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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 01-20-2014, 08:54 PM   #1
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Question AEO 27mm EDF thrust not there

I'm new to brushless motors, esc's, lipos ect. I purchased an AEO27mm EDF unit and set it up as follows.

Summary:
Motor: ELE RC ADF27-05 PLUS Brushless Ducted Fan Power System 10,000kV
7.4 V 4.1 A 58 Grams
8.0 V 4.6 A 66 Grams
8.4 V 4.9 A 72 Grams
ESC: Motrolfly 6A ESC
Battery: Cheetah Packs 7.4V 360mAh 35C lipo
Servo tester: E-sky from gobrushless


Now the way I understand the battery discharge amp info, a 360mAh 35c should provide 12.6amps (35*360=12600/1000=12.6), and the 7.4v lipo fully charged is 8.4v, and the esc is well over 4.9A. BUT I can only squeeze 58gm of thrust out of this setup.

I switched to a Spektrum AS6410NBL DSMX 6Ch AS3X Receiver with BL 5A ESC, and the same battery, using my Spektrum DX5, and I could only get 51-52gm of thrust.

What must change to get the advertised 72gm of thrust???
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Old 01-20-2014, 09:19 PM   #2
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While this is a small edf, without knowing these systems well you've jumped into the deep end! First, do you have a watt meter to see how much power the system is actually pulling? Second, that sounds like a very high kv motor which might need special timing settings in the esc to run right.

As for the lower power on your second test. That esc is really close to its limits. There's a possibility is affecting things. You may need to 'teach' the esc the tx's throttle range. Does the esc instructions cover that?

Lastly, intake and exhaust ducting play a big part in edf thrust. Especially an exhaust tube. The exit should be 80-85% of fan swept area. (FSA) That's the area of the edf that air actually passes through, total fan area - motor area = FSA.

Mind you, I'm no expert at this. Most of this is what I picked up reading through forums. I have some 64 mm and a 70 mm edf's, 2 of which I've upgraded. I think it's harder to set up an edf than a prop. But I think the above items are all possibilities. Hope something will help.
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Old 01-20-2014, 09:26 PM   #3
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Originally Posted by jibwalker View Post
I'm new to brushless motors, esc's, lipos ect. I purchased an AEO27mm EDF unit and set it up as follows.

Summary:
Motor: ELE RC ADF27-05 PLUS Brushless Ducted Fan Power System 10,000kV
7.4 V 4.1 A 58 Grams
8.0 V 4.6 A 66 Grams
8.4 V 4.9 A 72 Grams
ESC: Motrolfly 6A ESC
Battery: Cheetah Packs 7.4V 360mAh 35C lipo
Servo tester: E-sky from gobrushless


Now the way I understand the battery discharge amp info, a 360mAh 35c should provide 12.6amps (35*360=12600/1000=12.6), and the 7.4v lipo fully charged is 8.4v, and the esc is well over 4.9A. BUT I can only squeeze 58gm of thrust out of this setup.

I switched to a Spektrum AS6410NBL DSMX 6Ch AS3X Receiver with BL 5A ESC, and the same battery, using my Spektrum DX5, and I could only get 51-52gm of thrust.

What must change to get the advertised 72gm of thrust???
what must change is your Voltage. you may need to use a lifepo4 3 cell battery @ 9.6 volts, LiFePO4 is 3.2V per cell.

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Old 01-20-2014, 09:39 PM   #4
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http://www.batteryspace.com/LiFePO4-...-12A-rate.aspx

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Old 01-20-2014, 09:45 PM   #5
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Originally Posted by xmech2k View Post
While this is a small edf, without knowing these systems well you've jumped into the deep end! First, do you have a watt meter to see how much power the system is actually pulling? Second, that sounds like a very high kv motor which might need special timing settings in the esc to run right.

As for the lower power on your second test. That esc is really close to its limits. There's a possibility is affecting things. You may need to 'teach' the esc the tx's throttle range. Does the esc instructions cover that?

