I have found a way to easily and succesfully cool hub motors

[dogman dan]

That's a trip, he does have the fork on backwards in the picture on page one.

Tough crowd here on ES eh? I totally believe you that it's working. It should be effective on a dd motor. I still can't believe nobody makes a motor with some built in cooling fins.

But some insist on numbers. Best bet might be to get yourself one of those heat guns. You know, point it to see the temp on something you don't actually touch. If you have one 1/2" hole in a hub cover, with some metal tape over it, you could even pull the tape and get readings directly from the stator. Stator temps will really tell all. Or add a temp sensor right on the stator, that's the very best way to get real stator temps. Fascinating to see on one of those how much difference it makes how you ride. You see that as it heats up though, rest of the ride you just see how long it takes to finally cool off. Even small vent holes help a lot with cooling when stopped quicker.

Anything that helps cool the cover of the motor will create a better heat differential between the hot stator coils and the cooler cover. Bigger the difference, the faster the motor will cool. It's the same thing that happens in winter, when you can push one of these 28mm motors a lot harder, a lot longer, before it gets all hot.

Re the axle, yes, the axle is a shitty conductor. But nevertheless, it's the first part on the outside that gets hot. This is because the stator, which makes the heat, never touches any other part of the motor except the wires. The copper wires are good conductors, so they do get hot nice and fast too. Then the magnets are very close to the hot stator, so they get warm fairly quick. Lastly, the outside covers get warm, with a big air gap. Likely the hot magnets which are in contact with the covers heat the covers. So when checking a DD motor for heat, I feel the middle of the motor, not the side cover.

 

[ebikedelight]

when my wife returns from vacation..ill try and get some photos uploaded...some people also wanted some close up photos of how I built and attached my battery holder to my ebike frame...so Ill try and get that done also.

Sorry i didnt read all the posts.....but why did you build your fork in....... the wrong way?

In bikeforums there are threads about this......they share pictures of this to laugh about it.
But maybe you did this on purpose.......

ive already explained it , numerous times. It was part of a experiment done, in regards to mounting my battery/controller combo, and additional space. You see, im not afraid to experiment with different ideas....people can laugh all they want . I retired at age 33 and am a inventor with my own U.S. patent. I wonder if they would laugh about that ? :wink:

If i was really concerned about people laughing at me, because my front fork was inverted, I woulda took the photos after I put the front fork back to normal....

take a look at my battery mounting system...which I built . Its 2 simple pieces of aluminum bolted to the inside of the frame in a cross manner . Its lightweight and strong and inexpensive and it completely keeps the battery from moving in a side to side - front back position . The battery is held down using 12 " piece of cut seat belt with a spring attached to 1 end. It holds the battery down tightly in all conditions, and yet allows me to easily and quickly detach the battery from the frame, when needed.

 

[ebikedelight]

That's a trip, he does have the fork on backwards in the picture on page one.

Tough crowd here on ES eh? I totally believe you that it's working. It should be effective on a dd motor. I still can't believe nobody makes a motor with some built in cooling fins.

But some insist on numbers. Best bet might be to get yourself one of those heat guns. You know, point it to see the temp on something you don't actually touch. If you have one 1/2" hole in a hub cover, with some metal tape over it, you could even pull the tape and get readings directly from the stator. Stator temps will really tell all. Or add a temp sensor right on the stator, that's the very best way to get real stator temps. Fascinating to see on one of those how much difference it makes how you ride. You see that as it heats up though, rest of the ride you just see how long it takes to finally cool off. Even small vent holes help a lot with cooling when stopped quicker.

Anything that helps cool the cover of the motor will create a better heat differential between the hot stator coils and the cooler cover. Bigger the difference, the faster the motor will cool. It's the same thing that happens in winter, when you can push one of these 28mm motors a lot harder, a lot longer, before it gets all hot.

Re the axle, yes, the axle is a shitty conductor. But nevertheless, it's the first part on the outside that gets hot. This is because the stator, which makes the heat, never touches any other part of the motor except the wires. The copper wires are good conductors, so they do get hot nice and fast too. Then the magnets are very close to the hot stator, so they get warm fairly quick. Lastly, the outside covers get warm, with a big air gap. Likely the hot magnets which are in contact with the covers heat the covers. So when checking a DD motor for heat, I feel the middle of the motor, not the side cover.

