 grams), better to put some real power in there. At 10 grams each, why not put 3,4 or even 5 of them in there. The weight is negligible and powering them is not a big draw, but you have some real cooling power when you need it.

I'm still some time away from getting this all hooked up, I am just finishing regluing my magnets. I am going to take my time with this and get a real nice cooling solution.

 

[Cowardlyduck]

No worries Offroader. Glad to be throwing idea's around.

Your probably right, if you can get away with it, just run the blowers only. I can't really do that as easily as the hole size in the crystalyte would make it more difficult. That, and I've already bought 6 new 25mm fans (the Yeah Racing ones) for my next motor.

And yes, run as many as you can fit. The power draw is so small, compared to the motor's usage, and the efficiency gained from running a cooler motor outweighs any extra power used anyway. Just make sure you don't run too small wires. i.e. if you used 26awg wires like I did, don't push more than about 1A through them over more than about 1M otherwise the wires will add too much resistance.

Usually any 2 pin (not 3 phase) fans will be able to easily be controlled just by using a different voltage. Buy one and try it.

Cheers

 

[John in CR]

I'm not sure what you guys mean by "blowers". I use the term to differentiate between axial and radial fans, with the blowers I talk about being radial fans commonly used in computer servers and many other things. They're ideally suited for installs like Cowardlyduck's, because their intake would come from the other side of the motor just like his do now, but the output comes out at 90° via a duct that can direct the flow toward the perimeter of the stator instead of at the side cover. You can also install them to intake from that same direction and point the flow at the same side of the stator it is installed for more air blowing on that side of the stator too, though those wouldn't help with fresh air intake.

Another significant benefit of radial blowers is that they are better a pulling a pressure, so they handle tight places and nearby turbulence better. I scavenged the ones I have from Bosch toolpack chargers. They pulled air through the toolpack and then it's output spread across the inside of the charger to cool both the toolpack and the charger. On the 36fet controller that SteveO customized for extreme power (I ran at 30kw peak at 74V) he installed a doublestack of 30mm fans like Cowardlyducks on the rear plate of the controller, and the output seemed way to small on the controller but fine blowing in open air. The limited flow was due their inability to pull a pressure and suck much flow through the controller. I replaced the doublestack with a single blower that flowed many times the flow, and kept the controller much cooler. A nice part of this is that I could open the other end of the controller a limited amount through 2 or 3 pieces of 3/8" plastic tubing and direct the incoming air at the two rails of mosfets, getting the air where I needed it most, and if I got too restrictive with the intake area (tubing too long) the sound of the blower changed as it it became starved for air.

With the big opening of an aluminum spoke stator support, if I was going with active fans for the advantage at low speeds and while stopped, I'd get 60mm or larger blowers. Say something like this with ball bearings http://www.aliexpress.com/item/AVC-...earing-Fan-CPU-Fan-Cooling-Fan/542091701.html . A few of those will move a lot of air and directing output at the stator with an angle to complement the natural spinning flow is sure to be more effective. The motor I run with the SteveO controller has a stator the size of a triple Magic Pie, and if I ever decided to use it for mountain trail riding, I'd swiss cheese the intake cover, and use a large diameter and small diameter ring to bolt to the intake side with the rings holding a screen in place to filter the intake. 60mm or larger blowers would go between the stator spokes like Cowardlyduck's rig along with some to blow on the intake side of the stator too. That should pretty much eliminate thermal cutbacks even riding at 20kw or more controller settings. When I beefed up the wiring harness to 6ga to match the winding copper, I included 3 conductors to be able to do a temp sensor and fans later, but in street riding neither been needed, so the mods would be relatively straight forward if, but in street riding neither been needed. That motor doesn't even have exterior blades, so I'd do that mod first.

 

[Offroader]

John, I don't think one of those radial blowers would fit easily inside a hub motor, just too big.

I'm going to go with this 27mm EDF, which was actually recommended earlier in this thread.

http://www.hobbyking.com/hobbyking/store/__17144__EDF27_with_11000kv_Motor_Assembled.html

I ordered everything and will be shipping from Asia. I had to order an electronic speed controller and also a servo tester to run them.

Supposedly these things blow a lot of air, they are made to move RC airplanes. I don't know if they can be run silently at low speed. This will be key here to see if I can use them at low silent speed and also turn them up when I want to quickly cool the motor.

I have to decide also on what works best, a bunch of low CFM computer fans that can be run constantly, or a really powerful EDF like this or two of them which will push a tremendous amount of air but be ridiculously loud. For a comparison this EDF will blow like 100 or 200 CFM, while a computer fan only can do like 3 CFM. There is a tremendous amount of difference here.

