Water cooling information

[Mike Caruso]

Hi Folks',

I Love this place.
My new Re Volt should arrive today or Thursday.

I have been a racer since 1972 IMPBA 4261-S. Here is what I do for a living http://www.aera.org/tech-center/tech-hotline scroll down to me! I was reading late last night a thread about cooling. I think this site will explain what you need to know is on this site http://www.stewartcomponents.com/tec...ech_Tips_6.htm

Old wives tale I was there at that time.
In the 60's the car Drag race people complained that the small block Chevy 283 cu"or bored out to 301cu" @ 6500-7000+ was overheating. They thought it was because the water was moving through the engine too fast! And not being able to transfer the heat from the cast iron to the water. Their reason for this .... was if they changed the water pump pulley to crankshaft pulley ratio to slow the water pump down the engine DID cool better.
They slowed the STOCK water pump down to an RPM at which cavitation was reduced.

The truth is.
The STOCK water pump did have cavitation @ 6500-7000+ with stock ratio pulley's making the water into A+W Root Beer foam ( wish I had some now) which reduces the ability of the water to remove head.

I worked with Howard Stewart in the late 80's and along in the 90's when he built the first water pump Dyno. I know it is for racing engines but, we can still apply the basics and the one BIG ONE is keeping solid stream water...... not A+W Root Beer foam.
Anyway back to work and have a good 4th. Remember light fuse and get away fast !!!!!
Glad to be aboard.

Mike Caruso

[Fluid]

Mike makes an excellent point about solid water flow. This is another reason why a propwash water pickup is inferior to a rudder pickup - it ingests a lot of air along with the water. So it has more drag, less cooling, and is one more thing to break.



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[iamandrew]

I remember when i was looking into modding my boat, i found a few people who had actually crimped down on some of their water cooling pipes to create more pressure and a slower flow.
I ignored it and replaced all my water cooling with a lot bigger diameter pipe and found that yes, my boat was colder than before when it came back in from testing it.
you can also get a hose and aim it at the water intake of your boat and see the water in the clear pipe move around the water cooling setup. you even could adjust the spray to a wide spray and see if you get the air bubbles in the water tube.
remember that a boat dosent have a radiator, you can move water into the boat at what ever the water temperature is, its not getting recirculated (that much) but will gain temp in your setup as it passes through your cooling jackets and ESC.

[m4a1usr]

Interesting comments. Aireated water is not going to be seen exiting our passive cooling system designs. First we have no pump and its not closed loop. The pressure is only dynamic relative to either motor RPM or vehicle speed when in media. We cannot cavitate in any manner. While what Jay states is applicable in certain circumstances, almost all of you have a built in component that will remove aireation from the flow. Its called the motor water jacket. And it will behave as an accumulator. Reducing most or even removing the significant components of aireation. While true that its a bit too late in the cooling flow stream for your speedo, significant air bubbles in water collapse almost immediately at atmospherhic pressure. And if what some people are purporting to be actual line pressures in our systems, I dont buy the numbers being spread, because if true then we would be seeing streams 3ft or more in length of water coming out of those hull exit ports. Just for SAG and to bring about a perspective and real visual representation, why dont some of you connect a piece of 3/16" ID silicone tubing to a unregulated hose bib at home and see what you get? While you cannot do a decent job of regulating pressure you can mimmick it by flow regulation. Most dometic service is above 50psig, in places up to 65psig.

So for a good laugh, common its hot in some places right now, attach the small silicone tubing and barely crack the hose bib. Your going to see water flowing. Not much but thats obvious. Now turn the knob just another slight bit. Silgthly more right? Now turn the knob just a bit more? Is the end of the silicone tubing snaking around like a rattler on hot rocks? Now open it all the way. Whats that you say. The silicone tube blew off the end of your adapter. Hmmmmmmmmmm,....imagine that? And one end was wide open. No restrictions, no bends no line reductions anywhere. Anyone see where I'm going? No I'm not disputing whats been said so please dont read arguement on my part. Just want you folks to take a deeper look into some very basic science. Just my 3 cents 'cause I might get a raise next year!

John

[Fluid]

Not arguing, but what becomes of all the air that is separated by the motor jacket? I assume it accumulates at the top of the jacket at and above the water exit, meaning that aerated water is in contact with the motor as it accumulates then forms a void for a bit before exiting the jacket. Since air reduces cooling at the ESC and at the motor, why put up with it? Sure a prop blast pickup works, I used several years ago, but with better solutions today.... :noidea:


.

[JIM MARCUM]

Just my 3 cents 'cause I might get a raise next year!

