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Oil cooling your hub- NOT snake oil!
- Thread starter Spicerack
- Start date
jussumguy
100 mW
I was thinking 3in1.
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Farfle
100 kW
Or mineral ATF which has a few additives to prevent foaming, among other helpful things. And is also dollars a bottle.ian.mich said:
neithermovingnorstill
100 mW
I'm thinking Glycerin over Mineral Oil, for better heat dissipation and sound reduction:
Thermal Conductivity:
Mineral Oil = 0.133 W/mK
Glycerin = 0.290 W/mK (more than twice the heat dissipation of Mineral Oil)
It is more viscous, so it will produce more drag, but the viscosity will dampen sound more, and it's a very effective lubricant.
Like antifreeze, it will absorb a tiny bit of moisture over time, but it can be replaced yearly (it's fairly cheap). Probably needs more frequent changing in wet/humid area, depending on how well sealed the motor is.
It's so nontoxic that you can buy edible Glycerin (food grade). It's got a lot of uses, including as a plasticizer for soy resin*.
*soy resin: biodegradable homemade resin made from soy protein concentrate, water, baking soda, and glycerin, which can be soaked into hemp canvas or fibers, dried, and baked at low temp (240f) to make biodegradable composites.
Thermal Conductivity:
Mineral Oil = 0.133 W/mK
Glycerin = 0.290 W/mK (more than twice the heat dissipation of Mineral Oil)
It is more viscous, so it will produce more drag, but the viscosity will dampen sound more, and it's a very effective lubricant.
Like antifreeze, it will absorb a tiny bit of moisture over time, but it can be replaced yearly (it's fairly cheap). Probably needs more frequent changing in wet/humid area, depending on how well sealed the motor is.
It's so nontoxic that you can buy edible Glycerin (food grade). It's got a lot of uses, including as a plasticizer for soy resin*.
*soy resin: biodegradable homemade resin made from soy protein concentrate, water, baking soda, and glycerin, which can be soaked into hemp canvas or fibers, dried, and baked at low temp (240f) to make biodegradable composites.
hydro-one
10 kW
glycerine is too viscous when cold. its sugar, much like syrup. not for motors.......ATF is great as bigmoose mentioned....if u can stand that bleeding red stinky shit all over everything..........mineral oil is a good compromise imo, i mean u can drink it according to the governement.. 8) , (since standard oil developed the usp product in the 20s....thier first pharmaceutical drug)////// It is still distilled from crude oil i beieve, however water clear and tastless it is..... 
all my opinion as ive never oil cooled a hub
all my opinion as ive never oil cooled a hub
liveforphysics
100 TW
neithermovingnorstill said:
I don't see glycerin's improved thermal conductivity making up for it's increased viscosity (larger boundary layer, lower exchange/turnover rate etc). I also imagine it's drag may add another 50-200w of heat on it's own. Remember, all energy dumped into viscous drag in a fluid becomes heat.
ATF really seems to have every desirable quality we could want in an oil for our hub.
I've did a test with a 9c hub and the thermal imager that surprised me quite a bit. Pass current through the windings with a 67amp bench supply, I stopped when winding temp reached 180degC, the side plate of the motor was barely above room temp...
With oil in there, any point with oil touching the copper and touching the outside of the case is going to have the case sizzling hot.
The only thermal path out for a sealed motor is to transfer that thermal energy from the case into the air (and a tiny bit get radiated as IR). The amount of energy you can transfer to the air depends on the amount of temperature difference between the surface of the case and the air passing over it, along with the rate air passes over it. In other words, anything you can do to get the outside case hotter directly means you can shed more heat and operate at a higher continuous power (or, for running any given power level, the hotter the case of the motor gets, the cooler the heat generating parts inside the motor are).
neithermovingnorstill
100 mW
Ok, for starting the motor in a cold region, glycerin might be pretty viscous, although it's no where near as viscous as sugar syrup, because it's shares some properties with oil. (remember oil is a triglyceride with some hydrocarbons attached)
I am mainly concerned with noise reduction, that is my goal.
You might be overlooking how much the heat of the motor is going to affect the viscosity, just as cold thickens it, heat melts it.
In a temperate zone, there shouldn't be any issue, even starting on a cold morning can be done at low speed until the motor warms up.
The reasons I would opt for glycerin is:
1. I am in temperate zone.
2. Killing the motor noise is important to me, and viscosity is the key factor in a fluids ability to do that, it has to be viscous at room temp to have any viscosity left when the motor heats up.
3. Glycerin transfers 0.29 W/mK whereas ATF only transfers 0.20 w/mK.
I'm not recommending it for anyone else, it's probably what I would use if I wanted to quieten a motor.
It's also very eco friendly since it's a byproduct of refining biodiesel from veggie oil.
