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Author Topic: Submarine motor cooling ideas  (Read 4677 times)

lukehallbland

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Submarine motor cooling ideas
« on: August 24, 2009, 02:24:28 pm »

Does anyone have any good ideas for cooling motors and ESCs. I haven't tested it properly yet, but in the bath whilst holding the sub in place I tried increasing the throttle to about 2/3s for a short time it got rather warm but not hot.

I presume that being held in place its having to work a bit harder than normal but I figure cooling is probably required. Would you expect bending a fairly thick sheet of copper around the motor and passin it out of the hull as a keel would help?
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Sub driver

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Re: Submarine motor cooling ideas
« Reply #1 on: August 24, 2009, 03:06:03 pm »

If I may offer some advice,

If the motor is getting hot  then you have the wrong motor / esc fitted or prop / serious binding.

You do not have to cool a motor in a sub IF the motor is the right one etc.

This is an indication that something is not right............and you do not want to pump water into a sub unless its for ballast etc.

What motor is it ..?

what sub is it ?

What sized prop is it ?

And most important of all what AMPS is the motor pulling with what sized prop and voltage.

Regards.

Sub.
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Wasyl

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Re: Submarine motor cooling ideas
« Reply #2 on: August 24, 2009, 03:13:12 pm »

I had a similar problem with a liquid paraffin smoker that got dangerously hot,i fitted a cooling fanlike whats in a PC,and it did the trick perhaps you could fit one inside,
when i think about it,the sub is slow moving therefore why is the motor getting hot,"too much revs perhaps,wrong motor,??/

Wullie
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lukehallbland

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Re: Submarine motor cooling ideas
« Reply #3 on: August 24, 2009, 03:28:56 pm »

I'll test the draw when I get back but it's

A28-15 2000 RPM/V ENERG BRUSHLESS MOTOR

* Battery - 6-12 cell NiMH 2-3 cell Li-Poly

* Weight - 86g

* Working current - 5-20A : Peak 25A

* Shaft diameter - 4.0mm

* Motor Size - 28x30mm

* Speed Controller requirement - 25A

Used with a 80A Tunigy marine Brushless ESC at 12v



The submarine is based on a Norbert Brugen ball fish hull, the hull is very hydrodynamic, you barely have to touch it to get it gliding through the water.
http://www.modelluboot.de/KITS/Kugelfisch_Ordner/KugelfischE.html


Propeller is a 29mm one in a heavily modified Graupner jet booster 3

Its not getting hot as it's fine to touch and i'm not expecting to ever have it running that fast for long periods, and I figured being a high kv motor it would get warm. I know the mount needs improving as it wasn't straight enough and there's a large amount of wear on the coupling and was drawing 9amps at full speed (very short burst).

I have a new mount coming to replace my home made one which I think is a bit too flexible.

Edit for Wasyl's it's meant to be a fast moving sub, the slightest push and it really gets moving.
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FullLeatherJacket

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Re: Submarine motor cooling ideas
« Reply #4 on: August 24, 2009, 03:35:43 pm »

Sorry to point out the "elephant in the room", but a fan moves cool air over a hot thing. The cool air is thus heated up and moves elsewhere as hotter air. If the environment is vented then this hot air will rise and draw in cooler air through the fan etc etc.
If the environment is closed, like the water-tight bit of a submarine, then there's nowhere for this hot air to go except back through the fan. Thus the cooling system gets increasingly inefficient as the ambient air temperature rises.
Did I miss something out? Happy to be shot down if I'm off-beam.
In my experience a hot motor invariably indicates a mis-match with something else in circuit and/or the load.
FLJ
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stallspeed

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Re: Submarine motor cooling ideas
« Reply #5 on: August 24, 2009, 04:13:03 pm »

You can delay the timing via the esc.
An inrunner gets hot on the outside,so to speak.
You can read the blurb and do the watts,amps and stuff but doesn't a 14 watt low energy bulb get hot with a similar surface area?
I don't know that you are experiencing anything abnormal or worrying.
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lukehallbland

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Re: Submarine motor cooling ideas
« Reply #6 on: August 24, 2009, 04:38:45 pm »

I wasn't overly worried, I just was planning to put the fins in anyway and was thinking about turning them into heat sinks.