John

Informative thread. Hope you get that raise John.:banana:

JIM:spy:

[m4a1usr]

Hey I'm not disputing your claim Jay. And I thought or at least hoped no one would read my comments as being contractictory to your post. Maybe bettter wording should have been choosen on my part. It is true, water reduced in density will have a lower heat capacity. What I was trying to leverage off was not the use of a rudder pickup or a prop wash pickup but that capacity is influenced by some quantity of flow. And what amount none of us really know. We all know its trickle at low speeds but what is it truely when were up to some level of speed where we push these boats and feel it necessary to even bother with any effectiveness of water cooling. Didnt mean to imply anything or single you out.


John

[Shooter]

We’ve been struggling with water temp even in Northern Michigan! In an effort to improve cooling we tried the following:

Config #1 (3 runs): Propwash pickup to motor only, rudder pickup to esc
Config #2 (3 runs): Rudder pick-up only to both esc and motor

The water outlets were moved to the top of the boat to get an idea of flowrates. The propwash outlet shot water upwards nearly 18”, while even the rudder pick-up shot water a surprising 12”. Both were clean streams of water which might give merit to the “motor sleeve acts like an accumulator” theory…but the jury is still out regarding an air pocket at the top of the sleeve. Both measurements were done at half throttle (at full throttle, both streams end up carburizing/dispersing into the air due to the wind).

What was most surprising is that motor temps were coming back relatively the same for both configurations. An average speed loss of 1.5mph was observed when testing with the propwash pickup.

What it ‘boils’ down to unfortunately is that the water is just too hot….not enough delta T. Our flowrates with the rudder pick-up alone seem adequate. Before the haters chime in……I am a firm believer in more flow is better, but when lake temps are high, at some point you reach a point of limited bang for the buck (i.e. T of water coming out is not much greater than T of water going in).

Completely different results might be obtained when lake temps are much cooler!

Any cooling tips you guys could provide would be greatly appreciated! I’m at the point of trying a tupperware box with ICE inline with the cooling system.

[FRED]

Water pikup. Now a few years ago, a gentleman from UK> removed his under boat water pickup as said it sucked down his boat.. These were located within 2" of transom. Now it seems the place to put water pickup is right at the cg. This gives more of a stable boat and lipos don't need to be moved forward much if any. I agree with Paul Pachmeyer on a reducer at the outlet so water stats alittle longer in cooling sytem to grab more heated water. Now enlarging the rudder pickups holes do help but be careful. I tried the reducer and water was very warm exiting and can was cooling which convinced of its operation. The can be done on inrunner motors by feeling the exiting water.

[Fluid]

Both were clean streams of water which might give merit to the “motor sleeve acts like an accumulator” theory…but the jury is still out regarding an air pocket at the top of the sleeve...This makes no sense at all. If there is air in the water from the blast pickup, and no air in the exiting water or in the water jacket - where did the air go? It has to go out with the exiting water even if you can't see it - and how could you? If it is separated in the jacket it has to accumulate there before it is pushed out the exit......unless you just have a magic boat....:wink:

The higher exiting water from the blast pickup makes perfect sense since it is under higher pressure - the water hitting the blast pickup is going faster than that hitting the rudder. The "top of the sleeve" means that part of the sleeve above the water exit.

John, I was not meaning to be argumentative, just hoping for some additional thought. I know thermodynamics and model boats, but theory and practice don't always fit - often due to observation errors like those above.



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[LOVE6S]

I was thinking of putting two water pickups in the botttom of the boat, another member mentions some thing about not putting them to the rear and at the COG point, that portion of the boat 1/3 from the ream seems it would be not in much contact with the water at any speed. Where would be the ideal place for them. I always thought it would be nice to have the water come in toward the front of the boat, as much as you could and still get the pick up in the water and exit the transom at the very bottom of the sponsoons. You would not be able to see flow, but I was wondering if the speed of the boat and water passing by would pull the water thru the system as well as push it. I was thinking of putting two 1/4 tubes in the bottom at a angle facing forward and two out the bottom of the sponsoons facing back at a slight angle. The only draw back is you cant see the flow. I beleive the more water you put in the system the better you are, what I like about the prop wash system is the dia of the intake, but not the air, so why not put the tubes in the bottom angled forward just protruding for less drag. As far is out the back of the sponsoon, not sure if it would help pull the water out or if it would be to turbulant to do so, any thoughts?

