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Brushless replacement for a "380" brushed motor

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Tony Smith 703/06/2010 14:14:33
761 forum posts
28 photos
Hi,
 
My plane has a "380" brushed motor.  I am hoping that this is some sort of standard, and that someone could suggest what sort of kv and amp ratings I should be looking for in a brushless replacement to give the same sort of power and rpm.
 
I would prefer to keep the same prop, which is 6" x 3", and power pack which is 9.6v NiMH.    FYI the plane is a sort of motor glider, around 650g all up.
 
Ideally I want a cheap motor!
 
Reason for replacement is that I need to replace the ESC anyway, and hesitate to put more cash into old technology.  
 
A bit more power would be a bonus, but not the reason for change.
 
Thanks in advance,  Tony S
Jonathan Lewzey03/06/2010 14:20:40
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1136 forum posts
683 photos
glider will work better with an outrunner which needs a bigger prop. 650g is about 1.4lbs so go for a 150W outrunner, should be esay to find at BRC, hobbyking, RCM etc etc etc. lipo, esc and prop will all (or should all) be suggested in the specs of the motor which is really your starting point. kV not too high, not too low, roughly 1500 for this kind of size motor.
Jonathan Lewzey03/06/2010 14:22:52
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this would do for example with 3s about 1300mAh, 9" prop and 18-20A ESC
Romeo Whisky03/06/2010 15:49:46
657 forum posts
155 photos
You don't say if the 350 motor has a geared drive to the prop or direct, but surely the most obvious replacement is a can inrunner of about 2100kv.  (See Giant Cod or 4-Max websites)
 
It would be a dead easy straight swap.  Don't forget you'll need a brushless speed controller though.
Jonathan Lewzey03/06/2010 16:41:35
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1136 forum posts
683 photos
Posted by Romeo Whisky on 03/06/2010 15:49:46:
You don't say if the 350 motor has a geared drive to the prop or direct, but surely the most obvious replacement is a can inrunner of about 2100kv.  (See Giant Cod or 4-Max websites)
 
It would be a dead easy straight swap.  Don't forget you'll need a brushless speed controller though.

 
inrunner will be an easier swap, but outrunners are more efficent by driving larger props so will give longer flight times. However, both will work depends on the dimensions and motor mounting method at the moment. 
Tony Smith 703/06/2010 20:21:22
761 forum posts
28 photos
Thanks all.  Yes its direct drive at the moment, hence the small prop.   I don't want to go too large a prop as that would make it vulnerable when belly landing.
 
I would want to mount the motor inside the nose, like the existing setup, rather than out in front.   I intend to keep NiMH power at the moment, but I imagine that's an ESC issue rather than the motor - most advertised ESCs seem OK with either.
 
Do I assume that 2100kv would be round about the same speed as the existing 380?  and the 1400kv outrunner slower?
 
Thanks, I was really struggling for a starting point.
Romeo Whisky03/06/2010 22:00:50
657 forum posts
155 photos
Yes, 2100Kv  inrunner is about the same speed as your a 380/400, and should be no problem with your existing small prop.  I use both inrunners and outrunners on various models, I love the smoothness of inrunners, although outrunners have a bit more torque.
 
If you are upgrading from an existing brushed can, an inrunner is far away the easiest conversion.
Jonathan Lewzey04/06/2010 10:42:44
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1136 forum posts
683 photos
there's always the option of a folding prop on an electric glider if you're worried about landings. I wouldn't be though, i've belly landed my p-40 with a prop that protrudes past the air intake and never broken a prop in probably 50+ flights. Thats using a cloned APC, APS's themselves are a bit more fragile apparently although i don't think i've ever broken one. GWS's are a bit more flexible so might be worth fitting. Main thing is to land slow with no power, that shouldn't be a problem with an electric glider.
 
Up to you though, there is definite logic in the inrunner as it should be mechanically simpler (would be good to see a picture of the setup and motor mounting at the moment), but duration will probably be lower and an inrunner and higher amps ESC will probably cost more than an equivalent quality outrunner.

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