I am mainly concerned with noise reduction, that is my goal.
You might be overlooking how much the heat of the motor is going to affect the viscosity, just as cold thickens it, heat melts it.
In a temperate zone, there shouldn't be any issue, even starting on a cold morning can be done at low speed until the motor warms up.
The reasons I would opt for glycerin is:
1. I am in temperate zone.
2. Killing the motor noise is important to me, and viscosity is the key factor in a fluids ability to do that, it has to be viscous at room temp to have any viscosity left when the motor heats up.
3. Glycerin transfers 0.29 W/mK whereas ATF only transfers 0.20 w/mK.
I'm not recommending it for anyone else, it's probably what I would use if I wanted to quieten a motor.
It's also very eco friendly since it's a byproduct of refining biodiesel from veggie oil.
GCinDC
100 MW
how can i clean ATF out of the windings? can i use brake cleaner or will that damage the windings?
in vented side covers, the motor gets so hot now. my dry hs3540 stator (now dead) got nowhere near as hot in the vented side covers, and when i replaced it with the one that had been in the oil, it gets much hotter! i'm worried the ATF has now dried and gunked in the windings so it can't cool down.
thx
in vented side covers, the motor gets so hot now. my dry hs3540 stator (now dead) got nowhere near as hot in the vented side covers, and when i replaced it with the one that had been in the oil, it gets much hotter! i'm worried the ATF has now dried and gunked in the windings so it can't cool down.
thx
liveforphysics
100 TW
GCinDC said:
ATF doesn't dry up or varnish. It should be a free flowing liquid the whole time. Blowing it off with air seems like it would clean out residue from crevices in the motor pretty effectively, however I don't see a fine residue making a noticeable effect on cooling.
Can you check no-load current at full speed? You might have a shorted turn or something somewhere.
neithermovingnorstill
100 mW
Re Viscosity of Glycerin at cold temps:
I ran an experiment by putting some in my freezer overnight.
It does become more viscous, but not in the same way that sugar syrup does. If I tip the container, it moves slowly, but when I stir it, it's very easy to stir, very little resistance, so it is still effectively a fluid. Which is what you'd expect from something they put in antifreeze, because that wouldn't work if it became considerably more sticky at cold temperatures. It's a strange fluid, I'm confident it will work.
Re: GCinDC:
If you are confident that there is no glue used in the stator, you can probably use almost any solvent, as long as you remove the stator from the rest of the motor housing, and disconnect or cover any wires (the plastic shouldn't be soaked in solvent).
I like using orange oil for smaller jobs, but you'll likely need to soak your whole stator, so something cheap like gasoline should work fine.
If you think there is glue, and don't want to use solvent, I'd use a hair dryer rather than compressed air. Compressed air is very cold, but the hair dryer will make the ATF more runny. If it doesn't produce enough air pressure to push the ATF out, you could alternate with the hair dryer and a vacuum cleaner. Use gloves, the copper will be very hot.
Re: Liveforphysics:
That might be true, but even if the ATF doesn't dry, the motor running could heat it up and splatter it all over the stator, and since there isn't enough ATF to conduct the heat to the casing, and ATF isn't as conductive as Copper (almost nothing is), that might lead to some extra heat? There could be other stuff in there though, if it's a geared motor, fiberglass/resin powder from the composite gears, metal powder, dissolved plastic, etc. Probably a good idea to strip it by soaking it in solvent just to rule that out, because it's an easy fix if that's the problem.
I ran an experiment by putting some in my freezer overnight.
It does become more viscous, but not in the same way that sugar syrup does. If I tip the container, it moves slowly, but when I stir it, it's very easy to stir, very little resistance, so it is still effectively a fluid. Which is what you'd expect from something they put in antifreeze, because that wouldn't work if it became considerably more sticky at cold temperatures. It's a strange fluid, I'm confident it will work.
Re: GCinDC:
If you are confident that there is no glue used in the stator, you can probably use almost any solvent, as long as you remove the stator from the rest of the motor housing, and disconnect or cover any wires (the plastic shouldn't be soaked in solvent).
I like using orange oil for smaller jobs, but you'll likely need to soak your whole stator, so something cheap like gasoline should work fine.
If you think there is glue, and don't want to use solvent, I'd use a hair dryer rather than compressed air. Compressed air is very cold, but the hair dryer will make the ATF more runny. If it doesn't produce enough air pressure to push the ATF out, you could alternate with the hair dryer and a vacuum cleaner. Use gloves, the copper will be very hot.
