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Old 08-01-2018, 06:01 PM   #1 (permalink)
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Hey guys, I have a friend that got a used 600 with a md500e fuse and he needs a new motor. What kv should he use for this? It is fb and I think a esp Trex.
Thanks.

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Old 08-01-2018, 08:53 PM   #2 (permalink)
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You need to provide more information to get an answer.
Is he running a 6s or a 12s system - or something else in-between?
2-blade head, or multiblade?

What headspeed does he want to get?
Gearing?
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Old 08-02-2018, 05:30 AM   #3 (permalink)
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Quote:
Originally Posted by getsuyoubi View Post
You need to provide more information to get an answer.
Is he running a 6s or a 12s system - or something else in-between?
2-blade head, or multiblade?

What headspeed does he want to get?
Gearing?
6s, fb so 2 blade, stock gear don't know how many teeth, a head speed that will work well for scale.

Sent from my XT1254 using Tapatalk
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Old 08-02-2018, 09:22 PM   #4 (permalink)
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The cheapest option would be the Gartt 1220kV motor, around 40 bucks. Other than that, anything between ~1000 and 1200kV should work OK.
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Old 08-03-2018, 03:38 AM   #5 (permalink)
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Quote:
Originally Posted by Wind Spirit View Post
6s, fb so 2 blade, stock gear don't know how many teeth, a head speed that will work well for scale.

Sent from my XT1254 using Tapatalk

Really, without the gearing any recommendation is purely a guess. It is fine to guess at a 170T main gear, but it could be a 13T pinion or a 17T pinion. It also depends on the ESC - governed or not, active free wheeling or not.



Work it out for yourself (or your friend).


RPM = kV x (3.7V x 6) x 0.9 x pinion teeth / main gear teeth = rpm at 100% towards the end of the flight.


So, if it is a 170T main gear and a 13T pinion, and he plans to govern using a CC (or similar) ESC at 90%, and he plans to fly a 2x 600mm heli in gentle scale-like flying at about 1500rpm;


RPM = kV x 22.2V x 0.9 x 13T / 170T = (1500/0.9)rpm


So, kV = 1660 x 170 / (22.2 x 0.9 x13) = 282 200 / 260 = 1085kV, so you would pick the closest kV rating to 1085kV.


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