The real test comes in the summer months, when its 100 degrees out , with full sunshine beating down on the hub motor, and pushing the 1000 watt motor to the 2000-2500 watt ranges. If this mod results in keeping the hub motor in the ' warm: zones, under those conditions, then I will be completely satisfied with the results . I will not deem this mod a complete success, if it only keeps the hub motor warm, in the cooler months of the year. Ill have this info in about 3 months once the heat of summer kicks in...average temp in my area is still around 65 degrees right now .

 

[dogman dan]

Amen to that. I used to run 3000w all winter with no problems, but then some point in the spring, about when the afternoons reached the mid 90's F, I'd melt down another motor. Usually just fry the halls. I could afford this, since I had two motors. I'd swap on the other one, and put on the 1000w controller for the summer riding. Then I had till next spring to fix the melty motor. Swapping controllers at about Easter would have been smarter, but a few more days with 3000w was just too tempting each spring.

Not sure what kind of riding you do, but this was punishing dirt riding for me. Lots of tight turns where you brake then wot, or long grinds up 15% grade hills. Always wot, no grinding along pedaling up hills.

Temps to avoid, over 300F inside, some will say 250. Keep it under 200F on the actual coils and you will never even brown the winding varnish. Once you do overheat, stopping just cooks off your halls. You'll get a heat spike if you don't do a cool down run at 500w or so. That's what cooling holes, even if you keep them taped over for the ride can do for you. Stop, open the holes, and cool air will suck in the lower holes saving your motor. I eventually took a different approach. I drilled many tiny holes right by the stator. Too small for a rock or even large grain of sand, but for sure lots of dust gets inside. But even the tiny holes let some air flow, and use my nose as a temp sensor during the ride. Smell that motor, back off some, and start your cool down run. You'll smell it at 300f.

 

[ebikedelight]

Amen to that. I used to run 3000w all winter with no problems, but then some point in the spring, about when the afternoons reached the mid 90's F, I'd melt down another motor. Usually just fry the halls. I could afford this, since I had two motors. I'd swap on the other one, and put on the 1000w controller for the summer riding. Then I had till next spring to fix the melty motor. Swapping controllers at about Easter would have been smarter, but a few more days with 3000w was just too tempting each spring.

Not sure what kind of riding you do, but this was punishing dirt riding for me. Lots of tight turns where you brake then wot, or long grinds up 15% grade hills. Always wot, no grinding along pedaling up hills.

Temps to avoid, over 300F inside, some will say 250. Keep it under 200F on the actual coils and you will never even brown the winding varnish. Once you do overheat, stopping just cooks off your halls. You'll get a heat spike if you don't do a cool down run at 500w or so. That's what cooling holes, even if you keep them taped over for the ride can do for you. Stop, open the holes, and cool air will suck in the lower holes saving your motor. I eventually took a different approach. I drilled many tiny holes right by the stator. Too small for a rock or even large grain of sand, but for sure lots of dust gets inside. But even the tiny holes let some air flow, and use my nose as a temp sensor during the ride. Smell that motor, back off some. You'll smell it at 300f.

yeah...for me, im not as much concerned about debris getting in the open holes [ because the holes could be covered with something that still allows airflow, but keeps out debris } as I am having mositure build up in the hub from the humidity in the air..especially in summer months when you have 70 % and higher air humidity. That moisture from the air can result in a lot of dampness inside the hub motor

further proof of this is in storm shelters...where the shelter itself doesnt have water leaking in, but the walls get wet due to the humidity in the air.


its important to note that in the summer, when its not only hotter air temp , but the air is thicker with humidity and you have the blaring sun beating down on the hub motor , that can result in a tremendous loss of air cooling capabiltiies .

Just because its 30 degrees warmer out doesnt mean your motor will only get 30 degrees hotter...it could get 60 degrees hotter or more...just from the solar radiation beating down on the black hub motor while you ride in the heat.

 

[dogman dan]

Tiny holes will blow out any excess humidity every time the motor heats up. So even some very tiny holes will completely prevent water build up.
But humid air will suck in each time it cools too, so my stators are all rusty now, even in my dry climate. Not big rust, just a light coating along with the dirt.

