# Heat Sink Help?



## Voltswagen (Nov 13, 2008)

Enclosed is a pic of my D&D Motors ES-31B.
Motor is about 16" long x 6 7/8" wide.
What I would like to do is wrap the motor case with an aluminum heat sink with fins. This would help dissapate heat and improve the efficency.
So far I can't find any heat sinks online which would fit. Many for small applications but none for this motor.
Anyone have an idea?

Thanks for responding - Roy


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## major (Apr 4, 2008)

Voltswagen said:


> Anyone have an idea?


Hi Roy,

Blow air thru the motor, even when it is at standstill. That will be more effective than increasing the radiating area on the outside.

It will be hard to find something (heatsink) to fit the OD of the motor frame. That surface may not be even machined. If not, then thermal transfer to the heatsink from the frame will be poor. All this could be overcome with expensive turned and milled parts. But for the money, you'll be better off buying a blower and duct.

Regards,

major


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## Voltswagen (Nov 13, 2008)

Major
Thanks. I had considered a blower and may have to set one up since there don't seem to be any heat sinks of the size required.
The motor itself does have an internal fan and it appears to be on the trans end. I'm thinking that is the suction end and the brushes are the discharge end since it is screened.
I don't want to upset that balance so I guess the best way would be to just blow the cooling air across the center of the motor case? Any reduction in heat would result in greater efficiency.
Roy


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## Georgia Tech (Dec 5, 2008)

Voltswagen said:


> Major
> Thanks. I had considered a blower and may have to set one up since there don't seem to be any heat sinks of the size required.
> The motor itself does have an internal fan and it appears to be on the trans end. I'm thinking that is the suction end and the brushes are the discharge end since it is screened.
> I don't want to upset that balance so I guess the best way would be to just blow the cooling air across the center of the motor case? Any reduction in heat would result in greater efficiency.
> Roy


Sinking more heat away is not going to make the motor more efficient. All sinking away heat does is keep temperature sensitive componets cooler. To increase efficiency you would lower the internal resistance of the motor which usually involvs makeing the over all motor bigger..


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## major (Apr 4, 2008)

Voltswagen said:


> The motor itself does have an internal fan and it appears to be on the trans end. I'm thinking that is the suction end and the brushes are the discharge end since it is screened.


Hey Roy,

That type of fan only blows out. It sucks air in the comm end and blows it out the drive end. Use a good size blower and duct air into the comm end of the motor. That way you get good air flow and cooling thru the motor even when you come to a stop. And it should not impede the internal fan.

And it does help efficiency of the motor to keep it cooler as the resistance of copper increases with temperature. In the ranges we talk about here, it isn't much. Lucky if you can improve it a percent.

Regards,

major


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## Voltswagen (Nov 13, 2008)

Hmmmmmmmm....there must be a way to measure the difference in resistance before adding cooling air and after. My motor gets so hot you cannot hold your hand on it after an extended run but the Kelly Controller gets barely warm to the touch.


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## major (Apr 4, 2008)

Voltswagen said:


> Hmmmmmmmm....there must be a way to measure the difference in resistance before adding cooling air and after. My motor gets so hot you cannot hold your hand on it after an extended run but the Kelly Controller gets barely warm to the touch.


It is called a Wheatstone bridge. And you look up the copper resistance change coefficient vs temperature. Simple calculation to measure resistance before and after to determine temperature rise of copper.


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## Voltswagen (Nov 13, 2008)

Thanks Major.....I'll definetly look into that....so far I've been directed toward standard Ohm meters.


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## JRitt (Sep 29, 2009)

If you still want to add heatsinks on the outside of the motor what about something like this


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## Voltswagen (Nov 13, 2008)

Thanks JRitt. I have seen these but they are all mounted on flat collectors. If they had round collectors I might be able to adapt them.
But the fins alone dont supply enough surface area it seems.


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## JRitt (Sep 29, 2009)

You could also wrap the motor with 1/2" copper tubing and use This pump and then through a 5" x 10" heater core with 2 120mm high speed computer (100-150cfm) fans blowing through it. The whole setup would prob draw 40W. You would need a band around the whole thing to keep the tubing tight. The tubing would also flatten out some to get good surface contact on the motor.


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## Voltswagen (Nov 13, 2008)

That is quite a mighty little pump J Ritt. But now we're getting into complicated cooling, ie plumbing, radiator etc. which I wanted to avoid by using a heat sink.
I may mount a fan via Major's suggestion to increase the air flow through the motor.
But thanks for responding.


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## JRitt (Sep 29, 2009)

The setup above shoud be able to dissapate 10-15K Btus of heat (3-5kw) maybe even enough to heat the inside of the car in the winter. A ducted fan would probably work great also


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## bipole (Sep 8, 2009)

JRitt said:


> You could also wrap the motor with 1/2" copper tubing and use This pump and then through a 5" x 10" heater core with 2 120mm high speed computer (100-150cfm) fans blowing through it. The whole setup would prob draw 40W. You would need a band around the whole thing to keep the tubing tight. The tubing would also flatten out some to get good surface contact on the motor.


Nice! This gives me good ideas... great link!
I didn't see this until after I started a new thread on water cooling.

