Definitive Tests on the Heating and Cooling of Hub Motors

[Offroader]

The EDF design could also be improved by adding an external duct because the exhasut and intake air holes are on the same side. This causes a decent amount of exhaust air being sucked back into the motor. I had planned to make this with a 3d printer but never got around to actually doing it.

The other improvement would be adding a stronger power supply to really turn up the fan speed higher than 80 watts for hill climbing and even using more power. The motor is rated for 330 watts, so I could easily push it a lot harder. However, right now none of that is necessary at my power level and I'm not climbing up mountains.


Since I use my bike like a dirt bike, I really think this type of fan cooling is going to be the best solution for cooling. Being able to control the speed of the fan makes a huge difference. Most of the time I keep it at 30 - 50 watts, but when I'm really pushing it to extremes I turn it up to 80 watts, and that makes a big difference in how fast the motor cools.

when using the Max-E with overdrive / OVS, which allows you to run the hub motor at a much higher top speed really causes the motor to overheat fast if doing this for a long time. My motor would push maybe 35MPH without overdrive, but I'm pushing 50MPH with overdrive. This causes extreme heat, just like climbing really steep hills.

If you don't use overdrive on your controller you really wouldn't even need to cool the motor while driving on the street, your wattage would be greatly limited. For example, with overdrive I push 8000 KW at full throttle on the street, but if I turned overdrive off I would push maybe 2000 KW at full throttle. That extra 6000 KW really heats the motor up quickly.

 

[Cowardlyduck]

Nice write up Offroader, although something tells me your talking about 8000W....not 8000KW. :lol:

As one of the only other guy's out there still running fans in my hub, I guess I should provide an update on mine also. For those unaware, I'm using 12 x 25mm (6 on each side) RC esc cooling fans mounted in the existing hub support holes running in series directly off my main battery:


Well I haven't opened my motor in at least 1500km now and it's still going strong. I regularly push 6KW peaks, 3-4KW cont. through it and it only ever gets over 135C on very long climbs or on slow steep technical stuff where something like a MXUS 3K with FF is struggling just as much.
How do I know that? Well I now also have an Alpha with a MXUS 3K, 10ml FF and Hubsinks.
Granted, I'm still dialling in the Adaptto tune, the Alpha with MXUS 3K actually overheats faster than my Fighter on steep hill climbs, and then it also takes longer to cool down. Also, I am pushing 13KW peak through the MXUS with 8KW cont, but this is comparable to the 'over-clock' on my fan cooled '1500w' Leaf motor since in both cases the motors are being driven to about 3-4 x their nominal rating, and although my Alpha is twice the power of my Fighter, the Fighter is about 25-30% lighter than my Alpha.

I will keep seeing how each of them performs, especially once I get the MXUS tuning on my Adaptto more dialled in, but so far the FF + hubsinks combo only has simplicity and clean running over my fans setup, not performance. That being said I can definitely see the sense in the masses just going for FF + hubsinks vs a complex, difficult to setup and potentially dirty Fan setup even if it does perform better.

Cheers

 

[Allex]

Got my magnets unglued on a leafmotor and ferrofluid.
Dont know if they were badly glued or if the ferrofluid did dissolve the glue.

Running 300A phase amps and seeing temperatures over 100C most of the times on this 35mm wide stator so this could be anything really, just a report.

 

[Cowardlyduck]

Good to know Allex. I'm running FF + fans + sprayon varnish in my Leaf. So far 3000km+ and it's still going strong.

Cheers

 

[liveforphysics]

Awesome job fitting serious fan power inside that motor buddy!

I just wanted to give an update about my 40mm EDF fan in my MXUS 3000 Turbo hub motor. The motor is ducted using silicone to direct outside air through the coils. The side cover of my hub motor has holes drilled into it.

I can say that I've ran it the whole last summer, and am running it this summer without any issues. When the weather is hot outside and around 90F degrees, this is the time I like most to ride my bike and also the most difficult times to deal with motor cooling, I am pushing the MXUS motor hard at 8000KW for a very long time with my large 3 KWH battery. I ride extremely hard with only using full throttle.

The silicone ducting I made directly on the coils and aluminum stator has held up without any issues.