[Shooter]

This makes no sense at all. If there is air in the water from the blast pickup, and no air in the exiting water or in the water jacket - where did the air go? It has to go out with the exiting water even if you can't see it - and how could you? If it is separated in the jacket it has to accumulate there before it is pushed out the exit......unless you just have a magic boat....:wink:
.

Yes, the air must go somewhere. It accumulates in the upper most sections of the system (top of the motor sleeve for example) until enough air is accumulated and the water level in the sleeve drops below the outlet and it burps the air out.

It’s a well known concept in brake systems. You can bleed a brake system all day and if your bleeder screw is too low (height wise), it will be impossible to bleed the air out (without a vacuum). That’s why bleeder screws are always at the top of brake components. Most of our water cooling exits are below the motor sleeve cooler….so it is very possible to have air pockets forming in sleeve.

As for me not being able to see air coming out. Fair point. I can’t absolutely say for certain that the stream is solid. Not trying to mislead anyone.

[LOVE6S]

Can anyone tell me where the best location on the sponsoons is to put the water pickups?

[driftah]

well most of the under boat pickups are slightly behind cog... as to pickup water with that part of the boat in the water at speed otherwise your ingesting air it would seem correct? one or two small brass tubes angled rearwards and up for intakes.Flush with hull surface I believe otherwise there is drag.

[Grazacind]

Using a small like this http://www.offshoreelectrics.com/proddetail.php?prod=ose-80010 that has been put into a sealed container with the input and output outside the container.

Fill container with water and put a lid on it. Freeze this so as to use it to cool the incoming water on those where the ambient water temp is high. You could avoid freezing with water and just add some dry ice pellets.

Never know it may work. Seeing as the flow is not as fast as I first thought.

[ray schrauwen]

I tend to just put a restriction on the output that way the water stays in the system longer under higher pressure, I assume......:unsure:

Although in the summer heat, free flow may be better with 90F "cooling" water.

[ray schrauwen]

Using a small like this http://www.offshoreelectrics.com/proddetail.php?prod=ose-80010 that has been put into a sealed container with the input and output outside the container.

Fill container with water and put a lid on it. Freeze this so as to use it to cool the incoming water on those where the ambient water temp is high. You could avoid freezing with water and just add some dry ice pellets.

Never know it may work. Seeing as the flow is not as fast as I first thought.

If you add salt to your ice water mixture you can double the cooling ability compared to plain water.

[srislash]

I tend to just put a restriction on the output that way the water stays in the system longer under higher pressure, I assume......:unsure:

Although in the summer heat, free flow may be better with 90F "cooling" water.This is what I have done as well successfully.I run 1/8thI/D right thru from rudder and neck it down to 7/64 where it exits the hull.I have a vid of the stream to show the pressure.

Here is the vid http://www.youtube.com/watch?v=6XksK68P00g&feature=plcp The first little bit shows the stream coming out from under the cowls.This is at 65mph with a dual pick up gasser rudder so there is no question about flow capabilties.

[1945dave]

Sorry guys. I disagree with those that believe restricting the speed of flow of water cooling improves heat transfer. One of the first items covered in basic Thermodynamics is the study of BTU's and heat transfer. In engineering labs we found no matter how rapid the flow of a fluid (even air over cooling colls in AC systems) higher thermal transfer occurred at faster flow rates. This is not just theory it is fact. We can debate the qualifying terms of use such as laminar flow, turbulant flow, air dilution (foam) but faster flow is better period.

REducing the pressure build up in the system is an important consideration as well. It is nice and reassuring to see those strong visible streams of water exiting from the cooling system. Yet some of the fastest most demanding record holders in the Nitro world do other things not discussed here. Like relocating all the water exits for the heads of Nitro engines to the very top of the motor. Factory locations are typically straight out the side but no question the preferred location is at the highest point of the cooling chamber. This reduces trapped air in the chamber. The same logic used when automobiles went to the external plastic water reservor to remove as much air from the radiator and cooling sustem as possible. Another detail not mentioned here is many high performance Nitro boaters may only have one entrance from the water pickup but offen times had multible exits to reduce any restrictions and lower pressures in the system (water lines, and water fittings). My best boat had the water exit dribbling the exit water over the outside of the engine and out the auto-bailer. Note: water inside the cockpit was not something to worry about, we covered the carb intake but worry about a little water inside the boat? heck no!

Dave

[LOVE6S]

I say the more water you can flow the better, I am gona run some larger dia inlet, hose, and outlet.

[ManuelW]

@ 1945Dave :iagree:

After a few semesters of Thermodynamics and heat transfer at University I just can 100% agree on your post.

