Cooling fans inside Hub motors

[Cowardlyduck]

you could always get a simple dc-dc converter from ebay and either wire the voltage pot to an external pot so you could adjust yourself, or i imagine it'd be pretty simple to get an arduino and a 2nd temp probe and make the Vout temperature dependant, so it automatically ramps up as things get hot...

LOL :lol: - been there, done that...
http://endless-sphere.com/forums/viewtopic.php?f=30&t=56965&start=25#p946731 - from page 2 of this thread.

It worked, but was too complex. The on-board POT was too hard to adjust...an external one might have been easier...but still too complex. As pictured, I also had to cool the DC-DC with the power I was drawing (I had to add a second fan after the hot glue started to melt with just one)...efficiency of the whole system was quite poor also.
I estimate my current setup with 9 high speed fans draws just over 50W with 80%+ efficiency. The previous setup with DC-DC exceeded the 15W capacity of the converter (hence the need for cooling fans) so ~25W at a guess, but the efficiency would have been less than 60% I think.

I like being able to just switch it on and off.
There's also a pretty cool side effect of having the fans wired in series. When I mash the throttle, or otherwise load up the motor (like on a steep hill), I can hear the voltage drop in the fans. It kinda reminds me of a turbo spooling up and down. I quite like it as it gives me really good feedback for how much load is being placed on the battery without needing to watch my display at all.

Cheers

 

[Offroader]

Just an update, mounting the air duct has been such a pain I've thought of forgetting about the whole project. After finally getting the required parts and tap I found just how difficult it is to tap small (1.5mm) holes by hand.

I broke my first $12 dollar tap on the first hole, even with trying to go as easy and slow as possible. Broke multiple small drill bits trying to drill the required holes. I then decided to make the size bigger and use m2 screws and also use tap lube.

The tapping seems to be a bit easier with the m2 size 2mm, vs the 1.5mm I was using before and using lube helps. Experience helps to not break the drill bits.

However new problems, what I discovered is that if you don't have enough threads into the aluminum the m2 screws will easily break the threads on tightening. I have to now drill in deeper and hope it holds because the m2 screws don't really feel that solid into the aluminum, the fine threads easily pull right out. I kind of wonder if it is the tap tolerance or the screw tolerance because it doesn't have really a tight fit.

The whole project is just a mess and a real time consuming pain in the ass. Lining up and drilling each whole by hand, and making sure everything is centered through the air duct and the small area I need to tap into plain sucks. The bits are so tiny that any mess up while drilling it will break the tiny drill bits.

 

[Cowardlyduck]

Don't give up Offroader! Think of the result!

Maybe you could scratch the idea of bolting the duct on and use epoxy...wasn't that an option originally anyway?

Cheers

 

[Offroader]

Don't give up Offroader! Think of the result!

Maybe you could scratch the idea of bolting the duct on and use epoxy...wasn't that an option originally anyway?

Cheers

Hmm, I completely forgot about using epoxy but that isn't a bad idea. I know I wanted to use screws instead, but the screws are not working out.

They have this epoxy that works with delrin and also bonds to aluminum. Seems to get good reviews also.

http://www.loctiteproducts.com/p/epxy_plstc_s/overview/Loctite-Epoxy-Plastic-Bonder.htm

I'm going to try tomorrow one more time to try and screw it down and if that doesn't work I'm going to just epoxy it down. I think I just need to go deeper with the screws because I'm probably screwing up the top of the threads by not taping the hole perfectly even. I can't use a drill press and the axle gets in the way of most tap holders. I don't want to spend the money for proper tooling to do it also.

I did want to eventually use the air duct for another cromotor as the motor I am using it on I overheated and it seems to have lost a little bit of torque. Oh well, I'll figure that out when the time comes, I probably could just use the heat gun to break the epoxy bond.

 

[Cowardlyduck]

That's the spirit.