I can adjust the speed of the EDF fan and with the very hot summer days I need to turn it up to 80 watts (this is what the 12 volt power supply draws as read on my Max-E) to be able to drive my bike as hard as I can with any risk of overheating. The great thing is I run this 40mm EDF at these high speeds for my entire 1-2 hour bike rides without any issues. This tiny EDF is very reliable and very powerful also at moving air. When this tiny EDF is using 80 watts it is spinning extremely fast, if you held the fan at arms length away it would feel like sticking your head out of a car window driving on the highway. No computer fan would even come close, these fans are used to fly airplanes at very high speeds.

The noise isn't too bad but it isn't silent. At a speed above 15MPH you won't hear it over the wind noise. You do get used to the noise, just like you would the noise of your car, you just don't notice it. The great thing is I can adjust it by reaching back under my seat, so if I want it silent I just turn the knob and I can do this while riding also.

I'm going to finish my Cromotor wheel build to compare this to FF and hubsinks soon. I want to do a direct comparison to see if its worthwhile to do this kind of fan cooling when a more simpler solution is available.

Here is a link to the 40mm EDF I use:
https://hobbyking.com/en_us/dr-mad-thrust-40mm-8-blade-alloy-edf-8000kv-motor-330-watt-3s.html

 

[Offroader]

liveforphysics: Thanks. The surprising thing is that this small 40mm fan is spinning so fast, probably around 50K RPMs, and yet it is so reliable. I run it sometimes 2 hours for a ride and they last for years. I was worried that they were not built to be run for such long duration because most people use them for short RC flights.

 

[DasDouble]

Good to know Allex. I'm running FF + fans + sprayon varnish in my Leaf. So far 3000km+ and it's still going strong.

Cheers

Oh you do that? Great, I have planed to do the same. Have got already ff on my QS 3kW V3 and want add Sprayon to it. Did you heat your stator / motor after or something like that or did you just leave it until it became dry?

liveforphysics: Thanks. The surprising thing is that this small 40mm fan is spinning so fast, probably around 50K RPMs, and yet it is so reliable. I run it sometimes 2 hours for a ride and they last for years. I was worried that they were not built to be run for such long duration because most people use them for short RC flights.

Im not sure if you already mentioned it, but please could you tell us the exact name of the fan once again? Sorry if I missed it in the pasts.

Cheers

 

[Cowardlyduck]

Oh you do that? Great, I have planed to do the same. Have got already ff on my QS 3kW V3 and want add Sprayon to it. Did you heat your stator / motor after or something like that or did you just leave it until it became dry?

If you've already put the FF on, I don't think you will be able to get enough of it off again to put Sprayon varnish on. The oils will have penetrated all between the windings. Maybe if you used a really strong magnet you can get it off. I wouldn't worry about it TBH, the FF will do a decent enough job of protecting the windings which is the main point of the varnish anyway.

I just leave the varnish on until it dries typically. It gets hot when riding so that takes care of any that still isn't dry.

Cheers

 

[Baron]

I'm experimenting with adding ferrofluid to a vented/varnished hub. My goal is to add a mesh/screen over the holes, I mostly ride offroad so my concern is dirt getting into the motor and gumming up the ferrofluid.

1st pic below is my swiss cheese hub motor and 2nd pic is the proposed screen cover idea, using stocking material and duct tape just as a mock-up. For the final version I want to use some kind of metal mesh for durability and glue it to the hub. I'm having trouble finding anything with super fine holes though. I'd like to keep as much dirt etc. out of the motor as possible, so mesh with holes as small as possible is necessary.

Does anyone have experience with a vented hub and ferrofluid, how has the ferrofluid held up over time?

 

[Cowardlyduck]

Does anyone have experience with a vented hub and ferrofluid, how has the ferrofluid held up over time?

I did this...twice. Once it didn't work out so well resulting in the FF gumming up and eating into the insulating varnish somewhat although the motor was still fine. That was a HS4080 with forced fan cooling and large vent holes.

The other time I did it to a '1500W' Leaf motor run at about 5-6KW and still, it seems to be fine. Open once after about 1500km and there were very little signs of wear/tear so I added more FF and kept going.
I also run forced fan cooling so worst possible scenario for dirt dust mixing with the FF and so far I have not had any reason to open the hub back up after thousands of km. If it has any issues I'll be the first to let this forum know, but so far it's been fine and I can't complain about being able to regularly push 5-6KW though my '1500W' rated hub. 8)

I also have a small '1000W' 9C clone hub in my Recumbent which is vented on one side with FF. It doesn't have forced fan cooling and since the vents are only on one side I don't think much air gets pushed past the FF. So far it has well over 4000km on it and hasn't had a single issue. I have also varnished that hub so it will be interesting what it looks like when I finally get around to opening it...but I won't be doing that without good reason as it's a real PITA.

