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Old Aug 03, 2015, 03:54 AM
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Flybarless Fixed Pitch Conversions: Death to the Flybar!

Having started real (non coaxial) helicopters with the flybarred V911, I was introduced to a whole new world of performance, and the 45 degree flybar provided the stability to keep the bird up in the air (well some of the time at least!). Moving on, I started the steep learning curve into 3 axis CP with the V922, while the V912 provided a huge amount of fun with more speed, better size, higher power to weight ratio etc.

The 911 where it really began for me:


The more I learned to fly the 922, the more I started to appreciate the handling issues caused by the 912s flybar, and that the large number of crashes werent just because of my dubious, over enthusiastic piloting, but also because there are a number of manoeuvres the flybar doesnt like doing.

Electronic stabilisation has revolutionised radio control, first single axis gyros that ultimately became cheap and light enough to provide tail control right down to small birds like V911s, but then 3 axis control, followed by 3 axis gyro and 3 axis accelerometers (or 6 axis as we often call it) that have allowed the creation of multicopters and the next generation of FBL helicopter controllers. Even our yacht uses the technology. Our new autopilot has 3 axis gyro, 3x accelerometer, plus 3 axis magnetic compass. The pricepoint on this gear has been plummeting, so we can now buy OpenPilot 6 axis boards for US$15 or less.

Flying a good FBL bird is so rewarding that going back to flybarred helis is a shock! The combination of fast acting stabilisation, with instant dynamic response (instead of waiting for a flybar to level before initiating the next cyclic change) is most gratifying. The opportunity to take our existing inexpensive airframes, turbocharge them with brushless motors, and then use electronic rather than mechanical stabilisation is vastly appealing. The question is can we do this and achieve similar standards of handling to the better commercial FP offerings (such as FP100 V1, WL V930, Blade 200SRX etc)?

Is the Blade 200SRX the best flying FP on the market?


The FX70 CC3D thread has been pretty quiet for a while, so decided to set this thread up in the interests of getting more discussion going, and hopefully ferreting out people who have had some success in this area. It doesnt worry me whether these are 3 or 6 axis conversions, Im sure most of the fundamentals are the same.

So my trusty old V912 has been converted to double brushless, had a quick stint with an FX78 flybarred head (lets just say that wasnt a success!). then had the Tarot ZYX added while leaving the flybar in place (actually worked reasonably well). The next step was to remove the flybar and go FBL

Forgive me if youve already seen some of my posts with these vids, but I figure theyre relevant to the discussion.

First outdoor FBL v912 flight:
The age of the flybar has ended! V912 Flybarless with Tarot ZYX (4 min 23 sec)



Decent flying FBL FPs: HFP100:
Favourite Backyard Flier Hisky HFP100 V1 (2 min 41 sec)



Decent flying FPs V930:
V930 Parkfly In The Wind -Great Little Flyer!! (3 min 30 sec)



A bit of history: Double brushless 912 first parkfly:
Double Brushless V912 -Getting It Dialled In... (4 min 32 sec)



A bit of history: (A doomed development!!) Double brushless 912 with FX78 head:
Double Brushless V912 with FX078 head (5 min 35 sec)


A bit of history: ZYX controller plus a flybar, actually not too bad...
V912 ZYX with flybar (4 min 28 sec)
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Old Aug 03, 2015, 05:51 AM
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I don't have much to offer to the discussion but you might like to have at the "frankenheli workshop " thread for FP conversions and upgrades .
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Old Aug 03, 2015, 06:36 AM
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Here's a link.
http://www.rcgroups.com/forums/showt...nheli+workshop

As much time as I've spent here, I didn't even know of this thread. Funny I never spotted it with all the searches I've done here.

Yes, this is all about thinking outside the box when it comes to fairly inexpensive production helicopters.
Many of us found after market parts that helped improve performance of our fly barred units, Then went to as built flybarless.
I had a couple of the well known 200 SRX's, but didn't like them. High initial cost and they soon became money pits.

I think models like the FX series opened things up. A good solid airframe design that had lots of possibilities. The big down side was the brushed motors they used.
Then things got complicated.
Going to a brushless motor system turned into no walk in the park and for the non electronic savvy guys like me there was mind twisting jargon to try and understand.
I'm now at the point of installing standalone receivers and electronics into a stripped down frame.