I would assume that something spinning at 24000rpm or so would get warm, especially when the water has nowhere to go so is rebounding back into the jet

I may have the wrong motor as it was a rough guess and I'll see when I test it properly in the canal but in the mean time any views etc are welcome
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stallspeed

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Re: Submarine motor cooling ideas
« Reply #7 on: August 24, 2009, 04:46:48 pm »

I am sure you can buy inrunner heatsinks for a fair price.
Don't worry about the 24,000 mark if it is a 2kv motor.
It will get hot if you gun the throttle and it only does 12,000 rpm.
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lukehallbland

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Re: Submarine motor cooling ideas
« Reply #8 on: August 24, 2009, 04:51:24 pm »

Guess the thing to do when I put it it in the canal would be to find some thermal cut of that kills power to the motor at 70'c or so?
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stallspeed

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Re: Submarine motor cooling ideas
« Reply #9 on: August 24, 2009, 04:56:17 pm »

There are actually devices that replace bi-metallic strips now.
Try nearer 100o
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lukehallbland

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Re: Submarine motor cooling ideas
« Reply #10 on: August 24, 2009, 05:04:17 pm »

If it's 100 then i guess i don't have to worry, but the time it hits that I would expect the coupling to be too squidgy to transfer any power.
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Wasyl

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Re: Submarine motor cooling ideas
« Reply #11 on: August 24, 2009, 05:10:30 pm »

Sorry to point out the "elephant in the room", but a fan moves cool air over a hot thing. The cool air is thus heated up and moves elsewhere as hotter air. If the environment is vented then this hot air will rise and draw in cooler air through the fan etc etc.
If the environment is closed, like the water-tight bit of a submarine, then there's nowhere for this hot air to go except back through the fan. Thus the cooling system gets increasingly inefficient as the ambient air temperature rises.
Did I miss something out? Happy to be shot down if I'm off-beam.
In my experience a hot motor invariably indicates a mis-match with something else in circuit and/or the load.
FLJ
I hope you,re Not implying that I,m a Fat guy,cause if you are, there will be no hiding place for ya,I,ll find you,Ya............an Elephant never forgets, {-)Oops........I,ve just fallen off ma seat {-) {-)

Wullie,with Big Hands,and you know what they say about big hands {-)
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FullLeatherJacket

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Re: Submarine motor cooling ideas
« Reply #12 on: August 24, 2009, 08:00:55 pm »

As someone who won't see 110kg again myself, I would not risk being called a hypocrite (as well as everything else) by ridiculing anyone else's BMI. You'll find that "the elephant in the room" is a figure of speech, much used these days in the media, to describe what we used to call the "bleedin' obvious".

I have very small hands.............. %)

FLJ
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sheerline

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Re: Submarine motor cooling ideas
« Reply #13 on: August 24, 2009, 08:36:23 pm »

 {-) {-) Priceless!!!
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Subculture

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Re: Submarine motor cooling ideas
« Reply #14 on: August 24, 2009, 09:03:10 pm »

I reckon your kV is on the high side. A kV of between 750-1300 is nearer to what you should be aiming for.

You could try your sub on 7.4 volts, which will bring the RPM down to a more sensible level.

I'm sure Norbert could give you some suggestions for a good motor for your ballfish.
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Bunkerbarge

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Re: Submarine motor cooling ideas
« Reply #15 on: August 24, 2009, 11:23:57 pm »

From what I can see I really don't think we need to look much further than:




I know the mount needs improving as it wasn't straight enough and there's a large amount of wear on the coupling and was drawing 9amps at full speed (very short burst).

I have a new mount coming to replace my home made one which I think is a bit too flexible.



Let's see what happens with a new mount that is correctly aligned.
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