Definitive Tests on the Heating and Cooling of Hub Motors

[Arlo1]

This is what I use it was recommended by Big moose and its the right stuff.

 

[el Raptor]

Hi.
I have spoken with Loctite manufactures and they recommend me this
But i can see this product it is for only 150ºC....
[youtube]Pj_hyq5dIZ0[/youtube]

And here other with 180ºC and 190ºC:
(Sorry español this)
1) Loctite AA 3342 resiste exposiciones térmicas de hasta 180ºC, así que en ese sentido usted no debería tener problemas con este adhesivo. La Ficha Técnica habla del activador Loctite SF 7386 (u otros activadores parecidos) como formato más industrial, pero para el uso que usted le va a dar puede emplear perfectamente el aerosol de 150 m de Loctite SF 7388, que le saldrá más económico.

2) Loctite EA 9492 – adhesivo estructural bicomponente también apto para esta aplicación y que resiste en continuo hasta 190ºC, aprox, pero usted necesitará la pistola.

 

[el Raptor]

finally I preferred to send the engine to Zelena.
Nobody better than them for restore this engine.
now only wait...

 

[Merlin]

wow thats maybe the price of a new hub

 

[el Raptor]

This is my Machine:

Raptor 140, Adappto E-midi, Cromotor, Batery 20S17P, etc, etc,...

 

[fechter]

This is my Machine:

Raptor 140, Adappto E-midi, Cromotor, Batery 20S17P, etc, etc,...

Nice scenery. Where is that?

Most magnets are not rated for over 150C and will lose their magnetism if they get too hot. Some magnets are only good for 80C.

 

[Offroader]

This is what I use it was recommended by Big moose and its the right stuff.

When the epoxy failed on my magnets due to over heating, I used the Hysol EA9394 also based on Big Moose post here. No issues since and I push the motor to 130C many times.

The stock epoxy is really cheap stuff they use over in china. They had the temp prove epoxied to the side of the stator, and that epoxy just broke away like dirt when touching it.

 

[liveforphysics]

This is my Machine:

Raptor 140, Adappto E-midi, Cromotor, Batery 20S17P, etc, etc,...

Nice scenery. Where is that?

Most magnets are not rated for over 150C and will lose their magnetism if they get too hot. Some magnets are only good for 80C.

Something interesting I've learned in addition the Currie temp value, it also depends on flux induced stress the magnet is under. If a magnet is out sitting on a table with no iron near by, it's field has to extend out in large loops to complete it's magnetic loop. In this state, it will fail from temperature most easily and most completely.

When the magnet is bonded to adequate back-iron to tightly lens flux to complete it's magnetic loop, it can often survive higher temperatures in this environment without a de-mag event, and if it is pushed into de-mag, it often decays to a still functional point of perhaps half flux (2x BEMF Kv) rather than failing clear to almost nothing as magnets sitting away from iron tend to do if exposed to the same temperature for the same amount of time.

Cedric Lynch first told me this around 5-6 years ago, along with a handful more things at the time I had never heard of in any engineering texts on EM machines. I didn't believe him at the time he was telling me incredible things about EM device function that I had never seen or heard elsewhere. Filling in the gaps of the last 5-6years since of exploring the boundaries of various EV drivetrains, and I now have come to see for myself through the experiences of learning the hard-way that he was correct in perhaps everything he ever told me about motors in the handful of hours I had the pleasure of speaking with him.

He is so much more brilliant in the EM side of motor design than any other professor/engineer I've known, it would be a bargain for any serious EV company to jump through whatever eccentric requirements he may have to accept working somewhere, like being barefoot and using human powered tools and no CAD. That man has something special/genetic/mental going on and seems to see EM fields in his mind (like Nikola Tesla).

In the spirit of "definitive tests" on hubmotor cooling, I would love to see a trend-line for magnetic particle density vs heat-transfer. If more particle density directly corresponds with more flux induced fluid motion, we should explore the upper bounds of fluid motion rates to maintain useful cooling function up to higher RPM levels. In the spirit of definitive, a comparison of useful RPM range vs base fluid density could be compared with the particle density data to give a 3D plot for optimizing the fluid base and particle density.

Even a crude high speed camera with strong lighting should be able to get footage of what's happening in the gap and over what useful RPM range.

 

[Cowardlyduck]

Well I just did this to my HS4080. Surely this would help keep the magnet ring cooler.

The irony of doing this now is that I just removed all the Ferro Fluid from this motor after it did not work out with it being vented. I already had all the stuff to do the heat-sink mod though, and it will still make some difference so who cares.
There are 8 heat-sinks total, roughly evenly spaced. To attach them, since the thermal epoxy takes a couple of hours to start setting, I had to do them one at a time spaced out over a long period. That wasn't a problem as I just quickly did one at a time in-between other tasks over the course of a week. I also just shoved a small piece of cloth around each heat-sink when it was in place to prevent it moving while it set, usually over night.
I used far less epoxy than I thought I would with only 3/4 of one set of 7g tubes being enough for all 8. I'm going to do my Leaf motor next, and will probably use 12 or more heat-sinks on it.

