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Old 03-22-2009, 07:54 PM   #1 (permalink)
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Default What are flybars for?

Hi, I have a t-rex 450 se v2 and 600 ESP and keep reading about people converting them to a flybarless heads with great results and I'm curios why the manufactures dont just do away with flybars than? What pros and cons are their for flybarless and flybar heads. I've also read about flybarless electronic stabilization systems do you need them and what do they do.
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Old 03-22-2009, 07:59 PM   #2 (permalink)
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Quote:
Originally Posted by david.lunn View Post
Hi, I have a t-rex 450 se v2 and 600 ESP and keep reading about people converting them to a flybarless heads with great results and I'm curios why the manufactures dont just do away with flybars than? What pros and cons are their for flybarless and flybar heads. I've also read about flybarless electronic stabilization systems do you need them and what do they do.
Without the flybar, the rotor head is inherently unstable. The flybarless systems have gyros on all 3 axes to do the stabilization. It's just one more thing to go wrong: if one of the gyros on a flybarless system fails in flight, you're pretty much screwed. Also, flybarless systems drive up the cost considerably at this point.

The biggest advantage to flybarless is reduction of drag from the elimination of the flybar and paddles, providing more power.
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Old 03-22-2009, 08:03 PM   #3 (permalink)
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Flybars add stabilization to your helicopter.

Without a flybar, an RC helicopter will become very unstable. They must be included in order for the helicopter to be stable.

Flybarless helicopters use electronic stabilization systems to simulate the effects of a flybar.

The benefit of flybarless is a lighter helicopter supposedly with more power due to less drag/weight. Less parts to fix in a crash, and the programmability. The con would be that it is a lot to learn. Set up takes some tweaking to get it how you want it.

The benefit of flybar is it's simplicity. Bolt it on and you're good to go. Also it won't cost you several hundred dollars for a stabi system. The cons would be that it has limitations to programming and how your helicopter will respond to your input, whereas electronic flybarless stabilization systems such as the V-Bar are completely programmable. Also, when you crash you generally have to repair/replace the flybar and paddles.
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Old 03-22-2009, 08:19 PM   #4 (permalink)
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How are full scale helicopters stable without flybars?
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Old 03-22-2009, 08:29 PM   #5 (permalink)
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Originally Posted by X-Gear View Post
How are full scale helicopters stable without flybars?
Mass.

Comparitively speaking our RC helis have little of it. The flybar adds gyroscopic mass.

Having flown electronic flybarless for the first time today, all I can say is wow. Hover stability yet awesome cyclic. They are nice. Flybars work just fine too though. My 600E will have the flybar for a good while longer.

Some full sized helis do have flybars with weights on the end, mostly older ones like the UH-1B. You may not recognize them because they do not have paddles.

Also there are a lot of full scale helis with electronic stabilization systems.

In addition, the Skookum learning curve is pretty short. The default setting will usually get you going well. Once you get the trims set and the directions right you are good to go.
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Old 03-22-2009, 08:30 PM   #6 (permalink)
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Full scale helis have a lot more mass in the blades and therefore more gyroscopic effect, and therefore more stabilization. Same applies for RC models. You CAN just remove the flybar without an electronic stabilization system. Do it on a 450, and you're going to crash. Do it on a 90, and maybe not. Or so I've heard anyway.

Edit: Dangit!! Ya beat me to it!
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Old 03-22-2009, 08:36 PM   #7 (permalink)
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Originally Posted by rotormonkey View Post
Full scale helis have a lot more mass in the blades and therefore more gyroscopic effect, and therefore more stabilization. Same applies for RC models. You CAN just remove the flybar without an electronic stabilization system. Do it on a 450, and you're going to crash. Do it on a 90, and maybe not. Or so I've heard anyway.

Edit: Dangit!! Ya beat me to it!
LOL Good answer!

The bigger scale guys do it sometimes without electronics with weights in the blade tips.
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Old 03-22-2009, 09:11 PM   #8 (permalink)
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Popsicle's reply isn't quite on the mark - the flybar doesn't provide any stability whatsoever, what it does is to reduce the response rate of the rotor disc to the pilots inputs.
Look at this analogy - if you place a 6-foot long pole vertically on the palm of your hand, you can balance it upright quite easily. this is because it "falls over" more slowly than you are able to respond to, or "chase", its movement.
Now try the same thing with a 6-inch pencil - it "falls over" much more quickly - too quickly for your human responses, and thus you can't keep it balanced.
This size analogy holds true for rotors directly connected to the swash - the smaller the rotor, the quicker it responds, until a point is reached where it is too quick for the human pilot to respond to or "chase".
The flybar system is actually a method of controlling the main rotor via a slower responding system which has a "chase rate" slow enough for the human pilot to anticipate - typically half a second or so, which can be changed, for example, by adding weights to the flybar to reduce the response or chase rate, (which incidentally has no effect on the stability of the system, but simply makes it easier for the pilot to follow), or by shortening the flybar or using bigger or lighter paddles to increase or speed up the chase rate
Hope this helps you to understand what the flybar does.
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Old 03-22-2009, 09:23 PM   #9 (permalink)
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doesn't the flybar also provide leverage to assist moving the blade grips in their pitch range?
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Old 03-22-2009, 09:34 PM   #10 (permalink)
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Flybarless helis' servos burn about 50% more power... so I'd say yes?
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Old 03-22-2009, 10:14 PM   #11 (permalink)
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Default What are flybars for?