The problem is you can't really have a combination of both types of fans because I'm going to close the motor up with an air duct to circulate the air through more efficiently. The 27mm EDF may suck the air right through the other weaker fans.

 

[Cowardlyduck]

Hey that's great Offroader. Very keen to see how the EDF's work out for you.
You might find it doesn't like the heat generated by the hub since those EDF's are normally designed to suck in fresh air when flying an RC plane, but could work fine who knows.

Will you put an ESC inside the hub with it? Could generate some heat itself running these fans at full tilt, but if you place it in the flow it should keep cool enough.

Cheers

 

[Offroader]

Hey that's great Offroader. Very keen to see how the EDF's work out for you.
You might find it doesn't like the heat generated by the hub since those EDF's are normally designed to suck in fresh air when flying an RC plane, but could work fine who knows.

Will you put an ESC inside the hub with it? Could generate some heat itself running these fans at full tilt, but if you place it in the flow it should keep cool enough.

Cheers

I'm thinking that the EDF is going to suck so much air in that the air getting to it will be close to the outside air temp.

The issue is more the speed controller heating up when running the motor at lower speeds. I'm not sure if this is extra strain on it.

 

[Offroader]

So I finally got my EDF 27 from hobbyking and hooked it up to ESC. This tiny fan blows a ridiculous amount of air, I was literally blown away.

http://www.hobbyking.com/hobbyking/store/__17144__EDF27_with_11000kv_Motor_Assembled.html

If I hold it away from my face as far as I can and put it on full throttle it feels like I stuck my head out of the window driving like 40-50MPH. You can blow papers on the other side of the room with this tiny fan.

It is also not as loud as I thought it would be, but that is subjective.

I have to figure out how many holes I need to put in my motor side covers. I was thinking that it may be worth just putting a few small holes around the motor housing for the purpose of venting with the fan only. First since I upgraded to the Max-E my cromotor runs a lot cooler and I have a lot less overheating issues.

I'm thinking the EDF27 would be best just turned on every once in a while for quick cooling and when you're really pushing the motor off-road and are overheating it. This is why I think it is not worth drilling a lot of holes that leaves your motor exposed, when supposedly drilling for fanless air cooling doesn't do much anyway.

 

[fechter]

You might be able to set up a thermistor to control fan speed. Otherwise a thermostatic switch could make the fan turn off when not needed.

 

[Offroader]

You might be able to set up a thermistor to control fan speed. Otherwise a thermostatic switch could make the fan turn off when not needed.

That's actually a really good idea. This way I don't have to constantly monitor the temps and have to manually keep turning the fan on and off.

I would have to figure out what kind of thermistor and how to turn on and off the ESC, which is hooked to the servo tester.

 

[amberwolf]

there are a number of PC cooling fans that have thermal sensors built into them (usually a "green blob" that sticks out into the airflow from the core of the fan bracing). You might be able to just copy that.

I'll see if I can find any of the ones I have around here, and post a pic of it, along with it's p/n(s).

 

[fechter]

There are a bunch of fan controller chips out there.

Maybe something like this one:
http://www.ti.com/lit/ds/symlink/lm63.pdf

It has a PWM output designed to run a brushed motor, but if the frequency was low enough it might be able to take the place of a servo tester.

 

[Artur]

So I finally got my EDF 27 from hobbyking and hooked it up to ESC. This tiny fan blows a ridiculous amount of air, I was literally blown away.

http://www.hobbyking.com/hobbyking/store/__17144__EDF27_with_11000kv_Motor_Assembled.html

If I hold it away from my face as far as I can and put it on full throttle it feels like I stuck my head out of the window driving like 40-50MPH. You can blow papers on the other side of the room with this tiny fan.

It is also not as loud as I thought it would be, but that is subjective.

I have to figure out how many holes I need to put in my motor side covers. I was thinking that it may be worth just putting a few small holes around the motor housing for the purpose of venting with the fan only. First since I upgraded to the Max-E my cromotor runs a lot cooler and I have a lot less overheating issues.

I'm thinking the EDF27 would be best just turned on every once in a while for quick cooling and when you're really pushing the motor off-road and are overheating it. This is why I think it is not worth drilling a lot of holes that leaves your motor exposed, when supposedly drilling for fanless air cooling doesn't do much anyway.

Where do you wand to drill the holes? next to magnets or next to axel?

 

[Offroader]

What I plan on doing is the ducted air approach as was pointed out in this thread by madin88.