Lastly, intake and exhaust ducting play a big part in edf thrust. Especially an exhaust tube. The exit should be 80-85% of fan swept area. (FSA) That's the area of the edf that air actually passes through, total fan area - motor area = FSA.

Mind you, I'm no expert at this. Most of this is what I picked up reading through forums. I have some 64 mm and a 70 mm edf's, 2 of which I've upgraded. I think it's harder to set up an edf than a prop. But I think the above items are all possibilities. Hope something will help.
Currently, I'm running all tests on the bench. So zero restrictions on FSA. Are you saying that the outlet side needs a little restriction?
And, yes the esc's have instructions on how to program - I have a card to program the motorfly, and the Spektrum gives info on throttle/rx programming. - I just have no idea what settings need to be changed.
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Old 01-20-2014, 09:56 PM   #6
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Thanks Chellie, but at 29mm thick, that battery would be about 24mm larger than the space I'm trying to fit it into.

When you say the voltage needs to change, I suspect you mean that even though my multi-meter reads 8.4v when my 7.4v lipo is fully charged it really only pushes 7.4v under load. Right?

And if that's the case there's no 2s lipo that will provide that power right?

And if so, why does the EDF call for a 2s lipo and give performance data for some other battery?

http://www.bphobbies.com/view.asp?id...7&pid=F2893853
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Old 01-20-2014, 10:10 PM   #7
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Originally Posted by jibwalker View Post
Thanks Chellie, but at 29mm thick, that battery would be about 24mm larger than the space I'm trying to fit it into.

When you say the voltage needs to change, I suspect you mean that even though my multi-meter reads 8.4v when my 7.4v lipo is fully charged it really only pushes 7.4v under load. Right?

And if that's the case there's no 2s lipo that will provide that power right?

And if so, why does the EDF call for a 2s lipo and give performance data for some other battery?

http://www.bphobbies.com/view.asp?id...7&pid=F2893853
Hi a 7.4V 360mAh 35C lipo will not keep the voltage up for any length of time, thats a real dinky battery a 2 cell lipo that is 5000mah will hold the voltage up for a long time, what you are seeing is major voltage drop, and EDF eat up amps and volts real fast, EDF mfg really over rate their products, dont belive any of the Hype advertising, to see the thrust that you want, you will have to use a different battery, you may even need to make up your own lifepo4 battery pack to fit your plane, at 9.6 volts and after the draw and load on the lifepo 3 cell pack, you should see about 8.4 volts, and that will give you your thrust, in this Hobby, you have to Improvise, Adapt and Overcome issues, HURA LOL

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 01-20-2014, 10:31 PM   #8
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Originally Posted by CHELLIE View Post
Hi a 7.4V 360mAh 35C lipo will not keep the voltage up for any length of time, thats a real dinky battery a 2 cell lipo that is 5000mah will hold the voltage up for a long time, what you are seeing is major voltage drop, and EDF eat up amps and volts real fast, EDF mfg really over rate their products, dont belive any of the Hype advertising, to see the thrust that you want, you will have to use a different battery, you may even need to make up your own lifepo4 battery pack to fit your plane, at 9.6 volts and after the draw and load on the lifepo 3 cell pack, you should see about 8.4 volts, and that will give you your thrust, in this Hobby, you have to Improvise, Adapt and Overcome issues, HURA LOL
LOL, The battery I intend to use - if it ever gets here from Hobbyking - is an improvisation. I'll be combining two 1s 400mAh 30c's in series to make a 7.4v 400mAh 30c. Because that's the ONLY thing I could find that would fit in the space and come close to the amps.

A little disclosure: this isn't going in an airplane, it's actually for an "outlaw" pinewood derby car! (hope I don't get booted, lol) So space is at a premium, but run time is under 2 seconds, so I don't need the battery to preform very long or have a long life.
It won't have wings, but I expect it to really FLY!!!

https://www.facebook.com/photo.php?f...type=3&theater

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Old 01-20-2014, 10:40 PM   #9
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Originally Posted by jibwalker View Post
LOL, The battery I intend to use - if it ever gets here from Hobbyking - is an improvisation. I'll be combining two 1s 400mAh 30c's in series to make a 7.4v 400mAh 30c. Because that's the ONLY thing I could find that would fit in the space and come close to the amps.