It's a shame your stator core isn't steel. I've had great success holding things down and attaching things to my Fighter frame lately with little stick on 3M magnets. I don't know why I didn't think of it earlier...but for the stamped steel stators it would work really well.

Another option for you Offroader could be to epoxy some magnets to the aluminium, then embed/epoxy some in the back of the air duct. Then you can easily remove it when the time comes.

Cheers

 

[kiwiev]

Any updates Blake

really interested to see how your package is going now.

Cheers Kiwi

 

[Cowardlyduck]

Stalled due to controller issues...still troubleshooting and I've been working on my recumbent a lot so haven't managed to get back to this. However I've ordered a replacement connector so I can rig up my old controller in the mean time...maybe in the next few weeks.

The fans work though. In arbitrary testing around my back yard, they remove heat pretty dam fast. They seem to work much better on the controller than the motor, but that's to be expected since the controller fans are in the open air vs the motor fans being quite restricted in comparison.
What's cool (and I think I mentioned this already, but still very cool to me) is the way the fan noise pitch drops as the battery voltage sags under load. It's just a really cool indicator of the load on the battery without having to look at any screens. I've never experienced anything like it before on E-Bikes or ICE bikes/cars, so it's quite unique, but the closest thing I can think of is when your pushing an ICE lawn mower and you can hear the RPM drop when you hit a thick patch of grass.
The great thing about it is (when I finally get it up and running) I will be able to tell what terrain (besides the obvious, hills, sand, etc) is placing a high load on the battery. I think it will really help with guiding efficient riding styles for long range.

Cheers

 

[kiwiev]

I'm hooked

I really think this is a great idea, and it sounds cool.

I really like the feed back and lets face it there isn't a big exhaust to hear

I really like the sound of my Sonic EV the way it ramps up on the driveway

Cheers

 

[Offroader]

Finally got the air duct installed nice and tight. The problem I was having with taping was I wasn't drilling the holes straight and was also too cheap to get the proper tools to hold the tap. I fixed all my errors and I re-tapped all the holes without any issues. I made sure to drill the holes straight and support the wheel so it is flat. Then I put together a proper tap holder extension to get over the axle. It all went smooth and the m2 bolts hold strong and I made sure they went deep for more thread contact.

The clearance from the plastic air duct and side cover is about 1-2mm. The next step will be to apply silicone to the top of the air duct and then press the side cover on to mold it flush against the side cover to stop air from re-circulating. I assume the tolerances will not be perfect so some of the silicone will wear away when running the motor in some areas, but I don't think this silicone turning to dust in the motor will matter as there will be plenty of dirt getting in through the side cover holes anyway.

Hopefully I'll have this all finished in the next few days as long as the silicone holds to the slippery Delrin, which could be a problem, but from tests it seems that roughing the surface should be sufficient.

I don't even want to tell you how long this project has taken me, easily between 20-40+ hours so far invested. Took lots of learning and experimenting.

 

[Cowardlyduck]

Great stuff Offroader. Is that aluminum tape in the stator temporary?

I also notice you have a broken wire (looks like a hall wire) through your axle...but you were probably already aware of that.

Cheers

 

[Routybouty]

I have an idea I wanted to run by you guys to see if I'm crazy or not. I am planning on milling perimeter slots and near-axle holes on both covers. I also wanted to add internal fan blades (similar to what Madin88 pointed to, cutting a blower wheel down) to each cover in a radial fashion to help push the air over the winding ends and out the slots. The heat is generated in the windings, it then transfers out to everything else. The idea I have is what if I added a cover to the stator on each side to prevent air from entering the dead space that's not creating the heat anyway. This would help focus all the blown air onto the windings and not get caught up in the inner stator area. I feel like getting as much air as possible over the ends of the windings will have more benefit then randomly bouncing inside and eventually ending up near the windings.

Here is an example picture of the stator block plate, made possible via my dinner plate lol. Not the actual material I want to use.

 

[Cowardlyduck]

Cool idea Routybouty!