Re: Liveforphysics:
That might be true, but even if the ATF doesn't dry, the motor running could heat it up and splatter it all over the stator, and since there isn't enough ATF to conduct the heat to the casing, and ATF isn't as conductive as Copper (almost nothing is), that might lead to some extra heat? There could be other stuff in there though, if it's a geared motor, fiberglass/resin powder from the composite gears, metal powder, dissolved plastic, etc. Probably a good idea to strip it by soaking it in solvent just to rule that out, because it's an easy fix if that's the problem.
liveforphysics
100 TW
neithermovingnorstill said:
Any solvent you want to soak it in should first be tested not to disolve the epoxy used on the stator.
The idea is to get as much fluid splashing over hot windings as possible, which transfers heat into the fluid by direct conduction, then the fluid falls/drips/runs back to the bottom of the spinning rotor magnet ring and transfers that heat the fluid absorbed into the side plates and magnet ring, which has a good thermal path to the outside air passing over it.
The thinner the fluid, the better the cooling performance will be. ATF is nearly water thin, which means rapid flow across the surfaces it's sprayed across, more heat transfer cycles between copper to case made, and better heat exchange.
Something that would be very interesting to do is to machine up and install a lexan side plate with a bearing cup in it, just needs to be strong enough to support the weight of the free spinning rotor. Then set the motor in a wheel stand with oil in it, give it a spin, and observe what the oil does while the motor is spinning. My guess is that if you fill the motor up to the point it's nearly to the axle, when you spin the motor, the oil slings in a ring around the stator, submerging the copper all the way around the perimeter. But... It might just sit in the lower half and only splash/dribble oil on the top side, I really don't know.
jussumguy
100 mW
I'm quite sure you're right.
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GCinDC said:Temp C on left and minutes on bottom axis:
dang it. i can't find original video of oil-cooled run, to compare with longer vented run! :x i'm pretty sure the oiled motor started cooler, but got hotter and stayed hotter than vented, tho i should shut up till i find that vid.
notes:
the 'no oil' line is for the unvented/unoiled motor.
ambient temp was ~5C hotter when the vented run was conducted.
except for a couple sections, i was trying to pull as much current (4kw) as possible, esp going uphill, to make the motor heat up as fast as possible.
you mean this? looks effective to me
liveforphysics
100 TW
Punx0r said:
Oil cooling electric motors has been practiced for a century or so with excellent results in most applications. Adding oil to off the shelf NEMA frame induction motors can double or triple the continuous power handling in many cases (and there are many papers written on this topic). The prius and volt both use this method of cooling, along with various electric TTXGP race bikes that have the rotor spinning in an oil bath (often circulated oil going to a cooler somewhere in extremely high power density motors).
I do not doubt it's been implemented in ways that didn't perform well. I also know excellent results can be achieved with lots of large openings in the side covers and good air flow moving through the motor (I've played that game as much as anyone with mixed but generally good results). I think oil cooling has even greater potential though if done right.
Regarding removing/cleaning ATF or any oil: ammonia works pretty well on it, and does nto nromally harm plastic surfaces, unlike most petroleum-bases solvents. That's what I have used to take ATF off of my rim braking surfaces and tire when I overfilled the Fusin motor.
neithermovingnorstill
100 mW
Correction about my glycerin experiment:
The glycerin is not "easy" to stir as I described. I had stirred it with my finger, which I now realize warmed and melted it instantly(because it's similar to oil), explaining why I cut through it easily. Stirring it with a spoon shows that it was quite thick. Not syrup in the freezer thick, but pretty thick, like stiff gel.
So it's definately not for folks in cold regions, but it should work fine for moderate zones to quieten a motor.
Another thing to note is that it is water soluble, so I think it wouldn't work in a motor with air vent holes if there is rain.
Washes off the hands really easily (it's the main ingredient in soap) unlike oil.
Liveforphysics:
Thanks for clarifying that. I was meaning in his case, where he had drained the ATF but had concern that there was residual ATF absorbed into the copper windings; so there wouldn't be enough ATF to submerge the stator in a spinning "ring". But I get what you're saying about the centrifugal force, the residual ATF would spray onto the casing, so it couldn't be accumulated in the windings. I agree, it's probably something else going causing the heating.
Amberwolf / Re ammonia:
Not speaking from experience, but ammonia is corrosive to copper and if the air contains moisture, steel.
Do you do anything to remove the residual ammonia, or does it evaporate off or something? If there was noticable corrosion, it would cause the copper to produce blue-green stuff.
Ian.mich / Re the oil cooling test results:
I saw that too, I think the reason the results were determined to show air cooling was better, was that the oil cooling was done when the ambient temperature was 5 degrees Celsius cooler. So even though the air venting results were warmer than the oil on average, factoring in the temperature offset, the oil fell behind. But they both work. I like the idea of keeping rain out and quietening the motor, so I would opt for liquid myself.
The glycerin is not "easy" to stir as I described. I had stirred it with my finger, which I now realize warmed and melted it instantly(because it's similar to oil), explaining why I cut through it easily. Stirring it with a spoon shows that it was quite thick. Not syrup in the freezer thick, but pretty thick, like stiff gel.
