Cooling fans inside Hub motors

[Cowardlyduck]

My motor is far from being ready to ride (as should be obvious)...but I made a short video to show the noise levels of the fans as I crank them up.
Turn the volume up to hear it as it really sounds.
[youtube]aB7mak4Qvfg[/youtube]

This is why I plan to use a variable voltage DC-DC converter. I don't want noisy fans going when I'm just cruising down the bike path around other people, but I do want the option of cranking them up when things start to get hot.

Cheers

 

[madin88]

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.

why do you want these holes to be closed? better build an airduct out of the icecream container
do you have the other sidecover closed?
i guess the cooling is not very performant because pc fans do not provide enough air pressure to push the air through the small gaps between the windings and the magnet airgap.
maybe something like this will do it: http://www.hobbyking.com/hobbyking/store/__17144__EDF27_with_11000kv_Motor_Assembled.html
or this 28mm from eflite: http://www.horizonhobby.com/products/delta-v-180m-28mm-edf-unit-EFLDF180M

i have the Mig-15 with this impeller and it sucks the air like a vacuum cleaner.

 

[Cowardlyduck]

why do you want these holes to be closed?

I'm not closing off all the holes. Just the one's near the axle. I redid it properly today...and got rid of the tape. Ended up using some clear packaging I had lying around. I epoxied them in place, so they shouldn't move.

Now I can see inside my motor even once it's sealed up.

It's funny you should mention the EDF. That was my original plan...but try finding a reasonably priced 25mm EDF.
I previously posted about it here:
http://endless-sphere.com/forums/viewtopic.php?f=2&t=48753&start=275#p796868
The best I could find was the MICRONEL D241L-012GK-1 FAN, 24MM, 12VDC:
http://au.rs-online.com/web/p/axial-fans/3811392/

But at over $100 just for 1, I ain't so keen to try it out first.

Cheers

 

[madin88]

i cannot imagine the temps now will get better with the inner holes closed. what you need is a well made airduct with very small gap to the sidecover.

the air should flow like this:
air intake at small diameter holes -> pass inside of the airduct -> through fans -> turn around and through windings -> pass outside of the airduct -> go out at the large diameter holes

the RC fans will provide MUCH MORE airflow and pressure as the industrial types above.
industrial 25mm: 0,26W, 14400rpm
RC 28mm: 40W, about 70000rpm

trust me, those small rc fans suck like your vacuum cleaner
price for two fans (enough^^): i guess about 60-80$ because you also need a RC type BLDC controller to power them. these are 3-phase motors like our ebike motors :wink:

 

[Cowardlyduck]

I hear you...RC fans would work best, but for the extra cost, I may as well upgrade to a better motor.

The proof will be in the testing. I'm using every spare moment I've got to get my bike back on the road after a minor fall that took out a number of minor components. Once I do, I will do a test...same hill, same starting temp, same throttle position, with and without the fans running.
Together with my new temp sensor display I'm setting up, that should show whether or not this method works.

Cheers

 

[sardini]

Try watercooling the way I did it. If you are about to change motor you have nothing to worry about. If it gets above 70c poor little water inside the motor. 0 cost

 

[madin88]

Try watercooling the way I did it. If you are about to change motor you have nothing to worry about. If it gets above 70c poor little water inside the motor. 0 cost

can you give more details about this?^^

 

[sardini]

They use this Technic at Agni motors to double the constant power .... http://luigi500.blogspot.se/2012/06/performance-modifications.html

 

[madin88]

They use this Technic at Agni motors to double the constant power .... http://luigi500.blogspot.se/2012/06/performance-modifications.html

if you do this, the motor, bearings etc will corrode soon. i never would do that to my motor.

 

[sardini]

That is what i was expecting too, for my motor, but so far so good my friend. If you come to Greece for vacation we can open it together.
Is like riding in the rain but every day

 

[Offroader]

Any updates on this?

I am in the process of fixing an overheated cromotor and would like to possibly air cool it. I am also thinking I might as well add some fans or possibly one of those RC 70,000RPM fans.

 

[Cowardlyduck]

Any updates on this?

I am in the process of fixing an overheated cromotor and would like to possibly air cool it. I am also thinking I might as well add some fans or possibly one of those RC 70,000RPM fans.

Funny you should ask.
The fans have been great. They seem to do a really good job of cooling things down when off the throttle, or at slower speeds compared to running with no fans. I would say at normal cruising speeds things run 10-15C cooler, and the motor will cool off after a climb or acceleration about 2-3 times faster than without the fans. I still need to prove this with some videos, but it's what I think I have observed.

However...just the other day I was powering up a large hill and quickly hit over 100C on the stator (which is not uncommon). Once at the top, I turned the fans up to 17.5V to increase cooling capacity. I had done this many times before, and it's always been fine. I calculated there should be roughly 2V drop in the wires/load anyway, so the fans only see ~15V at that level anyway. These are 12V fans.
Well, I guess they didn't like the higher volts after all...they stopped running soon afterwards. I'm yet to full investigate and there's every chance the fans are still fine as my temp sensor also died at the same time, so it could be a connection, or severed wire as well.

