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Old Jul 09, 2014, 09:16 AM
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New coaxial concept

Can anyone try it out on a Coaxial with duct fans?

http://www.gizmag.com/radical-helico...-270mph/32840/
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Old Jul 09, 2014, 12:14 PM
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It's a cool concept, but would be very expensive to try, as everything would be scratch built.
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Old Jul 11, 2014, 07:03 PM
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I wonder if the add on aileron fans that also provide lift on the hp x-2 could be turned to add forward thrust..

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Old Jul 11, 2014, 11:45 PM
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Sure, but that doesn't really test this concept. Plus, if you really need 5 motors to provide adequate performance, you may want to rethink your design.
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Old Jul 14, 2014, 01:52 PM
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if you are trying to build a working scale RC of the AVX concept heli is one thing but using something like an hp x-2 with modified aileron fans to provide forward thrust on a working RC, possibly leaving off the tail rotor, could help guide the way to a working RC AVX like heli..

the AVX would still need at least 4 motors..

the RC sikorsky x2's have the physics worked out to use a pusher tail fan.. so an RC pusher dual ducked fan could work if, like you said, you have the resources to develop it..

there are video's on youtube of RC heli's with side mounted rocket motors..
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Old Jul 14, 2014, 02:26 PM
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The side pods on an X2 are not ducted fans and do not behave like ducted fans. The head design of the AVX uses one motor and special collective pitch rotors, with closely spaced rigid blades that have special advancing and trailing linkage. The widely spaced, slow rotating convex blades used on a conventional coax would shear off in 5 seconds. Another thing to consider is this configuration creates massive torque and is highly resistant to changes in the plane of rotation. It requires some very good flight controller programming to make this work. I've spent a few years playing with coax designs and it's much more complicated than it appears. As soon as you add collective pitch and remove that flybar, you introduce a host of handling and stability problems.
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Old Jul 14, 2014, 02:51 PM
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that is all very true.... an exact RC reproduction of the AVX design wise would be very difficult.. none of the RC sikorsky x2's were even close to the original mechanically.. allowances would have to be made in many design area's to get a simplified RC version to fly..

but... the side rocket assisted heli's on youtube flew at what looked like incredible speed, I'm not sure if I would call it controlled flight though..

I think some light weight low powered ducted fans could work with a lot of r&d..



hmm.. some of the old walkera coax used the single motor design with an fp upper rotor and a cp lower rotor..
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Old Jul 14, 2014, 04:13 PM
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Quote:
Originally Posted by mihcmac View Post
hmm.. some of the old walkera coax used the single motor design with an fp upper rotor and a cp lower rotor..
Yep, the Lama 3; I had one. It had very unusual handling characteristics. Overall, it was as difficult to fly as some of the CP helis I've had, just in a different way.

Maybe I'm a purist, but if I was going to invest the time and effort, I would put it in an RC version of the AVX head design and flight control software, not in something that sort of looks like and sort of flys like the AVX. There's just something about proving a new concept that I like.
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Old Jul 16, 2014, 08:34 PM View Post
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