RC-Monster Forums - Custom (very) Quark esc heatsink...

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- - Custom (very) Quark esc heatsink... (https://www.rc-monster.com/forum/showthread.php?t=6258)

Ok, there is some sort of air flow while driving, but it isn't constant and it isn't always coming from the same direction.

Hey, lets just wait until he installs it and see what happens. Who knows, I might be making one of these next week.

Quote:

Originally Posted by Serum

Artur; in some cases the magnets get loose/split on the feigao shafts.

I thought neodymium looses it's power at 110 degree C.

About the load that they put on the motor; they do give the Kv and the current it can 'handle'. i wouldn't be surprised if they used a fixed voltage for some odd reason. or they simple determine the max. load by the resistance/thickness of copper

Good point, Rene, centrifugal force can split magnet. And we seen number of motors with broken magnet not only from Feigao...

At 110C lots of things going bad, but at 130+C you will destroy magnet permanently, that what I was referring to. (I've got couple of those from my friends, saying they are weak... guess what they cannot even stick to refrigerator door :) )

About load, it is a dark territory with proprietary sign for RC, I guess.

For voltage measurment, keep in mind the correct is to measure voltage on the motor, not through connectors and FET's. Very difficult, but then do not expect exact matching with datasheets.

Quote:

Originally Posted by AAngel

I still don't get it. The sink obviously doesn't have any mass, so it can't pull much heat away from the esc before it gets to be as hot as the esc is. It has to rely on dissipating the heat into the air around the fins and then getting that hot air out and cool air in to repeat the process. I don't see how you can say that the sink will work without fans. So, this thin aluminum has all of these fins with the purpose of moving the heat from the sink to the air around the fins. So what happens when the air around the fins is the same temp as the sink itself and there's no fan to get the hot air out and cool air in. You have to move the air, because, as I said, air is a horrible heat conductor. The hot air isn't going to pass its heat off to the air around it.

I also don't know how you can say that the sink effectively dissipated that much heat with very little air flow. I'm going to assume that you are talking about the sink being inside of a computer case. If that is true, you can't say that there isn't a lot of air flow. Not only are fans in computer cases designed to move air, but they are placed inside the cases in places where they will be the most effective.

I'm also not getting your mentioning more fins working better with higher airflow and fewer fins working better with lower air flow. I can understand that if you have a given area with say 10 fins, you have to have a higher pressure air flow to cool it than the same area with 5 fins. It's kind of like flowing water through a pipe. With a 1" diameter pipe, you'd have to have a higher pressure/flow to move X amount of water in a given time than you would with a 2" diameter pipe. The larger pipe can flow the same amount of water at less pressure, but it is none the less moving the same amount of water. In this case, since you have lots of fins, the pressure of the air going through the fins is going to be higher than it would be if your sink had fewer fins. Are you saying that your sink is going to work better in this case with little air flow. If so, I'm not following.

I'm not trying to be argumentative. I'm must hoping to learn something.

It still seems to me that attaching the esc to the chassis is the best way to keep it cool. Lots of surface area, inspite of the lack of fins, and lots of mass to store heat until it can be dissipated. I wonder how long it would take an esc to heat a chassis up to 160 degrees F.

About the fewer fins working better with a lower airflow FAN I meant to say, also, when each individual fin is larger too. For a larger # of fins, they are usually small, and more densely packed, correct? So, for a given fan, it has to overcome alot more back pressure (because of surface area of fins, skin resistance), thereby reducing the overall amount of air actually traveling through the fins.

Another example, the PC i'm on now is highly overclocked, running a core 2 duo 2.4 overclocked to 3.6ghz. This takes upping the core voltage, and frequency, and some other settings.... anyways, the heat dissipation goes from the rated 65watt TDP, up to approx. 110 watts of heat at 100% CPU usage. The heatsink I am using is a large tower heatsink, anyways, it doesn't matter if I turn the heatsink fan ON, or OFF, the CPU temperature increases only up to 2 degrees. So then, the only thing keeping some cooler air inside the fins is the airflow through the case, which isn't a whole heck of alot.

This heatsink does have some mass to it btw, it's approx. 120 grams, or was it 140 grams, can't remember, it's on a previous post.

To get to the point, this heatsink will have more than enough airflow to work wonders if situated in a half decent spot.

Just for reference, I measured each fin, and came up with this surface area. Total surface area is about 1.23 square meters of area. The heatspreader is 2.5mm thick, the fins are .4mm thick, and the fin spacing is about 1.6mm.

The thin fins have something to do with not needing much airflow to stay cool. The amount of heat energy present with a Quark will won't need much like i've said before. It should have plento-airflow however. Also, surface texture has alot to do with surface resistance (obviously), they have a fine gold ball texture to them, with cuts down on resistance.

One last comment, when I was grinding this thing, after I took it off from heavy grinding, a few seconds, and the area I was grinding was only luke warm, before that I could not touch it; that was after moving the heatsink back and forth a few times in the air, not very fast either. It simply doesn't need much to work properly, it's an efficient cooler.

Any heatsink really has two parts; mass to pull heat away from whatever it is cooling; and surface area to dissipate that to the air. In my experience, tall fins don't work as well as shorter fins because the heat has to travel all the way up each fin. The only advantage to having tall fins is that more air goes through it.

Quote:

Originally Posted by BrianG

It is more complicated...
Depends on material of heatsink (heat transfer properties...) so longer fins (higher differential temp) will do better jobs on materials with higher heat transfer rates.
As example copper will work better with long fins while aluminum not. But fins configuration and flow design can improve that process.
And you can make thinner copper heatsink with longer fins, but complexity and mechanical softness will be a major problem.