So drill yourself some holes, large or small, and then spray coat your stator.

 

[ebikedelight]

Tiny holes will blow out any excess humidity every time the motor heats up. So even some very tiny holes will completely prevent water build up.
But humid air will suck in each time it cools too, so my stators are all rusty now, even in my dry climate. Not big rust, just a light coating along with the dirt.

So drill yourself some holes, large or small, and then spray coat your stator.

well if my heat sink mod works, in the summer months also, ill be happy to keep all the holes covered up, because in the end, I like a closed hub system , that can be kept from overheating or allowing contaminents to enter , with such a simple mod as heat sinks.

 

[gogo]

I like the IR thermometer idea. A calibrated IR camera would be even better.

IR cameras will soon be one of those things you feel naked without.

http://scienceshareware.com/bicycle-generator-faq.htm#exceeding-current

 

[BlueRain]

Waiting on pics ...

 

[dogman dan]

Certainly, if you must have holes to cool your motor, IMO, you are just pushing your motor too hard. Too much hill for the power you have, too much power for the motor you have, whatever. You want big power, get a big motor with fat magnets. It will haul ass, and not waste power into heat.

I DO like your cooling fin idea. I just wish it was built into motors, since I live in a flaming desert. I cannot run smaller gear motors in summer. I'll fry them too easy, because I have heat and hills. Be fine if I weighed less, but I'm about 180-190.

But you said you had a problem with water in the motor. If so, occasionally pulling the tape over the holes on a motor on a drier day, running it to blow the humidity out when the motor heats up, then putting the tape back is the easy way to dry out a soggy motor. You don't need to swiss cheese the motor to do this. Just two 1/4 inch holes will do the trick. One on one cover, the other on the other cover, 180 degrees opposite. So when you stop with the motor warm, air will suck in the low hole and chimney out the high one. After it cools, put the tape back. Aluminum tape for hot ducts is the kind of tape to use. It can be painted black to match your motor.

 

[ebikedelight]

I have never tried the " open holes" method of cooling on a hub motor because I dont like the idea of mositure forming in the hub via the humidity in the air. I realize that humidity may not result in alot of water inside the hub motor, but do think its enough mositure to cause surface rusting, which could eventually lead to other problems if not consistently tended to [ which means periodically taking the wheel off the bike, unhooking all connections, then taking hub apart }

My idea with the heat sinks, is a attempt to achieve siginificant cooling , with minimal price, complexity .

So far, im happy with the mod....but have to wait till the hottest part of summer to ensure this mod will work in all weather conditions. If my motor starts to get very hot again in summer months, then I still have options that may allow this simple mod, to work better...

1. Keep the heat sinks I have now...but grind down the base plates on them, so they are as thin as possible , then reattach them. This would mean less material the heat inside the hub would have to penetrate to make it to the cooling fins .

2. upgrade to heat sinks with larger fins

3. try cooper heatsinks

4. instead of using 4 heat sinks per hub side, use 6 per side

5. attach a radiator tube to the bike and position it so it funnels air flow from the forward moving motion of the bike, directly at the heat sinks.

FWIW...I would never paint my outside hub covers or heat sinks black. I think doing this just attracts more heat, thru the radiation effects of the bright hot sunlight in the summer months...and its the summer moneths when these motors are most likely to overheat the most.

As far as doing the 2 open holes method of cooling. If I were to do that , I would coat the inner hub compments with a urethane to keep them from rusting, and then attach one 90 degree elbow to each hole, facing forward....1 on the left side at the 12 o clock position..the other on the right side at the 6 o clock postion...

this would force air into the hub , as the bike moves forward...I think resulting in much better cooling , then just having 2 open holes that rely mainly on convection cooling of static air flow . Forced air flow would have to yield better cooling effects in this scenario.

my heat sink mod, relys on both conduction and convection cooling / wind chill effect.

the heat sink sucks the heat from the inside of the hub motor { conduction} ..then cools it thru the fins to the outside cooler air { convection}

 

[ebikedelight]

photos coming...wife should be home with digital camera by end of week.

 

[Ykick]

3. try cooper heatsinks

Do you have a link?