This stuff ain't for everyone and there's no cheap and easy way to do it.
For me it's become a challenge, and I'm going to get one built one way or the other.
After I solve the problems and learn how it's done, maybe do a couple and then on to building a larger full collective version.
Anything smaller, physically, than something about the size of the V-913 doesn't interest me.
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Old Aug 03, 2015, 01:35 PM
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OP, FYI, I have 90 degree flybars (look at my avatar) on all my helis except one. A 90 degree fly bar heli does not automatically stabilize like a 45 degree flybar or off set head balance bar like your 911 does. It's an important distinction. The 911 has a balance bar not a flybar...
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Old Aug 03, 2015, 03:00 PM
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Quote:
Originally Posted by elan View Post
OP, FYI, I have 90 degree flybars (look at my avatar) on all my helis except one. A 90 degree fly bar heli does not automatically stabilize like a 45 degree flybar or off set head balance bar like your 911 does. It's an important distinction. The 911 has a balance bar not a flybar...
I agree with this........A 90 fb behaves basically the same as your basic 3 axis stabilization. The only difference is maybe cyclic response(which can be easily improved with a bit of tinkering).....The cyclic response of my 90degree fly bared esky hbfp's is instantaneous and virtually indistinguishable from the response of a 3axis fbl heli........So i say death to 45 degree fb's/stabilizers/balancers.......90degree on the other hand still rocks................Kato
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Old Aug 03, 2015, 06:26 PM
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Haven't flown any 90 degree flybars. I have a 250 kit sitting in the cupboard but haven't got around to assembling it yet. I had read some comments that 90 degree flybars can be wind affected? 90 degree flybars still provide stability, however it's just they don't return the bird to level.

One other thing I like about FBL is that there is less mechanical complexity. It gets rid of a series of moving parts, linkages and weight... The 90 degree FP heads are engineering marvels!

Have some new video to post later and have some theories on what the problems are, but the issue I'm hitting with the FBL 912 currently is nose flaring, either gliding down (fwds and descending) off the throttle, or flying into the wind. It's the same issue the FX71's in particular have been bad with, although it has been discernible on the (but less so) on the bigger 67 and 70. More later....
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Old Aug 04, 2015, 04:50 AM
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Video clips from Sunday, and some ugly nose flaring! With almost no wind in the morning I had good flights at home, and I figured the 912 was getting to a stage where handling was half reasonable.

Second flight was with some space down at the pony club with a moderate but not what I consider a strong wind. The nose flare was horrendous into the wind, and the funny thing is that this is exactly the sort of behaviour that the stock FX71’s exhibit.

V912 Double Brushless & Flybarless -Slow steps towards good flight (3 min 46 sec)


I'd always thought the FX71's traits were something to do with the 6 axis settings, but following Moeder's Deviation hack and flying it in 3 axis, it was showing the same tendencies. So where is it coming from?

It's obviously tied up with the heavily pitched, heavily cambered blades on these helicopters. Once the nose starts pitching up the weight and lever arm of the tail takes over, and even full forward cyclic doesn't recover it. We've been overcoming this on the FX's by pushing the CoG further fwd, however it's still not 100% effective. It was interesting that the helicopter would fly sideways into the wind without doing it though. I' assuming that without the lever arm of the tail, the FBL can keep it under control.

In comparison the better flying FP's use less blade pitch, camber/depth, solid CP type blades, and much higher headspeed. They don't suffer from the nose flaring.

Also interesting to note the maximum depth of camber from the leading edge. In sailboats you change the shape of the sail so that in rough water the maximum depth is closer to the leading edge. This creates less maximum lift, but is much more tolerant of changing angles to the airflow. In smooth water you move the shape back for higher ultimate power, but it's much more sensitive to the attack angle. Interestingly the CP type blades have the max camber depth much further forward than the 912 blades (HCP100 blades at around 25% back whereas 912 blades are at ~40% back). Given the lower headspeed of the 912, it will automatically suffer from greater changes in attack angle, plus the maximum blade depth is backwards instead of fwds...

So the next trial will probably be to remove more material from the trailing edges of the blades (reduces the apparent pitch angle) to see whether that makes any significant difference, unless there are better suggestions (other than throw it away and buy a 200SRX ).
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Old Aug 04, 2015, 06:48 AM
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I've had the same experiences trimming blades. Flight characteristics, especially in wind, were improved the more I shaved off the trailing edges. Also helped when I reshaped the trailing edge back to a knife edge.

I know there's a big difference between the 90 and 45 flybars, but both are getting dated with developments in helicopter stabilization. Look what's happened in just a few short years.

Getting back to the original "Frankenheli", I'm slowly wading through it. After a 100 pages still old out of date posts by a lot of people who evidently have moved on talking about talking about heli models that are becoming uncommon.

