Definitive Tests on the Heating and Cooling of Hub Motors

Get all your technical information about electric bikes here.
User avatar
minde28383   1 kW

1 kW
Posts: 489
Joined: Apr 02 2010 7:11am

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by minde28383 » Mar 16 2019 12:24pm

To reach your goal you would need to design most effective air blades to scoop as much air as possible; blades being from the very rim to to the very hub ring, long as possible. The smaller the wheel the faster you need to spin it to reach the same travel speed on the road, but the smaller the wheel the shorter the blades becomes. Therefore it will be not enough air flow with short blades and low rpm. Wheel rpm might be ~700 max, but you won't spin it always that fast, sometimes you move very slow and generate heat and need motor to cool down and small blades are generating almost nothing at low rpm. So you theoretical cooling approach would work only for fast running ebike and possible small wheel, but again, smaller the wheel spins faster but has less space for air blades.

To test it in real life try supplying low voltage (or just slow it down by pressing it to make it spin slower) to reach low RPM to you house air FAN which is used in hot summer days to cool things down, and you will see that low RPM generates very low air flow. If you need big air flow from low rpm you need big vents which you can't install inside wheel because there is no enough space.

Let imagine that there was unlimited space to install air blades. These very light, strong, always dirty, blades would generate air flow only to outer hub ring, but hub side covers would get no air flow. To solve this you would need to make fan blades wider which would be wider than hub or make some air flow channels, wings to direct air flow to hub covers. After laying you bike on the ground you would brake those off or bent if soft metal. I have to admit it would look futuristic.

Artificially blowing air to your hub is secondary. Preferably first thing you you need to do is to remove air gap between rotor and stator ie between spinning thing inside motor and outer hub ring (magnets). And cheapest fastest solution to that is using already widely available Ferrofluid (Fero fluid), and if FF does not solve the heat problems than adding radiators which are available for 205 hubs like mxus205 and qs205, maybe it works in narrower 205s.
Another option is more technical, and requires hub modification - liquid cooling imlementaion. In that case you would require, small pump, houses, radiator, modifying axle. You can acquire hubs of 9kg, modified mxus with liquid cooling implemented, but these are twice the price and therefore not so much popular.

There are implemented cooling solutions where air is pushed with high rpm fan directly to copper to windings (not to outer hub ring). This solution did not appeal to masses and is almost solo approach due requiring quite big modifications from not readily available parts to be acquired. To reach that cooling solution you need hub motor which has static (not spinning) hub cover (like it is implemented in geared hubs); make a holes in both side covers; blow air to one side hole and suck from another hub cover hole. That possible and workable solution, but you will have more sophisticated ebike with more parts possible to brake. These geared hubs are prone to brake under high loads anyways and makes noise under high load because of gears, reduction.

But no matter above, most inventions are made by fail trial methods so think of another solution. Another brake through would be to design motor with higher efficiency so that there would be no need to cool it down. Maybe you need bigger motor?
ebike build in progress
CN 5.5kw scooter (on sale)
E Mindless Maverick Talisman longboard, 2.2KW motor, 150Amps controller (on sale)

John in CR   100 GW

100 GW
Posts: 13818
Joined: May 20 2008 12:58am
Location: Paradise

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by John in CR » Mar 16 2019 5:31pm

andrei-8 wrote:
Mar 16 2019 2:48am
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
No, such blades (wings you're calling them) will through air away from the motor like any centrifugal fan. It might cause very slightly more flow at the motor shell itself as the air is sucked away from center.

You can direct more air flow toward the hub shell with air scoops that direct air from the bike moving toward the motor that would otherwise bypass it completely. I've done that with some success, but the trick is making it look like part of the bike. Here's what I did:
SuperV air scoops side.JPG
SuperV air scoops side.JPG (32.82 KiB) Viewed 1318 times
SuperV air scoops rear.JPG
SuperV air scoops rear.JPG (30.01 KiB) Viewed 1318 times
While these worked to some extend due do my car type speeds, I didn't achieve great cooling until I vented the motor with intake slots on one side and exhaust slots at the perimeter of the other side with centrifugal blades outside of the exhaust slots that create great air flow through the motor.

