Cooling Solutions?

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Feb 6, 2019
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Noticed that the motor on my e bike (mini cyclone) runs pretty hot. On the outer casing while pushing the bike hard I can get it to go as high as around 140 degrees f or about 60 degrees c (can't touch the motor for more than a few seconds). I definitely would like this temperature to go down and I was looking at heat sinks. I'm not too familiar with electronics though so I don't really know how to install them on my motor? What do you use to attach them? Normal glue? Thermal paste? And what's to prevent them from falling off while doing some bumpy offroading? Also I was looking at the ferrofluid cooling solution that some people on here have done, but is my motor applicable for it? I'm guessing I would have to take the case off, and put the fluid between the magnets? Any help would be greatly appreciated as I really have no idea what I'm doing. :D
 
Have you tried the suggestion I made in your other thread of looking at the various Cyclone cooling threads and posts? Or the ones for the RC motors?

There is also the "definitive testing on heating and cooling of hubmotors" thread by Justin_LE, which has a number of cooling methods actually tested and discussed. Doesn't matter that yours is not a hubmotor.
 
speedyebikenoob said:
Noticed that the motor on my e bike (mini cyclone) runs pretty hot. On the outer casing while pushing the bike hard I can get it to go as high as around 140 degrees f or about 60 degrees c (can't touch the motor for more than a few seconds). I definitely would like this temperature to go down and I was looking at heat sinks.

Heat sinks are not a substitute for running the motor within its efficient RPM range, within its rated current.
 
Agree, your big problem may be running your cyclone in too high a gear at start up, or up hills.

Pretty darn hot is normal though, but 150f on the outside is getting about as hot as you would ever want it. It will get very hot normally, hard to touch, but not actually sizzle skin hot. Spray bottle for a quicker cool down.
 
Ferrofluid won't help as the motor is an inrunner. More fins will help and more air will help.
A fan that blows air on the motor would be one option. 60C is getting into the danger zone where things will fail.

I see on the mini, there aren't any fins at all.

One way to add fins would be to cut a bunch of pieces of small aluminum "U" channel and glue them to the side of the motor to make fins. You could use epoxy or silicone glue (I would use silicone).
 
amberwolf said:
Have you tried the suggestion I made in your other thread of looking at the various Cyclone cooling threads and posts? Or the ones for the RC motors?

There is also the "definitive testing on heating and cooling of hubmotors" thread by Justin_LE, which has a number of cooling methods actually tested and discussed. Doesn't matter that yours is not a hubmotor.

Yes I did actually. Most suggested lowering the gearing and some suggested heat sinks. I'm actually reading that thread right now, but it'll probably take me a while to get through it because there's 84 pages lol.
 
Chalo said:
speedyebikenoob said:
Noticed that the motor on my e bike (mini cyclone) runs pretty hot. On the outer casing while pushing the bike hard I can get it to go as high as around 140 degrees f or about 60 degrees c (can't touch the motor for more than a few seconds). I definitely would like this temperature to go down and I was looking at heat sinks.

Heat sinks are not a substitute for running the motor within its efficient RPM range, within its rated current.

Definitely been running it in it's most efficient rpm range, dunno about rated current though, I'm pushing 20 percent more than it's rated for. My goal is to get it to go down by 20 degrees fahrenheit on average, so right now when it's at 140 it would be at 120 instead. Honestly even 10-15 degrees for me though would be an improvement, is that too much to ask from these heatsinks? The motor never overheats during normal riding, it normally stays below 90 degrees f, it's only a problem when I start climbing hills or try to maintain speeds in excess of 30 mph.
 
dogman dan said:
Agree, your big problem may be running your cyclone in too high a gear at start up, or up hills.

Pretty darn hot is normal though, but 150f on the outside is getting about as hot as you would ever want it. It will get very hot normally, hard to touch, but not actually sizzle skin hot. Spray bottle for a quicker cool down.

I don't think it's at the point even at it's hottest where it will burn my skin though, I can usually keep my entire palm on the motor even at it's hottest for maybe three-four seconds, then it gets uncomfortable, which is why I'm not overly concerned about this, but then again I'm very new to this stuff so idk much. I'm used to my scooter's motor which I now think is probably underrated because it barely even gets warm. Carrying a spray bottle might be a good idea for me when going up mountains, thanks for that, I'll try that next time. Starting off in a higher gear for me though isn't an issue anymore, when going up hills I try to run the motor close to redline. At my 60 volts I can rev the motor up to nearly 8000 and I'm always somewhere around 6 grand when climbing hills.
 
fechter said:
Ferrofluid won't help as the motor is an inrunner. More fins will help and more air will help.
A fan that blows air on the motor would be one option. 60C is getting into the danger zone where things will fail.

