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HomeRC & PowerAircraftHelicopterFlybarless Rotor Head SystemsOther › FBL and latency?
01-11-2010 10:58 PM  8 years agoPost 1
ScotY

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USA

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Been away from the hobby for a while and am still living in the dark ages with a Futaba 9C on 72mHz but have been wanting to pick up a 2.4gHz transmitter. Read a lot about latency and am now wondering about how this relates to the current crop of FBL systems, specifically, the Mini Vbar. I want to try the Mini Vbar and am wondering if there's any reason to also update to 2.4? Will I notice a significant difference?

I need to remain on a budget, unfortunately, so if you had to choose between a Vbar and a 2.4 radio, which would be better to get first?

Also, I'm assuming there is some latency inherent in all FBL systems due to the need to process info, etc. Has anyone done tests to compare the various systems? Reference the question in the previous paragraph, if there's latency in the FBL system, does it really matter if there's also a lot in the radio?

Hope all these questions make sense?

Thanks, Scot

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01-11-2010 11:31 PM  8 years agoPost 2
LaurenceGough

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UK

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Hi,

The very small latency with V-Bar is nothing to worry about. It is still ultra fast compared to the slow responses you would get with the mechanical flybar.

That being said I would still upgrade to 2.4GHz first, it just offers more advantages. (Both are great upgrades though).

Cheers,

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01-14-2010 01:18 AM  8 years agoPost 3
Justin Stuart (RIP)

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Plano, Texas

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2.4GHz is really nice in the sense that you never have to worry about getting shot down. It gives you enormous piece of mind knowing that nobody with a 72MHz TX can cause your $2500 heli to crash.

Check out the Spektrum DX7SE. It is a very good radio, and works well with the mini-V-bar.

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01-14-2010 01:53 AM  8 years agoPost 4
darkfa8

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Brick, NJ - USA

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The very small latency with V-Bar is nothing to worry about. It is still ultra fast compared to the slow responses you would get with the mechanical flybar.
A flybar is more "active" and responsive in terms of its ability to stabilize the model because it is physically acting on the rotor system at all times and instantaneously reacting to the environment independantly of the servos.

All current gyro systems are reactive systems. An example:

Flybar system: Wind hits model, flybar is effected and directly corrects the rotor head via the gyro-scopic effect and direct mechanical linkages independantly of whatever the servos are doing.

Flybarless system: Wind hits the model, the gyro(s) need to sense and process this, send out a corrective signal to the servos, the servos need to move (they're not instantaneous yet), then the motion has to be carried up through the swash, swash links, driver and finally to the main blade grips - a lot more to go through to implement a correction.

Curtis acknowledged that flybar systems are still better at correcting in wind, though flybarless systems are better for aerobatics.

For F3C folks, the FBL systems and servos aren't fast enough to keep up with the instant stability a flybar system provides. However, they are very good for aerobatics.

The technology will get better to the point that much of the mechanical parts of a model may eventually be surplanted by small motion devices (motors/actuators in the main/tail grips grips, motor integrated into main shaft, etc...)

- Dan Goldstein
Team Revolectrix

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01-14-2010 03:59 AM  8 years agoPost 5
ScotY

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USA

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Flybar is quicker or flybarless is quicker? I suppose both answers could apply, depending on the setup...I hear what you're both saying. I guess I still am wondering how much of a difference a fast 2.4 ghz radio will show compared to an old, slow 72 mhz with a FBL setup. Has anyone done a direct comparison?

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01-14-2010 05:00 AM  8 years agoPost 6
Justin Stuart (RIP)

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Plano, Texas

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Are you sure that the PCM radios are really any slower than most of the 2.4GHz radios? I think the latency for the high end PCM radios was 22ms which is the same as most of the 2.4GHz radios.

As far as I am concerned, with the V-bar it is fly-by-wire such that you could probably have an extremely high latency and low resolution radio and not know it because the V-bar is flying by itself.

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01-14-2010 01:17 PM  8 years agoPost 7
darkfa8

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Brick, NJ - USA

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see: https://rc.runryder.com/t172571p1/?top=1263474850 for latency info on popular radios.

flybar systems are better at stabilizing a model in wind due to the instant gyroscopic effect applied to the rotorhead without the need for any servo movement. The correction is instantaneous.