User avatar
Cowardlyduck   100 MW

100 MW
Posts: 2633
Joined: Jun 26 2011 8:41pm
Location: Canberra, ACT, Australia

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by Cowardlyduck » Mar 16 2019 5:43pm

This...
DSC_2517 (Medium).jpg
DSC_2519 (Medium).jpg
It still going strong over 3 years on...still works great. :D

Cheers
Custom made 18650/21700 battery packs

Modified Stealth Fighter - Force air cooled motor @ 6KW, Adaptto Mini-E. 49AH, 52V 18650 - 2.5Kwhr
Cowardlyducks - Stealth Fighter Videos

BikeE recumbent commuter - 9C, 6Fet Grinfineon, internal 17AH, 52V, + on-board solar.

Ebike Garage - My YouTube Ebike ramblings.

High Power LiPo wiring harnesses - 4P - XT90, HXT4mm, 5.5mm. 200Amp+ capable. Global shipping.

andrei-8   1 µW

1 µW
Posts: 4
Joined: Mar 15 2019 5:50pm

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by andrei-8 » Mar 18 2019 2:50am

Thanks for answers!

User avatar
DasDouble   100 kW

100 kW
Posts: 1152
Joined: Jul 12 2015 1:35pm
Location: GERMANIA :D

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by DasDouble » Apr 05 2019 5:00am

John in CR wrote:
Mar 16 2019 5:31pm
andrei-8 wrote:
Mar 16 2019 2:48am
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
No, such blades (wings you're calling them) will through air away from the motor like any centrifugal fan. It might cause very slightly more flow at the motor shell itself as the air is sucked away from center.

You can direct more air flow toward the hub shell with air scoops that direct air from the bike moving toward the motor that would otherwise bypass it completely. I've done that with some success, but the trick is making it look like part of the bike. Here's what I did:
SuperV air scoops side.JPG
SuperV air scoops rear.JPG
While these worked to some extend due do my car type speeds, I didn't achieve great cooling until I vented the motor with intake slots on one side and exhaust slots at the perimeter of the other side with centrifugal blades outside of the exhaust slots that create great air flow through the motor.
have you made some serious tests on that or is it just a feeling that it became better?
Mechatronics-Engineering Student
-Built own ebike: ✔
-Built own 3.2kWh LiIon battery (300Amps): ✔
-Overtake Porsche with own Ebike: ✔
-Take off with ebike: ✖

~14kW, 3.2kWh LiIon, QS 205 8ml ff, hubsink

John in CR   100 GW

100 GW
Posts: 13818
Joined: May 20 2008 12:58am
Location: Paradise

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by John in CR » Apr 07 2019 11:28am

DasDouble wrote:
Apr 05 2019 5:00am
John in CR wrote:
Mar 16 2019 5:31pm
andrei-8 wrote:
Mar 16 2019 2:48am
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
No, such blades (wings you're calling them) will through air away from the motor like any centrifugal fan. It might cause very slightly more flow at the motor shell itself as the air is sucked away from center.

You can direct more air flow toward the hub shell with air scoops that direct air from the bike moving toward the motor that would otherwise bypass it completely. I've done that with some success, but the trick is making it look like part of the bike. Here's what I did:
SuperV air scoops side.JPG
SuperV air scoops rear.JPG
While these worked to some extend due do my car type speeds, I didn't achieve great cooling until I vented the motor with intake slots on one side and exhaust slots at the perimeter of the other side with centrifugal blades outside of the exhaust slots that create great air flow through the motor.
have you made some serious tests on that or is it just a feeling that it became better?
Almost 6 years of running higher power into a hubmotor than anyone else, and the motors run cooler than any running more than minimal power levels is serious enough testing for me. While I don't have the tools or patience to do the kind of work Justin does, that doesn't mean it doesn't work. The benefits at low rpm are more limited, but I did run a smoke test and starting at around 10mph the motor started drawing air through.

ltu   100 mW

100 mW
Posts: 47
Joined: Oct 24 2017 9:58am

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by ltu » Jun 21 2019 10:56am

its migth interest some test using the m3 liquid solution usuality used for cooling server.
have better heat transfer compare to AFT

User avatar
DasDouble   100 kW

100 kW
Posts: 1152
Joined: Jul 12 2015 1:35pm
Location: GERMANIA :D

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by DasDouble » Jun 21 2019 2:42pm

John in CR wrote:
Mar 16 2019 5:31pm
andrei-8 wrote:
Mar 16 2019 2:48am
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
No, such blades (wings you're calling them) will through air away from the motor like any centrifugal fan. It might cause very slightly more flow at the motor shell itself as the air is sucked away from center.