Cheers

 

[parabellum]

Are all spokes still replaceable?

 

[fechter]

Something interesting I've learned in addition the Currie temp value, it also depends on flux induced stress the magnet is under. If a magnet is out sitting on a table with no iron near by, it's field has to extend out in large loops to complete it's magnetic loop. In this state, it will fail from temperature most easily and most completely.

When the magnet is bonded to adequate back-iron to tightly lens flux to complete it's magnetic loop, it can often survive higher temperatures in this environment without a de-mag event, and if it is pushed into de-mag, it often decays to a still functional point of perhaps half flux (2x BEMF Kv) rather than failing clear to almost nothing as magnets sitting away from iron tend to do if exposed to the same temperature for the same amount of time.

Yes, this is true. In the days before Neodymium magnets, simply removing the rotor from the stator could cause the magnets to lose strength at room temperature. Neo magnets won't do this, even if left out for a long time at room temperature, but will demag at a lower temperature than if in a tight flux loop. It also depends on the flux from the stator when they are repelling. Super high currents can cause demagnetization at a lower temperature than if the motor was just heated at a low current. I demagnetized several motors with old-school ceramic magnets by running too much current.

It's amazing how much magnets have improved over the last 20 years.

 

[macribs]

How much is too much current?

 

[el Raptor]

This is my Machine:

Raptor 140, Adappto E-midi, Cromotor, Batery 20S17P, etc, etc,...

Nice scenery. Where is that?

Most magnets are not rated for over 150C and will lose their magnetism if they get too hot. Some magnets are only good for 80C.

I am live at Castro Urdiales, Cantabria, España!!

 

[Hyena]

I knew it. Do you know what they call a raptor in Spanish ?
El Raptor.
/deadpool

 

[Cowardlyduck]

Are all spokes still replaceable?

Probably not, but they are 10g spokes and I've never had one break so I'm not really worried.

Cheers

 

[fechter]

How much is too much current?

With ceramic magnets, it's about double the motor nameplate amp rating. With NdFeB magnets, I've never seen it happen. The windings burn out first. I have demagnetized some by placing them in the bore of a 3T MRI scanner. I was testing to see how hard a small one will pull in a MRI as part of a safety test. It was somewhat less than I expected but still impressive. If the magnet stayed aligned with the MRI field, it was OK. It demagnetized when I forced it into the reverse direction (repelling). After that it couldn't even pick up a paperclip. In a motor, half the magnet is attracting and half is repelling. It's the repelling part that can get demagnetized.

 

[el Raptor]

I knew it. Do you know what they call a raptor in Spanish ?
El Raptor.
/deadpool

you can to see how i build my raptor here:
http://www.enbicielectrica.com/t6292p150-presentacion-raptor

 

[sketchism]

I'm doing some testing on these hub heatsinks and ill be able to post some meaningful conclusive results shortly, but so far adding a heatsink/radiator been amazingly effective, in ride tests on the prototypes we've been seeing up to 70-80% improvement in thermal handling & even greater shedding at higher temps due to a bigger Delta T and high thermal diffusivity when attached with thermal paste/epoxy, when they're ready ill have some excess for cost soon in 15 and 30mm widths.

I have the magnet ring flange clearance for the MXUS, Leaf 1500w, 3540, and QS205 i'm always open to collecting more data if anyone's doesn't have at least 15mm of flat between the flanges let me know

While i don’t have much experience in thermal analysis, the law of conservation of energy dictates that the heat generated by the heat source must be equal to the heat dissipated by the heatsink to remain neutral under steady state conditions, so while we can’t dissipate all of the excess heat from running a hub motor at 14-20kw peaks and treating them like a room heater, we can do our best to improve the thermal path from stator to the outside air especially during varying loads to bring the mean temp down as much and as quickly as possible.

In my prototype testing with 4X smaller sinks around the hub, each one had 69 fins, with a length of 30mm and width of 20mm & 1mm fin thickness (it varies form bottom to top but 1mm is the mean) and a total length per sink of 145mm *4 Sinks which gives us a fin surface area of 1300 mm^2 times a total of 264 fins
They’re made of aluminium which has a general thermal conductivity of 205 W/m*c and glued on to the ring with Arctic Silver epoxy with approx the same conductivity, we’ll use a figure of 195 to allow for an imperfect thermal connection.
At 100 DegC hub temp and 21DegC outside we get an alpha T, temperature difference of 78 DegC
The convective heat transfer coefficient of air is HTC = 10.45 - v + 10 v1/2 (2)
Where v = the relative speed of the object through the air (m/s)
(50kph is 13.8889m/s) and we’ll have turbulent flow so the approx HTC across a wider range of speeds is about 20 W/m2*c
Using the formula for convection Q= (K*Ab*nΛT) It looks like the heatsinks, at around 50kph cruising speed with the hub at 100c on a 20 degree day, will be shedding an additional 500-600 Watts which is really quite efficient for an unpowered addition weighing only 300 grams.

