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Old Oct 30, 2009, 07:10 AM
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Joined Apr 2008
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Motor cooling

Guys
I would like to get some ideas for cooling the motors on my Emden.
I am building the Deans Marine kit and am using speed 400 6v motors with Proboat speed controls the blue anodized ones, and 6 volt 1.4aH sealed batteries, 1 to each motor and speed control.
I ran this same set up in my Schnellboot, and roasted the motors, I solved that problem with cooling coils, but with the Emden I dont think it will be moving fast enough to force water through the coils if I go that route. Any thoughts?
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Old Oct 30, 2009, 07:18 AM
NeverAgainVolunteerYourse lf
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Australia, QLD, Regents Park
Joined Mar 2007
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Hi boatsv,

Gear the motors, if the motor is running at near its no load rpm when its loaded then it wont get hot in the first place

What size props are on the Emden? while its a largish boat the power requirements would be modest in comparison to the Schnell boat

or run a separate cooling pump

Nick
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Old Oct 30, 2009, 07:49 AM
Registered User
Blackpool, Lancs
Joined Feb 2006
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Sounds like way too much power for the boat. Consider higher voltage 5 pole motors on the same battery.
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Old Oct 30, 2009, 09:07 AM
Veni, Vidi, Feci
patmat2350's Avatar
Motor City
Joined Dec 2004
12,298 Posts
Sounds like too SMALL motors... 400's are tiny, and need at least 3:1 gearing for even moderate sized props (e.g., 35-45mm).

Fast 500's will keep their cool if geared; slow 500's (like rock crawler or "lathe motor" winds) can be used in direct drive for slower scale models.

Instead of using a crutch (water cooling) for a mismatched motor, it's better just to get the right motor.

http://www.rcgroups.com/forums/showthread.php?t=906148
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Old Oct 30, 2009, 11:43 AM
GILL
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United States, NJ, Hopatcong
Joined Aug 2005
2,547 Posts
Pat is right it sounds like your motors are too small or your over propped. There is no scale boat that needs to have the motors "COOLED". Speed 400 are fine for the boats you have BUT they must be geared. Or as Pat says go with larger motors. The 5 pole (500-550) train motors work great in most scale models. Examples: Calypso - twin 400's 3.8:1 gear box, Andria Gail 1 400 3.3:1 gear box, 1:144 scale New Jersey 2 800 driving 4 props each motor drive a 4 blade at 2:1 and a 5 blade ay 1.85:1. Not 1 of my 103 boats ever even gets warm.
Pat is right water cooling a motor is a temporary fix the motor will still burn out.
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Old Oct 30, 2009, 07:13 PM
no wings any more, just dust!
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Joined Oct 2004
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Graupner's Speed400 range is basically a mabuchi 380 which pump out somewhere in the region of 17000rpm NLS, but give them a load, say a 3 blade propeller and they begin to struggle, and thats where your heat build up starts. may I sugest with your Emden that you install RS385 motors, due to having 5 poles they have more torque.

I run the following with no issues
4 in my yamato, each driving 4 blade 20mm props
2 in Nord Icelandia driving 30mm 3 blade props
1x in each neptun driving 30mm 3 blade props
1x in Nord Adiemus, driving 30mm 4 blade prop
1x in Elmshorn tug on 2:1 multispeed gearbox

and they run cool. after sailing for a constant 8 hours, the single 385 in Gemini, one of my Neptun's was cold to the touch, as if it had never been running.

another difference - Gemini ran on that 8 hour sail on ONE BATTERY, try do that with a 380 3 pole and you wont get anywhere near the run time!
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Old Oct 30, 2009, 08:47 PM
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Joined Apr 2008
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Thanks alot guys I am going to be using the speed 400's with some 3.8:1 gear boxes that I have. I think based on what has been recommended, that might work fine. Thanks again I really appreciate it.
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Old Oct 30, 2009, 10:24 PM
Webmaster, MMCNE
Acton, MA USA
Joined Feb 2000
580 Posts
On a related topic, can anyone recommend a suitable water pump for a twin motor cooling system? I'm not looking for a fire monitor pump-- a low volume/power pump is all I need-- preferably one with a low current draw. I know some people recommend WW washer pumps-- but aren't they overkill?
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Old Oct 30, 2009, 10:51 PM
Ken-Aurora,Co
Aurora, Co
Joined Apr 2008
248 Posts
For a small 6V pump take a look at

http://www.rcgroups.com/forums/showthread.php?t=1092190

Ken
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Old Oct 31, 2009, 09:51 AM
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Joined Apr 2008
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Small pump

Give the hobbico fuel pump a try. I picked one up for 12 bucks and they run on either 6 or 12 volts. I was going to use that if I had to water cool my motors.
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Old Oct 31, 2009, 10:52 AM
no wings any more, just dust!
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Joined Oct 2004
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bent piece of pipe at the back of the propeller to catch the prop wash, simple effective
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Old Nov 02, 2009, 12:02 PM
GILL
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United States, NJ, Hopatcong
Joined Aug 2005
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Ghost 2501 is right go with the 5 pole 385 motors those "400" in my boats are train motors all are 5 pole. They are a lower rpm then most 400's by the torque is much higher. The motors don't have to work as hard and as a result they run cool and draw much less current. The Calypso at full speed draws only 3.2 amps to run BOTH motors! With a 4 ah 12v gel cell (2-6v 4ah cells) that would be over 1 hour run time at full speed. My run time average is about 2.5 hours, that is at about half throttle (scale speed).
As I've said of my 103 running boats NOT ONE has a water cooled motor.
Even the race boats are not water cooled motors. One dose have water cooling on the batteries.
That uses a pump I found that a 1/4 inch dia. tube 1/4 inch in the water is like adding over 8 oz. to the model. So on that boat I used a pump running on a 4 cell receiver pack total 6 oz.
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Old Nov 02, 2009, 04:50 PM
no wings any more, just dust!
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gill I swapped out a temporary 380 in place of a 385, free load it spun quite happily but the moment the prop got wet, motor speed went down by around 80% and the can heated up accordingly due to the work the motor was having to do, spinning a 4 bladed 30mm propeller. the 385 on the other hand, dropped by around 25% when going from spinning in air to spinning in water.

My Najade "espirit d'atlantique" has a watercooled motor, (robbe 700/12) and it uses a thrust wash pick up, basically a piece of pipe in the prop wash, so as the boat speeds through the water, it picks up water and sends it through the system
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Old Nov 03, 2009, 09:05 AM
GILL
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United States, NJ, Hopatcong
Joined Aug 2005
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Exactly, the 380 is a 3 pole motor, I believe that if you could check the rpm the 380 will be faster. The 385 is a 5 pole, more torque. Even if both motors had the same wind the 385 would out perform the 380 under load. The 380's will accelerate faster, but the price is torque. The 3 pole motors are good when you want speed and acceleration. The 5 pole for smooth running and torque.
Too add to the confusion both are known as 400ís in the hobby world. Too this we can add different winds, magnets, brushes, and timing.
The type of water cooling you describe has been in use for many, many years. almost every fuel engine uses a water pick-up. But I still say that if you motor is getting hot, it is too small or over propped.
A quick test that I use is run the model for 2 minuets, if I can hold the motor for more then 30 seconds it's good. (at 120 degrees you will burn your fingers)
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