For flybarless systems, the model corrects to wind conditions after a series of processing, electrical signals and then mechanical movement is applied. Until processing speed and servo speed reach real-time transit, flybarless systems aren't going to stabilize a model in wind as well as a flybarred model - this is pretty much what Curtis Youngblood conveyed and why no one in the F3C crowd has adopted this technology yet.

- Dan Goldstein
Team Revolectrix

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01-14-2010 01:27 PM  8 years agoPost 8
Justin Stuart (RIP)

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Plano, Texas

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darkfa8, that's a good link. Thanks. However, I disagree with you on the benefits of flybarred vs. flybarless in the wind.

Although you're right about the need for a flybarless system to go through a long electronic control loop whereas a flybarred system has a direct mechanical linkage, the fact is that with a flybarless system you can program it to simulate very heavy paddles in a hover yet very light paddles for aerobatic maneuvers. In that way, you essentially have the best of both worlds: stability and agility. Yes, this system is not perfect and it appears to work best with the larger models, but it is nice to have a helicopters which hovers hands off upright (and inverted) even in gusty winds like a heli with very heavy paddles yet will flip and roll in a snap like a flybarred heli with very light paddles.

I have personally found that the flybarless system reaches it's limitations with the smaller helicopters such as the Trex 250. Although others may have better results with different setups, I have found that the servo speed on the 250 is too slow to react appropriately to the very low moment of inertia of the rotor disc. If they made some servos as fast as the 8717s that would fit in the 250, this might fix the problem, but once again the long electronic control loop does take time, and during that time the helicopter tends to drift to one side or the other.

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01-14-2010 01:40 PM  8 years agoPost 9
darkfa8

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Brick, NJ - USA

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servo speed is certainly directly related to how well any electronic gyro stabilization system is going to perform.

like you said, the flybarless systems can be setup to simulate this and that...but, it's still a simulation and like most simulators these days, isn't totally like the real thing just yet...

that said, like i mentioned earlier, the flybarless systems do beat a flybarred setup hands down in aerobatics and efficieny...and looks prettier too in my opinion. As Ben Minor mentioned to me, he'd love to give up the flybar for 20% more rotorhead efficiency and to not be accidentally wacking flybars carrying his models out the door, but in wind a FBL will move a few feet rather than just "sitting" like current flybar F3C models do.

For the majority of us, if the cost wasn't still as substancial, FBL would be the way to go. In wind we'd all just be having to add more corrections and just get used to it.

- Dan Goldstein
Team Revolectrix

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01-14-2010 02:29 PM  8 years agoPost 10
Justin Stuart (RIP)

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Plano, Texas

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In wind we'd all just be having to add more corrections and just get used to it.
See, I find just the opposite in my experience. My FBL helis will hover there in the wind, not motionlessly, but in one spot hands off. With a heading hold gyro on the cyclic, a gust of wind will tilt the heli and then it will return itself to it's original location a split second later. I had to add a lot more control inputs with my flybarred helis to keep them hovering in one place than I do now. The flybarred helis tend to drift around in a hover. They don't oscillate and wobble like the FBL helis, but they do drift. Do you disagree?

Well, whatever Curtis comes up with for his FBL system, you know it's going to be good.

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01-14-2010 03:59 PM  8 years agoPost 11
Joe90

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Quebec, Canada

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I think that most people never flyed a F3C heli.
Those guy spend a lot of hours to make them stable.
So I cannot compare a FAI heli with my flb system.

What I can compare is a vibe 90 and a trex700 with and without flybar.
Both were setup for 3D.

Everything is better with FBL on the trex700.
On the vibe it is different. hover feel a little more connected with flybar but not more stable. The gap is closing fast. For 3D there is no way to compare it is way better fbl. it fly faster too consuming less power. around 17% less based on pitch settings and Ampere draw on electric heli.

I dont fly F3C, just average, kind of soft precise, 3D

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01-14-2010 04:08 PM  8 years agoPost 12
darkfa8

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Brick, NJ - USA

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like Joe said, the F3C pilots spend a lot of time getting their models to "sit" well in wind. A good deal of time could be spent trying to acheive similar results with a FBL system, but it won't be as good as a finely tuned flybar system. An example, Gordie Meade once told me it takes him about 60 flights to get a new model dialed in for competition.

yes, it is clear that for aerobatics, FBL is the perferred choice. Like I said, for the majority of us pilots, if FBL was as cheap as slapping on a single HH gyro, it'd be pretty damn good and most of us wouldn't mind the slightly more correction needed to get a model to "sit" well. For most people it wouldn't really be an issue.

