Definitive Tests on the Heating and Cooling of Hub Motors

[Samd]

There's a lot of resources on the web for making your own FF.


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[parabellum]

There's a lot of resources on the web for making your own FF.


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Yes, it will be something in between clumpy, soapy oil mess and cheap fleabay FF that evaporates in a day at room temperature being not geometrically sealed opposite to 200C stable FF that is guaranteed to hold 10 years in shaky, hot and not sealed speaker coil/magnet assembly. I know only 1 company producing that stuff.
Do you have any link to former magic recipe?

 

[Merlin]

+1

nothing more to say.

even the ready to buy FF on ebay is just to play with. drip it on your desk, come back 2-3 hours. you will find only a dry dark spot.
cmon guys really? 25 bugs for THE cooling revolution. Justin find out, make a lot of tests, shared with us for frocking free....

and you want to cook your own FF to safe a few bugs on your 5000$ bike?

 

[macribs]

1+ what he said.
If nothing else buy the FF from Justin out of loyalty for all the work in this single thread alone.

 

[Samd]

No I want to make it while he's out of stock. And he's reselling it based on another persons idea by simply rebottling a standard acoustic grade ferrofluid so go easy.

You've got macribs handing the Chinese concentric bb design tips in the copyshit frame thread and I'm somehow the antichrist for having a play around in DIY ferrofluid and cutting people's lunch?
I can't even.


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[parabellum]

by simply rebottling a standard acoustic grade ferrofluid

Any cheaper source of acoustic grade ferrofluid? I have personally not seen cheaper then Justins rebottling by now.

 

[madin88]

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

Dude, i had exactly the same idea and already bought a few^^
such valve could be really helpful against moisture problems inside sealed motors. the pressure differences can be huge due to the big temperature differences.

from where you have bought yours?
mine i have from here: http://www.cycle-analyst.de
this guy installs them on CA

 

[macribs]

@samd Didn't mean for it to be harsh or critic of anyones action. It was only encouragement to support Justin if possible. As a little thank you to him for all the testing Justin has put into this great thread. I am all for any DIY approach for e-bikes, but the statorade I figured would be possible to ship across oceans without costing an arm and a leg due to its log weight and volume. I know for heavy or large volume parts, shipping across oceans rapidly adds costs, and when dealing with custom fee's, handling costs, taxes and VAT pretty soon ends up almost/more then doubling the initial part costs.

 

[Offroader]

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

Merlin did you ever do the wooden hill test like you mentioned?

 

[Cowardlyduck]

I finally got around to opening up my HS4080 to see how it had faired with Ferro Fluid (Statorade) together with venting and fan cooling.

Well, the pictures speak for themselves.
Before cleaning:

The dirt build-up isn't as bad as I was expecting TBH. I am a little surprised at how little of the Ferro Fluid was left however. I had hoped more of it would stick around, and I'm honestly not sure how it left the motor given how aggressively it sticks to the magnets.

After cleaning:

The surprising thing for me was that when I went to clean it up (with wet wipes), the red varnish wiped off also, but only on the steel surfaces. It did not wipe off the copper windings. Interesting!
I can't recall weather I used type A or B (Synthetic or Ester based) on this motor as I had one of each and used them both on different motors....I may have made mention of it earlier in this thread if that matters to anyone. I think, from memory I used about 5-6ml...maybe that wasn't enough?

Many people are probably thinking it was obvious that this would happen, however I needed to try it to be sure myself. I knew this would happen to some degree, but how fast, how much and what kind of impact were the real unanswered questions.
I used the motor for about 4 months and probably put about 800km on it, mostly off-road, a few times in the rain.
It did not get hotter than about 85C during this time as the motor has another strange problem where power drops off over this temperature. I think it could be the heat-shrink softening in the section through the axle and the phases may be shorting...really not sure TBH.

It will be interesting to see the results from my other 2 motor's in similar situations.
I have my Leaf motor also with Fans and Ferro Fluid, however I used slightly more Ferro Fluid, and the vent holes are smaller.
The other motor is a 28mm generic Golden motor (9C clone) that is only vented on one side with no fans, however is ridden almost daily on the road on my Recumbent commuter.