Cheers

 

[Rix]

Does anyone have experience with a vented hub and ferrofluid, how has the ferrofluid held up over time?

I did this...twice. Once it didn't work out so well resulting in the FF gumming up and eating into the insulating varnish somewhat although the motor was still fine. That was a HS4080 with forced fan cooling and large vent holes.

The other time I did it to a '1500W' Leaf motor run at about 5-6KW and still, it seems to be fine. Open once after about 1500km and there were very little signs of wear/tear so I added more FF and kept going.
I also run forced fan cooling so worst possible scenario for dirt dust mixing with the FF and so far I have not had any reason to open the hub back up after thousands of km. If it has any issues I'll be the first to let this forum know, but so far it's been fine and I can't complain about being able to regularly push 5-6KW though my '1500W' rated hub. 8)

I also have a small '1000W' 9C clone hub in my Recumbent which is vented on one side with FF. It doesn't have forced fan cooling and since the vents are only on one side I don't think much air gets pushed past the FF. So far it has well over 4000km on it and hasn't had a single issue. I have also varnished that hub so it will be interesting what it looks like when I finally get around to opening it...but I won't be doing that without good reason as it's a real PITA.

Cheers

I seem to remember that FF gummed up one of your varnish coated motors.

 

[Cowardlyduck]

I seem to remember that FF gummed up one of your varnish coated motors.

Yeah, it's a shame that postimg.org went down (or at least all the old images did) and almost all the embedded images I have posted on this forum over the years got taken down with it. :x

I'll see if I can dig those photo's back up again.

Cheers

 

[Rix]

I seem to remember that FF gummed up one of your varnish coated motors.

Yeah, it's a shame that postimg.org went down (or at least all the old images did) and almost all the embedded images I have posted on this forum over the years got taken down with it. :x

I'll see if I can dig those photo's back up again.

Cheers

I was just curious, don't go out of your way on my account.

 

[Baron]

I think I am gonna skip the screen/mesh altogether after thinking about it, it's really hard for rocks/debris to even get into the motor anyway and it's almost impossible to keep out dust or small particles that can gum up the ferrofluid since my motor is already vented. Thanks for the info.

 

[Cowardlyduck]

Yeah, I looked into a mesh/grate type solution for my fan cooling and decided against it because of the complexity and reduced air flow.

As for adding FF together with venting I think it should work fine. The gumming up I saw was only on the one motor and with forced fan cooling and large vent holes. It also did not impact performance in anyway and I only noticed it when opening it up for other reasons. I would say it's worth giving it a try and seeing how it goes. I highly doubt it would cause any problems in the medium term and the fact that my other motor with forced fan cooling + FF setup is still going strong after thousands of kms would attest to it lasting long term.

Cheers

 

[amberwolf]

Yeah, it's a shame that postimg.org went down (or at least all the old images did) and almost all the embedded images I have posted on this forum over the years got taken down with it. :x

That's one reason I recommend always attaching the images/etc directly to the post they're for, so they'll be backed up with the post itself if anything goes wrong.

 

[ElectricGod]

Looks like this thread is still alive and well. I've visited many times, but never posted.

I don't want to use FF and I don't want to add heat sinks to the already heavy hub motor. Also, I am not using a bike wheel. My tire mounts directly to the hub motor rim. Heat sinks around the hub perimeter and between the spokes is not an option.

What's the consensus on forced air vs FF?

Here's my forced air idea:
1. Drill holes in a ring towards the center of both covers and inline with the ducted fan exhaust side.
2. Put a ducted fan in between the spokes inside the hub as has been shown previously.
3. Attach a shallow bowl shape to the exhaust side of the fan that covers all of the exhaust holes. Position it very close to the inside of the side cover. The idea is to have it close enough that you get 90% air flow out of the shell and only a little leakage back into the motor cavity. The smaller the gap between the bowl covering the exhaust holes and the shell side the better! But obviously they can't actually touch.
4. Create an internal duct that redirects the suction side of the fan into the exhaust side of the motor through another internal spoke hole.
5. Close up any remaining internal holes through the motor.