If (or when) I do it again, I will go with these fans:
http://www.rcmart.com/rc-yeah-racing-ya0201-tornado-high-speed-25x25mm-p-29521.html

Apparently they do 5.13CFM which is more than double the one's I'm using currently, and they are cheaper too.

Cheers

 

[Cowardlyduck]

Well, I guess they didn't like the higher volts after all...they stopped running soon afterwards. I'm yet to full investigate and there's every chance the fans are still fine as my temp sensor also died at the same time, so it could be a connection, or severed wire as well.

Well the issue didn't turn out to be bad at all...I seriously feared I had killed the fans either through over voltage, or water ingress.
Water ingress was a serious concern...as the day before I had done this...
[youtube]iMIEGfayg30[/youtube]
(still uploading at time of posting)
However, as it turns out there are no issues at all. All that happened was my connectors (little JST 2pin) had come undone, probably from a heavy landing or other impact that caused the connectors to stretch apart underneath the bike.

Hopefully I can get around to doing the video to prove my observations on the cooling effectiveness of these fans this weekend.

Cheers

 

[Cowardlyduck]

Video was private...fixed now.

Cheers

 

[Cowardlyduck]

Ok, so I finally got around to doing some proper tests on this setup.

I tested this on a slightly breezy 18C day. The test run was 150m up a mild grade not too steep to stall the motor, so I didn't have to pedal, but still steep enough to generate a decent amount of heat for testing. I'm currently running on 21AH 12S LiPo. For the test I set my CA to limit current to 90A, so 4Kw of power...at least at the start of each run.

I barely have enough time to scratch myself these days, so I didn't do a fully scientific multiple test scenario, but I did manage 5 runs. One with no fans, and 4 with fans a different voltages. This test was as much about proving the concept as it was seeing what difference in heat dissipation the fan speeds make. It was interesting for me to see that there wasn't a huge difference between running the fans at 12V and 15V. This is good for me to know as these are only 12V rated fans (although good quality ones), so running them at anything north of 14V for prolonged periods is risky as it could burn them out. Running them at 18V is only something I would ever do if the motor looked like it was about to melt down, or I was escaping a zombie apocalypse. :lol:

Anyway, I won't ramble on too much, and try and let the video/graph speak for themselves.
[youtube]P-VXS-aZZkU[/youtube]
Apologies for the lengthy video, but it's necessary to validate my results below.

In order to see the temps and control the fan speed, I put together a little 'package' that sits where my CA used to sit. It consists of a DC-DC converter, voltage display, temp display, and a fan (since changed to 2 fans in series) to cool the DC-DC converter. In order to mount it, I built up layers of hot glue so that I could use double sided tape to attach it to the underside of my frame from the inside. It's mostly been working well and hasn't dislodged since I've properly mounted it.

The only issue I've faced as been the adjuster for the voltage. As in the second photo above, I originally epoxied a paper clip to the pot with the idea of gluing a valve cap to that. That failed, then I tried the same with a piece cut off screw driver, then with hot glue, then with super glue, which all failed. I think the problem is the small size of the pot does not offer enough surface area to properly attach anything. If anyone has any suggestions, I'm all ears as I've yet to really think of a good alternate solution to just trying again with more glue and hoping it works.

I hope that others see my success with this approach, and take if further. For me, so far, riding through water, dust, and mud have not negatively effected the fans. I'll find out if they can survive the 40C ambient temps of summer around this part of Australia soon, but I suspect they will be fine. I won't hesitate to recommend doing this mod to others, as it was relatively easy in comparison to some other mods like oil, or water cooling.

I'll likely be modding my other motor (HS4080) with the same mod at some stage. I might try and document it when I do it to show others how they might do the same, if that would be useful. 8)

Cheers

 

[pendragon8000]

...
I'm all ears as I've yet to really think of a good alternate solution to just trying again with more glue and hoping it works.

...

http://www.ebay.com.au/itm/like/141038811923?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=107
im not sure what the pot is for but i would assume something like this may be suitable?

thanks for testing your modification. Ive seen this on Snowchylds bike, it definately works well. I should probably do the fan mod to. I think he used name brand blower type fans though.,EDIT (wrong) running on a switch powered be the positive 5v from the halls

 

[Offroader]

cowardlyduck, great write up, very interesting.

If you are going to mod your 4080, can you try and do that fan blade approach to cooling like john in CR mentioned. Might as well have good cooling while the motor is moving also.

Why did you only increase the motor temp to 54c? Is it possible for you to push the motor to around 90-100c? This is what my cromotor usually runs at. It would be interesting to see how fast it falls from those higher levels.

54c I consider my cromotor still cold.

 

[Cowardlyduck]

Thanks heaps for the kind comments guy's. Inspires me to do more of the same.

im not sure what the pot is for but i would assume something like this may be suitable?

