Definitive Tests on the Heating and Cooling of Hub Motors

[parabellum]

I don't have the time to read the whole thread so I'm sorry if this has been answered. You can kindly point me to where the answer is as it has not come up in searches I did. Am I correct in thinking that Statorade will not help a scooter hub motor like mine because the rotor is actually the rim and heat transferred to the ''rotor/rim'' would simply heat up the air inside the tire? And that heat would have nowhere to escape?

Thanks
Ray

Any part in contact (metal to metal is best) with the rotor magnet ring will take heat out, then transfer it to everything surrounding it, ambient air flow in best case. I suppose, your hub has side covers which are still exposed to ambient airflow, are they?

 

[ecycler]

I don't have the time to read the whole thread so I'm sorry if this has been answered. You can kindly point me to where the answer is as it has not come up in searches I did. Am I correct in thinking that Statorade will not help a scooter hub motor like mine because the rotor is actually the rim and heat transferred to the ''rotor/rim'' would simply heat up the air inside the tire? And that heat would have nowhere to escape?

Thanks
Ray

I am pretty certain it would still be helpful. You could get a tire pressure monitor sensor and make sure it doesn't raise the pressure much (PV=nRT) and then you would have your answer. For about every 10 degrees in temp you are going to get 1 extra PSI which really isn't all that much. It is doubtful enough heat would transfer to damage the tire... could actually be helpful for traction. If you are using a softer compound tire for scooters and motorcycles you are likely going to get better traction with a hotter tire and I doubt you are going to run them hot enough to get them greasy like a racer would.

 

[mrbill]

I don't have the time to read the whole thread so I'm sorry if this has been answered. You can kindly point me to where the answer is as it has not come up in searches I did. Am I correct in thinking that Statorade will not help a scooter hub motor like mine because the rotor is actually the rim and heat transferred to the ''rotor/rim'' would simply heat up the air inside the tire? And that heat would have nowhere to escape?

Thanks
Ray

I am pretty certain it would still be helpful. You could get a tire pressure monitor sensor and make sure it doesn't raise the pressure much (PV=nRT) and then you would have your answer. For about every 10 degrees in temp you are going to get 1 extra PSI which really isn't all that much. It is doubtful enough heat would transfer to damage the tire... could actually be helpful for traction. If you are using a softer compound tire for scooters and motorcycles you are likely going to get better traction with a hotter tire and I doubt you are going to run them hot enough to get them greasy like a racer would.

A hot wheel rim by itself may not increase a tire's internal pressure enough to cause trouble, but the hot rim will soften the tire rubber at the bead, making it easier in combination with the increased tire pressure to ease the bead off the rim's hook and cause a blow-off. When the lifted tire exposes the inner tube, the tube blows out between the rim and the bead like bubble gum until it pops! This type of failure is often misunderstood because after the blow-off the tire settles back onto the rim, there being no apparent tire failure. One can observe this failure on an inner tube as a slice or irregular cut--see photo at the second link below--although some blow-offs cause a 1-2mm cut that can be mistaken for a glass cut.

I've been pretty lucky over the years with the many rim-brake heat induced blow-offs I've experienced where I had enough time to come to a controlled stop before my tire lost all pressure. But, my luck ran out on the most recent occasion when I lost control and crashed, suffering 3 cracked ribs along with other assorted bruises and abrasions. Not fun.

http://mrbill.homeip.net/rimTempStudy.php
http://mrbill.homeip.net/albums/brokenBikeParts/single-image/20090509-bicyclePartsFailures106-photo.html#anchor

 

[ecycler]

mrbill, my assumption is that he is not running tubed bicycle tires. Your data does seem interesting, but is not very relevant considering the difference in construction if he is using tubeless scooter or MC tires. Motorcycle wheels and tubeless road tires can safely get to much hotter temps than you have recorded. Also, if you want reliable performance out of your hub motor you should not be exceeding ~100c-110c at the stator for extended periods of time. The amount of heat that would be subsequently transferred to the rim and then the tire would thus mean it does not reach near the temps you are recording with your bicycle rim brakes.

