Is Going Flybarless on a FP Micro Realistic?

[T.J. Kong]

I’m flying a Hummingbird and my ultimate goal is to make a scale UH-1B/C. One thing I hate is the look of the flybars. I have read of some attempts on the micro-heli forum, but no conclusive results. I know flybarless will be more twitchy (as if micros aren’t unstable enough). But I was wondering if it is possible to get a FP micro reasonably stable as a flybarless scale helicopter. I would think the additional weight of the body would help some. Also, I’m running HS55 servos. Would it be wise to use a stronger servo with a flybarless head?

[Hoverup]

It's been done many times on Hornet CP's.

[ScaleBrad]

Huey? Did you say Huey?? Like this one??? :) http://home.earthlink.net/~btm0106/sitebuildercontent/sitebuilderpictures/im000479.jpg

[ScaleBrad]

http://home.earthlink.net/~btm0106/sitebuildercontent/sitebuilderpictures/hin.jpg

[T.J. Kong]

I saw one video of a FBL hornet and it seemed to do pretty well. Once fine tuned, how stable is it compared to stock Hornet? Also, will fixed pitch be a problem? There will be a lot more inertia to accelerate if you want to climb.

Brad’s Birds: Nice Huey. That’s exactly what I want to do. What’s your setup? I’ve got the same radio and I hate the JR Revo mix, but, I guess it will have to do. I’d like to stay away from a HH gyro due to the weight.

[BimmerM3]

If I understand the question, you are asking if a fixed pitch micro heli can be flown flybarless. If this is what you meant, the answer is no. The flybar is the only means of cyclic control. Without it, you will have no cyclic (directional) control at all. This will make the helicopter uncontrollable.

You can have a flybarless helicopter it has collective pitch instead of fixed pitch. This is a fairly common mod done on Hornets and uses the tail rotor hub from a 30-size nitro heli.

[aerohawk1]

it can be done...
replace flybar with a rod with 2 ball links on either end...this will transfer cyclic directly to main rotors.
never tried it,by have seen some threads.

[BimmerM3]

How can this work? The main rotors have fixed pitch. Transferring cyclic to them will do nothing because they can't change their pitch. Not to mention that the design of the control linkages won't allow it.

Cyclic commands on a collective pitch helicopter are directed at the flybar which then causes the pitch on the main blades to change as they cycle through 360 degrees of rotation, but not on a fixed pitch system. The main blades don't move.

I'd like to see a video of a flybarless fixed pitch helicopter in flight. Then I'll shut up.

[Hoverup]

I think you are right BimmerM3.

[BimmerM3]

Thanks, Boyd! I was beginning to wonder if anyone was listening :D

[glxy]

How can this work? The main rotors have fixed pitch. Transferring cyclic to them will do nothing because they can't change their pitch.
FP blades do change their pitch, to achieve cyclic control. Think it this way, instead of the flybar tilting the blades, the servo linkages can do it directly.

Not to mention that the design of the control linkages won't allow it.
You are thinking right. Flybarless would put too much stress on the control linkages, and increase servo load.

Cyclic commands on a collective pitch helicopter are directed at the flybar which then causes the pitch on the main blades to change as they cycle through 360 degrees of rotation, but not on a fixed pitch system. The main blades don't move.
On a fixed pitch system, the main blades change pitch only for cyclic control, i.e. tilt the rotating disc. But the two blades always do the opposite pitch change, pitch increase on one blade is equal to pitch decrease on the other.

I'd like to see a video of a flybarless fixed pitch helicopter in flight. Then I'll shut up.
I'm too lazy to do it myself, but if you search for "flybarless" at micro heli forum, you will find a few examples. It's doable and have been done.

[BimmerM3]

I remain unconvinced :D

I've seen plenty of flybarless collective pitch helis, so I have no arguement there. I have also seen some fixed pitch helis with unconventional control systems (like the Blade Runner). But were talking about a conventional fixed pitch design here.

I'm not going to bother looking for a video, because I know it's a snipe hunt. If somebody can provide a video of a fixed pitch Hummingbird-type heli flying without a flybar, I will eat my hat!

[helifrek]

well, I have been flying rc helis for going on 6 years and I do think a fp flybarless is doable. one, because I have one on the design table right now. I know one of the head designs I have seen on a hummingbird I believe the flybar does provide all the cyclic movement and the blades provide lift. I can't really explain it but you pivot the blades, I'll provide a pic of how my setup looks (not finished yet...) and maybe you'll get the idea. think of it this way, if you do the mod on the hornet with the tail hub and run the control rods from the swash to the blade arm thing (its late and I can't remember the word) and have the anti rotation pin, when you put in a cyclic input one blade will loose pitch and the other will gain pitch equally as long as it's 90 degrees from the control input. so, they may as well be connected, there isn't really a difference. you could use the t/r hub design or a piccolo head design with the blade connected directly, either way it's pretty much the same thing. if I had a piccolo to fool with I would mod it for flybarless to show ya but right now I don't have one on hand. hope this explains it enough.

