Best water pick-up ever!

[RandyatBBY]

Respectfully sir, we are not trying to HEAT the water. If so, then we would surely be interested in the amount of time the water sat in the cooling can (coffee maker).

Delta temperature is absolute king here. The best way to achieve delta T is MORE FLOW. No sense having warm water sitting in the can, it only reduces the delta T and the effectiveness of the system. The water is in constant contact with the motor. I work on systems like this everyday and graduated with a concentration in cooling systems. Not trying to change the laws of physics, just supporting them.

Regarding the automotive analogy, it is a closed system with increased complexity. The restriction was there to increase the pressure, thereby increasing the boiling point.

I'm only arguing now because I can't be boating!!!

I think there is a point of transfer rate that must be found with the flow of water. I like a good stream of water shooting out the side of the boat. But if the water goes too fast it misses picking up all the heat it can. If too slow the water gets too hot and this is not good either. Balance is key.

[Shooter]

You said it Doug. Backwards. They are looking at it from a 'heat the water' perspective (leaving the water in to absorb the heat). They are not one in the same. The coolest the motor can EVER be is the temp of the water coming out. More flow = coolest water in contact = maximum delta T = maximum potential for heat transfer OUT of the motor. Open system.

SailR - You're right, we don't have much control over volumetric flow rate (other than increasing the inlet and piping restrictions), so perhaps we should be concentrating on other things like the position of the inlet and outlet on our cooling cans, etc... but I like arguing with you guys because I know I won't end up sleeping on the couch afterwards!!! he he he!!!

I'm first in line to take advice from Mr. Fluid as I don't have near the smarts nor the boating knowledge, but for this particular issue I have to respectfully disagree with him.

[Brushless55]

Hey it's ok, we all can give input as I don't think there realy is just one on these forums who know all

[Jacked1]

Hmmm I would look at it like If you have a 200watt heater being sprayed with a fire hose or a 200watt heater being sprayed with a garden hose, which heater would be cooler?

If you sit down and do the thermodynamic calculations it is the mass flow rate (mdot in kg/s) multiplied by the change in enthalpy (delta h in joules/kg) of the water to get the Qout (in joules/s = watts). Sooo in both cases you are dissipating 200watts (Qout). So when your mass flow rate is increased (mdot) the change in enthalpy (delta h) is decreased. And since enthalpy is a function of temp and pressure, it increases with temp. So this means the more water flow the lower the temp for a given setup. Although to a point you stop seing any change in temp and there is no need for anymore water flow and you increase the likelihood of a tube bursting or a similar type of failure.
mdot * (h2 - h1) = Qout/s (<this equation is fact)

Either way tho you are still dissipating 200watts.

I love the discussion here. :)
Dr. Hearmanz and Dr. Muzumder would be proud.

[keithbradley]

Wrong. Water has a specific heat value and takes time to absorb heat. Turbullent flow is required for maximum heat transfer, but cooling water moving 'too fast' by hot objects does not absorb the heat as well as water moving slower. (That's why auto engines run cooler with a thermostat or restrictor in place instead of no restriction). But the heck with physics guys - believe whatever you want. I'll just keep having the coolest components in my boats!



.

Seriously? I thought we put this to bed guys. I'm not sure why this is so difficult to grasp. It's really a rather simple concept. I try to approach this topic without insulting anyone's intelligence, but it becomes difficult after a while. This is one of the oldest redneck theorys out there. I deal with it all of the time and have been listening to people mouth this nonsense for years.
Before anyone gets too uptight, Im not calling anyone a redneck. I call this a redneck theory because in my experience that's where it seems to come from in the automotive world.
LET ME BE CLEAR...There is only one type of person who believes that "cars run cooler with a thermostat/restrictor plate" crap: Someone who doesn't know cars from their rear end.
It's total nonsense. An engine will run coolest at the highest flow rate possible. Before you start to tell me that a car will run hotter with the thermostat removed, do me a favor and go remove your thermostat...let me know how that works out for you.
A thermostat is there to allow an engine to heat the coolant to a specified point. It serves no extra cooling purpose at all. It is an element of the cooling system that is in place to SLOW the cooling of the engine until a desire temperature is reached. I really don't know how this isn't obvious unless you just have no idea how a cooling system in an automotive engine works.
A restrictor can be used (though very uncommon and often unsuccessfully) to create pressure in a system where an insufficient (wrong) pump is used...but is much more commonly a product of stupidity. There are a lot of reasons people in low level racing use these but the primary one is ignorance.

Sorry to rant, but I work in this field and have worked in this field for a long time. It's tough to see the same statement made over and over despite how obviously wrong it is. This is not a subject that can be intelligently debated, because there is no intelligent debate. I thought I provided enough information to put the nail in the coffin on this one, but I guess it will just have to remain a popular urban myth to some people. There is no amount of reality that can can disprove some people's broscience.

[keithbradley]

One other thing...
Where do people get this idea of a relationship between heat absorbtion and speed? People speak of this like it's fact, but it seems to be something that is just made up for converstation/arguement purposes. The idea has been brought up a number of times that water doesnt have enough TIME to cool...are these people saying that we are bending time and space with the rate of our cooling flow? I must be missing something here...
A gallon per minute, or 10 gallons per minute. Two different flow rates. Which one has more time? The only difference between these two is that the 10gal/per minute setup spends the minute with a larger temperature delta...