You can direct more air flow toward the hub shell with air scoops that direct air from the bike moving toward the motor that would otherwise bypass it completely. I've done that with some success, but the trick is making it look like part of the bike. Here's what I did:
SuperV air scoops side.JPG
SuperV air scoops rear.JPG
While these worked to some extend due do my car type speeds, I didn't achieve great cooling until I vented the motor with intake slots on one side and exhaust slots at the perimeter of the other side with centrifugal blades outside of the exhaust slots that create great air flow through the motor.
I will design this and print it with my 3D printer for Vector frame in a week :)
Mechatronics-Engineering Student
-Built own ebike: ✔
-Built own 3.2kWh LiIon battery (300Amps): ✔
-Overtake Porsche with own Ebike: ✔
-Take off with ebike: ✖

~14kW, 3.2kWh LiIon, QS 205 8ml ff, hubsink

andrei-8   1 µW

1 µW
Posts: 4
Joined: Mar 15 2019 5:50pm

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by andrei-8 » Jun 27 2019 5:31pm

Hello ! Changed the configuration of my bike, 36V MXSYS direct drive front wheel, set 72 v controller instead of 36 v, dynamics significantly increased, speed from 35 to 55 km h, flies up the hill, but also became more heated - to a maximum of 55-60 degrees on the covers after stopping after 10 minutes. Can anyone say approximately how much it will be on the winding of the motor, how far is the critical temperature? I do not want to engage in unnecessary activities in vain: to drill the lid, put the fan ...

User avatar
wturber   10 MW

10 MW
Posts: 2006
Joined: Aug 23 2017 8:52pm
Location: Fountain Hills,AZ
Contact:

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by wturber » Jun 27 2019 5:38pm

andrei-8 wrote:
Jun 27 2019 5:31pm
Hello ! Changed the configuration of my bike, 36V MXSYS direct drive front wheel, set 72 v controller instead of 36 v, dynamics significantly increased, speed from 35 to 55 km h, flies up the hill, but also became more heated - to a maximum of 55-60 degrees on the covers after stopping after 10 minutes. Can anyone say approximately how much it will be on the winding of the motor, how far is the critical temperature? I do not want to engage in unnecessary activities in vain: to drill the lid, put the fan ...
You may be able to extrapolate/guess from some of the information and test results provided here:
https://www.ebikes.ca/product-info/statorade.html

I think Statorade is a good, perhaps necessary, step in keeping a DD motor's core at a reasonable temperature.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

User avatar
justin_le   10 MW

10 MW
Posts: 2233
Joined: May 28 2007 3:27am
Location: Vancouver
Contact:

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by justin_le » Jul 04 2019 4:05am

andrei-8 wrote:
Jun 27 2019 5:31pm
to a maximum of 55-60 degrees on the covers after stopping after 10 minutes. Can anyone say approximately how much it will be on the winding of the motor, how far is the critical temperature?
If you know the elevatation profile that you were riding around then you can use the nearest hub motor that I have thermally modeled on our trip simulator here to get a good idea of what the motor core temperature is like for a given shell temp when the bike is underway.
https://www.ebikes.ca/tools/trip-simulator.html