 

[mistercrash]

Yes I do have a tubeless rim and tire. It's not that I need the Statorade, my hub as been keeping cool as a cucmber but I am wondering where does the heat dissipate if it's trapped inside the tire. There are side plates but my hub is properly sealed so there is a thin layer insulating the side plates from the motor, so I'm assuming that most of the heat would be transferred to the rotor/rim assembly.

 

[mrbill]

Also, if you want reliable performance out of your hub motor you should not be exceeding ~100c-110c at the stator for extended periods of time.

I rode a stock Nine Continents M3006RC for a year, regularly seeing coil temperature exceed 150C during long regen sessions with the Infineon-style controller and as high as 135C during powered sessions. Recently I cracked opened the motor to apply Statorade and to examine it for high-temperature damage.



I discovered that the stator looked as good as new, but the non drive side bearing, the smaller 6904 bearing, had been cooked and was turning roughly. It needed to be replaced. While sourcing a replacement bearing I learned that most cartridge bearings are designed to run below 120C.

Since then I have switched to the ASI controller (that motor brakes without generating as much heat in the motor), have been using Statorade that reduces coil temperature by 20-40C typically, and have lowered my CA3 coil temperature thresholds to 100C (full current) and 120C (zero current), mainly to keep from cooking my bearings.

 

[macribs]

Are you sure your magnets are as strong as they used to be? If you have many high temps magnets could have started to demagnetize. Probably hard to tell too, just like when you drive a car and shocks get worn over time. As the shocks gets worst you are adjusting to less quality handling and it gets hard to tell by every day driving that shocks are bad. Then when at service your mechanic show you one or more shock(s) are blown. Could be the same with your motor? Maybe magnets are slowly getting weaker but you don't notice? I mean if a bearing is cooked seems to me other things could be cooked too. 150 degrees Celsius seems a bit high, wouldn't be comfy past 110-120 degrees.

 

[mrbill]

Are you sure your magnets are as strong as they used to be? If you have many high temps magnets could have started to demagnetize. Probably hard to tell too, just like when you drive a car and shocks get worn over time. As the shocks gets worst you are adjusting to less quality handling and it gets hard to tell by every day driving that shocks are bad. Then when at service your mechanic show you one or more shock(s) are blown. Could be the same with your motor? Maybe magnets are slowly getting weaker but you don't notice? I mean if a bearing is cooked seems to me other things could be cooked too. 150 degrees Celsius seems a bit high, wouldn't be comfy past 110-120 degrees.

I ran this question by Justin L-E some time ago, to which he replied in an email which I will assume he won't mind my sharing here:

MrBill:
2) With the heat being transferred [through Statorade] to the outer shell via the magnets, they will be seeing higher average temps but perhaps lower peak temps. Does the risk of magnet damage change?

Justin L-E:
It's only the peak temp that affects magnetic damage, average temp doesn't mean anything.

MrBill:
Some of the discussion on E-S suggests that absolute peak temperature may not be a sufficient metric to predict magnet damage. Would the integral of temperature over time be a better metric?

Justin L-E:
No. It's the combination of the temperature plus the operating point of the magnet. When the magnet is in part of a closed magnetic circuit (like in the motor), then it takes a much higher temperature to demagnetize it compared to being out in the open with stator removed etc.

My own testing of my motor under semi-controlled conditions both when it was new and again one year later has convinced me that its magnets have not been damaged in the slightest.

That said, now that I'm using Statorade where the thermal heat path flows directly through the magnets to the outer shell, I do not intend to allow my coil temperature to exceed 120C.

 

[bigbore]

I'm gong to try the Statorade on a QS205 motor, am I the first one to try this motor ferrofluid cooled?
What's the best way of putting 5ml of Statorade in the motor? Just all the 5ml in one spot or try to optimally around the entire circumference?

 

[Offroader]

I'm gong to try the Statorade on a QS205 motor, am I the first one to try this motor ferrofluid cooled?
What's the best way of putting 5ml of Statorade in the motor? Just all the 5ml in one spot or try to optimally around the entire circumference?

bigbore, have you been using the QS205 without statorade? Any overheating issues where you have to limit your use of the QS205?

I hope you come here and let us know how it compares with satorade and without.

 

[diff_lock]

Bit of a warning I might have missed somewhere: Do not stick the syringe nozzle near the magnets if you want a metered application. I popped my syringe cap open and brought the syringe tip into contact with the rotor magnets and half of the fluid was basically sucked out of the syringe.

