RunRyder - 50 Flights on a Flybarless?

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Flybarless Rotor Head Systems > 50 Flights on a Flybarless?

"Cam"
Veteran
Location: Japan

I don’t know why but I’ve always thought that you’d expect the cyclic servos to last about 50 flights, that is before they get pretty sloppy.

The above might be true; but does a Flybarless setup also put more stress on the servos?

10-08-2007 02:14 PM

the_jackal46464
Senior Heliman
Location: Preston & Guildford, UK

50 flight's

I hope not cos that would mean me changing my servos every month,

10-08-2007 02:18 PM

rcadd1ct
Elite Veteran
Location: Richardson, Texas

Yes, flybarless needs stronger servos than a standard flybar head.

-RCA .......... Making Cuisinarts Fly!!!!!!!

10-08-2007 02:23 PM

Super-Hornet
Veteran
Location: Singapore

Yup. In flybarred, your servo just change the paddles pitch. It is the lifting/dropping of paddles that drive the main blades pitch.

In flybarless, your servo drives the main blades pitch directly. Thus u need higher torque servo for the job.

I not sure about wear and tear after 50 flights. Maybe because I do not use it for 3D flying.

EDIT: In flybarred, the servo also change the blade pitch directly during collective but changes in collective is driven by all servo together.

SH

10-08-2007 02:30 PM

LoopZilla
Heliman
Location: Melbourne, FL

What servos? What platform?

LoopZilla

10-09-2007 12:21 AM

HOMEPAGE

"Cam"
Veteran
Location: Japan

That's cool. I get what the servos do to the rotor with and without the flybar.

What kinda servo specs are being used?

10-09-2007 02:17 PM

JKos
Elite Veteran
Location: City of California in the state of Maryland

> Yup. In flybarred, your servo just change the paddles pitch.

Last I checked, the servos also pitch the main blades for cyclic inputs (and thus measuring and setting the cyclic pitch on the main blades). Yes, there are some heads out there on micros which do not have direct swash to main blade pitch input but they are not common and most likely not what would be converted to flybarless.

Blade selection also influences servo requirements with or without a flybar.

- John

Protos -- Logo 10

10-09-2007 03:08 PM

Wheelhaus
Veteran
Location: Denver

Quote
Yup. In flybarred, your servo just change the paddles pitch. It is the lifting/dropping of paddles that drive the main blades pitch.

Not true... A standard Bell/Hiller head splits main blade input between the swashplate and the flybar. This ratio is called the Bell/Hiller ratio. There's more to it than just the length of the mixer arms, but it's roughly the % that each input has over the blades.

Since you're removing the flybar, the swashplate has full control over the blades, meaning it's input is doubled. You have to reduce this input either by dialing back travel in the Tx, or better, dial back travel mechanically from the servo horns. This is also the best way to "increase servo strength". This keeps their resolution but can literally double their torque rating since the servo horns are half length.

You can either half the input arm, or double the output arm. If shortening servo horns is not an option, then lengthen the blade grip arm by mounting the ball farther from center. If neither are an option, then get creative. The T600 mixing arms mounted to the side of the head block do the same trick.

..........
Dave
TT e620 SE and Mini Titan

10-09-2007 07:54 PM

Super-Hornet
Veteran
Location: Singapore

Hi all

Yes in bell-hiller configuration, the blade pitch is also control directly by servo. But it is like in ratio. It is like 90% from paddles and 10% from direct (some heli may have different ratio).

That mean by using mechanical linkages to provide the ratio, it also mean it "amplify" the servo torque through mechanical division. Notice the linkages is different in lenght?

As for collective is control by servo also.. well, read my first post. I also mention about it. Again, during collective, all servo move at the same time.

SH

10-10-2007 01:11 AM

Super-Hornet
Veteran
Location: Singapore

Addition:

U can do a simple experiment. Take your TRex or any Bell-Hiller configuration heli, take out the paddles and replace it with some weight.

Now try to see whether can u fly it using purely by Bell ratio(direct control...and no Hiller) configuration. U will notice the cyclic is very very sluggish because the pitch changes from cyclic movement is very little.

SH

10-10-2007 01:25 AM

JKos
Elite Veteran
Location: City of California in the state of Maryland

Super-Hornet,
Your comment about putting weights on instead of paddles just doesn't cut it as the flybar is then completely fighting all cyclic inputs because it wants to stay in its plane of rotation. That is completely different than taking the flybar totally out of the equation.