With a thermal conductivity of 0.195 W / (mm C) and Convection coefficient during rotation of 13W /mm2 and and ambient of 20c the final versions could shed up to 1000W of heat at speed.

In real-world testing we achieved an even better result than we projected, reducing the temps on identical rides repeatedly, from 127C to 48C at the same points on the ride under identical conditions, effetively solving any thermal issues even on intense rides, so i thought it would be a good idea to design these and maybe make it a bit easier for everyone else to solve their heat issues permanently.

in short, radiating heatsinks work well,especially adding almost 3sq ft of surface area, so i'm building some better ones

 

[Cowardlyduck]

Good stuff Sketch. I'm glad I'm not the only one who's trying something out with these heat-sinks.
Because I'm just adding them to all my other pre-existing cooling mods, it's hard for me to quantify there effectiveness, but it seems like they are pretty dam effective, even just arbitrarily.

I actually just re-did the job on my Leaf motor over the weekend with thermal epoxy (previous was just heat-pads).

Cheers

 

[madin88]

Those Heatsinks look fantastic. Nice find man

about the reliability of FF:

i recently have seen reports from users that after short time of usage the FF evaporates and those nice looking grubs disappear.
IIRC that was in CLOSED motors. Not sure if it was the synthetic or ester based Statorade.

 

[sketchism]

Good stuff Sketch. I'm glad I'm not the only one who's trying something out with these heat-sinks.
Because I'm just adding them to all my other pre-existing cooling mods, it's hard for me to quantify there effectiveness, but it seems like they are pretty dam effective, even just arbitrarily.

Cheers

Your ones have come up a lot during discussion about them too! The prototype i used was done similar to yours except i managed to bend them around the hub more through luck than talent lol but the testing has been exciting, adding around 3sqft of surface area to the ring was bound to do something, but the results so-far have been like an entirely new motor.

The hills where i was hitting thermal limits at 120c at 14-kw daily which inspired me to start looking for cooling options i can now ride almost indefinitely. temps start dropping as soon as i apply less than 5kw and i have only seen a high of 95 an an average of 80c on those same rides under the same conditions.

i'll be doing some proper testing on a new motor and plotting the results shortly (or i'm happy to send some to justin to test categorically?)

 

[parabellum]

@ sketchism
Cool sinks! What is the hub diameter they work on?
How do you fix them to the hub using thermal paste?
Is there some fancy clamp not present on the picture or screws?
If screws, how do you manage to insert and tighten them?

 

[sketchism]

@ sketchism
Cool sinks! What is the hub diameter they work on?
How do you fix them to the hub using thermal paste?
Is there some fancy clamp not present on the picture or screws?
If screws, how do you manage to insert and tighten them?

At the moment i'm still finalising the design, i played with having them slide over and be fixed in place using a 2 part Arctic silver thermal epoxy, but in testing i found the glue was so good they have become a permanent part of the hub.

They have a tab on each side and short M5 bolt with a nylock nut to apply clamping pressure around the hub allowing much cheaper CPU thermal paste to be used and making them removable. (i still may have to shorten the fins behind the tab for easier access)

These are standard DD hub diameter but can be 15 or 30mm wide to suit stator widths and flange gaps, MXUS,leaf,QS, Cro etc, luckily they all seem to use the same backing iron pipe OD.

 

[parabellum]

They have a tab on each side and short M5 bolt with a nylock nut to apply clamping pressure around the hub allowing much cheaper CPU thermal paste to be used and making them removable. (i still may have to shorten the fins behind the tab for easier access)

Thanks. Yea, removing 2 fins and 8mm wrench head bolt should leave me without questions. Removable sinks is a good idea, because of spoke replacement game and hub swaps. Good work. Exited to see them in sales section soon.

 

[sketchism]

They have a tab on each side and short M5 bolt with a nylock nut to apply clamping pressure around the hub allowing much cheaper CPU thermal paste to be used and making them removable. (i still may have to shorten the fins behind the tab for easier access)

Thanks. Yea, removing 2 fins and 8mm wrench head bolt should leave me without questions. Removable sinks is a good idea, because of spoke replacement game and hub swaps. Good work. Exited to see them in sales section soon.

This looks like it gives us room to get one in and fasten it

sorry my bolt has no thread