Yeah, material does matter. I can see copper having better results with longer fins while aluminum having better results with shorter but more numerous fins...

It's not that longer fins don't work as 'well' as shorter fins. If you want to look at it another way, from heat source, one side of fin, and temp measurement other side, it will lower the longer the fin. Longer fins will work better, only marginally better though. Heatsink design really is tricky, now there are fancy heatsinks (for CPU's) with a bunch of heatpipes and large amounts of fins. Heatpipes, if you don't know what they are, have distilled water, or alcohol under very low pressure, which vaporizes at a very low temp, which you know phase change takes alot of energy. Also, unlike a solid piece of metal (such as copper), heatpipes thermal resistance decreases as length is increased.

For this heatsink, it's good that the fins are of decent length, for one: to catch air, and two: inside the fins, there is a certain amount turbulence which spreads around the heat energy down the length of the fins.

I am thinking of mounting it in front of the transmission right behind the front shock tower. If not enough room, other side of chassis, where it will still get enough airflow.

I just did a little experiment with a 600 watt heatgun, with a low speed fan. With the heatgun of the heat spreader for almost 1 minute, with the fan running (rated 19cfm), after this period, the heatspreader was quite warm, I would guesstimate it was 45C (113F), and VERY quickly cooled down to room temp within 15 seconds.

Not convinced yet? :032: :005:

Quote:

Originally Posted by BrianG

Yeah, material does matter. I can see copper having better results with longer fins while aluminum having better results with shorter but more numerous fins...

It wouldn't make much of any difference using copper fins rather than aluminum fins. I've seen this lot's with CPU heatsinks, copper version of the very same one, was only 2-3 C lower temps than aluminum one. The most important part is the heatspreader, which SHOULD be copper, as that is where the highest heat density is, right?

Nope, not convinced! ;) You forget that I abhor the use of fans for R/C applications, so the majority of the tall-fin benefits are lost. Agreed, CPU applications are much different...

Which part are you not convinced about?

How about this, once I get my thermal adhesive, my thermal probe (infrared), and my truck up and running, we will see how well it works. I know with absolute certainty that this will work super fan-taz-magorical.

Don't forget about air convection through the fins too (without fan, or direct airflow), as I also tried using no fan with the heatgun. I couldn't get it over a temp that I couldn't put right to my cheek right after, from about 1 minute of blowing the heatgun directly on the heatspreader, about 2cm away.

Quote:

Originally Posted by zeropointbug

... Heatpipes...

even more complicated, because now you add gas to equation and gravity and direction and sensitivity to temperature range. What works or doesn't work for CPU is not true for every application. With heatpipes selecting correct fluid is very important, more important that pipe is long enough that fluid easily goes through all stages and there is some in liquid form not in gas othewise it stops working...

Quote:

Originally Posted by GriffinRU

They use wicking in heatpipes now, the texture inside the pipe. Also, these things are very efficient in transferring heat to some other place (fins). gravity has little to no affect on heatpipes now.

Why do you think this is SO complicated? Heatsink design is trucky yes, but the basic understanding of heat transfer is simple.

Quote:

Originally Posted by zeropointbug

Because, I've done some designs in the past and most of them didn't pass mil specs due to the little gravity effects and other heat related problems. And if it is simple then why there is no simple heatsink for CPU, but we see all kind of crazy designs flying around while copper and aluminum are still have the same properties with air included.
I didn't said that it is less efficient, I said it is complicated and has its limits due to its better efficiency in limited range of applications or temperatures.

Well, to be honest, MOST heatsinks for CPU nowadays are just designs, that's all they are. Lot's just looking cool, decent cooling capabilities, nothing great. Most heatsink design is coming from PC industry now.

Like i said, heatsink design is tricky, as there are several ways you can make it perform: such as LOT'S of airflow, NOISY, and guaranteed to work, with moderate fin count. OR another extreme, like these large tower heatsinks, using heatpies densely around the CPU, then efficiently transferring the heat as vapor to a large set of fins. This method works amazingly well, and better uses a given surface area of fins, than a simple heatspreader, fins design.

What kind of experiment did you do?

I figured I'll post here, instead of making a new thread, not to take away from zero's posts, but it's very similar..

ok, so i'm hoping my motor mount will be in tommorow, and i'll be ready to go, so i decided to do some last minute mods, to make sure my lsp's off on the right foot..

started to take the quark apart, and i'm stuck..
http://img261.imageshack.us/img261/1...0135pj8.th.jpg http://img261.imageshack.us/img261/4...0133wa6.th.jpg http://img261.imageshack.us/img261/1...0138ep5.th.jpg http://img261.imageshack.us/img261/2...0139ee1.th.jpg http://img45.imageshack.us/img45/687...0140yg6.th.jpg

I know there's another set of pins/jumpers tward the end with the motor plugs, but i can't seem to un-plug them, so not sure if there's something else in the way or not.. and the controller seems to be VERY secure to the bottom of the case.. so what do you guys think? my controller's a few months old now, so i'm guessing it's the same as all the others with heat problems, but i've yet to get it hot, because it's been in my onroad car.. I've got a big selection of computer heatsinks to choose from, and am thinking about ditching the quark's case all together.. but someone want to re-describe how to dissasemble this? sorry for being thick, but it just doesn't seem to want out of it's case :002: