Motor cooling

I'm guesssing your talking electric motors? anyone in particular?

I did have a an idea to watercool the Unite motor using
pc watercooling equipment. Was planing to coil 1/2 copper tubing around the motor, then use a Laing 655 or 355 pump to circulate the water (would use Tectalloy/water mix) and a 360 size pc radiator...Have since scrapped the idea as my motor hardly even gets warm...
 
I was thinking of doing an Ice Cooling technique where you just built some kind of wrapper around the shell of the motor and filled it with Ice. By the time the Ice melted your ride would be over.

I tried this last summer by simply placing an Ice pack onto the shell between rides to bring the temperature down and it worked great.

Sometimes low tech works fine... :wink:

(just pre-cooling the motor shell with Ice did a good job)
 
I'm too cheap for that. :wink:

Ice is easy because I just get it from my freezer... it's low tech.

Liquid nitrogen is high tech.
 
To answer the question, a watercooled motor works by circulating water around the hot bits, then pumping it into a radiator where large amounts of air can be passed over it. It can increase the amount of air you can use to cool the motor, and the liquid around the motor also helps increase the thermal mass (or better, makes a "changeable" thermal mass that constantly gets refreshed with cooler material) :D

The problem usually is that it is usually only practical on a motor that has a static armature..
Steve
 
For short distances (and times) the use of ice makes the most sense because the weight of ice relative to water in it's cooling ability is very good. (water 1g/1cal/1C verses ice 1g/80cal/1C)

The world speed record for an electric car (300 mph) used ice cooling.

It's only going to work if your ride is short... (it's a one shot deal)
 
Jozzer said:
To answer the question, a watercooled motor works by circulating water around the hot bits, then pumping it into a radiator where large amounts of air can be passed over it. It can increase the amount of air you can use to cool the motor, and the liquid around the motor also helps increase the thermal mass (or better, makes a "changeable" thermal mass that constantly gets refreshed with cooler material) :D

The problem usually is that it is usually only practical on a motor that has a static armature..
Steve
Click to expand...

That is what I was afraid of, with a rotating armature there was no way of circulating a cooling fluid around the coils of wire. You could still run cooling fluid through some heat sinks inside the motor and pick up some radiant and convection heat.

I guess the best least complicated way of getting heat out of the motor is still fan cooling. The only problem with fan cooling is keeping the dirt and water out on a bike setup.

Deron.
 
Theoretically, brushless motors should be capable of operating in completely submerged conditions. As long as the bearings are sealed, all electrical connections (winding terminations) are insulated, and there is no exposed iron that can rust, you're good to go.
Unfortunately at least one of those three criteria are not met in brushless motors, so you still have to watch out.

Anyway, yes, it is much easier to cool inrunners as the windings are more accessible. High power water-cooled AC induction motors are not all that uncommon. With outrunners, though, it's much more difficult to transfer heat from the internal windings through a liquid medium, though it can be done.
 
Another method of cooling is to wind the motor with copper pipe instead of solid copper wire. Cooling water is then circulated directly through the windings. I've seen this used on induction heating coils. It likely works best with short coils only, and the reduced copper fill from the tubing will likely reduce any power gains from the improved cooling.

Marty
 
safe said:
I guess the best least complicated way of getting heat out of the motor is still fan cooling. The only problem with fan cooling is keeping the dirt and water out on a bike setup.
Click to expand...

I would not worry about dirt too much. These motors have shielded or sealed bearings and are better protected then a lot of bike hubs that use loose balls and cones. Covering the motor and providing a large enough plenum for the water do drop out of the air stream should keep most of the water out. Using a jack shaft will allow you to keep the drive sprocket out of the motor enclosure, so that the chain to the wheel will not carry water to the motor. This is an untested idea, but if you are not in a hurry, you can watch my "Bubba's Expermient" tread to see if it works.

Bubba
 
I have found that with the Unite motors the shell is very thick steel and has a lot of thermal mass on it's own. By simply placing an ice pack on the shell while you are charging between rides you can get the shell to close to freezing when the outside temperature might be 100 degrees F. If nothing else it allowed me to ride the bike and come home with a super heated motor (probably 130 degrees F) and more quickly get the heat dissipated. Without the ice pack my second ride of the day would start off with a really hot motor and it would overheat all the more quickly.

Now if you were using a motor that doesn't have much thermal mass of it's own then this idea would not work. You could carry the ice with you as you rode if you built some special container for it that strapped to the motor. All this is contingent on the idea that you ride in half hour bursts. Not everyone wants to use up their whole battery in one intense ride and want instead to start and stop. Of course, for these people the need for cooling is not so critical.
 