So it's definately not for folks in cold regions, but it should work fine for moderate zones to quieten a motor.
Another thing to note is that it is water soluble, so I think it wouldn't work in a motor with air vent holes if there is rain.
Washes off the hands really easily (it's the main ingredient in soap) unlike oil.
Liveforphysics:
Thanks for clarifying that. I was meaning in his case, where he had drained the ATF but had concern that there was residual ATF absorbed into the copper windings; so there wouldn't be enough ATF to submerge the stator in a spinning "ring". But I get what you're saying about the centrifugal force, the residual ATF would spray onto the casing, so it couldn't be accumulated in the windings. I agree, it's probably something else going causing the heating.
Amberwolf / Re ammonia:
Not speaking from experience, but ammonia is corrosive to copper and if the air contains moisture, steel.
Do you do anything to remove the residual ammonia, or does it evaporate off or something? If there was noticable corrosion, it would cause the copper to produce blue-green stuff.
Ian.mich / Re the oil cooling test results:
I saw that too, I think the reason the results were determined to show air cooling was better, was that the oil cooling was done when the ambient temperature was 5 degrees Celsius cooler. So even though the air venting results were warmer than the oil on average, factoring in the temperature offset, the oil fell behind. But they both work. I like the idea of keeping rain out and quietening the motor, so I would opt for liquid myself.
GCinDC
100 MW
i found it incredibly effective compared to no cooling at all!Punx0r said:
but i found in my application, the motor stayed the same temp w/ drilled side covers and cooled quicker. tho i don't have proof that it did cool quicker.
i'm going to run my route again tonight to test the temps w/ this motor. it hit 110 after only 2 miles on my way home. :?
is that common? any way to test for it?liveforphysics said:
the motor ran great in oil. but after third ride in drilled side covers, i noticed how hot it got!
i love brake cleaner. i think i'm going to lay the bike on it's side and hit it with that thru the drill holes. is that idiotic?
I don't have any thermal monitoring on my 5404. I've been going with a good guestimate of winding temps based on recent activity and ambients, plus its generally noticeable when the windings get too hot, as the motor looses power. I plan on running about twice the power I'm running now, so it might not be a bad idea to assist the cooling a bit. I have been considering just drilling and tapping a hole in the side cover, pouring in some Honda DW-1 ATF and sealing it with a small set screw.
Sound reasonable? Is it going to be constantly slinging ATF everywhere no matter how well its sealed? Think I even need to bother sealing much? The side covers are super thick, and I don't have a mechanical rear brake to get ATF on.
Sound reasonable? Is it going to be constantly slinging ATF everywhere no matter how well its sealed? Think I even need to bother sealing much? The side covers are super thick, and I don't have a mechanical rear brake to get ATF on.
itchynackers
100 kW
I think you need some kind of vend (pressure activated or not), otherwise the hot air will expand causing a pressurized container (which will leak somewhere). I've been thinking about how to implement a good vent for some time now. It will probably be a winter project. The vent I have now may leak about a drop per ride. Not enough to get on the brake disk, but still annoying.
For me, the ideal valve/vent would:
be small,
allow hot air to escape,
not allow air in.
That way I would end up with a "vacuum" sealed motor. Anyone know of any tiny valves like I'm describing?
Adam
For me, the ideal valve/vent would:
be small,
allow hot air to escape,
not allow air in.
That way I would end up with a "vacuum" sealed motor. Anyone know of any tiny valves like I'm describing?
Adam
ZOMGVTEK said:
without doing more sealing? i dont think that will hold it unless you want to add oil every day. What i've done to my motor is installed sealed bearings, covered the seals with gasket silicone (designed to keep in oil up to 260C), more gasket silicone on the covers, just enough so that it spilled out the side of the covers when tightening the covers, and a bit more between where the bearing touches the axle. before sealing it all up i drilled a hole in the cover near the axle and plan to silicone a 1cm piece of red aerosol can straw after filling with mineral oil. i contemplated doing dexron 3 or some other dielectric mineral atf, but i decided to keep it simple and hope the mineral oil doesnt foam. shaking the bottle alot doesnt seem to make it foam.
Ah...that I didn't think of, but you're right--it shoudl be corrosive to bare metals like that. In my case I simply used it on the wheel and the tire, not on the motor, as I ahven't disassembled the motor yet to add the temperature sensor (once I find one I can use) and seal it back up.neithermovingnorstill said:
On my wheel and tires, I didn't do anything other than wipe them down with a rag after spraying the ammonia on there, but like glass, it left my brake surfaces VERY clean, squeakily so.
I guess it would be a bad idea to use it to clean the inside of the motor after all.
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