Reducers/Restrictors in cars have a use, but NOT to decrease the flow speed of water for better cooling. This is to increase pressure within the system, otherwise water would start to boil at 100°C and this would dramatically decrease cooling ability.

regards,
Manuel

[HRC]

Well guys I can only share what I have found a few years back when I started making cooling jackets.
Using a test stand with a few different motors (36 mm and 39 mm O. D. for example ) and mounting airplane props to put them under a max. rated amps load on each motor.
With temp. Thermometers on the water intake and exit to check the water temp. in and out as well as temp. sensors at each end of the motors this is what I found.

Each step involved boring out the I. D. of the jacket in .020 increments to find the sweet spot. I eventually reached an I. D. size where the jacket was no longer effective. Exit water temp dropped and motor temp. started rising. This testing told me one can have to much flow. All of the jackets we make have undergone this test.
Just saying.
Dave

[1945dave]

Let me see if I understand you correctly? Are you saying you increased the volumetric dimension of the inside of the cooling jacket and once you enlarged this volumn past the "sweet spot" the motor got warmer and the exit temp of the water got cooler? Is that correct?

A different Dave

[MassiveOverkill]

I could see how in a water jacket how you could get stale pockes of water vs using a coil cooler where water is always forced down a certain path. I wonder if the test was redone with a coil cooler if you'd have different results.

[HRC]

Yes Sir, indicating to me water was not removing as much heat with a larger volume of flow. A constant regulated supply pressure of 30 PSI being used for all test.
Dave



Let me see if I understand you correctly? Are you saying you increased the volumetric dimension of the inside of the cooling jacket and once you enlarged this volumn past the "sweet spot" the motor got warmer and the exit temp of the water got cooler? Is that correct?

A different Dave

[HRC]

Sorry I have not done any testing on coil cooling.


I could see how in a water jacket how you could get stale pockes of water vs using a coil cooler where water is always forced down a certain path. I wonder if the test was redone with a coil cooler if you'd have different results.

[1945dave]

Dave are we confusing flow with volumn? I don't care if your cooling jacket holds 2 quarts or 2 onces if it is a closed system what ever flows in has to equal exactly the same flow out. Also cooler water out is good while a warmer motor is bad. I applaud your efforts and testing but something is missing in your evaluation. You said "I eventually reached an I. D. size where the jacket was no longer effective." I think you meant to say once the interior volumn was large enough any further increase did not result in a cooler motor. That probably would be a correct evaluation. But it has nothing to do with flow just volumn of the cavity. Flow is dependant of the inlet size and exit size only.

Now with your testing you are the right guy to answer this question. How much temp. difference did you detect measuring each end of a motor? Is there a big difference or is it pretty similiar? How would you recommend aligning the cooling jacket? Centered between both ends or closer to the collet end of the power lead end?

1945Dave

[1945dave]

I could see how in a water jacket how you could get stale pockes of water vs using a coil cooler where water is always forced down a certain path. I wonder if the test was redone with a coil cooler if you'd have different results.

Massive, your question follows the thought process of several well known designs in water cooling chambers. The problem with true cooling coil water jackets for our small electric motors is the coils are always very cool but they do not remove the heat from the motor very well due to the tiny contact area actually touching the motor can.

Dave

[Shooter]

Finally, some people making sense.....

Higher flow = cooler water around the motor = higher delta T which is the driving force of heat transfer.

If you have HOT water coming out of your outlet, you need to increase the flow.....unless you want to make coffee. Not trying to heat a little amount of water here, we are trying to cool the motor.

I am very interested in Dave's analysis with the diameters, but am confused as well with the last statement regarding the outlet temp being too cool. This should be a good thing. :confused2:

[Alexgar]

I wonder if by increasing the volume past the sweetspot the pressure was affect thus slowing down the water and slowing the flow just a thought and basing this on my knowledge of neumatics, as i dont know all that much about the thermal characteristics of water

[Shooter]

His volume may have gotten so great that the cooling jacket was no longer filled. Water was only in contact with part of the motor.

[1945dave]

Alex in all my years as an engineer and 6 years of college I never heard of the "sweetspot" term as it applies to thermodynamics. Still the only variable that could enter the discussion when enlarging a cooling jacket has to be the trapped air inside the chamber and yes that could affect the over all efficiency of the heat transfer process. However, to slow the flow would take a restriction, not an increase in pressure. I would be interested in seeing the setup that Dave used to test his cooling jackets. I would like to know if they could trap air or if the exit was placed so that all the air could escape. I suspect that was not the case.

