Air Cooling my x5

[stew007]

The oil cooling could work, but! you have to take into consideration the effect of the viscosity of the oil/coolant acting between the stator and the magnets as it is a tight gap, so it will act like a torque converter, like which joins your auto transmission to the engine of your car, which may reduce your efficiency, the faster you go, the more friction would be generated.

Also, Air, when it is enclosed acts as an excellent insulator, thats the reason why double glazing is so effective, and other insulations act to trap air in order to retain heat. So any form of cooling fins to act on a sealed air cavity will probably have little effect. The most effective way would be to remove the hot air from inside the casing. If the shaft was bored and joined with flexible tubing to an air intake formed on the front of the bike in the form of an air scoop (with a particulate filter), the exit holes could be on the motor plates near the windings (so the air passes over the windings to get out, with mesh screens over the holes), this would enable proper air cooling, and at the same time remove the possibility of dust getting in. Also an inline fan (many high output RC ducted fan kits would be ideal for extreme CFM!) coupled to a thermostat on the motor could be used to assist the ram air effect from the forward motion of the bike during times of extreme ebiking . So this system could be set up so it is totally automated, and would be great for extreme high power setups

[solarbbq2003]

damn thought it might work, oh well back to the drawing board

[potatonet]

am I going to have to draw my system for people to understand it?

[The Stig]

The oil cooling could work, but! you have to take into consideration the effect of the viscosity of the oil/coolant acting between the stator and the magnets as it is a tight gap, so it will act like a torque converter, like which joins your auto transmission to the engine of your car, which may reduce your efficiency, the faster you go, the more friction would be generated.

Also, Air, when it is enclosed acts as an excellent insulator, thats the reason why double glazing is so effective, and other insulations act to trap air in order to retain heat. So any form of cooling fins to act on a sealed air cavity will probably have little effect. The most effective way would be to remove the hot air from inside the casing. If the shaft was bored and joined with flexible tubing to an air intake formed on the front of the bike in the form of an air scoop (with a particulate filter), the exit holes could be on the motor plates near the windings (so the air passes over the windings to get out, with mesh screens over the holes), this would enable proper air cooling, and at the same time remove the possibility of dust getting in. Also an inline fan (many high output RC ducted fan kits would be ideal for extreme CFM!) coupled to a thermostat on the motor could be used to assist the ram air effect from the forward motion of the bike during times of extreme ebiking . So this system could be set up so it is totally automated, and would be great for extreme high power setups

Thats not quite how Torque converters work... They dont really use friction as the driving force, they use the momentum of the fluid pushing against fins. (From what I gather watching this vid http://www.youtube.com/watch?v=MvLoX0z9qoY)


Come on people don't give the oil cooling idea the back seat!


I know the thread is about air cooling but this could be a lot easier and more effective! I think it has potential to provide excellent heat transfer from the stator to the outside of the casing, rather than the insulation that the air provides. The only problem it might cause is if it degrades the adhesives in the motor which seems highly unlikely, Reid Welch has flooded his Ezee hub with oil and kept it partially filled for a couple months and has had no problems yet. He has also observed no loss in efficiency while running the motor with little oil in it. http://endless-sphere.com/forums/viewtopic.php?f=6&t=7454&hilit=ping+battery&start=255#p148040

THE YELLOW LINE is the oil would be.

ebmstru.jpg (108.08 KiB) Viewed 1021 times

I think its worth considering that the oil might not add much friction to the system because any friction would occur between the flat, continuous surface of the magnets and the surface of the stator. You would only add enough oil to just touch those two surfaces when the motor is spinning fast. From the crystalyte website I see that the "available" rotors on the LEFT have nice flat surfaces. I suspect the ones on the right are very rare.



The other surface the oil would touching at high speed is this the stator. It seems to have a nice flat surface too. Not sure if the slots in the stator would cause much friction but if they do they could be filled with something so the surface is completely flat.



All I'm saying is it seems like having oil in there would be nice and frictionless. I know some chemical engineers and I can ask them if they think oil could degrade any type of adhesive, which is pretty unlikely because that would be a quite a design flaw for an adhesive.

[stew007]

yep, your right enough so it seems like this will be good idea, so lets hope for some good results the thinner the liquid the less friction. A non conductive liquid, with corrosion inhibitors http://www.acousticpc.com/feser_one_uv_ ... olant.html

[The Stig]

yep, your right enough so it seems like this will be good idea, so lets hope for some good results the thinner the liquid the less friction. A non conductive liquid, with corrosion inhibitors http://www.acousticpc.com/feser_one_uv_ ... olant.html

That may work even better, using some really low viscosity liquid like coolant:)

That particular one has corrosion protection for "COPPER, ALUMINIUM, BRASS and NICKEL." I think there are other metals in the motor's magnets.