I see on the mini, there aren't any fins at all.

One way to add fins would be to cut a bunch of pieces of small aluminum "U" channel and glue them to the side of the motor to make fins. You could use epoxy or silicone glue (I would use silicone).

Thanks! Aren't the fins basically heat sinks though? Ok I'll try using that glue, my only concern with glue was I was afraid it would melt off the motor.
 
AFT in Australia uses a similar motor, and they have an "extreme duty" kit that includes added aluminum fins...

Mid3.png
 
spinningmagnets said:
AFT in Australia uses a similar motor, and they have an "extreme duty" kit that includes added aluminum fins...

Mid3.png

I looked through the aft site to see if I could find any heatsinks and I couldn't find that one though. Anyone know where I can actually get one like that from? Other than of course buying a whole new motor from aft, lol.
 
Aluminum is typically fairly bendable. Perhaps you could buy some generic flat heat sinks and cut/bend the sections to fit reasonably close. Then tape sandpaper to the motor shell and rub the heat-sink bases to make a better fit. Once the curved "fit" is close enough, smear some thermal compound on the motor shell before using a large hose clamp to press it onto the motor?
 
spinningmagnets said:
Aluminum is typically fairly bendable. Perhaps you could buy some generic flat heat sinks and cut/bend the sections to fit reasonably close. Then tape sandpaper to the motor shell and rub the heat-sink bases to make a better fit. Once the curved "fit" is close enough, smear some thermal compound on the motor shell before using a large hose clamp to press it onto the motor?

Does the thermal compound act as a glue? Or are you saying to use a hose clamp to keep the sink there?
 
silence said:
Forced air cooling: https://endless-sphere.com/forums/viewtopic.php?f=28&t=56666

Thanks, I saw that, my bike doesn't have that much real estate unfortunately. :( Maybe I can do a smaller scale version of that
 
That doesn't sound very hot for an inrunner, since the main heat source, the copper windings, are attached via a good thermal pathway directly to the shell.

The best way to reduce temperature is to make less heat, and with heat in the copper increasing by the square of current, a relatively small reduction can pay big temperature dividends. Your can reduce the phase current the motor sees with a simple reduction in gearing, made more simple if your motor runs through the gears (ie accelerate using a lower gear). The motor draws current up to the controller limits based on load, and it sees a lower load pushing the same weight using a lower gear ratio. If your controller is programmable, then lowering just the phase current limit can be very effective in heat reduction.

To be sure that the heat isn't being caused by going to too high rpm (the iron side of the heat equation), go for a ride accelerating softly and then cruise for a while at high speed. If the motor still gets hot, then it's either not getting enough ventilation or you're running at an rpm that's too high. Using something to deflect more air toward the motor can be effective. What you want at the motor shell is maximum air velocity and turbulence. Also check the temp of the motor shaft relative to the motor shell. On an inrunner the most temperature sensitive thing (the magnets) are attached to the output shaft via a good themal connection, so if it's as as hot or hotter than the shell, then you're running in risky territory.

As mentioned above, attaching cooling fins with a good thermal connection to the motor shell will help cool the motor better, because it increases the effective surface area of the motor shell, and the more surface area you have, the more heat can be dissipated at a given temperature differential between the motor surface and the outside air.
 
speedyebikenoob said:
I looked through the aft site to see if I could find any heatsinks and I couldn't find that one though. Anyone know where I can actually get one like that from? Other than of course buying a whole new motor from aft, lol.

That heat sink in the pic used to be available from cyclone taiwan. Might still be if you look through their horror show of a website.

On my old ebike I used a heat sink as well as a small impeller mounted on the rotor shaft. I drilled some holes in the motor to allow some air flow.

TQRYlsA.jpg
 
Thermal compound does not act as a glue. It is a paste that fills-in all the tiny irregularities between the two surfaces. It is formulated to easily transfer heat between the two surfaces, but...it's pricey. So... try to attain a good fit before adding thermal compound.
 
spinningmagnets said:
Thermal compound does not act as a glue. It is a paste that fills-in all the tiny irregularities between the two surfaces. It is formulated to easily transfer heat between the two surfaces, but...it's pricey. So... try to attain a good fit before adding thermal compound.

Not only is is expensive, but it isn't actually that good at conducting heat. It's just much better than an air gap. It works best when applied in the thinnest possible coating.
 
John in CR said:
That doesn't sound very hot for an inrunner, since the main heat source, the copper windings, are attached via a good thermal pathway directly to the shell.