The other Dave

[Alexgar]

perhaps a lexan tube fitted as a water jacket would show us this evidence and using differant size orings would act as the volume increase

[HRC]

1945dave,
You are correct, by increasing the volume to a point where the cooling was less effective, the motor temp. actually increased. Having found the “sweet spot” if you will.

I found the higher end motors had a slight temp. difference from front (shaft end) to back (wire end). The more economical motors had a 8-10 degree split from front to back. The back being the hottest.

The position of the jacket on the motor had little effect. The location of the water in and out fittings however made a difference. The inlet side being on the bottom made about 6-8 degree cooler motor temp. as opposed to both being on top. I did try it having both water fittings in line and was very disappointed. Having them offset must help the circulation.
I just thought I would share my actual test results. Sometimes theory and actuality are different. We all have a tendency including myself to over think things.
Dave

[MassiveOverkill]

So I used to water cool my processors to increase my e-penis and a company called Swiftech at one point made a design that couldn't be beat at the time called the Storm (I still have it collecting dust in my garage) that used jet-impingment, which could support the higher pressure theory:

http://forums.bit-tech.net/showthread.php?t=114866

http://www.ecst.csuchico.edu/srproject/project_files/pdfs/ppt_jet_heat_sink.pdf

http://qats.com/cms/2010/06/09/jet-impingement-cooling-provides-high-heat-transfer-rates-for-thermal-management-of-high-power-electronics/

One problem with this water block, even using deionized water is that the jets would eventually get clogged.

I don't know how relevant this is to our application as we're not using jets, but maybe the higher pressure may have an effect. I would think the sweet spot would be the highest pressure/flow setup, not just the best of one or the other.

[Cooper]

More flow= lower temp .

Example, if you have a hot motor and you drip water over it how long would it take to cool it?

Now if you have a hot motor and throw it into the lake how long would it take to cool? :)

Can't compare to cars/radiators totally different system. In my opinion I prefer to have the restriction at the intake side of things as to not create pressure at my fittings, ever have a hose slide off? And I do not mean to restrict flow, I mean I have the smallest diameter of the whole system at the intake. As far as the air in the system, come on guys, what boat running holds perfectly still to where the air can accumulate in the top "pocket" of a cooling jacket? Just a little movement and that theory goes out. Example shake a caped water bottle and set it down, the air goes to the top right? Now shake the bottle again and keep shaking, the air stays mixed right? It's all just my opinion based on the first rule of thermodynamics fact of heat transfer. Heat is always trying to dissipate. Heat will always dissipate to it's surroundings.

[ManuelW]

For the most efficient water cooling jackets some time ago Hopf Modelltechnic manufacturer probably one of the best cooling jackets I had ever seen. They combine the best solutions of the coil type with a standard water jacket. Its basically a massive tube of aluminium with just a tight gap between OD of the motor and ID of the jacket. Then they used a milling chuck with the shape of a ball to mill a coil into the inner surface. This enables coil type cooling with direct water contact over the full motor surface.

Here a picture of these jackets:
http://www.mb-forum.at/baubericht_hfk_prototyp_manuel_190.JPG

regards,
manuel

[srislash]

Those are some work of art there Manuel.That would carry the water direction guaranteed.

[1945dave]

Those are sure pretty Manuel. Could you show us a photo showing the water inlet and outlet.

thanks Dave

[phil t]

I tend to just put a restriction on the output that way the water stays in the system longer under higher pressure, I assume......:unsure:

Although in the summer heat, free flow may be better with 90F "cooling" water.

We are cooling the motors, not heating water so get the water flowing fast as possible thru the system.

[1945dave]

Last comments on this thread. I think we have about beat this thing to death. I agree with Phil T. Cooling the motors is the goal. The exit temp of the water is totally a non issue, nobody cares and you don't learn anything knowing what it is. Free flowing as fast as possible is better and the fewer restrictions the better. Pressure is bad and holds no advantage except to create leaks and possibly push the water lines off their fittings.

Good luck, next thread?

Dave

[Shooter]

But Dave.......we need you!!:hug1:

Under the guise of a bathroom plumbing project (wife on watchful eye this morning..supposed to be tiling), I did this experiment. Flow provided from my airplane electric fuel pump, adjusted voltage to provide similar flow to what I observed in my boat.

Pic #1 (side outlet): Note the large air bubble.
Pic #2 (top outlet): Very small bubble at top since my outlet is still at a slight angle, but for the most part the air bubble is gone.

Point is that it's probably best to put the outlet on top. Both HRC's temp data (outlet top, inlet bottom) and this experiment support it.