I am going to drill the holes near the axle or maybe in line with the fan. Then the other holes I will drill all the way near the ends of the case (near the magnets) so that they work like in the diagram below. They will only be drilled on one case cover to work with the airflow diagram.

I am not going to drill many holes, just enough to equal or slightly larger than the area of the 30mm EDF, on both the intake and outtake holes.

The most difficult part is going to be building the airduct to block the air. The cromotor has wires on both sides for the halls. Maybe I will cut the wires for one set of the halls.

I was thinking about making the airduct out of epoxy. Building the epoxy up and then placing the side cover on the motor to crush it down to be almost a perfect tight fit. I would of course put tape on the side cover so it doesn't stick to it.

With the amount of airflow the EDF produces and I can easily use 2 or more of them. With directing the airflow through the windings at such high amounts of airflow and speed. This motor would have to cool down ridiculously fast. I wonder how this would compare to water cooling, I would think water cooling has it's limits and the EDF approach would actually move more heat.

 

[dnmun]

you can use one of those small thermal circuit breakers also. use one that is normally open NO with something like 85oC to flip to conducting and then glue or tie the thermal breaker to the stator so it has a straight thermal path. they do have insulating plastic sleeves on them as protection against the wires inside shorting to the case and then to the exterior contacts.

you can check continuity on them to see if either of the wires is in contact with the case and if not then you could epoxy the thermal breaker can directly to the stator.

 

[Offroader]

What about building your own cooling fan switch?

http://www.instructables.com/id/Heat-activated-cooler-fan/

 

[madin88]

yeah i told you those RC EDF are far better than any pc cooling fan
for the airduct maybe you can use the lid used for big plastic tubes if you find one in the right size.
i guess you could improve cooling if you leave a small gap between stator and airduct to also have some fast airflow over this part.
make the intake area larger than the fans - otherwise they will have it very hard to suck in air. it should be doable.

 

[Offroader]

I actually bought the same one you linked from hobby king.

These things are the coolest little things and unbelievable how much air they can move for being so tiny.

The one I bought was a AEORC brand which may be of the best quality. They have a 30mm version which produces like 2x-3x the thrust of the 27mm one I bought. That may be able to fit in the cromotor.

I want to keep air holes to a minimum, so I don't think it is worth putting more than 1 of these fans inside as you would need to increase the holes.

One issue that came up when researching these EDF fans is that supposedly if you run them at lower speeds you could burn out the ESC. I don't know if this is true or not and if you bought a large amp rated ESC if it would still burn out. It would be nice to run it at a slower speed where you can barely hear it but it still moves a lot of air. ESC are pretty cheap anyways.

One thing I am going to do is put fiberglass or aluminum screening over the EDF just incase it decides to fall apart. I believe I saw ruined hubmotors from fans or blades coming loose and cutting up the windings and wires. A piece of screening is cheap insurance if this happens.

Here is the side of the cromotor I am thinking of putting the airduct on. I think I got lucky in that there is a lot of room to work with placing it on the stator. I could also tap tiny screws into it to hold the air duct in place. I will have to look for a rubber lid like you say and then tap tiny screws into the stator to hold it firmly in place.

madin88, I don't think it makes sense to let air by the airduct. Wouldn't it be better just to put some tiny holes in that area for the air intake instead? I think it is going to be impossible anyway to stop air from getting by the air duct.

 

[madin88]

One issue that came up when researching these EDF fans is that supposedly if you run them at lower speeds you could burn out the ESC. I don't know if this is true or not and if you bought a large amp rated ESC if it would still burn out. It would be nice to run it at a slower speed where you can barely hear it but it still moves a lot of air. ESC are pretty cheap anyways.

with the cheap HK ESC its recommended to run them at 0-70% and 100% throttle. at 70-99% they can get very hot.
good ESC from famous manufacturer have a feature called "active freewheel" and they will not overheat at partial load.
i would say if you place the ESC in the airflow and do not push it to the limits it will not overheat or blow. maybe a 33, 66, and 100% setting fits your needs :wink:

madin88, I don't think it makes sense to let air by the airduct. Wouldn't it be better just to put some tiny holes in that area for the air intake instead? I think it is going to be impossible anyway to stop air from getting by the air duct.

i meant between duct and STATOR - not sidecover
you anyway cannot avoid this gap because there are the six half-round shapings and you also need space for the hall wires.

as for the gap between duct and sidecover: i would measure it and leave 1mm gap.
the cover is not smooth as i remeber, there are stiffeners right?
imo its not a big problem and the larger you make the intake holes, the less air will go round in circles across the gap.