I thought it was a place where insects go to have a drink.
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Old 03-22-2009, 10:34 PM   #12 (permalink)
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Quote:
Originally Posted by david.lunn View Post
Hi, I have a t-rex 450 se v2 and 600 ESP and keep reading about people converting them to a flybarless heads with great results and I'm curios why the manufactures dont just do away with flybars than? What pros and cons are their for flybarless and flybar heads. I've also read about flybarless electronic stabilization systems do you need them and what do they do.
Thanks so much for asking this question, I have been wondering the same thing myself.
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Old 03-22-2009, 10:40 PM   #13 (permalink)
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Originally Posted by heli-cuzz View Post
I thought it was a place where insects go to have a drink.
Or zippers.
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Old 03-22-2009, 10:51 PM   #14 (permalink)
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I thought they also made the blades pitch for movement
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Old 03-22-2009, 11:00 PM   #15 (permalink)
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Originally Posted by HoverHeaven View Post
Popsicle's reply isn't quite on the mark - the flybar doesn't provide any stability whatsoever, what it does is to reduce the response rate of the rotor disc to the pilots inputs.
Since I'm trying to put it simply for someone who doesn't understand what a flybar does; a flybar is essentially a stabilizer.
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Old 03-23-2009, 12:30 AM   #16 (permalink)
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Quote:
Originally Posted by HoverHeaven View Post
Popsicle's reply isn't quite on the mark - the flybar doesn't provide any stability whatsoever, what it does is to reduce the response rate of the rotor disc to the pilots inputs.
Look at this analogy - if you place a 6-foot long pole vertically on the palm of your hand, you can balance it upright quite easily. this is because it "falls over" more slowly than you are able to respond to, or "chase", its movement.
Now try the same thing with a 6-inch pencil - it "falls over" much more quickly - too quickly for your human responses, and thus you can't keep it balanced.
This size analogy holds true for rotors directly connected to the swash - the smaller the rotor, the quicker it responds, until a point is reached where it is too quick for the human pilot to respond to or "chase".
The flybar system is actually a method of controlling the main rotor via a slower responding system which has a "chase rate" slow enough for the human pilot to anticipate - typically half a second or so, which can be changed, for example, by adding weights to the flybar to reduce the response or chase rate, (which incidentally has no effect on the stability of the system, but simply makes it easier for the pilot to follow), or by shortening the flybar or using bigger or lighter paddles to increase or speed up the chase rate
Hope this helps you to understand what the flybar does.
One of Newtons laws says an object in motion tends to want to stay in motion unless acted upon by an external force. The flybar with it's angular momentum wants to stay spinning in the same plane. Much like a bicicle wheel stabalizing the rider. The more weight (actually mass), the more force is needed to change it's plane of revolution. The amount of influence (the ratio) it has to the main gripps helps to buffer out changes in the main rotor disk from veriations in the air as well as the heli's aerodynamics and drive train. A cyclic change needs to change the angle of the flybar as well as the blade pitch.
So the heavier the paddles, the less they want to change. The more aerodynamic the paddle (wider?), the more washout inputs to paddle pitch will make that change in disk angle faster. The longer the flybar, the more leverage the paddle has to effect those pitch (paddle pitch)changes. All of this gets mixed with the direct from swash to grips by way of the mixing lever.
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Old 03-23-2009, 01:03 AM   #17 (permalink)
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They keep watering holes from going dry...


Oops, that's a Barfly.
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Old 03-23-2009, 02:05 AM   #18 (permalink)
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Quote:
Originally Posted by david.lunn View Post
....I'm curios why the manufactures dont just do away with flybars than?....
I am really surprised that Finless hasn't weighed in on this... What you are reading is only half the story. While rotational momentum is important to how a heli flies and its stability. Flybar mass does slow the blades response to control inputs etc. But why are their paddles and not just weights??? Well you probably figured out that because they catch air and that moving air creates force which acts upon your blade grips. All that you have read so far is largely TRUE, for a heli in a hover. The better question is why when Igor Sikorski (who really invented the helicopter) had an amazing problem... his heli's hovered just fine but when they moved forward with any speed... they flipped over....

Why??..... Relative Wind! When a heli moves in any direction the wind and thus air mass encountered by the blade advancing into the wind (relative wind is created by its motion through still air) has more lift than the blade retreating from the wind.

I could get much more detailed but your flybar has paddles so that it can achieve directional flight at any appreciable speed. When the flybar encounters relative wind it acts to reduce the pitch of the advancing blade and decrease the pitch of the retreating blade. Flybarless systems monitor motion of the vertical axis and absent control inputs take actions to keep that axis in a constant orientation... think heading lock gyro for your rotor head but in two axis's instead of one.

Thx Igor.

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Old 03-23-2009, 02:08 AM   #19 (permalink)
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TYPO::: Should read "When the flybar encounters relative wind it acts to reduce the pitch of the advancing blade and INCREASE the pitch of the retreating blade.
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Old 03-23-2009, 02:48 AM   #20 (permalink)
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Quote:
Originally Posted by OverTemp View Post
Flybarless helis' servos burn about 50% more power... so I'd say yes?

About 5-8% actually, I have tested exact setups on a flybar machine and a flybarless machine, same servos etc.
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