You could always submerge the motor in a sort of no conductive cooling fluid. The PC guys use mineral oil but there is a couple more expensive liquids on the market that might be more suited.

http://www.removethelabels.com/2009/01/29/hardcore_computers_oil_submersed_compter_pc/

I plan on putting two holes in my motor for a forced air cooling but I am going to throw a cheap air filter on my blower fan just to keep out the bulk of crap.
 
Is anyone able to offer a rough guide, or share any experiences, with monitoring magnet temp on an outrunner by mounting a temp sensor say near the mounting screws?

E.g. if the fixed part is at 100 deg C, would the magnets be about two thirds of this temp?

I understand that it would all be dependant on airflows & conduction and it would move around a lot with time, and I guess the worst time would be at the end of a hard run when the motor stops spinning, the magnet temp would continue to rise.

I would imagine the windings would be running hotter than any other part of the motor.

At the moment I have to pull over and put my hand around the rotor to check. If it's too hot to hold my hand there I ease back a bit on the throttle. :?
 
I have not tried to measure the temp of the magnets, but I am measuring temp at the mounting face of the motor. My motor came with some grooves in the face that were a perfect spot for attaching a thermistor. The thermistor goes to my Eagle Tree data logger and is viewed on the LCD display. I had to extend the wires of the LCD to reach the handle bars. In my bench testing, I did not notice a difference between between the motor face plate and the bell of the motor when touching it. I have an IR temp sensor that would read about 5 deg F hotter when pointed at the coils through a slot in the motor face.

This is just an untried thought, but you might be able to use one of those small outdoor/indoor temp monitors. I have seen ones that are about 3" X 4" and are battery powered.

Bubba
 
Thanks for ideas guys.

I just had a look at the Astro 3210 motor. That would solve my problem beautifully because at more than 90% efficiency it just wouldn't get hot.

Only problem is the $$$, works out about $570 AUD, six times what my Turnigy cost. :(
 
Grinhil- Show some pictures of your mounting setup. I do cooling system engineering. I can help you find a passive method to improve cooling.

Whenever possible, it's always better to do passive cooling. Active cooling like watercooling should be a last resort.
 
Yeah, a typical 9mm handgun bullet goes 1150fps for a 115gr bullet. That's 7086joules. At 44v, you would only need to pull 100amps for 1.61seconds to equal the amount of energy in a 9mm bullet. I think they were getting well over 100amps for a few minutes straight, which would be many hundreds of times the energy in a bullet. Maybe they need to think of something other than bulletproof to call them :)
 
liveforphysics said:
Yeah, a typical 9mm handgun bullet goes 1150fps for a 115gr bullet. That's 7086joules. At 44v, you would only need to pull 100amps for 1.61seconds to equal the amount of energy in a 9mm bullet. I think they were getting well over 100amps for a few minutes straight, which would be many hundreds of times the energy in a bullet. Maybe they need to think of something other than bulletproof to call them :)
Click to expand...

Actually it's a bit worse of a situation than you've stated. See, the weight of bullets is measured with a funky unit of weight called Grains (gr). One Grain is 0.06479891 Grams. (well, that's what the 'all knowing' Google says) So adjusting Liveforphysic's energy content for the unit error 7086*.0648 = 459 Jules.

Let's assume the controller FETs just failed as an almost short, and are hooked to Liveforphysic's LiPo battery pack. With his pack I'd not be surprised if the short circuit current was north of 1500 amps. Let's say the dead FET is dropping 10 volts at this current just due to internal resistance. How long till the poor FET absorbs a bullet's worth of energy? (Whirr, thunk, thunk... CLAG! <= brain's got noisy gears :p ) Looks like it'd take all of about 0.031 seconds to generate a bullet's worth of heat in that FET :shock:... Right, that would explain why the controller shot "rocket like flames" the controller was turned into a @#$@ Arc Jet!

And now back to your regularly scheduled topic,
Lawson
 
speaking of cooling or pulling heat away from your motor
what about parifin wax...stop laughing...
ever melt wax? takes forever and uses alot of heat
even after 20 min you can stick your finger in
point being it absorbs alot of heat...for a while anyways
they also have specialty waxes with different temps
 
Hey wasp, that sounds like a readily-available version of "pcm cooling". There's a lot of stuff out there about phase change materials, even used by the military. I read about one guy using it to cool lithium batteries to get more power from them.
 
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