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....


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[JIM MARCUM]

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

John

Informative thread. Hope you get that raise John.

JIM

[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....

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....
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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/pro...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.