 

[Cowardlyduck]

I've been continuing to work on my other motor with the same mods done here (on page 1 and 2) previously.

This time it's a HS4080, and I'm using the much more powerful Yeah Racing fans. I'm also no longer going to use a DC-DC converter to power them. Instead I plan on running them in series straight off the battery. The current 6S config will only allow 12S (50V fully charged) to run the fans at approx 8V. This is a little over the max spec of 7.4V, but the pack voltage will quickly drop during use anyway, so the fans won't see the higher voltage for long. I'm thinking of adding another 3 fans in series inside my controller soon when I go to 18S to keep them within spec.

A few other mods are also being done, like a temp sensor, high efficiency bearings, and a slightly larger axle slot. I'm also planning on using some very thin gauge (teflon coated) wire for the temp sensor and hall sensor wires (but not the power) to maximize space in the slot. Not sure if I will use 12g silicone wire for the phases or not, or if I will possibly re-use the old hall sensor wires in parallel with the phases for that little extra current carrying capacity. Is that even worth it?
I'll let the pics tell the rest of the story.

Cheers

 

[Cowardlyduck]

In an attempt to minimize any potential damage caused by water, rust or dirt buildup, I'm coating the windings and magnets with red insulating varnish this time.

I also plan on fitting some dust filters to the intake holes as these fans are more than powerful enough to overcome the resistance. Hopefully they are easy enough to periodically clean, but I really won't know until I try.
Any suggestions for the best type of dust filter to use?
I also don't know how I will attach them at this stage. I'm thinking they will have to be attach to the outside since the inside will likely be too close to the windings. Epoxy would probably work, but won't look all too great, and will be tricky to do consistently. Other than that I can't really think of any other way to attach the filters. Any idea's anyone?

Cheers

 

[Cowardlyduck]

So I think I may have just come up with the best approach yet to the dust filter mounting problem.

I think I will use Coffee filters, like this:
http://www.ebay.com.au/itm/100-x-60...paper-MOKA-pot-fit-4-cup-HJ191-/261191628461?

They are dirt cheap, so I won't have any hesitations changing them regularly once they get dirty.

To hold them in place I will use some drain filters, or hole covers with a flange, like this:
http://www.ebay.com.au/itm/Bathroom...Floor-Drain-Cover-34x10mm-Pair-/271505111764?

As long as the flange is not too long (or shortened to fit) and doesn't hit the windings, I should be able to jam the drain cover over the filter paper and the tight fit will hold it in place. They should also be relatively easy to change...I think. Only problem may be the disc brake getting in the way as I've positioned the intake on that side this time, but I doubt it will be too much of a problem.

Now to find some smaller hole covers...all the one's I've seen so far are over 30cm diameter and have too deep a flange.

Anyone else have thoughts on this approach?

Cheers

Cheers

 

[amberwolf]

Before you go any farther with the filters, I think you should mount a fan in a tube with a filter sealing the end of it, and see how much (if any) airflow you get thru the filter.

I don't expect you'll get much, and possibly none, depending on exactly what kind of fan you use.

 

[Cowardlyduck]

Thanks for your input amberwolf.
Yes, I agree that a test is needed as coffee filters are normally meant to filter water, not air, so it is likely they may not let much through.

The idea to use the drain filters should still work though what ever type of dust/dirt filter I use. It's just a matter of finding the best material that lets air through, but not dirt/dust.

I think you would be surprised at how much air these little things can move though. I just tested them for the first time at full pack voltage running directly off my charger to also see how much power they need. I'm happy to say, these little things certainly deliver!
[youtube]z1T_Oe7KSLE[/youtube]
Just prior to this I also tested forcing the air through a gap near the windings (using a cardboard cutout) like they will when the side covers are on, and happy to say they produce quite the flow of air through a tight gap.
Coffee filters may still work yet!

Cheers

 

[Cowardlyduck]

And I think I just found the perfect hole cover.

Irrespective of whether I find a good filter paper to use, or even if I don't end up using any filter paper, these will make the perfect rock/ small stone protection.
http://www.ebay.com.au/itm/25mm-x-8...oom-Sink-Strainers-2-Pcs-Uitfl-/390993358888?

I might have to file/grind down the depth a little so they don't touch the windings, but that's no big deal.
If they don't fit snuggly with just the tightness of their fit, I will use some quality double sided tape on the flange to hold them to the side covers.
I just hope the raised flange doesn't interfere with my brake caliper as it sits really close to the side cover currently.

Cheers