Brandon

[helifrek]

sorry this pic is so fuzzy, the blade grips are directly connected and fp, there is a single control rod on one side for cyclic.

Brandon

Brad's Birds... send me more pics and info on your UH-1 model and your setup, I might just have to get one.

[BimmerM3]

The Hornet/Piccolo mod you're talking about has articulated blades. Not the same thing as a FP Hummingbird which has rigidly mounted blades. I understand the thinking that the head on a FP heli teeters (tilts with cyclic inputs). But it's not enough for control.

Let's see a video. I'd love to be proven wrong!!

[Hoverup]

Me too ;)

[glxy]

Hoverup, haven't you already got one for your collection? :D

Check this page here (http://www.rcgroups.com/forums/search.php?searchid=1134720).

At least the following 2 threads are about flybarless FP.

http://www.rcgroups.com/forums/showthread.php?t=221894

http://www.rcgroups.com/forums/showthread.php?t=231167

Don't remember if they got videos there.

[Hoverup]

Hoverup, haven't you already got one for your collection? :D

.............

No. Just a flybarless Hornet CP :(

Cheers - Boyd :D

[T.J. Kong]

Well, there's enough discussion that I think I should give it a go. Now all I need is time. Huh…..



Assuming the control can be figured out. How much of a problem do you think the blade inertia would be? i.e. accelerate, climb—decelerate, descend



Boyd: How different are the flying characteristics of your Hornet CP FBL vs. Flybar setup? I had two reasons for starting this post. First, I’d like to know if a properly setup flybarless micro is fun to fly or just too much work and is more of a novelty. Second, I’d love to see more activity in this forum and wanted to join the group.

[T.J. Kong]

Boyd: By the way, what is the weight of your Hornet cp fbl? How much weight did you put in your blades? (I've read 5-6 grams is usually sufficient) Also, what blades are you using?

[Lynxman]

The Hornet/Piccolo mod you're talking about has articulated blades. Not the same thing as a FP Hummingbird which has rigidly mounted blades. I understand the thinking that the head on a FP heli teeters (tilts with cyclic inputs). But it's not enough for control.

Let's see a video. I'd love to be proven wrong!!

A FP head tilts to change the pitch of the blades alternately, just like with cyclic input on a cp heli. It's the blades that apply the rolling or pitching force on a FP helicopter. I have made two animations to demonstrate the similarities. the top picture shows a cp head without the flybar for simplicity. Flybarless fp is possible but you need to replace the stability of the flybar somehow. Adding weights to the tip of the blades works. FP heads normally can't teeter so adding teeter as well will probably help but I dont' think it's necessary.

[BimmerM3]

I understand the concept you're trying to explain. I am not an engineer, but I stand by my statement that, while it looks good on paper, this system won't have enough authority to be able to control the helicopter.

[Lynxman]

The blades will be able to rotate just as much as if the flybar was tilting. The flybar doesn't tilt all that much in flight anyway. It will put a very high load on the servos and swashplate compared to a flybar system though.

[Lynxman]

Is this good enough proof that it's possible? ;)

http://www.rcgroups.com/forums/showthread.php?t=221894&highlight=flybarless+mod

[BimmerM3]

Well, put me in a dress and call me Sue! Mmmmmm, my hat tastes good. Hatty goodness! ;)

[JT]

Hi all,

It certainly is possible; I did it to my Piccolo a few years back. The main problem was that the extra tip weight on the blades (required to stabilise a flybarless setup) created a slow response time to rpm changes and therefore height holding.

2 cents,

JT

[jolllyroger]

http://www.rcgroups.com/forums/showthread.php?t=177141&highlight=fixed+pitch+flybarless
here is pics of a fix pitch flybarless
it does and will work but is less stable

[jolllyroger]

the fly bar conects to the cyclic and dampens such cyclic. in flybarless The prob that can arise is when the blades advance or retreat so you must have blades correctly ballanced leading edge to trailing edge to prevent this prob as well as having weight base to tip correct. The other soulution is to fix baldes so they cant retreat as advancing is not as much concern

[Lynxman]

My flybarless CP sub-micro: http://rcgroups.com/forums/showthread.php?t=297221

It's not fixed pitch but it proves flybarless can be stable at small sizes.