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Old Apr 10, 2011, 06:08 PM
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dragon snap burnt out motor

Hi Guys

Went great, but after 5 mins it stopped. Retrieved it, and the motor was jammed solid, no evidence of it burning out, as in no smoke etc

Anyway bought a replacement motor for it locally (2881kv FSD), ran it again for 2-3 mins or so, then brought it back in, the Batts and ESC were just warm to touch, but the motor was very hot !

Anyway I've put up a photo of the motor...any help would be appreciated.

Regards
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Last edited by f1disaster; Apr 18, 2011 at 12:26 PM.
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Old Apr 10, 2011, 06:15 PM
I feel the need for speed!
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Is the motor fried???

Which way are your water cooling tubes set up for the motor jacket? The intake tube needs to be the lower one, outflow on top..............that will have a big impact on cooling.
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Old Apr 10, 2011, 06:44 PM
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Hi Scorp

Yes fried...the water pipes were in and out opposite each other at the centre of the cooling jacket. I've now swiveled it round so the outet now exits at the top, but not tried it as yet.

Would a separate transom pick up to the motor help...I have one of those...if so would it need it's own water outlet (which I also have) or would it be better to 'Y piece' them together ?

Do you think my problem is water cooling or drive train ?, the rudder is very small but has 2 pickups in it, but both go to one outlet.
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Old Apr 10, 2011, 06:49 PM
I feel the need for speed!
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With the ESC being "quite cool" and the motor HOT, the cooling for the motor was most likely the issue, only half of the motor was getting cooled as water drained out before filling the jacket. Grab a replacement motor....Feigao, or Leopard..............what size is the motor?? I can give an opinion on motors if i know the size.

EDIT: just found the boat, nice looking! If it were mine, i'd throw a 380 10L in it on 3s and cool it properly.The stock motor is a 28 x 48mm and the 380L is 28 x 58mm and is probably a bit better quality.

http://www.offshoreelectrics.com/pro...-380-L&cat=116

I'd throw this balanced and sharpened prop on it as well

http://www.offshoreelectrics.com/pro...rod=octsb-x435
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Old Apr 10, 2011, 06:58 PM
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It's a 2848 2636kv no name on it, must be some Chinese clone. Got a picture of it....
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Old Apr 10, 2011, 07:02 PM
I feel the need for speed!
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I posted right before you.................post #4................
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Old Apr 11, 2011, 06:37 AM
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Het bud,iv got the dragon hobby saga,twin motor cat and its been fab,but same as you motors have finally gave.
Are you running 4s or 3s
running 4s on that motor is to much,there 3s motors hence why you fried it.
The dragon hobby motors are ok but not built to last for some reason.
What kv motor did you replace it with?

A guy at our club has 1 and had no trouble with his on 3s setup and 36mm,3 blade prop
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Old Apr 11, 2011, 02:53 PM
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Scorp..

One thing I haven't told you is that I was running a Graupner X440 prop..you guys are talking about props much smaller...so is a 40mm or 42mm to big ?, do I need to get something around 35mm max ?.

The motor I got from the local model shop which I quickly tested and found to be running very hot is an FSD 2881kv. So I'll run it up and see how it goes, if it behaves I'll take your advice and get the Feigo.

Cheers
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Old Apr 11, 2011, 03:00 PM
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Hi F1

No I ran it on 3s, other people have run 4s on this boat with the same result - fried motor.

Nice to know one of your members have had no trouble with the same boat I have, I was worried it might be a design fault.

The motor I have now is a 2881kv, I've positioned the cooling jacket correctly, and looks like I'll have to get a smaller prop, which I'll order up tonight.

Should get it back out on the water b4 weekend, and let you all know.

cheers
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Old Apr 11, 2011, 03:15 PM
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Quote:
Originally Posted by f1disaster View Post
Hi F1

No I ran it on 3s, other people have run 4s on this boat with the same result - fried motor.

Nice to know one of your members have had no trouble with the same boat I have, I was worried it might be a design fault.

The motor I have now is a 2881kv, I've positioned the cooling jacket correctly, and looks like I'll have to get a smaller prop, which I'll order up tonight.

Should get it back out on the water b4 weekend, and let you all know.

cheers
thats the same kv motor i run in my saga,is the can size 2860 if so use a 36,3 blade cf prop and you shouldnt have any trouble and still be quite quick
Good luck
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Old Apr 12, 2011, 06:54 AM
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Thx F1

I'll get one to try from PMB Boats...Are there any decent plastic ones, as in not the ones supplied ?
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Old Apr 17, 2011, 01:57 PM
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Hi Scorp

Did exactly as you said and hey presto ...

just have learn to drive better....but the end point and trim wasn't set properly...my excuse anyway.

28.5" Dragon Snap 2881kv - TEST 1 (1 min 25 sec)


After 5 mins checked the motor and it was COOL, so sorted
thanks
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Old Apr 17, 2011, 02:05 PM
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Also I think the liner is plastic (not teflon). I bought some 1/8" x 3/16" teflon but it's just slightly to big to go into the stuffing tube. Is there any liner that would fit?. I measured it and it's roughly 3.2mm ID and 4.7mm ish OD..any help on this ?
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