I'm not sure where you are getting your statement about 90% flybar and 10% direct either. In a truly balanced head setup, the flybar follows the plane of the main blades during cyclic inputs. That's why we have paddles which are pitched to force the flybar to follow the main blade plane.

In flight, the flybar doesn't deflect/teeter as much as you may think and thus is not responsible for "90%" of the main blade cyclic pitch input. If you check on your helis head you'll easily see that the flybar can't possibly be responsible for 90% of the cyclic pitch. For example, I just checked my Logo 14's head and the absolute maximum cyclic pitch the flybar could add is 8.5 degrees. And that's only if it went full deflection which it really doesn't. The direct input is set to 7 degrees.

It's been reported several times through the years that a flybarless head is faster than the flybar head with the same amount of cyclic pitch on both. That can only mean that the flybar is actually fighting the cyclic inputs, not adding to them.

I think what we are seeing with these 3D flybarless setups is that we are finally freeing ourselves of the negative affects of a flybar. People have spent a lot of time and money on paddles, flybar lengths, and flybar ratios simply trying to minimize the negative affects while maintaining hover and forward flight stability.

- John

Protos -- Logo 10

10-10-2007 03:00 AM

Wheelhaus
Veteran
Location: Denver

Super-Hornet, where are you getting your numbers from? 90/10 is definitely not correct, most helis are closer to 50/50. The weights will also not produce the effect you describe since it's not designed to work that way.

JKos nailed it on the head. The flybar is purely an aerodynamic mechanical gyro. It's purpose is not really "power steering", but dynamic stabilization. If you actually measure the change in pitch that each the flybar and the swash provide, you'll find most helis are closer to 50/50.

Converting a standard B/H head to go flybarless will cause it produce over +/- 20° of pitch. This happens for one sole reason, the flybar is gone, so it can't take away half the blade pitch it would otherwise control. If throws are then doubled from the swash, just reduce them by half to regain proper throws. Doing this will cut the servo load in half of what it would otherwise be by simply reducing throw in the transmitter.

You don't need more powerful servos (as long as they're good enough for the original setup), but you do need to increase their leverage for flybarless mostly incase the load axis of the blades isn't perfect.

IF the blades are designed correctly, the servos will have very little load because the blade CG and load axis should be inline. IF this is the case, then the servos have no more stress at 10° pitch than they do at 0° pitch.

..........
Dave
TT e620 SE and Mini Titan

10-10-2007 03:31 AM

uk2bx
Senior Heliman
Location: Bronx , NY

This post has realy peaked my interest in flybarless heads , can you direct to more info , is it possible to covert a raptor , evo or other main streem heli to flybarless? any info would be much appreciated thanks Jamie.

www.flysrw.com

10-10-2007 03:41 AM

HOMEPAGE

uk2bx
Senior Heliman
Location: Bronx , NY

i just found the flybarless thread , should have looked first..

www.flysrw.com

10-10-2007 03:43 AM

HOMEPAGE

Super-Hornet
Veteran
Location: Singapore

U all get misunderstand my post here.

I not referring to direct linkages here. If u are using direct linkages, yes the cyclic pitch will change alot.

What I trying to say is that, in normal bell-hiller flybarred heli, u will notice that there is a linkages from swash plate to the washout and then washout to the flybar (Changing the flybar pitch). This is the hiller configuration.

This one is in line to the blade grip. Then u have another linkages from swash plate to a mixer and then this mixer is connected to the blade grip. Now this is the Bell configuration.

What I trying to say is that, if u trace the line/linkages for the bell configuration, there is a mechanical reduction. It is like a plyer where one side is longer than the other. The longer one is connected to the swash plate and the shorter one to the blade grip. Thus the swash plate need to change more in order to have blade grip changes.

For the flybarless configuration, normally u connect the swash plate to the blade grip directly. Thus there is no mechanical reduction and thus the pitch changes is huge.

The purpose of taking the paddles out IS NOT TO CREATE flybarless...but to simulate of what if u do not have "Hiller" configuration and only the Bell configuration.

Now, if my explanation above still does not mean anything to u or u think it is wrong, then it is ok for me. U can just ignore it. Thanks for reading it.