[drwayne]

The one consistent thing I observe here, is variation.

Unlike nitro/gas engines, FE do not have need a 'running temp', where in fact cooler is better.

If your flow is slow.. heat ?
If your flow is fast ? .. go try.

end of day the advice in these forums is indicative the answers we seek... yet localized interpretation and application can present any type of cloned aberration. !

If yours works, stick with it.
If not.. experiment !

DocW
Adelaide
Au

[riksorensen]

I bought one of these from ose for my sv-27/stiletto outboard conversion and I have to say this is the highest flowing water pick-up I've ever used! It almost looks comical how much water shoots out the side of the hull even at low speeds. I know its not the most hydro-dynamic piece, but there is no doubt that my esc is getting all the cool water it can handle. I will definitely be using more of these!!

http://www.offshoreelectrics.com/pro...?prod=oct-ocsw

I just invented this....
It is a new and hopefully improved way of feeding your FEs with a high PSI water flow for cooling....
Before I explain... Here is what I know...
•More PSI = More Flow
•Greter Tube Diameter = More Flow and Volume (Provided there are no bottlenecks in the design)
•Faster and greater flow volume = Better cooling
•A colder motor = More power and less energy consuption
•Air in cooling/water lines is not great

Anyway... so I JB welded a 5/32 brass tube to the back of my HK Genesis rudder and wrapped it around and underneath...
It should offer awesome waterflow into the boat with very minimal extra drag as the tube is tucked behind the rudder..
Additionally, it should improve the flow of water over the rudder reducing drag as it will now have a rounded trailing edge as opposed to a square one...
This is just to compliment and run parallel with the rudder internal water inlet... It sits deep, will never (rarely) get air sucked into it and will yeild a super high water flow!!!
I will be using both... The new mod for the motor and the other for the ESC...
Im not sure if I will put 90deg fittings on top of the rudder or leave it with direct nipples in parallel...

photo 1.jpgphoto 2.jpgphoto 1.jpgphoto 3.jpgphoto 4.jpg

[riksorensen]

Agreed...
Its the gross delta that can dictate the rate of heat loss/transfer.
The bigger and more consistant the delta (as what you get with a higher flow) the better the heat transfer/loss.
The less and more intermittant the delta (slower flow) the less heat transfer/loss.

I won't go into a crazy amount of detail... Suffice to say, the greater the flow the better the cooling...

[desmobob]

Sorry but what kieth is sayin is not opinion it physics and it doesnt change for anyone . Let it go keith coa all anyone has to do is open up a physics book;read it and prove it to themselves. Your wasting your time when people argue with basic physics.

Listen to keith... Q = M x C x Delta T

If you want to know more: http://en.wikipedia.org/wiki/Heat_transfer_coefficient

Take it easy,
desmobob

[Rumdog]

That rudder is going to seriously effect your handling.

[riksorensen]

That rudder is going to seriously effect your handling.

How so?
There is no change in surface area... the only change is the revision of the rudders trailing edge... i.e. less drag...

Im curious to know why you think it will "seriously effect" the handling?

[Rumdog]

There is a reason rudder pickups are flush with the rudder. Yours will cause drag, and either lift, or pull the transom down depending in the rudder's angle and boats ride attitude.

[riksorensen]

Wrong. Water has a specific heat value and takes time to absorb heat. Turbullent flow is required for maximum heat transfer, but cooling water moving 'too fast' by hot objects does not absorb the heat as well as water moving slower. (That's why auto engines run cooler with a thermostat or restrictor in place instead of no restriction). But the heck with physics guys - believe whatever you want. I'll just keep having the coolest components in my boats! .

Fluid;
Just a note on the thermostat thing... They are in place to moderate flow to ensure the engine runs a consistant and desirable temp.
More importantly, it ensures that there is steady pressure throughout the system between the water pump, through the engine and its cooling ports and back to the backside of the thermostat.
Thermostats ensure that all areas of the engine get coolant and that the coolant does not follow the path of the least resistance and introduce air...
Engines without thermostats as you noted can and do run hotter. There are 2 reasons.
One - The temp sensor is located in the thermostat housing provididng a temp measurement of the coolant as it leaves the engine.
Two - Systems without thermostats are not as presurized and therefore some areas of the engine do not recieve coolant and therefore are not cooled the same as other areas. Cars that have thermostats removed tend to have temprature inbalances between ther cylinders.

How does this translate to RC Boat Motor cooling.... More pressure and more flow = Greater cooling...

RC Boat electric motor cooling is not restricted to being a sealed system so restricting the flow is detrimental to the overall cooling.
Additionally, as already mentioned... Electric engines run most efficient when cool/cold unlike nitro or gas engines that need to be at optimal operating temprature.
Essentially, the comparrison of car engine cooling in a sealed system to electric motor cooling in an open system is the same as apples and oranges.

They are not the same.... and based on your understanding, I don't think you will "just keep having the coolest components your boats."

No offence...

[riksorensen]

There is a reason rudder pickups are flush with the rudder. Yours will cause drag, and either lift, or pull the transom down depending in the rudder's angle and boats ride attitude.

Interesting observation... I may just modify the design to satisfy the concern...

Stay tuned...