 

[ebikedelight]

3. try cooper heatsinks

Do you have a link?

my fault...

meant to type

copper heat sinks.

copper is supposedly a much better conductor then aluminum heat sinks ..but more expensive.

for now...ill stick with the aluminum, since I have them, and am hopeful they will provide adequate cooling for my needs in the summer months.

the aluminum side covers also use conduction and convection , like the heat sinks...but they dont do it as well.

The heat sinks allow one to pinpoint where much of the heat originates , then attach the heat sinks directly above that area to whisk away the heat quicker and more efficiently.

The flat surface of the aluminum side covers, is very ineffective in the convection process, and thats why it holds the heat for so long, once its hot. The moving outside cooler air, to easily slides over the smooth surface of the side covers.....

its kinda like the opposite effects of a heat exchanger on a woodstove....

if you just have a straight chimney pipe , going up, you will generally lose more heat to the outside of the house, then if you put in a 90 degree bend, with a square heat exchanger in the middle of the stove pipe , that is inside the house.

on our ebikes...the flat aluminum side covers do not provide the needed surface area to best release the heat...the aluminum heat sinks have the fins , which disperse the heat better with more surface area for the outside cooler air to not only circulate over , but also thru ...which is 2 means of cooling using the outside air.

 

[ebikedelight]

I would imagine, the absoulote best heat sinks for this application, would be made of silver , but im not aware of anyone that makes them .

With silver around $17 a oz...it would be more expensive..but should provide much better cooling them aluminum or copper.

silver is fantastic at temperature conduction. If anyone has a silver coin { like a american silver eagle or canadian maple leaf} you can prove this by putting a ice cube on top of the silver coin...it will melt the ice cube right before your eyes.

its amazing.

 

[friendly1uk]

Nice to see someone acted upon this idea. Did I miss the pics though?

 

[ebikedelight]

Nice to see someone acted upon this idea. Did I miss the pics though?

pics coming...have to wait for my wifes return from vacation...she has the digital camera.

 

[Kyle201]

Cool, curious to see pics.

I'm actually going to do a very similar mod on my H4060 really soon.. mostly with heat sinks between the spokes to cool the magnets, and possibly on the side covers too.

I wanted to use copper sinks, but there's not too many easily found with longer fins, only really low profile ones for computer ram. Lots of tall aluminum ones though, and perhaps I will install those with a copper base plate.

Alibaba has some vendors who will make custom sized heat sinks in copper or aluminum... can get some with nice tall 'splayed' pin fins... but probably just look for something off the shelf for now.

 

[macribs]

Just a word of warning when mixing different types of metal. Galvanic corrosion.
Copper and aluminum does not mix well. Not sure if steel/copper works. Look into it before you strap on cooling fins that you have chosen the right material.

 

[Kyle201]

Just a word of warning when mixing different types of metal. Galvanic corrosion.
Copper and aluminum does not mix well. Not sure if steel/copper works. Look into it before you strap on cooling fins that you have chosen the right material.

Well there would need to be a thermal adhesive between the differing metals, wouldn't that prevent galvanic corrosion?

 

[ebikedelight]

1. (highest) Silver: 4.29 W /cm K
2. Copper: 4.01
3. Gold: 3.17
4. Aluminum: 2.37

as we can see, silver has almost double the thermal conductivity rating of aluminum.

if I could think of a way to make some silver heat sinks, with fins, I would try it...I have several silver coins to experiment with.


but in the end, copper is probably the best metal to use...its not nearly as expensive as silver....and is still much better then aluminum.

 

[ebikedelight]

be nice to find some type of heat sink mold...then be able to melt down some copper or silver...and make some really conductive heat sinks....

 

[macribs]

Yeah a big bad silver heat sink in the middle of the hub between the spoke holes. All the way around. Should really help, the total surface/cooling area would be the size of a football field. :lol:

If you can find a way to have those custom made count me in for 1.

Btw this impeller will go well with fins I think. 20 AUS.

 

[chucho]

i will stay around

 

[made_in_the_alps_legacy]

what about using "plain copper" rivets or screws as similar "heat transfer bridges"
(flat side on the Inside, rivet protrubing outside like a single "pined" heat sink multiplied as many times as possible)

...appart from the "sea urchin" look the hub would have