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Old Jun 22, 2016, 02:18 PM
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Help with motor selection for 120mm EDF

After looking at the market for quite a while its seeming like building an EDF fan is cheaper than buying a prebuilt unit. This is the fan Im considering using at the moment:

http://www.hobbyking.com/hobbyking/s...e_4_5inch.html

Interpreting the product description is something I am having a hard time with. This fan says its recommended motor is: "36-50 4 Turn"

I dont know if this means 36mm up to 50mm diameter, or a 36mm diameter/50mm length motor. In addition to this many of the EDF motors HK sells arent rated for 100amps, which doesnt make sense to me for the fans they state in their descriptions. The KV rating I understand correctly. Can anyone shed some light on what motor I would need for this fan? Thanks
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Old Jun 22, 2016, 05:19 PM
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If $25 is your budget play with something smaller!!
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Old Jun 22, 2016, 05:35 PM
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Lee Liddle
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RE, I did a whole thread using that fan as the starting point. There were lots of people who said I was wasting my time, but the results speak for themselves.

You can build a fan/esc system for about $225 that will give you up to 15lbs of thrust on12s. All the details are in the thread. Also many people duplicated my efforts with much success.

It's a lot of power, so take proper safety precautions. Happy reading and good luck. You can do it.

http://www.rcgroups.com/forums/showthread.php?t=1324088
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Old Jun 23, 2016, 10:26 AM
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Quote:
Originally Posted by Chris True View Post
If $25 is your budget play with something smaller!!
I dont know where you are pulling this $25 number from, this fan alone costs that much. Im going to have to pair it with an ESC and Motor along with the rest of the Jet. No one is thinking about a $25 EDF build here lol

Quote:
Originally Posted by Knife Liddle View Post
RE, I did a whole thread using that fan as the starting point. There were lots of people who said I was wasting my time, but the results speak for themselves.

You can build a fan/esc system for about $225 that will give you up to 15lbs of thrust on12s. All the details are in the thread. Also many people duplicated my efforts with much success.

It's a lot of power, so take proper safety precautions. Happy reading and good luck. You can do it.

http://www.rcgroups.com/forums/showthread.php?t=1324088
Well I dont need anywhere near 15 lbs of thrust lol. Can you take a look at the specific question I asked in regards to how the motor selection is made from the product description? There are 2 possible interpretations I can see being made, they are outlined in the OP. Can you take a look there and tell me which is correct about choosing a motor?
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Old Jun 23, 2016, 11:49 AM
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Lee Liddle
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Any motor up to 50mm dia will fit. So it looks like they are sayung 36mm-50mm, but the 4turn info is usless. You need to pick a motor based on what voltage you want to run and what power level you need.

You have much to learn about edf power. Either duplicate someone's tested setup, or plan on much trial and error and expense
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Old Jun 23, 2016, 11:53 AM
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No one can help you pick a motor without a bunch of info such as v, a, thrust, durration, flying style, ect that you plan for the fan. There is a ton of info in the thread. Read up.
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Old Jun 23, 2016, 09:45 PM
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Guys. The OP was looking for a 3-4.5kg setup in another thread. I assume that hasn't changed.

Reece. If I recall correctly that fan has been on the market a while, for years. The motor numbers HK put up are junk imho and at present I dont see any motors listed that are suitable for that fan. 49mm max diameter and <1000 kv.
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Old Jun 24, 2016, 12:07 AM
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I run that fan in my Bruce Tharp's Reaction 54 that I redesigned to 82% specifically for this fan. Wing span is 64 inches, area is 970 square inches

Fan: Turnigy 4.5"
Motor: Scorpion HK-4035-630
ESC: Turnigy 100amp
Battery: 12s 5000 25C LiPo

Thrust : 10 lb
Amp draw: 62

Model weighs 14 pounds, timer is set for 8 minutes, has been radared at 140mph.
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Old Jun 24, 2016, 05:12 PM
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Ok 36 to 50mm as possible diameters was what I was leaning towards, that really opens up motor selection. On that note the goal was 3-4.5 KG of thrust mostly aiming for maximum duration in flight for a good distance traveled per MAH used. I was thinking of running 8S and setting up to carry 10,000 mah.

However at this point Im thinking I should do a prop setup to reduce complexity; I'll need to have this wrapped up to the point I can fly for fun by the Fall. The impending School Year is going to prevent me from developing an amazing EDF Jet at this early on.

Loosing the complexity of developing the intakes, thrust tube and battery compartments packaged neatly inside the fuselage will speed up construction by a lot, and should reduce cost as well. Ive seen many documentaries of Military Jets in development where cost overruns sank the project or ran far higher than expected. I'm assuming its not much different in the RC world.
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Old Jun 24, 2016, 05:16 PM
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Quote:
Originally Posted by Bob Reynolds View Post
I run that fan in my Bruce Tharp's Reaction 54 that I redesigned to 82% specifically for this fan. Wing span is 64 inches, area is 970 square inches

Fan: Turnigy 4.5"
Motor: Scorpion HK-4035-630
ESC: Turnigy 100amp
Battery: 12s 5000 25C LiPo

Thrust : 10 lb
Amp draw: 62

Model weighs 14 pounds, timer is set for 8 minutes, has been radared at 140mph.
Thats amazing. Im aiming (or was aiming) for a 3 foot wingspan at maximum. I would really expect that to pull more than 60 amps but it seems the larger fans work really well compared to the smaller ones. How much MAH do you fly with to yield 8 minutes? What is the average speed traveled in that 8 minutes?
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Old Jun 24, 2016, 11:19 PM
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Don't know the answer to either question. full power for take off and any speed runs. Rest of the time is just having fun goofing off. 14 pounds with 970 square inches says it floats fairly well and being a clean model says that energy is not lost very quickly, so not much power is needed.

I will say that the cross wind leg to final turn when the barn door flaps go down you can see the plane almost stop in midair and settle in at a brisk walking speed for a nose high landing.
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