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Jul 03, 2012, 08:12 PM
James not bond
jy0933's Avatar
that'd be a fresh new program.. but i feel im totally in
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Jul 03, 2012, 08:24 PM
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Wouhou! Sky is the limit!!!
Jul 04, 2012, 05:54 AM
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rimshotcopter's Avatar
Looks as someone bet us to the idea. Hmmmm.

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

Jul 04, 2012, 09:25 AM
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rimshotcopter's Avatar
Yea, there is nothing new about this stuff.

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

http://www.youtube.com/watch?v=P9i7WKdimPU
Last edited by rimshotcopter; Jul 04, 2012 at 09:34 AM.
Jul 04, 2012, 11:46 AM
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Mortimer's Avatar
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.
Jul 04, 2012, 11:48 AM
James not bond
jy0933's Avatar
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
Jul 04, 2012, 12:05 PM
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rimshotcopter's Avatar
another reason is, many people simply follow what they have been told and never venture beyond that point.
Jul 04, 2012, 12:10 PM
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Mortimer's Avatar
Look at "Disadvantages" here : http://en.wikipedia.org/wiki/Ducted_fan
Maybe some of the reasons Boeing or Lockheed have not used it.
Jul 04, 2012, 12:12 PM
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rimshotcopter's Avatar
There are disadvantages to breathing air and even living... Hmmm.,
Jul 25, 2012, 09:33 PM
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rimshotcopter's Avatar
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.
Last edited by rimshotcopter; Jul 25, 2012 at 09:56 PM.
Jul 25, 2012, 09:40 PM
James not bond
jy0933's Avatar
it is quiet.. the original of this fan is designed to be quiet.. they use pretty good bearings and ac motor
Jul 25, 2012, 09:47 PM
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rimshotcopter's Avatar
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.
Jul 27, 2012, 01:29 AM
Registered User
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.
Last edited by recharged95; Jul 27, 2012 at 01:35 AM.
Jul 27, 2012, 08:00 AM
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rimshotcopter's Avatar
what makes the present DF inefficient is the diameter. So the solution is to increase the diameter and reduce the RPMs they spin at.
Last edited by rimshotcopter; Jul 27, 2012 at 08:07 AM.


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