Definitive Tests on the Heating and Cooling of Hub Motors

[macribs]

+1 to what amberwolf said. I too was into overclocking and what we did back then was sand paper and wetsand up to 2000 grit to get a mirror finish and then a really light layer of thermal paste. Mind you we only did polish the cpu cooling block, didn't do the cpu itself.

Rather then spending too much time looking into the very latest and greatest of thermal paste I would get busy polishing the heat sink itself and if you got easy access (motor without spokes) do the same for all of the area between the flanges. Afaik our hub motors are casted so a close peak in a micro scope would reveal rather uneven finish. If you can work the finish more even that should make for less isolating air being trapped and better thermal contact between motor and hub sink.

 

[madin88]

it was foreseeable that there will come up a discussion about thermal pastes :lol:

 

[amberwolf]

Assuming a really accurate curvature fit of hubsink segments, does this mean a significant loss in heat conductivity will result from the the original paint on my H40 hub ring?

Probably not, just air gaps, cuz air is a pretty good insulator (hence the reason for people using FF, or oil-filling the hubs, etc).

But if you can remove anything between the metal-to-metal contact surfaces, it will have better conduction. How much better? Depends on thickness of stuff and what it's particular thermal properties are.

Generally I wouldn't worry about the paint and such, just the air gaps, but if you want the "best" performance everything has to fit "perfectly" together metal to metal.


Thermal paste fllling air gaps is WAY better than the air gap, but the paste will eventually degrade or be washed out and how long that takes will depend on environmental conditions. I expect people that actually need FF and hubsinks are much more likely to be using them in relatively extreme conditions and be more likely to lose the paste out of larger gaps more quickly; it might be replaced by dirt or oxidation, or just air.

 

[Cowardlyduck]

It's interesting timing that this discussion around pastes etc should occur now.

Everyone probably remembers this:

I secured those heat-sinks using Arctic Silver Thermal Epoxy:

They've been great for over 1000km or so since then.
Last night I was out riding hard and as I landed a large jump at high speed I heard a metal tingeing behind me. Assuming I had just run over something on the road I kept riding. When I got home I discovered one of my Heat-Sinks had let go and flung off. :lol: At the time it came off the motor was hitting 130-140C as I was riding quite hard.
That's the first and only heat-sink to fall off so far, so I'm hoping it was just a weak bond or something. I'll probably just replace it, as I have spares, and see if it happens again.
In terms of cooling performance I've noticed the heat-sinks definitely do help a lot. When the motor gets over 80C, I can feel a lot of heat on the fins of the heat-sinks radiating away, and the time it takes the motor to cool down arbitrarily seems to be about 3/4 to half what a standard motor would be.

Cheers

 

[spinningmagnets]

I am certain the included paste would work very well (cheap paste is MUCH better than no paste). I had planned to lay fine sandpaper over the hub rim, and "lap" the bases of the fins onto the hub, so that they had the best possible fit. I am suddenly liking the idea of thermal epoxy (I missed that in the previous discussion). Since these fins are bolted together, the epoxy sounds like a very good pairing.

I have no concerns about problems with spoke interference if one breaks and needs to be replaced, but I am sure potential customers will express concerns, and we may be able to change the design to pre-empt that as an issue.

 

[Jestronix]

130-140c ! Wow I hit 100c and back off, how long can a motor handle those temps ?

 

[Cowardlyduck]

130-140c ! Wow I hit 100c and back off, how long can a motor handle those temps ?

Your right. Not long.
Which is why it wouldn't be advisable in any sealed, or even just vented motor. On something with heat-sinks + vents in my case it's a bit more acceptable as the motor cools off so quickly.

Cheers

 

[Offroader]

130-140c ! Wow I hit 100c and back off, how long can a motor handle those temps ?

The first thing to go is the epoxy holding the magnets will fail and the magnets will loosen up. I've done this on a cromotor. The bike will still be rideable but you may hear scratching sometimes as the magnets get pulled off the magnet ring.

 

[Baron]

130-140c ! Wow I hit 100c and back off, how long can a motor handle those temps ?

The first thing to go is the epoxy holding the magnets will fail and the magnets will loosen up. I've done this on a cromotor. The bike will still be rideable but you may hear scratching sometimes as the magnets get pulled off the magnet ring.

or maybe you got the aluminum parts of the hub so hot that it started to warp/expand, and moved the magnet ring. IIRC bearings can also be the first point of failure around 120-130C.

 

[Cowardlyduck]

You guy's are right, but your assuming even heat through out the hub.

I have 2 thermistors. One KTY84 for my Adaptto which is embedded right into the windings, the other is a cheap BBQ type thermometer that maxes out at 110C and is sitting just below the windings in-between the stator steel and windings.