SH

10-10-2007 01:15 PM

Wheelhaus
Veteran
Location: Denver

Ok, that makes much more sense when you explain it that way. I still think it's a flawed method, because the current system NEEDS the flybar paddles to work properly. If you were to only use weights, the linkages would also need to be changed. As-is, the system is designed to change flybar paddle pitch as a necessity, that's the only way it will work correctly. If you only change to weights instead of paddles, you're eliminating a required feature. The system will still attempt to change pitch but it won't have any effect, resulting in a very numb, sedated feeling.

For a system designed to use a weighted flybar, the mechanism that changes paddle pitch needs to be removed entirely. Simply using weights won't give you a pure "bell" head because it's just not designed to work that way, more things would have to change. Does that make sense? You have the right idea but the method isn't complete.

..........
Dave
TT e620 SE and Mini Titan

10-10-2007 05:49 PM

Super-Hornet
Veteran
Location: Singapore

Well, I not going to create a pure bell heli.
What I trying to say is that, in normal bell-hiller heli, u have about 90-10 percent ratio. (Again, the 90-10 percent ratio varies from heli to heli some may have different value. 90-10 is just a example).

What I trying to say that by removing the hiller portion (that is removing the paddles) and only left the bell portion, u have only 10 percent ratio of bell controlling it. (AGAIN 90-10 ratio is an example!!!) That is why the control will be sluggish.

The sluggishness is due to the mechanical reduction. The mechanical reduction also meaning it "amplify" the servo torque.

Now, if u connect directly from swash plate to blade grip in a flybarless configuration, u do not have that mechanical reduction. Thus it is more stressful as compare to bell-hiller.

It does not mean your existing servo cannot handle the flybarless load, it mean if u can get higher torque servo for flybarless, it will be better choice.

SH

10-11-2007 12:21 AM

"Cam"
Veteran
Location: Japan

Bottom line is you need higher torque servos for a flbarless?

Would your normal cyclic servos not be ok if you used servo arms that are half the length? (As needed for the flybarless setup)?

10-12-2007 09:25 AM

Wheelhaus
Veteran
Location: Denver

Yes and no. You need higher torque output, but there's two ways to achieve this. If your servos have decent ratings now for your flybarred head, you should be fine. In a flybarless head, much of the strain on the servos comes from the blade CG positon. If they lag too much it will burden the servos because the blade wants to trail and not change pitch. If they lead too much the helicopter can feel hyper responsive, also burdening the servos because the blade will want to change pitch before the servo moves it, so they will fight to retain pitch where it should be. If the blades can fly neutrally, then changing pitch is a non issue and the servo load is minimal. (This is the same with tail blades. Some "high end" tail blades I've found will lag a lot, meaning the servo has to strain to hold pitch at extreme angles)...

Most current head designs reduce the servo throw roughly 50% at the Bell/Hiller mixer. This doubles their torque by reducing output travel. Flybarless heads will not have this reduction, so you end up with doubled throws (100% travel goes straight into the blade without any reduction). You'll need to reduce this throw back to around 50% to regain throw, but by doing so you also double torque again. You could do this by using shorter servo horns, or better, use extended grip controls so the ball links are farther from the head.

If you plan to reduce travel in the Tx only, then YES you WILL need higher torque servos. This is a poor method since you lose resolution from the servos.

For CCPM you don't need insane torque because the three servos share the load. I'd say 60oz is good up to a .50 size. (Together that makes 180oz for collective power and 120oz for cyclic, (once travel is reduced, its roughly 360oz for collective, 240oz for cyclic, that's insane!) But for a standard single-servo head (mechanical mixing) on a 30 size or up, I'd highly recommend using high torque servos (100+ oz minimum), especially for collective since they do not share any load.

Sweet, yet another response that ended up WAY longer than intended...

..........
Dave
TT e620 SE and Mini Titan

10-12-2007 04:37 PM

"Cam"
Veteran
Location: Japan

Big reply thanks.

Ok I think 100 oz-inch is about 7.2Kg-cm

So three servos on a CCPM at that would be ok?

Its got to be ccpm as I want the motor and battery above the main gear!

10-13-2007 09:35 AM

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Flybarless Rotor Head Systems > 50 Flights on a Flybarless?

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