Will you just be relying on centrifugal forces to pull air in and across the windings?
If you could find a large radial blower fan with a large hollow center, you could put it over the axle and power it for some very decent air flow. Combined with the internal covers you could put one on each side for some serious cooling effect.
The hard part might be getting the cover + blower fan blades to fit within the recess on the side where the phase wires connect to the windings.

Cheers

 

[Cowardlyduck]

Here you go...Just found these.
http://www.amazon.com/Black-Plastic-Centrifugal-Blower-Impeller/dp/B00G9Q05I6

http://www.amazon.com/Replacing-Black-Plastic-Vacuum-Impeller/dp/B00NQ2MGEM

And there are plenty of others...so I'm sure you could find one that fits.
You could glue or bolt that sort of thing to the inside of your side cover. Then there's no need for powering it.
I would just be making certain there's no way it can catch any of the wires inside the stator...would be disastrous if it did!

Cheers

 

[Routybouty]

If you could find a large radial blower fan with a large hollow center, you could put it over the axle and power it for some very decent air flow. Combined with the internal covers you could put one on each side for some serious cooling effect.

This was actually the original idea! It would be really cool if someone designed an outrunner motor we could slip onto the axle shaft between the cover bearing and the stator. Then you could attach an impeller right to the outrunner. Sooooo much air could be moving then!

After getting this motor apart, there just isn't much room for an active impeller like I originally thought. So I will be adding something similar to the impellers like you found, for passive cooling. I will also paint it with the Krlon 1602 as Doc has been mentioning in the Definitive Cooling thread.

I have a bunch of measuring to do!

 

[Cowardlyduck]

I wish you the very best of luck and look forward to seeing how you go.

Another option could be to mount the impeller on a bearing on the axle allowing it to spin freely. The rotation of the air coming in from the side covers should spin it up to speed, then it would continue to spin after stopping for a little while. Could have some interesting results.

Cheers

 

[Offroader]

I have an idea I wanted to run by you guys to see if I'm crazy or not. I am planning on milling perimeter slots and near-axle holes on both covers. I also wanted to add internal fan blades (similar to what Madin88 pointed to, cutting a blower wheel down) to each cover in a radial fashion to help push the air over the winding ends and out the slots. The heat is generated in the windings, it then transfers out to everything else. The idea I have is what if I added a cover to the stator on each side to prevent air from entering the dead space that's not creating the heat anyway. This would help focus all the blown air onto the windings and not get caught up in the inner stator area. I feel like getting as much air as possible over the ends of the windings will have more benefit then randomly bouncing inside and eventually ending up near the windings.

Here is an example picture of the stator block plate, made possible via my dinner plate lol. Not the actual material I want to use.

Maybe make some drawings about your idea. Will you make it so that fresh air will be blown through the windings and out? That is what I'm currently working on with my EDF project.

 

[Offroader]

Finally made some progress on my EDF air duct project. Got all the electronics worked out and everything should be up and running within the next few days, well that's what I said a few weeks ago but this time I don't see any issues.

I decided to get some power supplies to power my EDF fan which draws 8 amps at 8 volts. I want to draw from my 18s battery on my bike and not deal with a separate battery.


Here is a picture of the electronics, I can't find any good 72 volt to 8 volt power supplies that will handle 10 amps, so I decided to use a 72 volt to 12 volt power supply rated at 10 amps, and then have another power supply that turns the 12 volt into 8 volts.
There is no trim pot in the 72 to 12 volts so I had to use two down converter power supplies to get the 8 volts. I did lose some efficiency which I actually tested. My EDF fan draws 64 watts, but the draw from my main batteries are 85 watts. So I lose 20 watts due to using two down converter DC-DC power supplies. Not the biggest issue on my over 2KW battery pack.

Both of these power supplies got great reviews and seem to be of high quality. They power my 8 volt 8 amp EDF fan without issue. The 8 volt power supply is actually variable so I have room for adjustments and is dead accurate once set with no voltage drop. It does get a bit hot but I may add another heat sink to the top of it, supposedly you can pull 200 watts from it with increased cooling.