I won't be doing this again as the increased cooling performance seen was not that great in comparison to the fan cooling. Perhaps that was because the Ferro Fluid didn't stick around, however I did arbitrarily test it straight after adding the Ferro Fluid and only saw 5-10C decrease in temps while running my fans vs no Ferro Fluid.

All in all, it was a good little experiment and I'm glad I was able to easily undo it with no permanent damage to my motor.

Cheers

 

[Merlin]

Merlin did you ever do the wooden hill test like you mentioned?

sry, not really...just speed shit tested. the buyer of my frame was faster, so atm i have no big bike to ride and iam waiting of an answer from ziva *doh!

 

[madin88]

I want to share a few pics of my MXUS after adding 6ml of FF. Additionally i have added a pressure valve and completely sealed it up.
looking forward to see how it performs

thats only a guess now, but i think if the motor operates, the FF will be pulled from the magnets to the stator and the greater the flux densitiy (thus torque), the more it will move.
because of that and due to the fact that it everywhere leaves oil stains, i'm afraid it could sooner or later disappear somewhere in the stator (between lams for instance), but as said, it's only a guess from me.

 

[ecycler]

I have a batch of ferrofluid that I made a while back and have been testing. So far it is proving to work as well as the results from Justin's tests. I will post some more data soon and my methods.

 

[ecycler]

Also, I want to come to SamD's defense. Why is it a problem if he or I want to test other formulas or types of ferrofluid? This is not a novel concept or patented use case... I see it is no different as any other product whether you build or buy it from wherever you want.

 

[macribs]

Let me be the first to apologize for the comments about samd's Ferrofluid. I misread and thought it was to make a competing product to sell to others.
And that was why I thought it was kind of sneaky, seen in the light of what huge amount of work Justin did for this thread and for the community with all the testing.
After more thought about the subject I do realize that FF is not Justin's monopoly, and like every niche competitors are to be expected.

So, samd sorry for the grumpy comments. I publicly retract my previous statement.

 

[parabellum]

I have a batch of ferrofluid that I made a while back and have been testing. So far it is proving to work as well as the results from Justin's tests. I will post some more data soon and my methods.

Cool, you will be my hero if what you write turns to be truth. As Justin got out of stock I passed weeks in the net trying to find any FF recipe that would work at least for a month in ambient going up to 120C. Have not found a single success story. There may also be a reason this stuff is so expensive.

 

[Samd]

Ferrofluid in bulk retails at $1.50 per ml from the manufacturer plus freight, GST and import fees. Then the cost to put it to a syringe. And you have to buy 1000ml.

I agree that it's cheap from Canada and would always support the owner of this forum even if the idea came from a few audio enthusiasts in this thread.

But the freight to our part of the world doubles it even when it is in stock guys. If we want to make ferrofluid affordable for the masses then a home few solution would be good.

I'm finding my own batch very lumpy.

Whatever you do don't use efh1 off eBay. The flash point is gonna make your back wheel go bang at 80 Celsius.


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[imsamib]

Ebike commuter, It's summer. The hottest day yet this year, 99 degrees F resulted in some brief shutdowns. When the ambient temp is around 85 F or less I experience no problems. I was considering passive cooling solutions like heat sinks and painting the shiny silver colored motor black, even just a wet sponge around hub axle for evaporative cooling. I think I am right to say that passive cooling techniques will only lower engine temperatures to the ambient temperature [at best]. Drilling holes in the motor casing will only expose it to hot air , moisture, dirt and insects. Heat sinks don't work if the environment you are sinking the heat to is already near the optimal temp for the engine.

I am making ice packs with alcohol water in zip lock bags. Planning to use shaped swamp cooler pad sponges and make icepack donuts to cover the outer motor parts on each side and make a long strip icepack to leave on the axle when riding. Before riding I'll put thr donuts on for 15 minutes, put them back on at my mid trip stop and hopefully not burn out my motor or damage it.

I realize this is primitive but I believe passive cooling wont work during hot summer months when the outside air is over 90 degrees F.

