Definitive Tests on the Heating and Cooling of Hub Motors

[Merlin]

yesterday was my first ride to work.
riding home i pushed a bit faster as normal to heat the hubbie.....its unbelivable stuff.
27°c outside temp. 32wh/km. last 4km 108km/h full throttle.

at home CA shows 85°c and fallin.
a few minutes later it was back to 75°c...measured Case Temp with ir thermo = 60° (on the Magnet Ring)
the sideplates had 55°

my experience with all motors are:

60°c Case = 1,5/2x Temp inside.

now shell and core are very close. i will measure more MagnetRing/Stator temps.

thats only my first test. i will ride my wooden hills to compare.
if the heat transfer to the ring is that good, i will try a magnet-ring-waterbottle-cool-down next time.
i tried this before with a 3540.....and to be honest. it does not work

lets try some things.....
if that helps a bit maybe a "scottoiler" (filled with water) could be a monster cooling solution

 

[ziltoid81]

Again we need that like button..... :wink:

These specs are awesome, the 4t performs better than my 5t i guess.
Even the consumption is lower.......in a bigger wheel.

Maybe you can glue some heatsinks on the case between the spokes.
I will do that.

With ff there is no need to make this motor so heavy.
QS could design it lighter with less metal at the shell but with lighter aluminium heatsinks.
A special ff edition......

 

[macribs]

1+ for FF Edition. Could be possible to shave off 2-3 kilos from the back iron and flanges between the spoke holes hopefully.
A clamp style heat sink like AFT motors uses, clamp it on back iron between flanges. Could even be done with embedded heat tubes.

This is the heat sink for AFT motors. Something like this would be wonderful and should help with cooling.

 

[madin88]

With ff there is no need to make this motor so heavy.
QS could design it lighter with less metal at the shell but with lighter aluminium heatsinks.
A special ff edition......

for best strength / weight, the spoke flange would need to be on the sidecovers.
if someone decide to use larger spokes (would say bigger than 12GA or M3) and lacing the motor into a moped rim with properly tension, the ring-shaped flange must hold high forces so it necessarily must have big wall thickness which makes it heavy.

thats only a guess, but i think the magnets from merlins motor could have become loose due to the forces from the spokes pulling on the ring.
I know that cromotor with the loose magnets i had to deal with was laced into a moped rim with PROPERLY tensioned 4mm spokes (thats 8 or 9GA i think).
now imagine the forces on the ring! the few bolts to the sidecover don't add much to strength..

 

[parabellum]

thats only a guess, but i think the magnets from merlins motor could have become loose

I got same result on Mxus 500 motors (in moto rims) after they where oil filled , 3 to be specific, other 4 (with no oil) are holding magnets just fine, oil filled hs35 did not have this problem. I believe it is glue to oil incompatibility in my case.
Did merlin use any oil, FF or other substance that could dissolve the glue?
P.S. There are many DD hubs (cros) in Moto rims doing just fine.

 

[Merlin]

....but after cooling down the "epoxy" is rock solid and you cant move the magnets anymore?!

edit:

no this v3 cro had never seen anything other then air inside. this motor has/had about 15000km on it.

 

[parabellum]

....but after cooling down the "epoxy" is rock solid and you cant move the magnets anymore?!

If you are asking me. Mxus 500 magnets got loose over few day/weeks filled with oil . You just turn throttle in the morning (cold motor) and hear your magnets rotate with the magnetic field inside the hub, with no forward motion of the bike.
After disassembly, the original glue looks more like very hard rubber cement and just glueing magnets back in with cheap cold weld epoxy fixes it forever. Cleaning from oil is a pain. I tried to re glue magnets on new motor, before oil filling, but it seems next to impossible to get magnets off as is, before oil destroys the glue. Have not tried any solvents though.

 

[Cowardlyduck]

I decided to add some extra thermal heat shedding capability to my Leaf Motor and since I added Ferro Fluid, it makes more sense to do now.

So I bough 50 of these 25x25mm black heat-sinks for this and other projects:

And a bunch of cheap 1.5mm thick thermal padding
I cut up the thermal padding to match the heat-sinks:

Then stuck them all around the magnet ring and tied them down with some thick string:

It was pretty fiddly/tricky to get all the heat-sinks to stay in place while I tied it all down as the thermal padding doesn't really provide much sticking force and it was a game of catch up for a while until they all stopped falling off.

However the end result was worth it, looks great and feels pretty solid:

I also added some glue in the only gaps left to lock in the threads and prevent movement:

Given the hottest I was regularly seeing the magnet ring get before was about 75C, I don't expect a huge improvement from just these alone, but combined with the Ferro Fluid, side cover vents and 7 x cooling fans I'm running with, I think only the most extreme use cases will cause me heat problems now.

