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Electric Ducted Fan Jets Discuss electric ducted fan jets here including setup tips, power systems, flying techniques, etc.

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Old 08-18-2011, 05:12 PM   #1
olhoss
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Default Twin EDF question

This question is electrical (who would guess). I have 2 55mm ducted fan motors. Each is 4200kv, 11.1v, 2a no load, 22.7a full load. The wiring diagram with the kit shows the 2 wired to a single ESC with a single battery. Does the amp rating for the ESC and battery need to be for the 22.7 amps or does it need to be for 45.4 amps? Thanks for your help.
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Old 08-18-2011, 05:32 PM   #2
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45.4 Amps (parallel connection). Must be a brushed setup.

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Old 08-18-2011, 06:56 PM   #3
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Originally Posted by olhoss View Post
This question is electrical (who would guess). I have 2 55mm ducted fan motors. Each is 4200kv, 11.1v, 2a no load, 22.7a full load. The wiring diagram with the kit shows the 2 wired to a single ESC with a single battery. Does the amp rating for the ESC and battery need to be for the 22.7 amps or does it need to be for 45.4 amps? Thanks for your help.
Your instructions may assume brushed motors but if the motor has a KV rating its brushless. So you really need a pair of ESC's. I'd use a pair of 30 amp to give yourself some headroom. Probably a 30C 2200 mAh battery minimum for 3-4 minute flight times depending on how you fly. Your battery(s) need to safely handle 45A.

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Old 08-18-2011, 07:22 PM   #4
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Originally Posted by olhoss View Post
This question is electrical (who would guess). I have 2 55mm ducted fan motors. Each is 4200kv, 11.1v, 2a no load, 22.7a full load. The wiring diagram with the kit shows the 2 wired to a single ESC with a single battery. Does the amp rating for the ESC and battery need to be for the 22.7 amps or does it need to be for 45.4 amps? Thanks for your help.
Years ago I did run two brushless motors from a single Castle Creations ESC. It did work, the motors stayed exactly syncronized, BUT the setup resulted in significant RPM loss at full throttle. That lead to a loss of some 40% in watts, as compared to running both motors with separate ESC's.

It did work, but not recommended. I was probably lucky anyhow that it even did work.

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Old 08-18-2011, 10:51 PM   #5
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while it may work, if it does,

if somethig happens you could damage a lotof stuff all at once.
are you planning on useing the esc BEC also?

if i wanted to to do that set up .. i would have 2 esc and a sep small bec.

my smallest edf(of all my brushless twins) is a 64mm sr71.. and it is set up that way.

WHAT ARE YOU BUILDING

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Old 08-19-2011, 12:39 AM   #6
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Originally Posted by tampaflyer View Post
while it may work, if it does,

if somethig happens you could damage a lotof stuff all at once.
are you planning on useing the esc BEC also?

if i wanted to to do that set up .. i would have 2 esc and a sep small bec.

my smallest edf(of all my brushless twins) is a 64mm sr71.. and it is set up that way.

WHAT ARE YOU BUILDING
works for All Twin'sbubsteve


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Old 08-19-2011, 01:42 AM   #7
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Its a Guanli A-10 foamie. Was on sale at an freekishly low price so I couldn't pass it up. Then you combine my lack of experience with electrics and add to that twin engines and add to that the lack of information provided in Guanli planes and the questions just pile up.

Here's another; why can't I use the BEC off one Esc to provide RX power?
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Old 08-19-2011, 03:19 AM   #8
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You probably could, if the bec is rated high enough to power all your servos and rx at the same time.

Otherwise I'm with Tampa. My HET Me262 uses a separate bec, just to be on the safe side. But then again, it has electric retracts the bec has to power.

Also check your bec's rating. On some esc's the higher the cell count the lower the bec's amp capability. Can get you in trouble real quick if you don't.