The amount of modification necessary to fluid cool the engine is more than I can do and will drain my battery and cost me $$$.

 

[Cowardlyduck]

I have found passive cooling to air is still effective when ambient temps are high. Obviously it's not as effective, but it does make a difference.

It's all about the delta between motor temp and air temp. The greater the difference the more effective the cooling that uses ambient temps.

Where I am we get a number of days approaching 40C (104f). Since the motor doesn't start to have problems till it reaches over 110-120C, there is still a 70-80C delta that does make a good difference.

Cheers

 

[Offroader]

Ebike commuter, It's summer. The hottest day yet this year, 99 degrees F resulted in some brief shutdowns. When the ambient temp is around 85 F or less I experience no problems. I was considering passive cooling solutions like heat sinks and painting the shiny silver colored motor black, even just a wet sponge around hub axle for evaporative cooling. I think I am right to say that passive cooling techniques will only lower engine temperatures to the ambient temperature [at best]. Drilling holes in the motor casing will only expose it to hot air , moisture, dirt and insects. Heat sinks don't work if the environment you are sinking the heat to is already near the optimal temp for the engine.

I am making ice packs with alcohol water in zip lock bags. Planning to use shaped swamp cooler pad sponges and make icepack donuts to cover the outer motor parts on each side and make a long strip icepack to leave on the axle when riding. Before riding I'll put thr donuts on for 15 minutes, put them back on at my mid trip stop and hopefully not burn out my motor or damage it.

I realize this is primitive but I believe passive cooling wont work during hot summer months when the outside air is over 90 degrees F.

The amount of modification necessary to fluid cool the engine is more than I can do and will drain my battery and cost me $$$.

Have you tried FF? Cooling the outside of the motor won't do much. The airflow over the motor is enough to keep the outside cool if you are above like 10 MPH.
Just test it, when the motor is hot let it sit for a couple of minutes and the motor case will be very hot. Drive slowly for 30 seconds and touch it again you will notice it will be a lot cooler.

The only way to cool these motors properly is by using fans. Like the one I have here which sucks cool air in and blows it out. Very reliable, and just simply works especially on those 90F+ days. My bike was not really usable for fun riding on days which were above 80F. Once these motors heat up, they take a long time to cool, this is where you need a very good cooling.

 

[el Raptor]

Hi.
i have the same problem with mine Cromotor.
temperature up to 150°C, and magnets have gone out.
Sorry ... i speak español only, but you can to see mi pictures:

Please can you tell me that glue is best for gluing magnets?
tomorrow i want buy glue...
Thank you
Best regard

 

[parabellum]

I used different kinds of 2 component metal "J-B" epoxy weld, but try find slow curing one or someone to help mixing, if you only get 3 o 5 min stuff. Some of them react to magnetics and try to flow all around the magnet, because of shavings inside I believe, but I did not have problem with that, just wipe excess that can interfere with the stator after hardening. Good luck.

 

[Arlo1]

Hi.
i have the same problem with mine Cromotor.
temperature up to 150°C, and magnets have gone out.
Sorry ... i speak español only, but you can to see mi pictures:

Please can you tell me that glue is best for gluing magnets?
tomorrow i want buy glue...
Thank you
Best regard

Loctite Hysol. I am not sure if the is the stuff I have I will look later.... http://www.na.henkel-adhesives.com/adhesives/product-search-1554.htm?nodeid=8797906075649

JB weld will fail

 

[parabellum]

JB weld will fail

Can you share more information about that?

 

[el Raptor]

Hi.
i have the same problem with mine Cromotor.
temperature up to 150°C, and magnets have gone out.
Sorry ... i speak español only, but you can to see mi pictures:

Please can you tell me that glue is best for gluing magnets?
tomorrow i want buy glue...
Thank you
Best regard

Loctite Hysol. I am not sure if the is the stuff I have I will look later.... http://www.na.henkel-adhesives.com/adhesives/product-search-1554.htm?nodeid=8797906075649

JB weld will fail

hi.
i can to see there are many differents products,.. Can you specify which product is exactly? thank you
http://www.henkel-adhesives.es/ess/content_data/86749_Epoxy_E.pdf