The best way to reduce temperature is to make less heat, and with heat in the copper increasing by the square of current, a relatively small reduction can pay big temperature dividends. Your can reduce the phase current the motor sees with a simple reduction in gearing, made more simple if your motor runs through the gears (ie accelerate using a lower gear). The motor draws current up to the controller limits based on load, and it sees a lower load pushing the same weight using a lower gear ratio. If your controller is programmable, then lowering just the phase current limit can be very effective in heat reduction.

To be sure that the heat isn't being caused by going to too high rpm (the iron side of the heat equation), go for a ride accelerating softly and then cruise for a while at high speed. If the motor still gets hot, then it's either not getting enough ventilation or you're running at an rpm that's too high. Using something to deflect more air toward the motor can be effective. What you want at the motor shell is maximum air velocity and turbulence. Also check the temp of the motor shaft relative to the motor shell. On an inrunner the most temperature sensitive thing (the magnets) are attached to the output shaft via a good themal connection, so if it's as as hot or hotter than the shell, then you're running in risky territory.

As mentioned above, attaching cooling fins with a good thermal connection to the motor shell will help cool the motor better, because it increases the effective surface area of the motor shell, and the more surface area you have, the more heat can be dissipated at a given temperature differential between the motor surface and the outside air.

That's a good point, I'll check the temperature of the motor shaft the next time I ride. I never knew that motors could overheat by running too high of an rpm? I thought electric motors like to rev? I usually run my motor close to redline while climbing hills. Is that a bad idea? I've always done this to try and keep the heat down
 
district9prawn said:
speedyebikenoob said:
I looked through the aft site to see if I could find any heatsinks and I couldn't find that one though. Anyone know where I can actually get one like that from? Other than of course buying a whole new motor from aft, lol.

That heat sink in the pic used to be available from cyclone taiwan. Might still be if you look through their horror show of a website.

On my old ebike I used a heat sink as well as a small impeller mounted on the rotor shaft. I drilled some holes in the motor to allow some air flow.

TQRYlsA.jpg

Thank you, I'll take a look. I was considering drilling holes but it rains too much here and I do too much offroading for it to be safe.
 
spinningmagnets said:
Thermal compound does not act as a glue. It is a paste that fills-in all the tiny irregularities between the two surfaces. It is formulated to easily transfer heat between the two surfaces, but...it's pricey. So... try to attain a good fit before adding thermal compound.

Okay I'll order some heat sinks and try. I can't imagine that thermal paste doing much though if that's all it really does.
 
speedyebikenoob said:
That's a good point, I'll check the temperature of the motor shaft the next time I ride. I never knew that motors could overheat by running too high of an rpm? I thought electric motors like to rev? I usually run my motor close to redline while climbing hills. Is that a bad idea? I've always done this to try and keep the heat down

There is heat from eddy currents and hysterisis that are generated in the magnets and iron laminations that increase in a generally linear manner with rpm. They result from the alternating magnetic polarity. To get an idea of the maximum loss, run just your motor (no chain or belt connected), and measure the current used at max rpm. Since current is pretty low, the copper loss is minimal, so voltage X no load current, is your maximum iron loss.

Yes, generally it's good to attack hills, and do it with low gearing. However, if you are over-speeding your motor, it's possible to create extra heat for no reason.
 
John in CR said:
speedyebikenoob said:
That's a good point, I'll check the temperature of the motor shaft the next time I ride. I never knew that motors could overheat by running too high of an rpm? I thought electric motors like to rev? I usually run my motor close to redline while climbing hills. Is that a bad idea? I've always done this to try and keep the heat down

There is heat from eddy currents and hysterisis that are generated in the magnets and iron laminations that increase in a generally linear manner with rpm. They result from the alternating magnetic polarity. To get an idea of the maximum loss, run just your motor (no chain or belt connected), and measure the current used at max rpm. Since current is pretty low, the copper loss is minimal, so voltage X no load current, is your maximum iron loss.

Yes, generally it's good to attack hills, and do it with low gearing. However, if you are over-speeding your motor, it's possible to create extra heat for no reason.

Okay, I've just always assumed that the controller will limit the rpm before it actually becomes dangerous for the motor, I guess not. I'll take a look next time I go for a ride.
 
speedyebikenoob said:
Okay, I've just always assumed that the controller will limit the rpm before it actually becomes dangerous for the motor, I guess not.
Generic controllers genrally don't check or limit anything at all, other than battery current (and even that can be significantly different than what it's rated for, above or below, because of inconsistent materials or parts used, or poor manufacturing causing too little or too much solder at the shunts).

There *are* controllers that do various checks and limits, but they generally are significantly more expensive, and also require setup for the specific motor you're using them with, which can be kind of complicated for some of them.

Some of the Kelly controllers, Lebowski's, Incememed's SFOC, Phaserunner / ASI, Sevcon, others I cna't think of off the top of my head.
 
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