A little disclosure: this isn't going in an airplane, it's actually for an "outlaw" pinewood derby car! (hope I don't get booted, lol) So space is at a premium, but run time is under 2 seconds, so I don't need the battery to preform very long or have a long life.
It won't have wings, but I expect it to really FLY!!!

https://www.facebook.com/photo.php?f...type=3&theater

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Your Secret is Safe with me I wont tell anyone thats its not going into an AIRCRAFT LOL

BTW, if you can squeeze 1 more battery in there, you will be ok since its only a 2 sec run. Hope that helps, Dont forget to give us a video of the Racer, Chellie

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 01-20-2014, 10:50 PM   #10
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Originally Posted by jibwalker View Post
Currently, I'm running all tests on the bench. So zero restrictions on FSA. Are you saying that the outlet side needs a little restriction?
And, yes the esc's have instructions on how to program - I have a card to program the motorfly, and the Spektrum gives info on throttle/rx programming. - I just have no idea what settings need to be changed.
Holy cow. I just did the math. Is this right? EDF 27mm - motor Dia 14mm = 13mm * .85 = Outlet tube 11.05mm ? That's a LOT of tapering
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Old 01-20-2014, 10:56 PM   #11
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Originally Posted by jibwalker View Post
Holy cow. I just did the math. Is this right? EDF 27mm - motor Dia 14mm = 13mm * .85 = Outlet tube 11.05mm ? That's a LOT of tapering
you may not need to tapper the nossel, thats just for top end speed, i think you will need the duct to be wide open for the 2 second speed run, you will need all the low end torque and air flow you can get.

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Old 01-20-2014, 10:57 PM   #12
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Originally Posted by CHELLIE View Post
Your Secret is Safe with me I wont tell anyone thats its not going into an AIRCRAFT LOL

BTW, if you can squeeze 1 more battery in there, you will be ok since its only a 2 sec run. Hope that helps, Dont forget to give us a video of the Racer, Chellie
Will do Chellie. And thanks
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Old 01-21-2014, 01:32 AM   #13
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Originally Posted by CHELLIE View Post
I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
AMEN!!!!
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Old 01-21-2014, 08:17 AM   #14
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might want to look into CO2 also


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Old 01-21-2014, 11:34 AM   #15
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As already said by another - forget advertised specs - I have never been able to get better than about 70% of what they quote ...

The small EDF's are particularly bad for lack of performance.

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Old 01-21-2014, 12:15 PM   #16
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Originally Posted by jibwalker View Post
Holy cow. I just did the math. Is this right? EDF 27mm - motor Dia 14mm = 13mm * .85 = Outlet tube 11.05mm ? That's a LOT of tapering
No. that's not 'right,

It's area reduction you should be basing the calc on, not diameter.

Outlet diameter = 0.85 x sq root(27^2 - 14^2) = 19.6mm
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Old 01-21-2014, 12:19 PM   #17
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Originally Posted by solentlife View Post
As already said by another - forget advertised specs - I have never been able to get better than about 70% of what they quote ...

The small EDF's are particularly bad for lack of performance.

Nigel
+1, dont believe a word of the quoted figures. Plus as noted previously, 8.4v is an unrealistic voltage, 7.4 is more realistic for a LiPo under load.

58g sounds about right based on testing of 30mm fans i did a while ago. You will loose some of that when you add ducting, so budget for about 45g thrust if built into a duct, if ducting isnt required for aethetic purposes than leave it off.

Fanatical weight control is required if you are going to get something like this to fly, but as this is a car weight control is not quite so critical..

