Views: 158

Comment by Dustin Romero on August 25, 2010 at 7:39am
i have been intrigued with the monocopter uav's. why would you go monocopter? is there any advantages?
Comment by Victor Maldonado on August 25, 2010 at 5:20pm
I worked with this guy on this project back at my internship at ATL when it was phase one 3 years ago!! What a surprise to see him here.
Comment by Patrick Hammer on August 26, 2010 at 2:55am
Dustin ... Australian Aborigine's Uni thesis (21st Century hunting utensil) .... haven't got a clue what advantages such a configuration would offer. Its like so much in this business (at this stage) - it's an idea, a proof of concept that could lead onto something else.

What gets me is how do you keep the root end centred i.e. centrifugal force plays a role here doesn't it (does it?) - otherwise at some point it's likely to start behaving like a helicopter rotor thats come off . The larger one that the demonstrator picked up had an extension at the root end with a motor/prop on it - to keep the root end centred on around an axis? .... otherwise I can't see how it would be able to fly efficeintly.
Comment by Mike Bakula on August 26, 2010 at 3:09am
The advantages are mechanical simplicity and robustness; it's also probably the lightest structure for a given rotor span (at small spans). Disadvantages are more complex dynamics, and the restriction to only scanning sensors. Keeping balance is simply a matter of setting the center of gravity, as with any aircraft. (I infer that their smaller vehicle has a relatively heavy hub, to be so short agains the wing.)
Comment by Patrick Hammer on August 26, 2010 at 3:46am
Mike

It obviously flies (else a man wearing a Lockheed shirt would not likely be standing there claiming it does) - but what I can't get my head around is this:

The wing at its end is passing through the air at x velocity - which genrates a certain amount of lift. But for the cente hub section to also generate sufficent lift, it too is going to have to be moving through the air at a similar velocity - which means it cannot be rotating centred on its axis. If it was it would generate nowhere near the same amount of lift as the other end.

The only way that arrangement could fly around the hub axis is if the end of the wing/blade had a chord & profile that compensated for its reduced velocity through the air - so that it generated similar lift to the faster moving motor-end of the wing.

The only way that blade can fly [level] and with any degree of efficiency (as I can see it - what do I know about flying!!) is if the hub does not rotate on its centre i.e. the motor/prop combination endf "throws" the hub centre off its centre axis - causing it to swing round in an eliptical manner so sorts.

..... I really want to see how that flys staright and or level with any degree of control

Patrick
Comment by Victor Maldonado on August 26, 2010 at 7:20am
The aircraft does not actually fly level, it traces out a slight "V" shape as it flies because as you guys pointed out, the blade creates more lift at the tip due to the increased tangential velocity and you have a hub which creates essentially no lift. However, because of the gyroscopic stability as it spins, it's able to stay in the air, though directional control is difficult because you have to supply aileron input at the same frequency of rotation. It was definitely not a very stable or controllable platform back then, hopefully they'be been able to work out the issues.
Comment by Jack Crossfire on August 26, 2010 at 1:18pm
The main problem, & the guy at Horizon Hobby agreed, is dynamic instability at low RPM. Looks like they tried increasing the moment of inertia by having the motor on the end.
Comment by Darren on August 27, 2010 at 9:00pm
I love the use of flat copper foil in lieu of wires out to the motor.
Comment by bGatti on August 27, 2010 at 9:06pm
Darren,
You should pay your local dollhouse store a visit? They sell it by the reel
Comment by bGatti on August 27, 2010 at 9:09pm
Anyone know what they use as a servo - just guessing the speed of deflection is a bit fast for ordinary servos? have they moved to a floating coil?

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