[TylerDurden]

You would only add enough oil to just touch those two surfaces when the motor is spinning fast.

If that's were case, how much heat conduction could you expect: stator->oil->case... and how much surface area would the oil cover in areas that can expell heat (side covers)?

Also, How would you determine that amount?

That may work even better, using some really low viscosity liquid like coolant:)

Electrically non-conductive, of course...

[The Stig]

You would only add enough oil to just touch those two surfaces when the motor is spinning fast.

If that's were case, how much heat conduction could you expect: stator->oil->case... and how much surface area would the oil cover in areas that can expell heat (side covers)?

Also, How would you determine that amount?

A hell of a lot more than air! The stator is the part that heats up and there is a nice big surface area around that stator. The oil would move that heat to the casing. Casing, side covers... it's all one piece. It gets a very big surface area and gets lot of wind so it will dissipate that heat. You could even put some heat sink compound were the spokes attach to the hub so the spokes act as fins.

That may work even better, using some really low viscosity liquid like coolant:)

Electrically non-conductive, of course...

Yup, just like oil, a very non-conductive substance.

[TylerDurden]

The stator is the part that heats up and there is a nice big surface area around that stator. The oil would move that heat to the casing. Casing, side covers... it's all one piece.

I'm skeptical.
Based on the above illustration, the oil would be mainly between the laminations and the magnets; barely touching the sidecovers, which have the most surface-area/mass . The sidecovers only contact the case on the flange... a few square inches at best.

By contrast, airflow in the motor is turbulent, not pinned to the perimeter by centrifugal action like the oil is. Simple open ventilation may cool much better than oil, unless the oil is circulated through some sort of heat-exchanger.

[potatonet]

and what did I say?

-.-

[Ben]

I like potatonet's idea.

Link was thinking about doing something quite similar a while ago:

http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=7296

[steveo]

Hey Everyone,

I can not believe the amount of replies I have gotten on this subject .. !! .. There have been many great suggestions made on how to cool this hub motor .. some very intersting ones as well ..

Personally I still think air cooling is the best & EASIEST way to cool your own x-lite motor ..

may not be the best for motor life .. however .. some precautions could be meet to do you best to ensure long engine life!

There have been a few suggestions .. but not many on if we where to drill out the side covers.. what is the best way to have air forced in to cool the windings most effectively?

-steveo

[Zoot Katz]

. . .
There have been a few suggestions .. but not many on if we where to drill out the side covers.. what is the best way to have air forced in to cool the windings most effectively?

The general rule of thumb for drillium is to keep drilling until the part fails, then eliminate the last set of holes on the next one.

[curious]

Technically ugly but you can get coolant in/out the hub in a closed system (potatonet idea) without custom axle by:
- replacing two phase wires with short pieces of small diameter copper tube covered with heat shrink isolation;
- running these pipes where wires currently are;
- attaching inner and outer exchangers to these two pipes with non-conductive couplers;
- soldering the replaced phase wires to the corresponding tube inside/outside before couplers.

[curious]

But I am still kind of like the helium fill idea. I wonder if one properly seals the sideplates and wire path (also good for waterproofing) how fast helium will diffuse from the hub without excess pressure ? OK helium is leaky but it has to be replaced with air, otherwise there will be negative pressure in the hub.

If suitable helium concentration can remain there for a week or so what is the big deal keeping a helium tank in the garage ? Will keep kids happy. And one could be proud of using true nuclear reactor technology in their hub

[solarbbq2003]

how about this, big thin disc of aluminium, heatpaste/glue onto the coils, some holes in it also, lots of space in the middle could put some big junks of aluminium in there ( with thermal contact to teh big aluminium disc) also to soak up some heat, might not be much space between the coils and side plates could be a problem

cooling1.jpg (133.93 KiB) Viewed 915 times

[solarbbq2003]

just something of interest, to flatten down the coils ( on the sides where they are near to the side plates) they just use wooden mallets, and bash/squash it into place.

[Link]

I like potatonet's idea.

Link was thinking about doing something quite similar a while ago:

http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=7296

Still working on it. Only reason I didn't finish it a week or two ago is because I'm still waiting on that LiPo order from Hobby City. Got the chargers restocked thrice. Batteries?

FWIW, the specific heat capacity of water is 4186 J kg–1 K–1 (4186 joules to raise the temperature of 1kg of water 1 kelvin [aka celcius starting from absolute zero]). I'm expecting 200kg/hr through the hub. Rounding down to 4000 J kg-1 K-1 to compensate for whatever I put in it to keep bacteria from growing, that calculates out to about 222Wh/hr/K, which, assuming the radiators are able to cool the water coming from the hub by even 10°C (which I think they should; there's a total of 2m^2 of surface area on their fins), I could theoretically STALL the hub on a 2kW controller and it wouldn't be able to overheat.