Thanks


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## 69bug (Sep 17, 2009)

I think there was a post on the forums where someone used one of these boat bilge blowers.

http://www.google.com/products?clie...a=X&oi=product_result_group&ct=title&resnum=1


Edit: I will try to find that post.
-


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## Voltswagen (Nov 13, 2008)

Thanks 69Bug
I have two of those 12v fans. They came installed in my 73 beetle under the back seat in the heating ducts. They increase the heat flow to the passenger compartment and defroster. A little noisy tho. I may use one.
Thanks - Roy


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## TheSGC (Nov 15, 2007)

I used one of those Inline blowers when I had my 6.7" motor in my Civic. It made a HUGE difference in cooling the motor. The air flows through the brush end of the motor and out the fan end, so I installed the blower over the brushes and it would always be on.


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## Georgia Tech (Dec 5, 2008)

major said:


> Hey Roy,
> 
> That type of fan only blows out. It sucks air in the comm end and blows it out the drive end. Use a good size blower and duct air into the comm end of the motor. That way you get good air flow and cooling thru the motor even when you come to a stop. And it should not impede the internal fan.
> 
> ...


OK to be proven wrong here....YES you lower the resistance when you lower the temperature of Copper...But this is negligible in our design, you will not see more than a mile extra of distance. You will use more energy with a blower trying to keep it cool than NOT trying to keep it cool. Keeping it cool is a necessary evil to keep the wires from welding them selves together in the motor.


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## Voltswagen (Nov 13, 2008)

Georgia Tech
So if you are right that running a 12v blower would use more energy than it would save and it's conceivable that it might, then a passive heat sink would make more sense. I'm referring here to my first post under this thread which asked for a supplier of an aluminum finned sink which would wrap the motor casing.
Roy


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## Georgia Tech (Dec 5, 2008)

Voltswagen said:


> Georgia Tech
> So if you are right that running a 12v blower would use more energy than it would save and it's conceivable that it might, then a passive heat sink would make more sense. I'm referring here to my first post under this thread which asked for a supplier of an aluminum finned sink which would wrap the motor casing.
> Roy


Yeah but Roy, the amount of "energy" you use will not be that much less because you have sunk away more heat. Think about it, lets say if your motor pulled 200 amps and in this process it wasted 300 watts in the from of heat, just because you put a heat sink on this motor does not mean the motor is now going to produce 150 or 200 watts. Yes, like I said, copper wires at a lower temperature have a lower resistance than wires at a higher temperature. And yes the lower resistance is more effecient, but this is very neglegible in the case of these EVs. It will buy you very little, you will not notice it. The reason for keeping motors cool is so they will not melt or burn up internally. The heat destroys the insulation of the motor Coils when this insulation breaks down due to heat then the motor fails. This would be your only reasoning for sinking the heat away.

So, if your wanting to use a sophiticated Heat sink because it uses NO ENERGY compared to the Blower to keep the motor Cool, then Yes it will save you a little bit there.


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## Voltswagen (Nov 13, 2008)

I understand what you are saying. So it's more about motor life than extended range.
Would you agree that a 6 7/8" motor is likely to run hotter than an 8" or 9" motor in the same vehicle?


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## Guest (Oct 7, 2009)

Voltswagen said:


> I understand what you are saying. So it's more about motor life than extended range.
> Would you agree that a 6 7/8" motor is likely to run hotter than an 8" or 9" motor in the same vehicle?


Yes it is about keeping your motor alive and not extra range. Your small motor will get hot faster that the large motor but they will all get hot. The larger motor has a thicker case and takes a bit longer for the case to soak up the heat. All need good cooling. I just got my blower on but it's not on good enough. I need to do some duct work to make the blower move more air into the 2" opening. 

Pete


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## Georgia Tech (Dec 5, 2008)

Voltswagen said:


> I understand what you are saying. So it's more about motor life than extended range.
> Would you agree that a 6 7/8" motor is likely to run hotter than an 8" or 9" motor in the same vehicle?


Yes and..... Yes, thats right in general, (if the motor is a good design), the Larger motor USUALY has wires or Coils with a larger cross sectional area therefor has less DC resistance than Coils with a smaller Cross sectional area which in turn has less I squared R losses.

Now there are a few Large motors that are nothing more than Zillions of turns of thin coils, which would be a high voltage motor....But in our case using these forklift motors and EV motors we don't have to worry about this..


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## PHAT_pudding (Oct 8, 2009)

what about using heat pipes? you could get say 8, and wrap then about the motor, and then attach them to a passive heatsink close by. kindof like a radiator sitting over the top of the motor or something. 

might be cheaper getting a bigger motor though! haha

linky
http://www.enertron-inc.com/enertron-products/heat-pipes.php

they look a bit short as well. only 300mm length, but you could run them lengthways onto a round heat sink at the non drive end. (i'm pretty sure they work sideways)


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## 300zxev (Dec 5, 2008)

While we are talking cooling ... are there any recommendations to the amount of air (CFM) you should try and blow through a motor for it to be effective.

I realise that it would depend on the size of motor you are trying to cool.
and it would have to be a balance of the amount of amps the fan consumes.

Maybe someone that has supplied electric blower cooling can provide an example of what type of blower they are using on what size motor


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## major (Apr 4, 2008)

300zxev said:


> While we are talking cooling ... are there any recommendations to the amount of air (CFM) you should try and blow through a motor for it to be effective.


The more the better  I don't have any CFM numbers, but what I've seen work well is automotive heater blower fans/motors. Also bilge fan assemblies, perhaps easier to connect to round duct.

Regards,

major


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## Guest (Oct 19, 2009)

Amp draw is negligible to the amount of amps drawn for moving the vehicle and any loss of distance won't be noticed. It really is not drawing that much from a blower motor for cooling. My fan on my older controller was blowing mega CFM yet takes almost no amperage. My Blower for my motor will pull a max of 4 amps. 

Pete


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