From Hack-a-day. This ducted-fan beast uses the Sparkfun 6DoF IMU that Jordi wrote the software for. No, it hasn't flown yet.


Behold the Land-Bear-Shark, a quadcopter on a rather grand scale. At a full eight kilograms it’s an easy target to compare the [Howard Hughes] behemoth, but in addition to the weight, this still has yet to make its first flight.

To give you some scale to the image above, the board at the center is an Arduino. It controls the beast, along with the help of a SparkFun IMU board which rides atop. Really, if any quadcopter of this size has a chance of working, this should be the one. The construction is beautiful, making use of carbon fiber rod along with 3D-printed connectors to assemble the frame. A lot of thought has gone into small things like conserving weight used on the landing gear, which are incorporated into the bottom corner brackets. The batteries are connected in a manner that makes them easy to adjust, acting as ballast for balancing the craft.

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Comment by Ita G on July 19, 2011 at 2:33pm
Am I the only one that thinks this can NEVER work? (at least the way this guy's doing it...)
I don't think he's going to get anywhere near the required control bandwidth from a fixed vector, fixed pitch quad.

In my mind, a larger quad will only be viable with either variable-pitch rotors, control surfaces, or full-on vector thrust capabilities...

Comment by Randy on July 19, 2011 at 2:39pm

@Ita, but why does the size of the quad matter when it comes to the speed of response?  If everything is bigger (i.e props, motors, frame) won't it act just like a normal sized quad?

Comment by Ita G on July 19, 2011 at 2:56pm
You'll start having major problems really fast - even if you could ramp up the thrust linearly with rotor weight (and you can't) - the intertia of the rotor will rise with the square of the radius.
Also, it would be very hard (and heavy) to find/create motor drivers with enough oomph to rapidly change the speed of a EDF that size.

These are just some of the reasons it's very hard to make rapid changes to the speed of a larger rotor, and that's why most rc helis and all real helis use variable-pitch rotors.
Comment by brandon sharp on July 19, 2011 at 3:44pm
more info on the builders site
Comment by Roman Krashanitsa on July 19, 2011 at 4:47pm
I am curious if this will be a flying quad. My reasoning : motors are bigger, so the spin-up time is longer and reaction time will be slower. But on the other hand, the frame is bigger, so the inertia is larger (remember I~distance^2), so this quad will not be very agile and we don't need that fast reaction to disturbance.
Comment by Steve on July 19, 2011 at 7:32pm
Has he even made a traditional quadcopter before? Looking around his site I am not convinced he has. Looks like he saw other quadcopters and said "hey I bet I can make the biggest one out there". Kudos to him if it actually flies.
Comment by fibrewire on July 19, 2011 at 11:08pm

That was one of the first designs I thought would work. Boy, was I ever wrong! Seems there is this brillant guy who sank his entire life into making a quad-ducted fan vehicle into a reality. It never worked, but at least he got to see part of his dreams realized. A nice article about the Moller SkyCar can be seen here

Okay, back to the Variable Pitch Quad Rotor...

Comment by Coptaire on July 19, 2011 at 11:12pm

Which model is the ducted fan?

Found used components:

HK 120mm EDF +Turnigy T600 Brushless + Turnigy Sentilon 100A + Nanotech 5Ah 10S


Comment by Lauri on July 19, 2011 at 11:30pm
On control bandwidth - thrust response is one thing. But a larger diameter also means more inherent stability of the platform (moment of inertia).
Comment by fibrewire on July 20, 2011 at 12:10am

How quickly can the control surfaces be changed? Back in the atomic age, people thought they would get rocket packs and fly around. Now that the general population is more mature in aerodynamics, we can see the value of larger control surfaces and little power. Devices like the Gen H-4 are a more likely substitution to realize our predecessors' dreams.

IF someone wanted to SUCCESSFULLY build a ducted fan design, the key is to keep the speed of the ducted fan constant, and use a plenum with a control surface to direct the flow of air.

Similarly, I don't know why someone hasn't figured out to make a variable pitch quad rotor with huge blades that require little power. You could even use solar panel film on hydrogen filled blades themseves to power the aircraft, and use magnetic bearings to eliminate friction at extremely high altitudes. To be continued...


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