These are some really good power supplies and I did some research, you really can't beat them for the price of around $10 USD each. They all have a very high amp rating also.

If Adaptto ever releases its DC-DC converter then I can probably do away with the 12 volt power supply.

In the picture you can see a blue aluminum power supply that will be used for 5 volt usb to power my front action cam and future rear mounted action cam. This will also power from my 72 to 12 volt power supply.
http://www.amazon.com/gp/product/B00BYRJXGA?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00

In the center is my 8 volt power supply good for 12 amps.
http://www.amazon.com/DROK-Regulator-Application-transformers-adjustable/dp/B00C4QVTNU/ref=cm_cd_al_qh_dp_i

On the right is my 12 volt 10 amp power supply with input voltage good to 100 volts.
http://www.aliexpress.com/store/product/E-bike-DC-DC-Converter-24V-36V-48V-60V-72VDC-universal-to-12VDC-10A-72V-Electric/313864_522806594.html



Here is my 30mm EDF finally installed. I decided to use the 30mm EDF instead of the 27mm EDF. It is way more powerful pulling 8 amps at 8 volts, or 64 watts at full power. This thing is ridiculously powerful. It creates so much pressure you can really feel it blow between the stator and magnets with decent force.

[youtube]iU9ti000LuU[/youtube]

 

[Routybouty]

It sounds mean :lol:! Is there still a decent flow if you put on the cover on the intake side of the EDF?

Maybe make some drawings about your idea. Will you make it so that fresh air will be blown through the windings and out? That is what I'm currently working on with my EDF project.

Here is a slightly busy drawing...
Yellow are fan blades, grey are the stator covers with hatching.


It doesn't shove air through the windings as in across the width of the motor. I am hoping the extra clean path can move a larger amount of air across the winding ends since it won't be getting caught in the stator "dead space" area.

 

[John in CR]

RoutyBouty,

Closing all that metal that is part of the stator assembly in an insulating layer of stagnant air would be hugely counterproductive.

Interior blades work, and not only ensure the air gets spinning up to wheel rpm, but I've found that using them to deflect the air toward the hottest parts of the stator helps increase the coefficient of convective heat transfer to make good use of the flow you create instead of it taking the easiest path along the inside surface of the covers.

Centrifugal blades on the outside can drastically increase flow, because the blade tips (where the action really takes place with centrifugal fans) can be much larger, and there velocity can be significantly greater due to the greater radius at the tips.

I've settled on one sided intake and exhaust out of the other side at the extreme perimeter, because it ensure much of the flow goes through the magnet gap, which is often has the biggest surface area closest to where heat is generated.

Passive approaches rely on rpm for flow, which is why Mr Duck is going for active ventilation, since he wants to creep slowly up the hills offroad instead of blasting up them.

 

[Routybouty]

Thanks John, without knowing, I was guessing (maybe just wondering) some extra air across the heater (windings) might be more beneficial than ensuring secondary heated surfaces have flow. The path I will probably take is most likely what you stated, since it's easier/effective. Slots on the perimeter, holes on opposite axle, interior blades, see how it reacts and add external if necessary. I do mostly at speed riding, so I have that advantage for passive cooling.

I've settled on one sided intake and exhaust out of the other side at the extreme perimeter, because it ensure much of the flow goes through the magnet gap

Without an obstruction in the stator, does the air go through the magnet gap mainly from centrifugal force?

 

[Cowardlyduck]

Finally made some progress on my EDF air duct project.

Awesome stuff Offroader!
I can't help but think you should put 6 of those things in there to use all available space, but it would be massive overkill. That being said, if I was building a light weight dragster, or even race bike, this would be a great way to use an underspeced lighter weight hub motor and push it way past it's normal limits.