8080780808

[1945dave]

Shooter great job. That is good to see. Now do the same thing while shaking the container and see how long you can keep air in the container.

No question choosing an exit hole at the highest point possible is the best plan. Again good job.

Dave

[Shooter]

The set-up was still out there, so I ran it a few more times while shaking. No doubt, the up and down shaking improves the size of the air bubble (makes it smaller), but it takes some extremely vigorous shaking up and down. Most definitely more than what our boats experience, and I still wasn't able to completely eliminate the bubble.

The wide open tupperware container doesn't quite simulate the water jacket, but it's an easy way to demonstrate the concept. Alex hit the nail on the head with a lexan jacket. Would make a great experiment.

[ReddyWatts]

Heat Transfer


Heat transfer works best with the biggest temp differential: The most efficient transfer happens at the greatest temperature differential, therefore higher flow rates will always help with all other variables remaining the same.
It is the Heat Transfer that we want to maintain as efficiently as possible, and that is best done with a higher flow rate. Rather than thinking that there won't be enough time for heat to move towards the cool water, and therefore compromising heat loss, it is better to think that there is more fresh water moving onto the motor and therefore, there is increased cooling.

The reason higher flow rates work better in boat water cooling is this:
There is more water with a larger temperature differential moving through the motor cooling jacket- this removes more heat.

This is true even though a boat with a lower flow rate will have more time to heat the water in the jacket: since the heat exchange works best with the greatest temperature differential, longer “stay time” is counter-productive.

[ReddyWatts]

Water Flow
Water moving through a motor cooling sleeve meets resistance at the walls; this causes the water at the walls to move more slowly than the water in the center of the tube: this is Laminar Flow.
Laminar flow is bad for heat exchange because the water against the vessel’s walls is slower than the water in the center. Flow rate at the heat exchange surface has diminished.
This is where turbulence comes in - if we can get fluid from the center of the vessel to mix with fluid toward the walls, we end up with more efficient heat removal. Turbulence increases heat transfer significantly over slower Laminar flow.

So, in short moving water through the motor cooling sleeve faster improves heat transfer between the motor and the water, which reduces the temperature differential between the motor and water required to move an amount of heat.
It is NOT intended to reduce the temperature increase in the water as it travels through the motor cooling sleeve, but rather to allow more heat to be removed.

Faster flow means more turbulence, and that is a good thing.


I really like the design on the inside of these jackets.

http://www.mb-forum.at/baubericht_hfk_prototyp_manuel_190.JPG

[LOVE6S]

I bet those cans in the pic were alot of money, can those or anything like them be purchased?

[LOVE6S]

I have a 45mm motor, there is not alot of cooling jackets around for it, I was gona wrap copper tube around it and tack it with JB weld, would this give me enough cooling? Sorry a little off topic, dont mean to disrupt thread, Shawn.

[ray schrauwen]

We are cooling the motors, not heating water so get the water flowing fast as possible thru the system.


So then, let it flow, let it flow!

[ray schrauwen]

I bet those cans in the pic were alot of money, can those or anything like them be purchased?

Made by "ETTI" I think...

[ray schrauwen]

New cooling fluids out of Germany!

http://ca.news.yahoo.com/german-scientists-concoct-coolant-electric-cars-160458347.html

[martin]

If you use a coiled pipe your suppose to use a thermal compound between the pipe & motor so it fills the gaps between each coil & the motor can to give better heat transferance.

[ray schrauwen]

....and just an FYI, thermal compounds are carcenogenic. Nasty stuff but, keeps it all cool.

[martin]

Ray i dont think the stuff my local electronics store here in the UK sells is.

[LOVE6S]

I got some thermal transfer past for some esc's I am working on, but this stuff you are talking about would have to turn solid when dry, I dont know where to get that?

[Alexgar]

Thermal epoxy? I bought from frys

[martin]

Go to www.fastelectrics.net & then click on watercooling in the list at the top left of page, the idea is to fill the air gap between the radius of the coils.

[LOVE6S]

Thermal epoxy? I bought from frys Can I ask what fyrs is?

[LOVE6S]

Go to www.fastelectrics.net & then click on watercooling in the list at the top left of page, the idea is to fill the air gap between the radius of the coils. Thank you very much.