Underway with most DD hub motors a shell temp of 55-60oC would means a very hot motor core, ex:
TripSim Core Shell Temp Examples.jpg
Once you stop riding the bike, then the motor shell temperature will increase quite rapidly even as the core temperature decreases since there is no longer any air flow on the motor shell. It will peak in 5-10 minutes, then it will decrease again, as you can see here from actual test data on a MXUS DD motor in our wind tunnel thermal characterization. It was running at 400 rpm / 40kph and then stopped where you see the power (red line) drop to zero.
MXUS Thermal Chars.jpg
Your best bet for sure is to install an actual temperature sensor inside the motor stator itself to really know what is going on with the core temperature.
Previously competed in the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver learning to be a dad with my Big Dummy Frame (yes This One, thanks ES!) with GMAC 10T rear hub motor, Phaserunner controller, and 52V 19Ah EM3EV pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

User avatar
DasDouble   100 kW

100 kW
Posts: 1152
Joined: Jul 12 2015 1:35pm
Location: GERMANIA :D

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by DasDouble » Sep 17 2019 6:01pm

Sorry for kidnapping the post, but does anyone remember where you could get these 3D printed files from? I remember having seen it on endless sphere, originally I guess from the russian forum but 1. don´t speak russian 2. can´t remember from where exactly.

I have a 3D printer now and want to test it out. Thanks a lot for help!
Attachments
WhatsApp Image 2018-04-16 at 22.56.46(1).jpeg
WhatsApp Image 2018-04-16 at 22.56.46(1).jpeg (37.96 KiB) Viewed 517 times
WhatsApp Image 2018-04-16 at 22.56.46.jpeg
WhatsApp Image 2018-04-16 at 22.56.46.jpeg (36.98 KiB) Viewed 517 times
Mechatronics-Engineering Student
-Built own ebike: ✔
-Built own 3.2kWh LiIon battery (300Amps): ✔
-Overtake Porsche with own Ebike: ✔
-Take off with ebike: ✖

~14kW, 3.2kWh LiIon, QS 205 8ml ff, hubsink

User avatar
Rix   100 GW

100 GW
Posts: 6655
Joined: Mar 29 2012 11:26am
Location: Fallon NV USA

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by Rix » Sep 18 2019 10:31am

DasDouble wrote:
Sep 17 2019 6:01pm
Sorry for kidnapping the post, but does anyone remember where you could get these 3D printed files from? I remember having seen it on endless sphere, originally I guess from the russian forum but 1. don´t speak russian 2. can´t remember from where exactly.

I have a 3D printer now and want to test it out. Thanks a lot for help!
This unit was developed in Russia, as you alluded too, and the one I had seen was on a Mac 10 hub motor running 6kw reliably.

Hummina Shadeeba   1 MW

1 MW
Posts: 1765
Joined: Apr 25 2014 10:26pm

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by Hummina Shadeeba » Sep 20 2019 9:52am

DasDouble wrote:
Sep 17 2019 6:01pm
Sorry for kidnapping the post, but does anyone remember where you could get these 3D printed files from? I remember having seen it on endless sphere, originally I guess from the russian forum but 1. don´t speak russian 2. can´t remember from where exactly.

I have a 3D printer now and want to test it out. Thanks a lot for help!

does this spin? wouldnt a scoop need to be stationary? if its spinning it's going to be throwing air out through centrifugal force in the same direction its trying to scoop it in

User avatar
wturber   10 MW

10 MW
Posts: 2006
Joined: Aug 23 2017 8:52pm
Location: Fountain Hills,AZ
Contact:

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by wturber » Sep 20 2019 10:15am

Hummina Shadeeba wrote:
Sep 20 2019 9:52am
DasDouble wrote:
Sep 17 2019 6:01pm
Sorry for kidnapping the post, but does anyone remember where you could get these 3D printed files from? I remember having seen it on endless sphere, originally I guess from the russian forum but 1. don´t speak russian 2. can´t remember from where exactly.

I have a 3D printer now and want to test it out. Thanks a lot for help!

does this spin? wouldnt a scoop need to be stationary? if its spinning it's going to be throwing air out through centrifugal force in the same direction its trying to scoop it in
As I recall, it is stationary.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

Hummina Shadeeba   1 MW

1 MW
Posts: 1765
Joined: Apr 25 2014 10:26pm

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by Hummina Shadeeba » Sep 20 2019 7:07pm

how much of the heat from the motor could be removed as radiant with black magnet plating and painted motor case. but there's no black just a dark grey at least.