The effect is you draw air in from one side of the hub motor (intake side). There is no air flow path except through the stators and magnet gap at the perimeter of the motor since all other air flow paths are now blocked. You get lots of swirling air inside the intake side of the motor picking up heat before it passes through the stators. Air is sucked through the stators and into the exhaust side of the hub motor. It is then redirected through that duct and into the intake side of the fan. Hot air exits the exhaust side of the fan and out through the bowl and exhaust holes. In theory, the intake side will be all cool air coming in, sucked through the stators and magnet gap and then into the blower and out the exit holes. There won't be any dead air space inside the motor since the entire internal space of the motor will have air flow through it, but will be forced through the stators since that's the only air flow path. Air flow will have little choice but to enter near the center on one side of the motor, be sucked through the stator teeth and exit on the other side of the motor near the center.

Here's a quick sketch of my idea...and of course I missed something...close off the area around the fan so air can't go any direction but through the fan.

And a few close-ups since it's not so easy to see...

 

[Cowardlyduck]

Looks like your reinventing Offroaders design.
Check the cooling fans inside hub motors thread:
https://endless-sphere.com/forums/viewtopic.php?f=30&t=56965&p=1305466#p1291143

Cheers

 

[ElectricGod]

Looks like your reinventing Offroaders design.
Check the cooling fans inside hub motors thread:
https://endless-sphere.com/forums/viewtopic.php?f=30&t=56965&p=1305466#p1291143

Cheers

Ah yes...knew there had to be a thread for this...lol

Reposting over there.

 

[macribs]

Electric God, the weight of the hubsink is not an issue in my eyes. I mean for a heavy hub motor the weight of the hub sink is negotiable at best. If you worry put the hub on the lathe and shave down the back iron a millimeter or so before attaching. Now your hub is lighter even with the hubsink and the ff.

 

[sketchism]

Electric God, the weight of the hubsink is not an issue in my eyes. I mean for a heavy hub motor the weight of the hub sink is negotiable at best. If you worry put the hub on the lathe and shave down the back iron a millimeter or so before attaching. Now your hub is lighter even with the hubsink and the ff.

if i read correctly his issue was that he isn't using a spoked wheel so there was nowhere to mount the Hubsink itself, it would solve his heating problems but it doesn't look like he can physically fit it on his style of wheel

 

[andrei-8]

Hello, will such a thing work:
the wings stretched between the spokes ,
directly near the hub , directed along the wheel ,deflecting air flow to the hub ?
Does not allow to attach an image :?

 

[minde28383]

Hello,
who knows, show your pic.

There are two ways. Adding from you PC or adding from elsewhere by inserting picture link to you post.

Adding pic from your PC:
Select the "Attachments" tab
Click "Add files" and navigate to your *.JPG located on your PC, click "Open"


Adding from pic from your PC means it will be here aeternum.
Adding pic from a link is more temp solution because third parties remove pics and it disappears elsewhere.


If want to find out more about adding pics into ES. It is not strict instructions how to do it but it's rather discussion:
https://endless-sphere.com/forums/viewtopic.php?f=1&t=14748

 

[justin_le]

Hello, will such a thing work:
the wings stretched between the spokes ,
directly near the hub , directed along the wheel ,deflecting air flow to the hub ?

I would say in generally no. The air flow you get from the forwards velocity of the bike is much higher than the rotational component from the wheel spinning and anything you can do to play of that (wings, scoops, etc. you name it). Think about the relative diameter of the motor rotor to the actual tire diameter, you have about 3X more forwards velocity as a result of forwards motion than you have circular velocity from spinning.

So the best bet for cooling the motor side plates is to have the least barrier in the way to that air stream. Enclosing the wheel in the shell like in a velomobile will make cooling much worse, and so will having side panier bags and other things around the hub which will produce a wind shadow. It's quite probably that a super wide fat bike tire also has measurable cooling penalty compared to a skinny tire. Haven't quantified that yet in the wind tunnel but it might be a fun experiment to do.

 

[andrei-8]

Hello, will such a thing work:
the wings stretched between the spokes ,
directly near the hub , directed along the wheel ,deflecting air flow to the hub ?
only the game with the size, name and file editing helped