Do I have that right? Even for watercooling, that sounds like a little more than I'd expect to be able to hope for...


The Stig's idea might have some merit. Even though there will be some increased friction and they don't transfer heat as quickly as water (which does it about 30 times faster than air), most alcohols and oils still conduct heat between 5 and 10 times better than air according to Wiki. Tradeoff might be worth it.

[michaelplogue]

Most water-cooled computer projects used distilled water with an anti-corrosion /algae growth additive. A good source for this sort of stuff is Frozencpu.com

http://www.frozencpu.com/cat/l2/g30/c103/list/p1/Liquid_Cooling-Coolant_Additives.html

[markcycle]

I'm hesitant to show my work on air cooling because it seem to instill passionate responses beyond the technical review. But I did a crude form of air cooling on my X6 while I wait for my next X6 prototypes. The air is pulled in across the winding and out the disc rotor side. The fans are on both side of the stator and the stator is drilled out to let air pass. This was a fast and dirty experiment but it definitely works. Whats even more surprising is my WH/mile went from 125 to 100 just by adding the fans. I did 2 test loops on a course I have done 100's of times, and really believe air cooling improved the motors EFF about 20% Even the AH used for the ride went down from 12 to 10 AH I was stunned by the results. The course is 9 miles (14.4Km) and the air temp was 85F. I hope to repeat the test a few more time before I have to swap out the wheel for the new prototypes.

Just wanted to add this is doable on any X5

Mark

[TylerDurden]

Even though there will be some increased friction and they don't transfer heat as quickly as water (which does it about 30 times faster than air), most alcohols and oils still conduct heat between 5 and 10 times better than air according to Wiki. Tradeoff might be worth it.

Only if the media can circulate as fast, or faster than air can; plus similar or greater surface area and airflow is needed to extract the heat from the media to air at the other end of the circuit.

Since air is the final destination for the heat, any cooling system needs to convey heat and transfer it to air faster than air alone (to be an improvement).

As Reid pointed out many moons ago, a small hairdryer fan can continuously extract 1500W of heat from a hairdryer... the coils having a surface area of only a few square inches.

[fechter]

Markcycle's approach seems very practical. I run forced air cooling on my non-hub motors and have not had problems with contamination from road grime. The inlet screens should be good enough. A little rain water won't hurt anything.

You can actually get the cover on with those fans in there?

Even if you could get good thermal conductivity from the windings to the outside of the case, the amount of heat you can dissipate by directly blowing air on the windings would be more.

If the actual motor windings were made from tiny copper tubes with water circulating through them, you might be able to do slightly better, but that would be insanely difficult. If you try to run a copper cooling tube from one winding to the next, you would need a non-conductive section between windings to prevent the cooling line from acting like a shorted winding.

[markcycle]

Markcycle's approach seems very practical. I run forced air cooling on my non-hub motors and have not had problems with contamination from road grime. The inlet screens should be good enough. A little rain water won't hurt anything.

You can actually get the cover on with those fans in there?

I had no problem getting the covers on with my X6 but have not tried it with an X5. hopefully I have inspired someone to try it on an X5 as my current work is with the X6. The fans are only 10mm high so I think it will work. The key is the fans need to be under the bearing and the holes in the covers need to be over the windings. I do have a X5 stator in my junk pile and covers so I'll try and do a dry fit with the fans in place later in the week.

The only thing is, you need to be very careful not to nick the winding when drilling the screw holes for the fans and tapping the holes is tricky because the aluminum is very gummy, use cutting oil when tapping. Also use locktight on the threads.

Mark

[Link]

Even though there will be some increased friction and they don't transfer heat as quickly as water (which does it about 30 times faster than air), most alcohols and oils still conduct heat between 5 and 10 times better than air according to Wiki. Tradeoff might be worth it.

Only if the media can circulate as fast, or faster than air can; plus similar or greater surface area and airflow is needed to extract the heat from the media to air at the other end of the circuit.

Eh? I meant they're better than air when it comes to thermal conductivity. Their specific heat capacity is far greater than air's. If it already conducts heat faster than air, why does it need to circulate at all?

As for actually getting it OUT of the hub...uh...glue on some fins/heatsinks?

[TylerDurden]

Eh? I meant they're better than air when it comes to thermal conductivity. Their specific heat capacity is far greater than air's. If it already conducts heat faster than air, why does it need to circulate at all?

So you don't have a motor full of hot oil. (It's just more hot mass unless you can cool the oil.) The oil will absorb less and less heat from the windings the hotter it gets.