User avatar
Cowardlyduck   100 MW

100 MW
Posts: 2633
Joined: Jun 26 2011 8:41pm
Location: Canberra, ACT, Australia

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by Cowardlyduck » Sep 20 2019 8:54pm

Hummina Shadeeba wrote:
Sep 20 2019 7:07pm
how much of the heat from the motor could be removed as radiant with black magnet plating and painted motor case. but there's no black just a dark grey at least.
I painted the inside of a hub black years ago for this same reason. No idea how effective it's been, but at the time I thought why not...4+ years and 15000km later that motor is still going strong on my daily commuter with no signs of overheating, mind you I only run it at 25% over spec.

Cheers
Custom made 18650/21700 battery packs

Modified Stealth Fighter - Force air cooled motor @ 6KW, Adaptto Mini-E. 49AH, 52V 18650 - 2.5Kwhr
Cowardlyducks - Stealth Fighter Videos

BikeE recumbent commuter - 9C, 6Fet Grinfineon, internal 17AH, 52V, + on-board solar.

Ebike Garage - My YouTube Ebike ramblings.

High Power LiPo wiring harnesses - 4P - XT90, HXT4mm, 5.5mm. 200Amp+ capable. Global shipping.

Hummina Shadeeba   1 MW

1 MW
Posts: 1765
Joined: Apr 25 2014 10:26pm

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by Hummina Shadeeba » Sep 22 2019 11:29am

What would be the breakdown of heat leaving the coils from a sealed motor?

Conductive transfer- the stator thermal conductivity sucks being electrical steel which is likely as bad thermally as electrically conductive as typical, with layers of epoxy as well.


Convective transfer- I've seen fans in a motor but forget was it sealed? If sealed and heating the air and then the air transferring the heat to the motor case, if that were effective it would seem a passive method with integrated blades in the motor rotor sides would be worth doing and maybe could set up a circular path for the air to be forced through at high speed,no?

Radiant heat transfer, I guess since no visible light would be infrared and maybe ultaviolet? NASA made some new carbon nanotube black paint to catch like 99% of radiation- nano-velvet. What electromagnetic radiation is catchable w just black and what would be emitted by the coils? Maybe the highly reflective magnets and rotor are bouncing and trapping it?

User avatar
Cowardlyduck   100 MW

100 MW
Posts: 2633
Joined: Jun 26 2011 8:41pm
Location: Canberra, ACT, Australia

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by Cowardlyduck » Sep 23 2019 3:44am

Hummina Shadeeba wrote:
Sep 22 2019 11:29am
Convective transfer- I've seen fans in a motor but forget was it sealed?
Yeah that was me and a few others:
viewtopic.php?f=30&t=56965&start=400#p1198704

Unfortunately a lot of the images were hosted on a site that went under...but here's a few I still have showing how I mounted the fans (12 of them) and cooling holes in the hub:
DSC_2427.jpg
DSC_2427.jpg (206.91 KiB) Viewed 313 times
DSC_2763.jpg
DSC_2763.jpg (281.79 KiB) Viewed 313 times
DSC_3209.JPG
DSC_3209.JPG (221.53 KiB) Viewed 313 times
I did this to several motor's (Leaf motor and HS4080) as well as adding ferro fluid. They are both still going strong to this day. :D

Cheers
Custom made 18650/21700 battery packs

Modified Stealth Fighter - Force air cooled motor @ 6KW, Adaptto Mini-E. 49AH, 52V 18650 - 2.5Kwhr
Cowardlyducks - Stealth Fighter Videos

BikeE recumbent commuter - 9C, 6Fet Grinfineon, internal 17AH, 52V, + on-board solar.

Ebike Garage - My YouTube Ebike ramblings.

High Power LiPo wiring harnesses - 4P - XT90, HXT4mm, 5.5mm. 200Amp+ capable. Global shipping.

John in CR   100 GW

100 GW
Posts: 13818
Joined: May 20 2008 12:58am
Location: Paradise

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by John in CR » Sep 23 2019 8:19pm

Hummina Shadeeba wrote:
Sep 22 2019 11:29am
What would be the breakdown of heat leaving the coils from a sealed motor?