Your DC-DC setup seems a bit complex...I mean I can see that it works, but surely there is a better way. What about putting another fan in series to take up some of the voltage and only using the 12V DC-DC...then you would get 2 fans at 6V which might move more air and be quieter also.

Here is a slightly busy drawing

That looks neat Routybouty. Will be interested to see the results.

Passive approaches rely on rpm for flow, which is why Mr Duck is going for active ventilation, since he wants to creep slowly up the hills offroad instead of blasting up them.

John, I thought you left this discussion? :lol:
Anyway, seems like you might finally be coming around to understanding why we are taking the active cooling approach.
Yes we want to crawl slowly up hills in stead of blasting up them. We also get the added benefit of cooling when stopped/resting, or when not to going fast.

If I wasn't doing this active cooling, I would probably be doing passive like you John or maybe trying oil cooling, but I enjoy trying something different like this.

Cheers

 

[Offroader]

I've been thinking about where the heat goes in the motor and it may be a bad idea to close up the center. I take it the windings heat up and somehow transfer that heat to the stator. I assume that the windings running through the stator must pass the heat to the stator, but how much of this heat is from the windings in the stator or the air heated from the windings that then get passed into the stator.

With active cooling from a fan you would think the stator wouldn't get that hot because the fans would remove the hot air immediately, but maybe it will still get hot from the windings running through it, even though these windings are wrapped in my motor where it is inside the stator with some kind of red plastic or rubber.

I just don't know how the stator is getting hot because the windings heat the air inside the motor and this heated air could be getting the stator hot.

What I would need to do is attach a temp probe into the stator to check how hot it is getting. If it is getting hot even with active air cooling then it would make sense to add heat sinks to the inside of the stator, this would really increase the surface area to get the heat into the air and removed with the fans.

 

[Offroader]

I can't help but think you should put 6 of those things in there to use all available space, but it would be massive overkill. That being said, if I was building a light weight dragster, or even race bike, this would be a great way to use an underspeced lighter weight hub motor and push it way past it's normal limits.

Your DC-DC setup seems a bit complex...I mean I can see that it works, but surely there is a better way. What about putting another fan in series to take up some of the voltage and only using the 12V DC-DC...then you would get 2 fans at 6V which might move more air and be quieter also.

One of these EDF draws 64 watts and blows a lot of air. This one is a 30mm and 13,000 KV, it will fill up a huge garbage bag in seconds.

I don't think a stronger air flow will make all that much of a difference. What would probably be better would be to add another duct to help direct the air into the windings.

I'll have to see after I hook everything up. I am thinking this single fan will be enough where I can run my bike as hard as I want and never get into the overheating stage. I still have the option of adding heat sinks on the inside of the stator also if the airflow is not able to cool down the windings that run inside the stator.

yeah all the Dc-DC converters are a bit much. I need to use external ESC's and I'm not sure if I can just run them in a series.

 

[Offroader]

Cwardlyduck, how exactly does your cooling work? Do you only have your hub motor drilled on one side and pull air from the side with holes?

If that is the case you are probably recirculating like 80%+ air, which is better than no circulation.

 

[Cowardlyduck]

Cwardlyduck, how exactly does your cooling work? Do you only have your hub motor drilled on one side and pull air from the side with holes?

If that is the case you are probably recirculating like 80%+ air, which is better than no circulation.

No, it's drilled on both sides, at the perimeter. Air goes in from the freewheel side, and out on the disk side.
The disc brake creates a small amount of centrifugal force which helps pull air through to that side also when in motion.

This is the same way I did it last time, and the results spoke for themselves. With my hand I can feel fresh air being sucked in on one side and hot air blowing out the other, so if it's recirculating, it's not enough to prevent this method from being functional.
Also, since I've placed a fan in every hole, and filled in all other gaps, the only way air can recirculate with my setup is up and over the magnet gap. If it's doing that, it could not be much at all since that is a much harder path for the air to take than just leaving via my drilled side covers.

Cheers