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Old Jul 03, 2012, 08:12 PM
James not bond
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that'd be a fresh new program.. but i feel im totally in
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Old Jul 03, 2012, 08:24 PM
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Wouhou! Sky is the limit!!!
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Old Jul 04, 2012, 05:54 AM
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Looks as someone bet us to the idea. Hmmmm.

Dualcopter (4 min 55 sec)
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Old Jul 04, 2012, 09:16 AM
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With a pilot on board you get the 1955 Hiller Pawnee.

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Old Jul 04, 2012, 09:25 AM
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Yea, there is nothing new about this stuff.

http://www.youtube.com/watch?v=JAQIgdMLeHs

http://www.youtube.com/watch?v=P9i7WKdimPU
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Old Jul 04, 2012, 11:46 AM
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The question is : Why don't we see today any real helicopter or airplane with ducted fans ?
There is a reason.

On the other hand, RC aircrafts can suffer a lack of efficiency, it's not really a problem.
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Old Jul 04, 2012, 11:48 AM
James not bond
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Quote:
Originally Posted by Mortimer View Post
The question is : Why don't we see today any real helicopter or airplane with ducted fans ?
There is a reason.

On the other hand, RC aircrafts can suffer a lack of efficiency, it's not really a problem.
you need space for loading crew.... for this type of aircraft.. you want the mass to be as center as possible to reduce the mass moment of inertia
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Old Jul 04, 2012, 12:05 PM
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another reason is, many people simply follow what they have been told and never venture beyond that point.
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Old Jul 04, 2012, 12:10 PM
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Look at "Disadvantages" here : http://en.wikipedia.org/wiki/Ducted_fan
Maybe some of the reasons Boeing or Lockheed have not used it.
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Old Jul 04, 2012, 12:12 PM
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There are disadvantages to breathing air and even living... Hmmm.,
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Old Jul 25, 2012, 09:33 PM
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Here is an experiment made from an old computer power supply cooling fan. I had some 4mm motor shafts made when I was experimenting with direct drive variable pitch tail rotors for my Swepback copter that worked perfectly for this application after adding some threads to the end of the shaft. I did a preliminary test to make sure the motor was spinning in the right direction and just had to hit the throttle once to see what it will do. At present, it is very closely balanced but I want to do some very precision adjustments and do some stress testing to make sure this system does not self-destruct under continuous load and stress.

Oh, Did I mention, it was quiet? Now if this thing will produce enough thrust, I will be in heaven.
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Old Jul 25, 2012, 09:40 PM
James not bond
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it is quiet.. the original of this fan is designed to be quiet.. they use pretty good bearings and ac motor
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Old Jul 25, 2012, 09:47 PM
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Yea but I stripped out the original motor and bearings and replaced it with a 3700KV motor. So the bearings used are the ones in the motor.
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Old Jul 27, 2012, 01:29 AM
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Something like this:
Scarab Quad with Ducted Fans (2 min 23 sec)


or a military version (which is loud):
http://www.honeywell.com/sites/servl...E-A667BE2E41A8

Also, having built a tri-ducted fan out of 3 65mm DFs myself to less success:

Main reason DF's are not used is
a. they are loud, very loud 19dB or more. Ok for an R/C Park, but any place else...? not really.
b. Uses more power (since you're using smaller dia, and higher rpms).
c. Less efficient on descent: no autorotation effect
d. hovering issues: higher rpms, harder to control (thrust vectoring), more demanding on ESCs
e. horizontal motion issues, not like a fixed-pitched copter... need to tilt more to go forward, but it's harder to keep alt. Those flying saucers designs do bring a lot of sail-effect to the table, though the above open design is a good balance. Heck there's a reason they call it the ARDrone [i]indoor hull[/].

There are many advantages (safety, simplicity, more responsive, less yaw issues, etc..) but it's easier to construct a heli-based quad at this time, it's a more mature design, reliable and has a longer running time (for now). And quieter for the AP crowd, though my mind still likes the design of a DF-based quad as it does hasve some compelling advantages.
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Old Jul 27, 2012, 08:00 AM
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what makes the present DF inefficient is the diameter. So the solution is to increase the diameter and reduce the RPMs they spin at.
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