It was interesting to note, that early on, someone made a comment about how hard it was to get a second ESC installed to run a tail motor.
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Old Aug 04, 2015, 08:37 AM
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Was looking at the Castle Talon ESCs as maybe an alternative to going through this BLHeli process.
Probably do what I need, but wow!, way too expensive for this project.
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Old Aug 04, 2015, 10:55 AM
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Quote:
Originally Posted by elan View Post
OP, FYI, I have 90 degree flybars (look at my avatar) on all my helis except one. A 90 degree fly bar heli does not automatically stabilize like a 45 degree flybar or off set head balance bar like your 911 does. It's an important distinction. The 911 has a balance bar not a flybar...
That is an excellent point that I am glad someone brought up because there is a whole lot of confusion about that distinction.

Technically, v911/v912/v913 etc. use a mechanically stabilized head that uses a weighted balance bar (no paddles) with 45 degree latent phasing. The force they exert is based on the gyroscopic effect of the spinning weights.

A collective pitch helicopter with a flybar on the head has paddles on it that "fly" in the sense that they change pitch and therefore exert varying force based on that change in pitch. One interesting design note is that the flybar actually can be used to assist the servos by amplifying the force of the servos and applying the amplified force to the head, so the servos do not need to be as powerful as ones used in FBL heads.

I think I would rather die than set up a CP head with a flybar after every crash. The complexity and number of parts has always turned me off.

I love the old Frankenheli thread. Back when I was convinced that I didn't ever want to fly CP, I read that thread a lot. I even went so far as to take a flybarred 450 CP in RealFlight, model a 450-size fixed pitch head with a 45 degree latent balance bar for it, and tune the physics model to get it to fly correctly. It flew like a gigantic v911! Then I started learning how to tone down CP helicopters and I realized that there is no difference between a toned down CP heli and a FBL FP heli, and I've never looked back at the Frankenheli thread. Take a CP, limit your pitch range (or if you want to prove the point set it flat) and reduce your head speed, and you get the same result as a CP to FP conversion without all the work and expense. It makes no difference if you use a CP head or a FP head as far as flying. The CP head does use an extra servo though. Really, it's all about the head speed, as noted above. One of the greatest things about the tiny FBL FP v930 is its reduced pitch and high head speed. It flies just like a CP heli except that you have to wait for the motor to spin up and spin down to change altitude, which got annoying after a while.

I do wish that FBL controller manufacturers would implement the range of features provided by current quad copter flight controllers. The features available on my $24 FLIP32+ quad flight controller put my KBAR FBL controller to shame. I know that some people have tried the CC3D in single rotor helicopters. I wish someone would try a FLIP32+ in a single rotor, but I have no idea how you convert outputs that are supposed to control 4 ESC's into inputs for 2 cyclic servos, one ESC, and a tail motor, or in the case of a CP four servos and an ESC. I am quite sure that it could be done with some programming in CleanFlight, which is open source, but I see nobody working on it. I don't see many people working with the CC3D on single rotor either. That's a shame because I think quad controllers have grown by leaps and bounds while FBL units for single rotor seem to be sitting stagnant (and expensive unless you fly a KBAR or other clone like me).

-Florida Heli-
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Old Aug 04, 2015, 01:27 PM
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I finally finished the original "Frankenheli" thread. It seemed to have run it's course.

So now back to these mods of some popular inexpensive helis to make them better.
If they ain't better, they'll damn sure be different.

I found at a vendor named Rotorgeeks a list of ESCs already set up with BLHeli, and not too bad prices.
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Old Aug 04, 2015, 02:22 PM
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I think the reason that the old frankenheli thread suggested the tail ESC was problematic was due to problems with the older versions of blheli's bltail programming having faults , bltail is good now .
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Old Aug 04, 2015, 03:06 PM
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bltail ?
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Old Aug 04, 2015, 08:15 PM
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I assume using BLHeli for a brushless tail. There have been a number of guys doing double brushless conversions on HCP100/V922's etc. The BLHeli code updates have fixed bugs in the earlier software versions....

Great to see reference to the Frankenheli thread. Going back further was the DH9116 modders thread, that eventually morphed into FrankenHeli. There was some great work done by Steve, LaidBackRacer, PaFlyer, GyGax, MikeFromGermany etc. Seems like most have carried on into CP etc now, but at the time they did some really cool experimentation with 45 degree flybar heads and got their birds flying way better than the "experts" ever expected. Took quite a bit of reading back through the thread to discover what "Member of SSOBB" stood for. It's Secret Society Of the Barking Blades, and great reference to how they got their DH9116's cranked up and flying hard. Funny just noticed the webpage address with highlight=barking+blades. Epic!

http://www.rcgroups.com/forums/showt...barking+blades
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Old Aug 05, 2015, 05:56 AM
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Yes BLheli has a specific model programme for use with a BL tail motor ,when I first did a BL conversion it was on a v944 (hfp100) ,when I used the early bltail programme it did some odd things ,notably when the main was spooling down on landing the tail went max rpm and chicken dance followed.
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