 

[Offroader]

Am I missing something here? I thought as long as you get the Ferro Fluid anywhere inside the motor it will eventually flow down into the magnets and spread itself around.

 

[bigbore]

I'm gong to try the Statorade on a QS205 motor, am I the first one to try this motor ferrofluid cooled?
What's the best way of putting 5ml of Statorade in the motor? Just all the 5ml in one spot or try to optimally around the entire circumference?

bigbore, have you been using the QS205 without statorade? Any overheating issues where you have to limit your use of the QS205?

I hope you come here and let us know how it compares with satorade and without.

Yes I have overheated at 130°C the motor while riding at 10Kw power on flat straight road at the speed of about 85-90 Km/h for 3 or 4 Km. This was with OVS = 3°.
I have to say that by lowering the power at 7Kw with OVS at 0° for off road use I have a good amount of torque with out overheating issues. Last saturday I made a test on a steep off road trail, I have rode for 10 minutes at an average speed of 26Km/h for a distance of 4,3Km climbing 268m (gradient 3.5%) and the motor was at 75°C. Then I can try the same with ferrofluid.

But are there directions to follow to put 5ml of ferrofluid inside the motor?

 

[Merlin]

the best idea i like is to drill a small hole in one of your 6 disc brake holes.
so you can fill it up and didnt have any holes after filling it with ferrofluid.

 

[ecycler]

I just pull a cover off and spread it around. I like to inspect the internals of my motors periodically anyways to check for rust, rubbing wires, bearings, etc. If you ever intended to cross drill the covers now is a good time anyways to do since has proven it works well in conjunction with FF.

 

[macribs]

I just pull a cover off and spread it around. I like to inspect the internals of my motors periodically anyways to check for rust, rubbing wires, bearings, etc. If you ever intended to cross drill the covers now is a good time anyways to do since has proven it works well in conjunction with FF.

Cross drill the covers? What do you mean?

 

[Cowardlyduck]

Cross drill the covers? What do you mean?

Maybe he means this:

I've been running my FF in this hub without issue for quite a few months now...although I haven't opened it since adding the FF yet.

Cheers

 

[Samd]

I recently 3D printed some aluminium/nylon powder based Venturi covers for hubs. Tests on the way.

Sent from my iPhone using Tapatalk

 

[Mammalian04]

Anyone have some spare wind tunnel time? :lol:

 

[Merlin]

yesterday a buddy and me checked in for fill some cromotors up with that black magic...

unfortunately his cromotor did this to him...

so we filled up only one.......mine

it was very funny to see how this stuff JUMPS out of my syringe without pressing it

this is a QS v3 and 7ml of juice...

 

[macribs]

@Samd very clever done. Look forward to hear how it goes.

@Merlin your friend shouldn't park his cro so close to your QS, your magnets pulled his loose :lol:

 

[Merlin]

LOL

he is really pissed enough of his "high quality" motor atm ....but i will say it anyway, thx :lol: :lol:

 

[madin88]

LOL

he is really pissed enough of his "high quality" motor atm ....but i will say it anyway, thx :lol: :lol:

i know one who had the same problem. so much about the quality control of original Cromotors :lol:
the glue they use for the magnets isn't the best and in addition there is that big airgap which is not optimal for adhesive power.
the bended magnets used in your Cro V4 or other newer motors should stick alot better because there is no airgap behind.

Merlin, with the FF i believe your only limit now is the battery juice if you're riding 100kmh on the highway :lol:

 

[Merlin]

:lol: :lol:

this forum needs absolutley a like or dislike button ^^

 

[ziltoid81]

the best idea i like is to drill a small hole in one of your 6 disc brake holes.
so you can fill it up and didnt have any holes after filling it with ferrofluid.

Its always better to open the motor.
If you apply it trough a hole you will mess your whole stator.
If you put it directly to the magnets it will stay there.

You also wont know how much ff actually is between the magnets.

Anyway, what are your temps at this sunny weather and with ff?
Maybe you can make a video?
Im not sure if i stick with my 5t in 18 inch or go to a 4t in a smaller rim.
Your other video was impressive......this thing stayed cool for a long time at relatively high amps.