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Old 03-12-2013, 09:33 PM   #1
Shogun71
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Default Hmm why no dual rotor helis?

I am wondering truly how difficult a dual rotor setu would be with 2 swashplates, ie a chinook style.

I think it would make for some fun flying and interesting acrobatics.

You could also have competitions for lift and carry over a course....

Just saying, could be fun.
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Old 03-12-2013, 09:41 PM   #2
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Here you go

http://www.helifreak.com/showthread.php?t=34748
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Old 03-12-2013, 09:49 PM   #3
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Yeah, nothing since 2010.

I just saw the hirobo one but at 3k without electronics..... As soon as I win the lottery!
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Old 03-12-2013, 10:13 PM   #4
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Default Duelly

This concept made me smile...



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Old 03-12-2013, 11:16 PM   #5
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How about this one.

http://www.rotormast.com/rm/index.ph...=63&Itemid=196
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Old 03-13-2013, 12:53 AM   #6
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Quote:
Originally Posted by Shogun71 View Post
I am wondering truly how difficult a dual rotor setu would be with 2 swashplates, ie a chinook style.

I think it would make for some fun flying and interesting acrobatics.

You could also have competitions for lift and carry over a course....

Just saying, could be fun.
What I want is something like this:


Or like this:


That second one has the highest lift to weight ratio of any helicopter and uses servo controlled flaps on the rotor blades to control collective and cyclic. As I understand it there is no swashplate or pitch control links. I have no idea how they get cyclic and collective control up to the flaps on the blades though, I've never been able to find any details on that.
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Old 03-13-2013, 02:58 AM   #7
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I dunno, I'm totally unqualified so pinch of salt, I think getting a solid tail would be hard.
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Old 03-13-2013, 04:24 AM   #8
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I dunno, I'm totally unqualified so pinch of salt, I think getting a solid tail would be hard.
Not sure howfull scale tandems do it but full scale coaxials and eggbeaters use differential collective for yaw control. Collective is increased on one rotor disk and decreased on the other and the helicopter turns in the opposite direction of the rotor disk that has more collective. No anti torque is needed because both rotors cancel each other out.

Pretty much every existing full scale coaxial and eggbeater helicopter is a successful design so I don't know why this isn't used more. Possibly because they don't fly like single rotor helicopters so special pilot training is needed.

The Kamen HH-43 Huskie (which also used the servo flaps system that the K-Max uses) was used by the USMC from the early 50's till the 70's and was used by civilian operators long after that.

You can see the flaps on the rotors in the image below. Also note the "WARNING APPROACH FROM FRONT" sign.



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Old 03-13-2013, 09:02 AM   #9
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You could build a kickass Avatar helicopter with the mechanics of that New Concept thing.
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Old 03-13-2013, 10:21 AM   #10
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It would appear that the controller would need to control 6 servos and a throttle and the servo controls would be different especially for piro types of motions but not outside of programming possibilities....

Probably just not enough demand, hence the hirobo cost....
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Old 03-13-2013, 10:27 AM   #11
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Actually, the new multi-rotors by guys like CY that are variable pitch, are in essence similar to what you're talking about.
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Old 03-13-2013, 01:59 PM   #12
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I spent three years working in coaxial CP dual swash design. They can truly out fly our cp single rotor helis and become a total handful to explore. Problem is. No one mass produces them. Also, the costs of a complex dual swash cp coaxial head are staggering. The last one I custom built has over 1k in the head alone. Imagine piling that up? Which is why most guys that do build these don't fly them this way. They are actually more efficient than the current single cp head with tail rotor designs we are currently using. They achieve faster forward flight speeds, have far more rotor lift. And the ability to turn over on themselves in 3d patterns to the point the body is nothing but a blur. They also suffer very little from ground effect.

The current accepted dual swash head is ran by 3 servos. (4 in the helibaby design) The ratio between the upper and lower swash angularity can be adjusted at the grips. Which dictates how aggressive the heli will respond to cyclic commands. The 6 servo system has been discussed but as of yet there are no electronics that are sophisticated enough to run the heads, although the mechanical layout has been penned out. So as of now both swashes lean in the same direction but are phased differently. The only controllers capable of working have been a few one offs and ones from Skookum robotics. Due to their infinite programming parameters.

