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Old Sep 29, 2009, 04:33 PM
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Brushless Direct Drive vs. Geared Brushless

Hi everyone, my custom made helicopter(from several micro blade, honeybees..etc) needs a tail motor and I want to know wether if it is any good to have a brushless direct drive tail motor rather than a brushless geared one. the thing is that it seems very hard to find a small high kv with the right shaft diam. and pinion that fits the gear on the tail. Also it looks like it will be more expensive.

Therefore, I wanted to actually just buy a small outrunner around 1100-1800kv to drive a prop directly.. is this any good or aint tere anyone here to recommend this? the real question comes to eficiency, will it be a "battery eater" to have a directdrive back there?


Kalle
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Old Sep 29, 2009, 04:55 PM
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direct drive means less parts,i,d be going for that if you can get the right motor.
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Old Oct 02, 2009, 05:30 PM
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the hard part I think is to find the right motor, what kv should I aim at which power do you guys think ?


the tailrotor to be used is about 5 to 6 inches

so there are couple of choices I have here:

all P.E.M motors

RPM / V: 1400 80w
7.5A / 60 sek
weight: 19 gram ...this seems to have the right kv? but little too heavy? and overkill
Propeller: 7x3.5-8x4.3



RPM / V: 2200
8.5A / 60 sek
16 gram .... a little too fast?
Propeller: 5x3 - 7x3.5


or?

RPM / V: 2200 60w
7.5A / 60 sek
Vikt: 9 gram
Propeller: 6x4 - 8x4

one thing that I have noticed experimenting with tail rotors/motors was that when I used a 50g 900kv tail motor with a 5.5 inch prop , the motor got real real hot very fast!! how is that logical?(i mean insane hot) it was much hotter than the 3600kv main motor? could it be that the motor was "overnning" i.e. it had no load at all and got hot?
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