Conductive transfer- the stator thermal conductivity sucks being electrical steel which is likely as bad thermally as electrically conductive as typical, with layers of epoxy as well.


Convective transfer- I've seen fans in a motor but forget was it sealed? If sealed and heating the air and then the air transferring the heat to the motor case, if that were effective it would seem a passive method with integrated blades in the motor rotor sides would be worth doing and maybe could set up a circular path for the air to be forced through at high speed,no?

Radiant heat transfer, I guess since no visible light would be infrared and maybe ultaviolet? NASA made some new carbon nanotube black paint to catch like 99% of radiation- nano-velvet. What electromagnetic radiation is catchable w just black and what would be emitted by the coils? Maybe the highly reflective magnets and rotor are bouncing and trapping it?
Some heat conducts from the stator out of the motor via the axle, but that's a pretty small amount due to the small outside surface area of the axle. Radiation is also pretty small due to the low temps involved. The lion's share of heat transfer is first convection to the inside surfaces, conduction through the magnets and metal to the outer surfaces, and then convection to the outside world.

I run extreme power, up to 31kw peak input, into some of my high efficiency hubmotors. On bikes I have with more than 17kw peak input, I ventilate them for the bulk of heat transfer by convection directly from the stator to the outside world. I tried a number of passive ventilation strategies with modest results until I tried taking air in on one side of the motor through small holes all over the side cover on the intake side, and larger holes or slots at the extreme perimeter of the cover on the exhaust side. The exhaust vents have radial blades in front of them to turn the motor itself into a centrifugal fan. A smoke test demonstrated that blades create flow into the intake side starts at about 10mph and gets so strong a high speeds that smoke was even drawn across the shell on the outside as well as through the motor.

This system works so well that I rarely see stator temps above 70°C, and with hard riding on mountain climbs the highest I've seen is 103°C, and that was up a continuous 20% grade accelerating hard up to 80kph after every switchback of the road. Without pushing them to failure, not even hubbies weighing almost 3X as much have exceeded the performance of my modded motors, and due to the relatively low internal temps I doubt even a liquid cooled system could fare better.

Here's a shot of the exhaust side of one:
Hubmonster slots and blades.JPG
Hubmonster slots and blades.JPG (26.92 KiB) Viewed 284 times

User avatar
Cowardlyduck   100 MW

100 MW
Posts: 2633
Joined: Jun 26 2011 8:41pm
Location: Canberra, ACT, Australia

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by Cowardlyduck » Sep 24 2019 4:12am

Yeah, certainly Johns method works also...if you ride like him. aka high speeds, on road where the centrifugal forces can actually do something.

In my case I ride predominantly below 50kph and lots of 20-30kph off-road up large/long hills. Not ideal for a hub motor I know, but to make it work without resorting to a giant anchor, the fans work for me. :)

I will also add, that for 90%+ of people simply adding Ferro Fluid + HubSinks is sufficient, and what I would recommend for most now. In my and Johns case we did all this before Ferro Fluid and Hubsinks were a thing.

Cheers
Custom made 18650/21700 battery packs

Modified Stealth Fighter - Force air cooled motor @ 6KW, Adaptto Mini-E. 49AH, 52V 18650 - 2.5Kwhr
Cowardlyducks - Stealth Fighter Videos

BikeE recumbent commuter - 9C, 6Fet Grinfineon, internal 17AH, 52V, + on-board solar.

Ebike Garage - My YouTube Ebike ramblings.

High Power LiPo wiring harnesses - 4P - XT90, HXT4mm, 5.5mm. 200Amp+ capable. Global shipping.

John in CR   100 GW

100 GW
Posts: 13818
Joined: May 20 2008 12:58am
Location: Paradise

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by John in CR » Sep 24 2019 12:10pm

Cowardlyduck wrote:
Sep 24 2019 4:12am
Yeah, certainly Johns method works also...if you ride like him. aka high speeds, on road where the centrifugal forces can actually do something.