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Old 01-10-2012, 09:23 PM   #9
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Default Re: Twin EDF question

So how did it turn out? I'm fixing a stock brushless version and trying to remove all weight that i can. So far, that means gearless with 2 servos instead of 3...
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Old 01-25-2012, 02:49 PM   #10
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Originally Posted by kyleservicetech View Post
Years ago I did run two brushless motors from a single Castle Creations ESC. It did work, the motors stayed exactly syncronized, BUT the setup resulted in significant RPM loss at full throttle. That lead to a loss of some 40% in watts, as compared to running both motors with separate ESC's.

It did work, but not recommended. I was probably lucky anyhow that it even did work.
Originally Posted by tampaflyer View Post
while it may work, if it does,

if somethig happens you could damage a lotof stuff all at once.
are you planning on useing the esc BEC also?

if i wanted to to do that set up .. i would have 2 esc and a sep small bec.

my smallest edf(of all my brushless twins) is a 64mm sr71.. and it is set up that way.

WHAT ARE YOU BUILDING
You have to experiment with the setups. Like anything, it takes a good bit of experimentation to determine what works, and determine reasonable specs for it. Castle is the only ESC that has worked well for this, from my experimentation, and not all inrunners will perform well. I've used Castles for everything from EDF30 twin, to EDF55 twins, all inrunners. I never had a failure or even a single problem, other than maybe 2 initial throttle starts to get both motors running. They will only drop out at very low RPM, which can be overcome by setting idle with trim. I've never bothered, nor have had the need to do that.

The ESC is derated somewhat, although Castle uses quality fets and has honest ratings. With the TBird6, I've had no issues running at 5A continuous. I didn't find any notable performance loss from the using this setup, such as notably lower max rpm. The reason I used the single ESC setups was to reduce ESC and related wiring weight. A small, twin EDF, especially when sheeted/detailed for scale appearance, can get heavy. The use of a single ESC is probably the single most reason that the smaller projects were successful. A few of them really didn't need to push the scales any further, as there is a fine line between a good micro flyer, and an underpowered micro flyer. All have flown WOT on adequately rated 3s lipo.
Here are some of them below:


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Old 02-26-2012, 11:37 PM   #11
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Not all ESCs appear to be able to handle two motors. The cheap Mystery 30A definitely would not. Could not even get both motors running at the same time but I do understand the weight issue. Two ESCs and wiring added as much weight as another motor.
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Old 07-01-2013, 08:20 AM   #12
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For a twin or multiple brushless motor set up you need two ESC (of the same type, rating and branding) , a twin matching EDF & motors. If you are powering from the same battery use a Y harness from battery to the 2 ESC . Don't use separate battery pack.
Here is the successful flight of my early twin EDF experimental aircraft.

http://youtu.be/Ugg0YHmGpz8
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Old 09-24-2013, 06:13 AM   #13
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I re-modified my mugi to a twin EDF(2x55mm edf using 3.9kv motor)
Here is the video.
It draws about 40-46amps on a 3S lipo.


Cheers
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Old 09-24-2013, 06:44 AM   #14
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All electric motors have kV ratings. This is not something that was invented for brushless.
Some may not list the kV but they should instead state a no-load rpm rating at expected normal operating voltage.
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Old 09-24-2013, 07:03 AM   #15
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Originally Posted by fhhuber View Post
All electric motors have kV ratings. This is not something that was invented for brushless.
Some may not list the kV but they should instead state a no-load rpm rating at expected normal operating voltage.
Yup, this does apply to our brush and brushless motors used in our models. These motors all use permanent magnets, resulting in that KV rating.

FYI, it does not apply to the typical electric motors found in the home such as the air conditioner compressor, bench grinders, sump pumps and the like. These motors run at a constant RPM, usually slightly below 1800 or 3600 RPM. That RPM is fixed by the 60 Hertz frequency of the 120 VAC power input. Or 50 Hertz in some countries outside of the USA.

As for the universal motors found in AC powered drills, saws and so on, again, the KV rating would not apply.

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Old 10-27-2013, 04:25 PM   #16
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I sure wish somebody had asked him how many wires were on each motor to definately be sure about everything.

Leftovers can bite someone new, very hard.
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