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Old Oct 28, 2008, 07:06 AM
Coaxially Fixated
copperclad's Avatar
Rochester N.Y.
Joined Oct 2005
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art-tech K22 transverse array dual rotor

hi
i just saw this advertised in FLY RC , it's not up on their website yet , but i thought i would post a photo from the ad

it looks pretty cool and looks to be very similar to the Gress machine that was posted here a few years ago
http://www.gressaero.com/index.html

i will post back here when i see it up on their site , cheers , dana
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Old Nov 08, 2008, 12:21 PM
Coaxially Fixated
copperclad's Avatar
Rochester N.Y.
Joined Oct 2005
1,899 Posts
hi
i've been thinking this would make for an interesting project and have spent some time thinking about how to go about it , and putzing around in the shop on some parts that would be needed , here are a few photos of my progress so far , this is the setup for the motor pods , i am using some old BCX parts i have laying around for the motors , shafting , gears heads and blades , i have a pair of 8mm knitting needles from wal-mart i will use for the motor booms and the main body will just be lite-ply for the first trial , the mounts in the photos were made from PVC i got from home depot , cheers dana
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Old Nov 09, 2008, 08:13 AM
One Thirty Second
oldtamiyaphile's Avatar
Western Australia
Joined Feb 2004
133 Posts
Great project! I would love to build one of those pre-war helis, possibly using a 5#6.

How does yaw work, do the swashs have to be tilted fore and aft? I imagine there's no need for a gyro at all?
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Old Nov 09, 2008, 09:33 AM
Coaxially Fixated
copperclad's Avatar
Rochester N.Y.
Joined Oct 2005
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hi oldtamiyaphile
i jumped in after seeing the photo art-tek posted in their ad , i have seen setups like this done with standard props , but if you look at the art-tek ad you can see they are using stabilized rotors like the top rotors on a coaxial , there are no swash plates and the only control , besides motor speed , is that , each motor pod is connected to the main body of the machine with a boom and each boom is controlled with a servo , so the parts list would be roughly

2 @ rotors
2 @ motors
2 @ servos
2 @ ESC's

so control is effected with motor speed and two servos , one on each boom

i believe you want a gyro between the two ESC's to ballance the thrust from both props

and i have a pair of GWS "V" tail mixers to play with , i am not sure if i just need one or both , at first i was thinking you would use two "V" tail mixers ,

one would be between the two ESC's , this would let the throttle stick speed both up or down together , and it would let the aileron stick , speed one up and the other down to effect roll

the other mixer would be between the two servos , so the elevator stick would tip both booms forward or backward together , and the rudder stick would cause them to tip opposite eachother , to effect yaw

and from all i have read , it is the yaw that is easiest to perform , the servos will twist one boom forward slightly and the other back , both actions cancel eachother out except for causeing a pirouette

where i expect it to get strange is in trying for forward flight , if you twist both booms forward slightly , a couple of things happen that are backwards of what you want , the center of lift shifts foreward and the center of gravity shifts back , if you think about it , shifting the center of lift forward is the same as shifting the center of gravity back , it is easy to see that pitching both props forward could cause the machine to move back , just opposite of what you might expect

one thing i can do to help is mount the booms to the pods , so that they are inline with the motors C/G , this will help to cancel out the C/G shifting back some , but the center of lift will still shift

you can also set it up where the center of lift could be made to stay the same but the C/G would then shift , so it is one or the other

i think it would be interesting to see it hover and yaw , and if i could get these two stable , then it would be interesting to see about forward flight , i will post back to this thread as i get it closer to completion

i have the booms mounted now and just have to build the fuse , cheers , dana
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Last edited by copperclad; Nov 09, 2008 at 10:34 AM.
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Old Nov 09, 2008, 07:26 PM
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Nice find and good luck with your build. Should be fun.
Getting closer to the Osprey type aircraft that I'm after.
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Old Nov 09, 2008, 08:13 PM
Coaxially Fixated
copperclad's Avatar
Rochester N.Y.
Joined Oct 2005
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hi RCvertt
i saw this link posted today , and it seems to be a very similar platform , using two stabilized rotors , no swash , and i am guessing a couple of servos , they have a video of it flying

http://www.rcgroups.com/forums/showthread.php?t=950054

i have been thinking , it would also be possible to use just a single servo and have it fly like a standard tandem heli , i believe the Revel tandems are this way , dana
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Old Nov 09, 2008, 08:33 PM
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USA, NC, Mooresville
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When is this supposed to come out, I can't find any info about it.
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Old Nov 10, 2008, 01:30 AM
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Hi copperclad. Just purchased one of those so I can find out what makes it tick. It only has two controlls Up, down, Left and Right using no servos so your craft should be more fun with the addition of Forward and Reverse functionality.