You would of course get MUCH more performance from the same power if you used a prop, or drove the wheels.
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Old 01-22-2014, 09:49 PM   #18
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Originally Posted by CHELLIE View Post
Your Secret is Safe with me I wont tell anyone thats its not going into an AIRCRAFT LOL

BTW, if you can squeeze 1 more battery in there, you will be ok since its only a 2 sec run. Hope that helps, Dont forget to give us a video of the Racer, Chellie
Eureka! Chellie, you nailed it. I dissected a little 7.4v 180mAh I had lying around, and took one cell out. I just managed to find enough space sandwiched under the rx, and with the 2 zippy cells and that one wired in series, the Spektrum all-in-one, That little blue screamer shot right up to 72 grams thrust!!!
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Old 01-22-2014, 09:53 PM   #19
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Originally Posted by jibwalker View Post
Eureka! Chellie, you nailed it. I dissected a little 7.4v 180mAh I had lying around, and took one cell out. I just managed to find enough space sandwiched under the rx, and with the 2 zippy cells and that one wired in series, the Spektrum all-in-one, That little blue screamer shot right up to 72 grams thrust!!!
Thats Great to hear dont run it for more than a couple of seconds or you could burn up the esc, Take care and have fun, Chellie.

We are Waiting for the Video

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Old 01-22-2014, 10:23 PM   #20
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Running a fan that's designed for 2s on a 3s battery is pretty much certain to burn the motor up, if the ESC or battery doesn't fail first.

Even short burst could be enough to fry something.
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Old 01-23-2014, 01:13 AM   #21
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I always like to put on a correct shaped inlet lip also.

Not sure if your fan comes with a inlet lip. It increases the thrust with less voltage. All real jet engines have a flared inlet lip for a reason.

So much to learn.
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Old 01-23-2014, 03:42 AM   #22
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Originally Posted by JetPlaneFlyer View Post
Running a fan that's designed for 2s on a 3s battery is pretty much certain to burn the motor up, if the ESC or battery doesn't fail first.

Even short burst could be enough to fry something.
I think he will be ok, reason being, is that he put in a 180mah lipo cell in series with the 2 - 360mah lipo cells, making a 3 cell lipo, basicly he put in a battery resistor that will help to keep the amps down while letting the volts flow, not something that you should do for rc aircraft, but in this configuration, its quite ok. Take care and have fun, Chellie


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Old 01-23-2014, 10:02 AM   #23
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Thanks for all the advise from everyone here. It's been really helpful. I think I'm getting push I was looking for, and I've found a place for everything to fit. Before I can start installing the electronics though, I've got to get the undercharge built. I'm still not sure how to trigger the start. On my last car - with brushed motor, and capacitors for the 2 sec burst - I used a pressure switch on the front that opened when the starting gate dropped. Anyone know of a wire somewhere on the esc, motor, or battery loop that if this wire were cut (opened); 1. the esc and rx would maintain function and communication, 2. the TX could be throttled up full and the motor does nothing. THEN, when the said wire were reconnected (closed), the motor would go to full throttle.?
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Old 01-23-2014, 06:39 PM   #24
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The issue with putting different capacities in series is a VERY high chance of damaging the lower capacity cell(s)

The higher capacity cells will potentially force enough current through the low capacity one to fry it.

The low capacity cell will deplete long before the higher capacity cells, pushing its voltage low enough to damage the cell.

You can get away with it for very short runs... for a while but you really need to do it right.
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Old 01-23-2014, 07:54 PM   #25
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Originally Posted by jibwalker View Post
Thanks for all the advise from everyone here. It's been really helpful. I think I'm getting push I was looking for, and I've found a place for everything to fit. Before I can start installing the electronics though, I've got to get the undercharge built. I'm still not sure how to trigger the start. On my last car - with brushed motor, and capacitors for the 2 sec burst - I used a pressure switch on the front that opened when the starting gate dropped. Anyone know of a wire somewhere on the esc, motor, or battery loop that if this wire were cut (opened); 1. the esc and rx would maintain function and communication, 2. the TX could be throttled up full and the motor does nothing. THEN, when the said wire were reconnected (closed), the motor would go to full throttle.?
Hi I Belive the Signal wire from the esc to the receiver can be cut and switched on/off

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