The 130-140C I saw above was on the KTY84, but the BBQ thermometer at that same time was only reading about 105C. Once the BBQ thermometer reaches over 110C it's display changes to HHH....that's usually when I start worrying and back right off. 8)

Cheers

 

[fechter]

I have a thermistor stuck to the copper between two stator poles. It's right in the middle, so it only sees the copper winding temp. I routinely get it to over 150C. If I start out cold and climb continuously until it hits 150, the shell temp will be around 40C. If I stop and let it cool, and go again, the shell temp will continue to get hotter each cycle. It should be ok up to shell temp of 80C which is where I would start worrying about the magnets. I never let the shell get that hot though.

The winding insulation will fail at some point. The hall sensors are rated for 125C.

 

[Emmett]

If I start out cold and climb continuously until it hits 150, the shell temp will be around 40C. If I stop and let it cool, and go again, the shell temp will continue to get hotter each cycle.

I remember those days, when I had air around the stator. The heat of the shell lags far behind what the stator is experiencing. My stator would get super hot (as per the temp gauge) and my ride was effectively over in less than 30 minutes. I was thinking my bike is useless for my needs. The original motor was a H4065 run at 54V and up to 3700W.

With oil in there, the shell obviously heats up way way faster (seconds not minutes), and starts shedding heat. So for on/off loads the stator temp is much lower. Immediately I could ride until end of battery range, no problem. The temp of the shell (can also be checked by hand) matches the temp gauge for the stator. I've switched to a H4040 motor running with 74V and up to 6300W, and want to fit some hubsinks, but as is with 90ml of oil it's way more usable then the original 3700W setup with air in there.

 

[pedros]

Hello out there .
Forgive an old man his english. I am a metalworker from denmark,that has experimentated a bit with these ebikes. I have looked with interess in your oilcooling playing.
I think that, it is the finest way to lubricate small geared hubs .I have a question for you,: have you had problems with magnets broken of ?,and problems with the insulation on the windings? :wink: Pedros

 

[Emmett]

Hello out there .
I have a question for you,: have you had problems with magnets broken of ?,and problems with the insulation on the windings?

No problems for windings or magnets in my H4040 and H4065 stators that have been saturated with castor (vegetable) oil for over 12 months each.

The magnets in my TC3065 came loose when using 6000W. All of them starting spinning. However the amount of factory glue on them was a joke. Like a drip of superglue on each one. They are now rebonded with JB-Weld reinforced epoxy. Pretty easy job to smear around the hub rig and drop each magnet in place. Cleaning off the oil was the time consuming part.

 

[sketchism]

OK, I have the Ferro-Fluid, fins, and the fins came with a small tube to thermal paste. I'm sure the amount is adequate, and the brand is good. however, I was wondering if anyone has any ideas about the top-three thermal pastes to buy (when purchasing from North America, the paste I now have was supplied by the Australian vendor for the fins).

Since we are using a higher volume than a tiny heat-sink in a computer CPU, I would guess something that performs at about 90% of the thermal transfer as the top-of-the-line stuff would be adequate, if that also meant that it cost half as much as the best stuff.

sorry ive been a bit quiet it's been a crazy period for me and iv'e been dealing with material price increases and delays in the final order but i am assured they will be in the air before the end of the week


further back in this thread (or the one on FB i actually can't find it at the moment) i listed the 10 brands that i purchased off their spec sheets and then tested with FLIR cam the before coming up with the version i decided to use.

Some of the regular ones (8 of the brands and the thermal tapes) were all floating between .8 and 1.2 W/m-K the HY880 i decided on was by far the best of that group (nearly 5X better at >5.15 W/m-K)

the only stuff with better bench figures was arctic silver at 8 W/m-K but it was more than 5X the cost again for a much smaller increase in performance (unnoticeable on FLIR)

 

[robo4]

so if applying hub sinks with artic silver, do I need to remove the black paint on the QS205 or leave it on ?
adhesion vs corrosion ?

 

[sketchism]

Initially we were removing the paint with a dremel wheel and if you feel it necessary to do so feel free, i have on my personal bike,
but most of the Beta Testers have seen very similar results with the paint still in place just cleaned with acetone or alcohol before application of the paste and HubSInks

 

[Offroader]

For you guys using hubsinks + FF. Do you ever have to stop to let the motor cool down, if so for how long?

Do you even over heat anymore?

Thanks.

 

[Quokka]

Cant wait to try out these heatsinks sketch. Mines on order 8) . Its hot as hell in WA at the moment, cracking 40 deg c and i am sick of riding like a grandpa when the QS gets heat soaked

 

[mrbill]

For you guys using hubsinks + FF. Do you ever have to stop to let the motor cool down, if so for how long?

Do you even over heat anymore?

Thanks.

I haven't had to stop to let the motor cool down since I started using Statorade and Hubsinks in my motors. That said, I haven't yet tested the combination on a long, steep uphill on a hot summer day, since I only started using the combination of heat-shedding aids this fall.

