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Mar 23, 2018, 12:18 PM
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Lynxman's Avatar
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3D printed 120mm EDF - 3D printed 1:6,5 scale L-39


I'm trying to make a high thrust to watt 3D printed 120 mm EDF, and might design a printable plane around it. Possibly a big UL-39 Albi. I have an old Neumotor 1907/2Y motor, which is good for 900 W continous, and 1800 W peak, which I designed the fan around, using 8S batteries.

I'm testing different blade designs to try to achieve a high thrust to watt ratio. I get 2000 g thrust at 850 W and 3700 g thrust at 1750 W with the latest 12 blade fan I printed. 1750 is a little too much for the little motor, so that's probably why the efficiency is lower at that level. 2000 g at 850 W is pretty good though. The fan was printed with 0,2 mm layers and hasn't been sanded or smoothed in any other way. I'd like to test the fan to destruction, but I don't have a motor or ESC powerful enough to do it.

It sounds good too. At first I had the stators very close to the fan blades, and that gave slightly more thrust, but screamed quite a lot too. When I moved the stator 15 mm away from the fan it turned into a woosh fan.
Last edited by Lynxman; Apr 23, 2018 at 05:37 AM.
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Mar 23, 2018, 02:07 PM
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You might try to make rotor blades that look like this - note the shape of the leading edges. More efficient...
Mar 23, 2018, 02:27 PM
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What's the pitch distribution along the blade? Is it constant?
Mar 23, 2018, 08:55 PM
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Quote:
Originally Posted by Lynxman
I'm trying to make a high thrust to watt 3D printed 120 mm EDF, and might design a printable plane around it. Possibly a big UL-39 Albi. I have an old Neumotor 1907/2Y motor, which is good for 900 W continous, and 1800 W peak, which I designed the fan around, using 8S batteries.

I'm testing different blade designs to try to achieve a high thrust to watt ratio. I get 2000 g thrust at 850 W and 3700 g thrust at 1750 W with the latest 12 blade fan I printed. 1750 is a little too much for the little motor, so that's probably why the efficiency is lower at that level. 2000 g at 850 W is pretty good though. The fan was printed with 0,2 mm layers and hasn't been sanded or smoothed in any other way. I'd like to test the fan to destruction, but I don't have a motor or ESC powerful enough to do it.

It sounds good too. At first I had the stators very close to the fan blades, and that gave slightly more thrust, but screamed quite a lot too. When I moved the stator 15 mm away from the fan it turned into a woosh fan.
Are you using an intake lip?

If you can get close to 1 lbs of thrust to 250 watts that would be breaking some ground in my experience so 5000 watts would be 20 lbs of thrust

If you can engineer a contra-rotating rotors (not counter rotating) my understanding the efficiency could go up to max of 16%

really neat project

Do you mind sharing the .stl files?

Regards
Last edited by erh7771; Mar 23, 2018 at 09:12 PM.
Mar 24, 2018, 06:15 AM
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I get 930 g at 250 W. That's more than two lbs. It's a small motor wo it's most efficient at low power. I use a bell intake when I test. The thrust is a lot lower without the bell intake.

I attached a photo of my test stand. A 5 kg kitchen weight with a 3D-printed stand.

I changed to an 11 blade fan now which I printed before. Rough figures:
910 g at 250 W
1500 g at 500 W
2000 g at 750 W
2500 g at 1000 W
3600 g at 1700 W full throttle.
Last edited by Lynxman; Mar 24, 2018 at 06:34 AM.
Mar 24, 2018, 06:58 AM
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Here are the files I made so far:
https://www.thingiverse.com/thing:2838324
Mar 24, 2018, 07:53 AM
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I ordered one of these now to test higher power: https://hobbyking.com/en_us/turnigy-...eli-880kv.html
Mar 24, 2018, 10:16 PM
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Quote:
Originally Posted by lynxman
here are the files i made so far:
https://www.thingiverse.com/thing:2838324
thx !!!!
Mar 24, 2018, 10:20 PM
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Quote:
Originally Posted by Lynxman
I ordered one of these now to test higher power: https://hobbyking.com/en_us/turnigy-...eli-880kv.html
Good choice of motor, I think someone took it past 6000 watts and it doesn't burn up but with brushless motors its a crap shoot, so many variables in their design.
Last edited by erh7771; Mar 24, 2018 at 10:33 PM.
Mar 24, 2018, 10:32 PM
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erh7771's Avatar
Quote:
Originally Posted by Lynxman
I get 930 g at 250 W. That's more than two lbs. It's a small motor wo it's most efficient at low power. I use a bell intake when I test. The thrust is a lot lower without the bell intake.

I attached a photo of my test stand. A 5 kg kitchen weight with a 3D-printed stand.

I changed to an 11 blade fan now which I printed before. Rough figures:
910 g at 250 W
1500 g at 500 W
2000 g at 750 W
2500 g at 1000 W
3600 g at 1700 W full throttle.
You have a pretty efficient fan design so far, I'm sure the 1907 can absorb more than 1700 watts too

Looks like you're using a 675 kv motor

Do you have a 12s esc?

Thx in advance
Last edited by erh7771; Mar 24, 2018 at 11:00 PM.
Mar 25, 2018, 04:06 AM
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I currently only have an 8s ESC. I ordered a 12S ESC with the new motor. Yes, 675. The 880 kv motor should give a good power boost at 8S. I'd like to have a cool running motor and good static thrust at 8S if I'm going to design a 3D printable plane around it. I use 8S 4200 mAh batteries for most of my big planes, and would like an EDF that has great low speed performance.
Mar 25, 2018, 09:10 AM
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BTW, the 1907 motor is very short, and only weighs 232 g. It's an amazing motor for the size, but it gets hot at 1700 W. I'm really looking forward to seeing what the thrust figure will look like with a motor that runs those power levels more efficiently. The thrust at low power, 250 and 500 W, is very promising if it scales well.
Mar 25, 2018, 09:53 AM
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Here's a screenshot from 3D Studio Max 2018. The colored spirals are the pitch guide lines I use for the different positions along the blade. I am trying different blade shapes and pitch distributions.
Mar 26, 2018, 04:20 AM
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I'm going to make an 11 blade version of the one that gives the most thrust per watt so far. The difference between the different fan shapes is pretty small. The pitch is 360 mm, which gives a pitch speed of 350 km/h at 16200 rpm, which is 80% of the calculated unloaded KV speed at 30 V. I think I could make the fan lower pitch than this for more thrust per W, but it's hard to print it successfully because the blade angle becomes to shallow and becomes unprintable overhang unless I use support structure.
Mar 26, 2018, 12:07 PM
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I turned up the cooling a little and will try to print a 13 blade fan with 300 mm pitch. Hope it goes well.


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