In my case I ride predominantly below 50kph and lots of 20-30kph off-road up large/long hills. Not ideal for a hub motor I know, but to make it work without resorting to a giant anchor, the fans work for me. :)

I will also add, that for 90%+ of people simply adding Ferro Fluid + HubSinks is sufficient, and what I would recommend for most now. In my and Johns case we did all this before Ferro Fluid and Hubsinks were a thing.

Cheers
I only go fast on the highway. Most is in town, lot's of stop and go with speeds generally 20-30 and some 40's on bigger roads, and that really heats up motors. My motors flow air above 10mph. Cars go slower here than stateside. Most highway limits are 80kph (50mph) with some empty stretches 100kph (62 mph). That is with smaller wheels 19" up to a biggest on my enduro of 21.5", so higher rpm at same speed. If my blade thing wouldn't have worked so well I would have gone actively blown, but thank goodness I don't have to listen to fans or change them when broken. My motors don't have any space for fans...very little internal air compared to common DD hubbies. That makes them transfer heat when sealed, and I can get away with sealed on my commuter rocket getting 17kw peak geared with the 16" OD wheel for a top end of only 65mph or so. On the 20km commute in to the shop, I use to douse it with water upon arrival when I rode it hard on the highway with hard launches at it's 3 lights. The way in was a net climb of 40mm with wind in my face so it used 30-50% more energy on the way in depending how I rode each way.

Hummina Shadeeba   1 MW

1 MW
Posts: 1765
Joined: Apr 25 2014 10:26pm

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by Hummina Shadeeba » Sep 24 2019 2:55pm

An open motor has a great ability to be cooled with a passive or active fan as you guys did. And a motor case with little air shows to transfer heat better to the case. How much heat could be transferred to the case through radiant heating if an ideal black lining were on the magnets and all in the case? And how much heat could be transferred to the case through a sealed motor with internal blades by transferring the heat from windings to the air and then the case?
An open motor seems great for passive cooling potential but an open skateboard motor will be picking up dust and want to keep it sealed.

Does anyone do a passive fan inside a sealed motor with blades on either side circulating air through the airgap and then back through gaps within the windings? That paired with the all black inside seems worth a shot.

Looking above in the thread at the large difference temp between the motor case and actual windings, and with the deterioration of winding enamel with heat and just increased resistance with increasing heat..what's ur actual winding temps and what are u considering acceptable and anything concrete worth looking towards as a guide? In practice I'll cook bearing grease if not the thick heat resistant stuff but otherwise not obvious. I plan to put temp sensors in.

Just talked to Epic Resins that do winding epoxy n don't even know if their thin unfilled stuff will increase the dialectic strength and winding longevity. Anyone had good experience w thermally conductive epoxy coating or potting?

User avatar
justin_le   10 MW

10 MW
Posts: 2233
Joined: May 28 2007 3:27am
Location: Vancouver
Contact:

Re: Definitive Tests on the Heating and Cooling of Hub Motors

Post by justin_le » Sep 30 2019 5:31pm

Hummina Shadeeba wrote:
Sep 24 2019 2:55pm
An open motor has a great ability to be cooled with a passive or active fan as you guys did. And a motor case with little air shows to transfer heat better to the case. How much heat could be transferred to the case through radiant heating if an ideal black lining were on the magnets and all in the case?
You can see my test results here on a large DD hub motor with vent holes:
viewtopic.php?f=2&t=48753&p=1095507#p1095507

Have a read of that.

The thermal improvement by having the motor insides fully painted in black was slight, going from 0.154 oC/watt to 0.147 oC/watt, so only about 2% better. If we started with a hub that didn't have open vent holes on it in the first place then I suspect the percentage improvement would be higher as there wouldn't be as much convective cooling from outside air so the effect of radiant exchange would be higher as a percentage. Probably like 5-6% if I was to hazard a guess. It's not nearly as much as actual convective transfer from a fluid in the gap, but I suppose even a small improvement is better than nothing!
Previously competed in the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver learning to be a dad with my Big Dummy Frame (yes This One, thanks ES!) with GMAC 10T rear hub motor, Phaserunner controller, and 52V 19Ah EM3EV pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

Post Reply