[Alexgar]

Frys electronics is a computer store like best buy google it its pretty cheap

[Shooter]

Here a picture of these jackets:
http://www.mb-forum.at/baubericht_hfk_prototyp_manuel_190.JPG

regards,
manuel

Just something to think about with these jackets. It seems that if the ID of the jacket was a close fit to the motor can, we could get transfer of heat from the motor to the jacket by direct contact (heat sink). Advantage here is that the water flowing through the spiral passages takes heat from both the motor directly (bottom side of flow) and the jacket (top side of flow). One step further, making the jacket out of a better heat sink material (Cu?) would further help. I'd be curious if anyone else agrees. I could machine up one of these, but Cu is extremely expensive, and it would probably take me an easy 3 hours.

[ManuelW]

Hello,

well the ID of that water jacket is not that tight. I'd guess the gap around 0.2-0.3mm or something like that. I think a tight fit is almost impossible as when the ID is a little too big there is no direct contact but also no real space for the water to flow and if its a little to small you can simply not mount it.
So I think a style like the one I showed is the right one. Aluminium is in my eyes also the material to go. Easy to machined, excellent heat conductor and way lighter than copper.

regards,
manuel

[1945dave]

Just something to think about with these jackets. It seems that if the ID of the jacket was a close fit to the motor can, we could get transfer of heat from the motor to the jacket by direct contact (heat sink). Advantage here is that the water flowing through the spiral passages takes heat from both the motor directly (bottom side of flow) and the jacket (top side of flow). One step further, making the jacket out of a better heat sink material (Cu?) would further help. I'd be curious if anyone else agrees. I could machine up one of these, but Cu is extremely expensive, and it would probably take me an easy 3 hours.

Shooter I really think this comes under the heading if it ain't broke don't fix it. Any small additional gain that could be derived by refining the basic cooling jacket design is so marginal that it doesn't make the effort worth it. For example, the heat sink concern. This jacket like most others have two "O" rings holding the jacket and breaking the direct contact that would be required to qualify as a heat sink. I have made a cooling clamp chamber that would come closer to what you seem to want. Essentially it was a clamping cyclinder that had a split down the middle and when tightened it physically gripped the motor tightly and with a little dielectric heat transfer compound qualitfied as a heat sink. Then to further assist the transfer of heat I had four tubular paths through the clamp that water passed through. It worked well but was rather heavy compared to traditional cooling jackets so I doubt if the gain justified the design.

Dave

[martin]

This is why the good old fashioned coiled tube cooler works so well, you have every coil touching the motor transfering heat from the motor to the pipe along with the water cooling the tube, add to that heat transfer compound & youve got pretty good cooling.None of these coolers with o rings transfer heat directly from the motor they only disapate heat from the water & not direct heat from the motor can.

[1945dave]

I find it interesting that you seem pretty convinced that coils (with transfer compound) are better than water chambers. You know that the big problem with our electric brushless motors is we are cooling the wrong component. The can is just the part we can cool the easiest. The heat is generated at the armature inside the motor can and ofcourse never actually touches the motor can. Just the same The out runner design is conceptually better at heat transfer than inrunner styles. But there are limitations in size and space. I think you need to look into a freon cooling system that works inside the can. <SMILE>

dave

[jcald2000]

Dave, the heat is generated in the wire windings (resistence) and they are next to the can in an inrunner, so the water in the can is next to the heat source with a good conduit. Out runners are backwards, windings are in the middle and the heat conduit is thur the shaft and bearings.

[Shooter]

Shooter I really think this comes under the heading if it ain't broke don't fix it.

Yep, yep...... I hear ya. Just grasping at straws at this point. No matter what I tried up north resulted in temps in the 140-150's. Speeds were 52-54 (spec power UL-1 motor, esc, props M445, M545, 645 cut down to ~43mm, etc...). Turns out I might just have to prop down and live with slower speeds when the water is hot (ran a few times at the club pond with smaller props 42x55 that someone loaned me, about 49mph and achieved 130° motor temps).

I did try a small container full of (4) ice cubes and it actually worked well on the bench. Ice remained for nearly 140 seconds at 10cc/s water flow and 90° inlet water temp. Outlet temp started at 68° and worked it's way up to 88°. I can share the data if anyone is interested. Essentially it does prove to be feasible if you are willing to deal with the extra weight of water (after the cubes melt), the 'sloshing effect', and the extra complexity. I ran it in the boat once today and my temps came back in the high 120's with the bigger prop, but there was some water in the boat most likely due to a bad connection and/or condensation from the ice. Fun stuff.

[srislash]

Just to throw this in there for the racers in the crowd,I used to use a container of ice and water with a 12V pump between races to get my motor ice cold before running.This was the old brushed days in the Puget Sound but it did keep my temps within reason for the duration.Just had to mention it as Shooter was talkin ice.