I was just making a point from a technical stand-point, a pro-pilot in F3C and that the technology hasn't fully matured in a way to acheive every ability of the traditional system it replaces. It will though, just a matter of time, money and some smart people.

- Dan Goldstein
Team Revolectrix

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01-14-2010 04:42 PM  8 years agoPost 13
Justin Stuart (RIP)

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Plano, Texas

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To better understand your argument, can you please explain (other than the streamlined fuselage) how a F3C heli differs from a typical 3D heli?

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01-14-2010 05:08 PM  8 years agoPost 14
MrMel

rrProfessor

Gotland

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As I understand it;

a FBL heli (electronically stabilized) will bob up and down, so even if it dont drift or tilt, its not stable in a 3D view.

a F3C machine is heavy with soft dampers, super-tweaked head, which makes it possible to "lean" into the wind, it will not sit straight as the FBL machine, but it wont move in 3D space either.

I'm sure if F3C allowed VBar etc, that someone would build a better "F3C" firmware for it, as it sure is possible if you really wanted to do it.
Then we come into play where if its "good or bad" in a competitive standpoint, but that's a different story.

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01-14-2010 05:57 PM  8 years agoPost 15
Justin Stuart (RIP)

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Plano, Texas

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I've watched some videos of the F3C competition, and they seem to have two parts to them. A hovering exercise, and an aerobatics exercise. I had to fast forward through most of the hovering, but the aerobatics seemed to me to be similar to the FAI pattern airplane competition with points being awarded for smooth, precise lines and round loops.

My V-barred helis are so incredible in aerobatics that it feels like flying a pattern airplane. Vertical, horizontal, and oblique lines straight as an arrow. I have NEVER had such an experience with a flybarred heli.

If FBL setups were allowed in F3C competition, I see no reason why the pilot couldn't simply program two different flybarless programs--one for the hover portion and one for the aerobatics portion, and toggle between them from one portion of the flight to the other.

I was looking at some MKS servos which supposedly have a response speed of 0.03sec/60 degrees. With speeds that fast, even with the long electronic control loop, a FBL heli could outperform any flybarred heli in any competition environment so long as the heli had a relatively large moment of inertia--such as an electric 90.

As related to the topic of this thread, even with a very slow transmitter, the "autopilot" function of the FBL system allows the helicopter to be actively stabilized without any input from the pilot.

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01-15-2010 03:27 PM  8 years agoPost 16
Bundian

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Fort Lauderdale, FL USA

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If you have a 9C radio just get the TM-8 module and pop a HS receiver with it you will get 2048 resolution.

I am using the same thing and it works great!

Now that my V-Bar is setup thanks to MrMel and all the others whole helped me I can't wait to get out and fly the heck out of it again

Last weekend the weather was soo bad I couldn't try it

Fly it like you stole it!!!

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01-15-2010 06:35 PM  8 years agoPost 17
KWH

rrApprentice

Canada

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If you have a 9C radio just get the TM-8 module and pop a HS receiver with it you will get 2048 resolution.
The 9c is a 1024 radio how will changing a module make it 2048? and the main problem with the 9c was the horrible servo phasing problem. When I would do flips one servo would operate first and would give me crooked flips. I flew for years with this problem and almost swore off of Futaba. Terrible radio unload it on ebay and buy yourself a 8fg.

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01-15-2010 06:56 PM  8 years agoPost 18
MrMel

rrProfessor

Gotland

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The 9c is a 1024 radio how will changing a module make it 2048? and the main problem with the 9c was the horrible servo phasing problem. When I would do flips one servo would operate first and would give me crooked flips. I flew for years with this problem and almost swore off of Futaba. Terrible radio unload it on ebay and buy yourself a 8fg.
With Mixing in a VBar or simular FBL solution it matters less since Radios shortfall in eCCPM mixing doesnt matter anymore.

Gone fishing..or hunting..or something
My site: http://heli.dacsa.net - VBar videos and more

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01-15-2010 07:29 PM  8 years agoPost 19
Justin Stuart (RIP)

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Plano, Texas

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Terrible radio unload it on ebay and buy yourself a 8fg.
Or buy a DX7se.

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01-15-2010 07:49 PM  8 years agoPost 20
twguns

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Indianapolis, IN

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Why buy a DX7se (11ms) when you can get much more comprehensive programing and more channels (8+2) and faster responce time in the 8fg (7ms)????

bigTim

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