There are some modelers I know currently working on the Russian Heli scale body that Atomic Skull posted a link to. Even those cost well over $1500 for a basic fg shell.
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Old 03-13-2013, 05:22 PM   #13
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the kits say out of stock but the electronics for it are available....

http://www.tech-mp.com/kits.php
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Old 03-13-2013, 06:04 PM   #14
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Quote:
Originally Posted by Luvmyhelis View Post
I spent three years working in coaxial CP dual swash design. They can truly out fly our cp single rotor helis and become a total handful to explore. Problem is. No one mass produces them. Also, the costs of a complex dual swash cp coaxial head are staggering. The last one I custom built has over 1k in the head alone. Imagine piling that up? Which is why most guys that do build these don't fly them this way. They are actually more efficient than the current single cp head with tail rotor designs we are currently using. They achieve faster forward flight speeds, have far more rotor lift. And the ability to turn over on themselves in 3d patterns to the point the body is nothing but a blur. They also suffer very little from ground effect.

The current accepted dual swash head is ran by 3 servos. (4 in the helibaby design) The ratio between the upper and lower swash angularity can be adjusted at the grips. Which dictates how aggressive the heli will respond to cyclic commands. The 6 servo system has been discussed but as of yet there are no electronics that are sophisticated enough to run the heads, although the mechanical layout has been penned out. So as of now both swashes lean in the same direction but are phased differently. The only controllers capable of working have been a few one offs and ones from Skookum robotics. Due to their infinite programming parameters.

There are some modelers I know currently working on the Russian Heli scale body that Atomic Skull posted a link to. Even those cost well over $1500 for a basic fg shell.
The Kamen "eggbeater" design has the same advantages as coaxial but with lower mechanical complexity. In a model it would just be two single rotor CP mechanics with an umbrella pinion driving the two main gears. If you used 6 cyclic servos then the only custom parts would be the frame and the motor pinion. If you wanted to mechanically link the two swashplates so that you could use fewer servos then you'd need a few more custom mechanical parts.

Really wish I could find details on how the Kamen servo flap system works, I've always wondered if that could be applied to model helis.
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Old 03-13-2013, 08:56 PM   #15
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Here ya go



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Old 03-13-2013, 09:26 PM   #16
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Walkera actually had a dual swash coaxial they were testing but it never made it into production.





I bet you could simplify all that by cutting it down to 2 blades per disk and using DFC style links. (or semi flexible links like the Compass head uses)
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Old 03-13-2013, 11:10 PM   #17
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Skull

The Kamen designs still leverage a swash- they just require far less force for their control mechanism, so the swash is much smaller. There are prototype systems leveraging piezo electric control as well. You can find details in patent filings- this technology is borrowed from the Italians way back…

As regards dual rotors- they have their place, but they have major downsides. People look at the TR as a major waste of power, not realizing that a coax loses the same in interference effects, a tandem in wash impact on the rear rotor, more drag in forward flight for all types, etc. Also consider that many failures on a conventional machine are survivable. Conversely, if you lose a mesh gear, or lose sync with an intermeshed system, or have a coax blade impact, you are doomed.
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Old 03-13-2013, 11:59 PM   #18
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Skull

The Kamen designs still leverage a swash- they just require far less force for their control mechanism, so the swash is much smaller. There are prototype systems leveraging piezo electric control as well. You can find details in patent filings- this technology is borrowed from the Italians way back…

As regards dual rotors- they have their place, but they have major downsides. People look at the TR as a major waste of power, not realizing that a coax loses the same in interference effects, a tandem in wash impact on the rear rotor, more drag in forward flight for all types, etc. Also consider that many failures on a conventional machine are survivable. Conversely, if you lose a mesh gear, or lose sync with an intermeshed system, or have a coax blade impact, you are doomed.
Well it's a fact that the CH-47's have to slow down in order for the AH-64's to keep up with them.

I'd say the KA-50 and KA-52 are probably more survivable than a single rotor helicopter, they have ejection seats.
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Old 03-14-2013, 12:10 AM   #19
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Quote:
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The Kamen HH-43 Huskie (which also used the servo flaps system that the K-Max uses) was used by the USMC from the early 50's till the 70's and was used by civilian operators long after that.
Don't forget the servo flap equipped Kaman SH-2 Sea Sprite used by the U.S. Navy well into the '80s and beyond. The last active SH-2G Super Sea Sprite was retired in 2001.
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Old 03-14-2013, 12:55 AM   #20
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Here ya go



This is gorgeous!! Any more pics of this mechanical pin up?
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