Cheers

 

[Merlin]

...and this is it how it looks when magic appears

[youtube]OYlhbc5iW_E[/youtube]

 

[Mammalian04]

Nice! How many ounces did you use? (Sorry if you said in the video, I can't use audio here).

 

[markz]

Cowardlyduck -

I don't expect a huge improvement from just these alone

So I bought 50 of these 25x25mm black heat-sinks for this and other projects:

Whats the height on those?



WOW! I hope those were not the ones you bought. There has got to be cheaper ones out there.
Otherwise, that is an expensive modification.

 

[Merlin]

Nice! How many ounces did you use? (Sorry if you said in the video, I can't use audio here).

ounces, jesus...i dont know iam a metric guy

canada is selling milliliters...10 of them, i'll used 7ml for this motor.

 

[Mammalian04]

Thanks Merlin. Sorry, I meant ML.

So is the general wisdom to use pullers and open the motor for this or is anyone drilling a hole like Grin started out doing?

 

[Black6spdZ]

so a mix if printer toner and oil "ferrofluid" is better than ATF now? The ferrofluid thing, would the solid like properties of it in the presence of a magnetic field create substantial drag? Does it also actually bridge between the stator and rotor to conduct the heat?

 

[Mammalian04]

so a mix if printer toner and oil "ferrofluid" is better than ATF now? The ferrofluid thing, would the solid like properties of it in the presence of a magnetic field create substantial drag? Does it also actually bridge between the stator and rotor to conduct the heat?

To save you a bunch of reading in this thread, yes. While an ATF bath "may" cool better with the proper setup, there are a whole host of problems with sealing that many don't really want to deal with. Justin was on track to test the oil bath cooling but I don't know the ultimate outcome. Either way, this seems to be a simpler solution with good results.

Regarding increased drag, it is minimal up to a certain point. In the test MXUS test motor, 5ml seemed to be the sweet spot. More than that produced greatly diminished heat shedding properties while the minimal drag began to increase more steeply.

 

[Cowardlyduck]

Whats the height on those?

10mm.

WOW! I hope those were not the ones you bought. There has got to be cheaper ones out there.
Otherwise, that is an expensive modification.

They were only $20USD for 50 and I used them for more than just this project, so not too expensive IMO.

Cheers

 

[Merlin]

Thanks Merlin. Sorry, I meant ML.

So is the general wisdom to use pullers and open the motor for this or is anyone drilling a hole like Grin started out doing?

dont know if some aluminium debris from drilling sideplates are a problem.
justin just drilled a hole. so it looks ok.....but give your hubbie another hour of devotion and take a look inside

 

[macribs]

You might be able to just drill without opening. If you drill just a little each time and use ie vacuum to remove drill shavings as you ease through the side wall of the side cover. Thing is those covers are not really that thick and it might be hard to drill with several stops to remove drill shaving and debris.

 

[Merlin]

i will install next week this Gore Valve....
iam a bit snoopy how it looks after some miles riding with that stuff.

 

[macribs]

i will install next week this Gore Valve....
iam a bit snoopy how it looks after some miles riding with that stuff.

Why Gore Valve? Is FF leaking out from the motor?

 

[spinningmagnets]

Goretex fabric allows air to pass in and out of the motor (but not oil or water), which keeps the interior air pressure the same as the outside regardless of heating and cool-down.

One of the surprising effects that Justin documented by doing pure research (and publishing it) was that as the interior of the motor gets hot and then cools down, a surprising amount of humidity was drawn into the interior of the hub through the phase wires. There is actually enough air-space between the strands to allow flow. Moisture would condense inside the hub, creating rust. Once re-heated on the next run, the resident moisture would evaporate.

Many ways to deal with this, but the general consensus has been that some type of 2-way vent (coupled with a rust-proof interior coating) is the best bang for your buck.

 

[macribs]

Oh I just went the easy way and drilled a tiny hole in the side cover as small as possible
Hopefully it is small enough to keep debris out and big enough to even out the pressure.
I did varnish and pint the motors internals so not really worried.

 

[Samd]

Yeah I just drill small holes in my motors too. Small plug of silicone to close. Opening a motor is a waste of time that could be spent riding.


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[Samd]

so a mix if printer toner and oil "ferrofluid" is better than ATF now? The ferrofluid thing, would the solid like properties of it in the presence of a magnetic field create substantial drag? Does it also actually bridge between the stator and rotor to conduct the heat?

Specifically MICR toner.


Sent from my iPhone using Tapatalk

 

[Black6spdZ]

so a mix if printer toner and oil "ferrofluid" is better than ATF now? The ferrofluid thing, would the solid like properties of it in the presence of a magnetic field create substantial drag? Does it also actually bridge between the stator and rotor to conduct the heat?

Specifically MICR toner.


Sent from my iPhone using Tapatalk

and a dash of Tetra-methyl Ammonium Hydroxide?