Have the Revel Firestrike. They use 4 motors and no servos for full 3 function control. It's similar to those nonswashplate three channel coax helis with the horizontal mounted prop in the back for forward flight. They just stick another coax helicopter in the back instead of the horizontal prop.
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Old Nov 10, 2008, 04:48 AM
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Denmark, Capital Region of Denmark, CPH
Joined Mar 2006
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Looking good, how about the mirrored flybar mechanics of the CW rotor?
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Last edited by SebastianJ; Nov 10, 2008 at 04:53 AM.
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Old Nov 10, 2008, 07:00 AM
Coaxially Fixated
copperclad's Avatar
Rochester N.Y.
Joined Oct 2005
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hi RCvertt
thanks for the info on the firestrike , i see now how a twin coaxial could have up-down , forward-backward , and yaw , with just the motors and no servos

i was confused about the firestrike , i thought i had seen a photo of a swashless twin coaxial that "looked" like one of the axles came up through a slotted hole to allow for servo tipping , i can see now that yaw could be achived without having to tip one rotor

the surfer looks like it is just two single rotors ( not twin coaxial ) and again i had assumed it used servos

cheers dana

hi heli-parkflyer
they have an ad in one of the RC mags , as though it is available , but when i get on thier site it is not listed , i don't have any info as to a release date or price


Quote:
Looking good, how about the mirrored flybar mechanics of the CW rotor?
hi bas10an

i am running the axles from two BCX's , and using just the top heads , with the upper blades on one and the lower blades on the other , and with the BCX you can pop the stabilized bar pivot off and rotate it 90 degrees and pop it back on , so both stabilizers will be synced correctly

.
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Old Nov 10, 2008, 04:47 PM
Hang on, turbulence ahead
Heli Hacker's Avatar
St. Louis
Joined Dec 2007
534 Posts
Quote:
Originally Posted by copperclad
..... and with the BCX you can pop the stabilized bar pivot off and rotate it 90 degrees and pop it back on , so both stabilizers will be synced correctly

.
Copperclad; In your arrangement, is the flybar pivot/upper head mounted on a length of inner BCX shaft, and the inner shaft somehow locked into the outer shaft? Or did you find a way to eliminate the inner shaft entirely?

Also, this ability of the flybar pivot to be removed and rotated is news to me. I have only seen the aluminum CX2 head, which will not do this. Do you think this is maybe a feature only of the older CX plastic heads?
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Old Nov 10, 2008, 05:21 PM
Coaxially Fixated
copperclad's Avatar
Rochester N.Y.
Joined Oct 2005
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hi Heli Hacker

i posted a group of four photos above and in the forth one you can just see the shortened inner and outer shafts ( at the top of the photo next to the motor and maingear ) , so there is a shortened outer shaft that is just a support ( holds the bearings ) for the inner shaft that has the maingear on one end and the upper head on the other

and yes , when the BCX first came out the stabilizer pivot piece could be popped on and off the upper head , it caused a lot of confusion as people were popping them on wrong and having trouble , so e-flite started glueing them on , dana
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Old Nov 11, 2008, 06:25 PM
Coaxially Fixated
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Rochester N.Y.
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hi
just wanted to post some photos from today , not pretty , but getting closer for a trial run , dana
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Old Nov 17, 2008, 01:15 PM
Coaxially Fixated
copperclad's Avatar
Rochester N.Y.
Joined Oct 2005
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hi
i got to hover it today , not worked out yet , but enough to see it hover both steady and in a slow pirouette , interesting to see it fly

i ended up using four programmable mixers in my TX instead of the GWS "V" tail mixers

i want to add a gyro for the yaw and get some time on it before i redo the fuse to something more aircraft like , pretty fun project so far , cheers dana
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Old Nov 18, 2008, 09:23 AM
Scammers need to go!
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Slidell, La
Joined Oct 2006
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Quote:
Originally Posted by copperclad
hi
i got to hover it today , not worked out yet , but enough to see it hover both steady and in a slow pirouette , interesting to see it fly

i ended up using four programmable mixers in my TX instead of the GWS "V" tail mixers

i want to add a gyro for the yaw and get some time on it before i redo the fuse to something more aircraft like , pretty fun project so far , cheers dana
Great job, now lets see a small vid because i'm hooked and already planning mine
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