Shawn

[1945dave]

No matter what I tried up north resulted in temps in the 140-150's. I can share the data if anyone is interested.

Shooter, are we talking motor temp and ESC temp? What is your ESC running? I agree 120 degree motor is better than 150 degree motor but if the ESC and batteries are okay how bad is a 150 degree motor?

Dave

[Shooter]

Roger that. A guy at our club mentioned the same thing, except with a syringe.

Regarding the ice canister, here is the data I collected. (4) cubes seems to be adequate capacity for a 6 lap race. The cubes will be gone by lap 4/5 or so, but the temp differential achieved early on is very beneficial for motor/esc temps at the end. The test was somewhat conservative because my flowrate is probably a bit high (10cc/s). If anyone has actual measured flow rates with a single rudder intake, please chime in.

Thanks,
Pete

81073

[Shooter]

Dave, I was referring to motor temps. Measured on the windings near the wires coming in (found to be the hottest in my experience), 30sec after the run.

[ray schrauwen]

I've seen Terry Davis add a homemade wire cooler. just block of aluminum with 3 holes for wires drilled through it, then cut so 2 bolts can clamp it to the wires and a last hole with a tube to flow water through. It was pretty neat. I might make a pair.

[1945dave]

Dave, I was referring to motor temps. Measured on the windings near the wires coming in (found to be the hottest in my experience), 30sec after the run.

Shooter, I agree with you. I sometimes wonder if many of the guys that respond to these discussions ever read the original post. A while back I asked how should you align the cooling jacket on a can that is longer than the jacket. I expected at least one serious answer that took a position and justified what they suggested, yet, not one ever came forward. I slide the jacket as close to the wire lead endas posible and leave any gap on the shaft end principly because the shaft end almost always has a water cooled end mount so why not try to cool the other end? Works for me.

Dave

[ray schrauwen]

There is also debate about where you exit the water from the jacket. I say the exit should be at 12 o'clock and as far back as possible so it fills up completely. SOme have said if the water exits the side the jacket does not fully fill up and cool the topof the motor. I have nno idea but, I do it because Lehner does it (I think) and it seems like the right thing to do.

[1945dave]

There is also debate about where you exit the water from the jacket. I say the exit should be at 12 o'clock and as far back as possible so it fills up completely. SOme have said if the water exits the side the jacket does not fully fill up and cool the topof the motor. I have nno idea but, I do it because Lehner does it (I think) and it seems like the right thing to do.

There should be no debate on this. You are 100% correct the exit needs to be at the highest point of the jacket possible. To do other wise is just lazy or careless. There would be no justifiable reason to on purpose place the exit anywhere else.

Dave

[Mike Caruso]

Highest point please like Dave said.
HB Dave.
MC

[ray schrauwen]

Thats what I figured but, you can't tell that to some people in my club. They don't get that like electricity, water takes path of least resistance.

My 2 new UL-1 motors came in.... time to add some extras...

I burnt them out of stupidity, too hot of setups on 90F day.

[ManuelW]

Position of jacket:

-at the end of the motor towards the wire leads: not good

-in perfect conditions water jacket should be at least have the length of the magnetic backiron section within the can and be positioned right over it to cover this area. This ensures best heat transfer.

regards,
Manuel

[Shooter]

I've seen Terry Davis add a homemade wire cooler. just block of aluminum with 3 holes for wires drilled through it, then cut so 2 bolts can clamp it to the wires and a last hole with a tube to flow water through. It was pretty neat. I might make a pair.

Yep, I know that guy. I saw him start a car once with a 4S lipo. He is a very cool cat.

So, another guy at the club had a heat sink on the end bell of his motor. Great idea. He was running a pretty big prop and it didn't seem like he was having temp issues. Might want to consider something like that. I might even try screwing a nitro motor cooling head onto mine! ....or a marine nitro cooling head w/water cooling.

[ray schrauwen]

I've started my 99 Pontiac several times with a 1/2 charged 14.8v lipo pack. Not a problem but, I don't reccomend you do it.

[Michael Pullen]

Just something to think about with these jackets. It seems that if the ID of the jacket was a close fit to the motor can, we could get transfer of heat from the motor to the jacket by direct contact (heat sink). Advantage here is that the water flowing through the spiral passages takes heat from both the motor directly (bottom side of flow) and the jacket (top side of flow). One step further, making the jacket out of a better heat sink material (Cu?) would further help. I'd be curious if anyone else agrees. I could machine up one of these, but Cu is extremely expensive, and it would probably take me an easy 3 hours.



Would life a set of these for my Lehner 2250's