Here's a recent report I wrote up on the Edge1500 DD hub motor:

https://mrbill.homeip.net/hybridBike.php#edge1500Testing

 

[litespeed]

Off-roader,

By the time I got my ferrofluid and Hubsinks the temps had dropped here as well but I found I could keep on at higher power way longer and drain my battery faster than ever before. I wrote,

"I finally got to put a good hard but short run on my Hubsinks now that I have ferrofluid and boy what a change it made. Spots were I would peak at 175 degrees stayed in the 150's. As previously mentioned I still get peaks but the temps drop quickly. I was peaking at 150 to 180 amps till my battery was hitting low volt and the temps were infact lower than ever before.

I'm going to go hit the trails hard here in just a bit and see what that does. Still haven't got a card reader for my iPad so no GoPro, iPhone stills will have to do.

Tom"

And,

"Well I finally got a chance to put a good hard ride on the Hubsinks/ferrofluid combo and the verdict is in.

My rides have now gotten shorter!!! I can run harder longer and it sucks the power right out of my battery. I used to have to take it easy for awhile to cool the motor down....not any longer. Thought I'd be stopping to take pictures once I heated things up but that didn't happen. Now granted I wasn't doing any hill climbing as most of this was pretty flat like a motor cross track but I ran the trails 20 to 30 mph average. I just couldn't cook the motor. I was really on the throttle hard, not flowing. Coming out of hair pin corners full throttle and the 205 still kept its cool.

I need to go to a 20s13 to 15p VTC5 pack which I plan to do this winter. Maybe with a 39 amp pack capable of 200 amps continuos I can heat the motor up better.

Thanks a lot Sketch, I really appreciate you contribution to the community and to my enjoyment.

Tom"

I have a MaxE/QS205 V3 3.5T/20s15p Koinion pack now and all temps were in Fahrenheit. Only downside I have noticed to ferrofluid so far as it adds a lot of drag when it gets cold out. When it started getting really cold about 20 degrees out I put my bike in the basement and noticed the rear wheel reall felt like it had a ton of drag on it......almost like touching the phase wires together. Once in the basement and warmed up it was just like normal.

Tom

 

[Offroader]

I honestly have a hard time believing this FF + hubsinks will work for me for the type of riding I do but maybe it will. I may try it and then if it doesn't work well enough I will try and clean all the FF out and then modify for fan air cooling.

I do most of my riding in the hot summer, so ambient is usually 85-90F and then I do stuff like riding up large dirt hills, riding down, then riding back up again. Wheelies which constantly has me pushing full throttle and not moving very fast. Stuff like that which really heats my motor up and I know the RC EDF fan works.

I just need to determine if I can somehow spray all that FF out of the stator if it doesn't work well enough and convert over to air cooling. I've heard the FF gets into everything and sits inside the stator, maybe gets stuck between the laminations. If this will constantly leak out into the windings and get dirt stuck inside the windings, especially where they pass through the stator, this will prevent the high air flow from cooling the windings. But maybe I can get all that FF out.

It is a hard decision because I know the air cooling will work, the only drawback is that there is fan noise, which honestly you don't hear it when you are moving and you don't really recognize it after a while. But it is still an open motor and you have to deal with the electronics to run the high speed fan and an open motor.

 

[macribs]

@offroader why don't you keep your eyes open for a used motor with a low price and just fill it up with FF and slap on a heat sink.
If FF/heatsink turns out working for you, you now have a well working motor you scored at a decent price, if it does not work for your specific riding conditions, outside temperatures, and your style of riding, I am pretty sure if you are then selling the FF/heatsink motor "ready to ride " you will for sure get your money back as there are people who would never open a motor due to lack the skills, workspace or tools to do any customization. By selling a ready made motor you will lower the bar so much even people that never do custom work can easily swap a rear wheel.

 

[Offroader]

@offroader why don't you keep your eyes open for a used motor with a low price and just fill it up with FF and slap on a heat sink.
If FF/heatsink turns out working for you, you now have a well working motor you scored at a decent price, if it does not work for your specific riding conditions, outside temperatures, and your style of riding, I am pretty sure if you are then selling the FF/heatsink motor "ready to ride " you will for sure get your money back as there are people who would never open a motor due to lack the skills, workspace or tools to do any customization. By selling a ready made motor you will lower the bar so much even people that never do custom work can easily swap a rear wheel.

hmm, you know what I actually had this idea before because I do have a 2nd cromotor. I just delaced the motor for my MXUS and wanted to sell it. Maybe I will use that and relace it as my test motor for both removing steel to lighten it and using the FF + hubsinks on it. Then I can compare it straight against my other cromotor which has air cooling vs the FF + hubsinks and finally put the question to an end.

 

[Rix]

Mac Ribs got you thinking Offroader, I like it, if you do this, please let us know the results. I haven't jumped on the FF bandwagon yet. My venting and riding with some mechanical sympathy has thus far worked on all my builds.