The pot is built into the DC-DC converter so can't be replaced. It's used for adjusting the voltage. Currently I carry a small screwdriver and have to stop and line up the screwdriver through the hole in the frame to adjust the pot. It's quite tricky and easy to miss the pot inside since it's recessed and barely visible. It's kind of like trying to shot a target blindfolded, then turn on the spot multiple times without falling over.
I'm after any suggestions on how to make it work the way I've currently got it setup as I don't want to re-make my little 'package' if I can help it. Another thought I had was to glue a short piece of something with magnetic surface to the pot. Then I could use another piece, also with a magnet, for the end that I turn from outside the frame. That way if it gets bumped it won't rip off the pot...again.

thanks for testing your modification. Ive seen this on Snowchylds bike, it definately works well. I should probably do the fan mod to. I think he used name brand blower type fans though.,EDIT (wrong) running on a switch powered be the positive 5v from the halls

I originally proposed using the hall power at the beginning of this thread I think. Others talked me out of it as that power source barely has enough power to run 2 fans, let alone 6. If you overload that circuit it could kill your hall sensors and controllers hall sensing ability, so not the best option. In my case I just ran new 26AWG wires through the axle after enlarging it slightly with a rotary tool.

If you are going to mod your 4080, can you try and do that fan blade approach to cooling like john in CR mentioned. Might as well have good cooling while the motor is moving also.

I may try this, but it's the low speed climbing that I mainly need it for. The fan blade approach won't do much at slower speeds. Additionally, I would only want to do it on one side as it would be fighting the flow on one side if I did it to both side covers. In this motor I blow from right to left, so gear cluster side to disk brake side. As the phase wiring and fans are mounted on the disk side, I wouldn't be able to do it to this motor since there is no room left for fan blades on that side of the side cover.

Why did you only increase the motor temp to 54c? Is it possible for you to push the motor to around 90-100c? This is what my cromotor usually runs at. It would be interesting to see how fast it falls from those higher levels.
54c I consider my cromotor still cold.

I agree 54C is still cold. This was for purely for the sake of testing. Similar behavior is seen at higher temps, only the drop off speed increases exponentially with temp. I regularly see temps of 60-80C when going up longer or steeper hills even with the fans running. A handful of times I've hit 110C+ with them running also. In those cases the fans seemed to cool the motor off very rapidly and I could see the temps dropping down below 90C even when still pushing 1KW+ through the motor as the hill tapered off.
I might do another test at some stage where I do an actual (short) trail ride a couple of times with/without the fans and plot the temps.

Cheers

 

[Offroader]

cowardlyduck, I think with the fan blade approach you put fins on both sides, but the fins on one side push air in, and the fins on the other side are like a negative air fin or something that help suck air out. The fins on one side may even go inside the motor.

Nobody really wrote up exactly how to do this properly but with enough reading of old posts you can kind of figure out how its best done. I may be able to help you design something.

I think what you said about the air fighting doesn't hold true with proper fin placement. It needs to act like a centrifugal fan, however that works with a hub motor.

Maybe with your 4080 design you could also fit one of those $20 dollar high speed blowers also.

 

[Peter Sternersson]

I´m kind of looking forward to what these little bastards can do for the cooling in my V2 Cromotor



They blow crazy amounts of air on 7V each (7,2V max), makes lots of noise also but hey...

3D-printed inlays for the pockets in the stator, and just some hot glue here and there.

 

[Offroader]

Peter, just a few questions.

How hot were you getting your cromotor before adding the fans?

What have you sprayed on the windings?

Can you take pictures of how you drilled your cromotor side covers, and are you going to use any fan blades to direct air flow?

Thanks

 

[Peter Sternersson]

I have hit 120C a couple of times when riding in the woods, slow, up steep hills and with 8-10kW of power. Bike is 55kg with an additional 95kg of me on it.

The windings are sprayed with a special paint made for electric motors "Ultimeg 2000/372" reads on the can. It has something like 30kV/mm resistance and withstands 150-160C.
This coating has been on there 200km with vented side covers.

The covers are milled as follows, and I intend to use fan blades on the exhaust side for extra suction.

 

[madin88]

good job Peter and very well milled intake and outtake holes, but you will also have almost no airflow through the windings and stator teeth where the surface is the biggest and also the heat is generated. you could achieve this if you have intake and outtake at the same side with an AIRDUCT between.

 

[cal3thousand]

Good job guys!

The video and plot from Cowardlyduck are enough evidence for me. This mod certainly has it's benefits and I look forward to any developments you have.

 

[Offroader]

good job Peter and very well milled intake and outtake holes, but you will also have almost no airflow through the windings and stator teeth where the surface is the biggest and also the heat is generated. you could achieve this if you have intake and outtake at the same side with an AIRDUCT between.

Are you saying you would need the holes drilled only on one side? How would you position an airduct exactly? Do you have any links or pictures of this solution?