RunRyder RC
 26  Topic Subscribe
WATCH
 5 pages [ <<    <     1     ( 2 )     3      4     NEXT    >> ] 7417 views POST REPLY
HomeAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › Virtual Flybar - what would you like to have?
11-24-2006 04:15 PM  11 years agoPost 21
Colin Mill

rrVeteran

England

My Posts: All  Forum  Topic

Hi Mr Mel

Yes, the use of three 720s and mixer will be around around $800 (or about $700 for a non CCPM heli). If you already have a tail gyro then an e-flybar based on 2 x SL720 and mixer would be around $560 ( or $470 for a non CCPM helicopter)

Colin (CSM)

PM  EMAIL  Attn:RR  Quote
11-24-2006 04:15 PM  11 years agoPost 22
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

Sounds like Deja Vous.

http://www.AirWolfRC.com and see my virtual flybar from back in 2001.

Colin, as far as your speed sensor goes, that is only a crutch and would need more than just one sensor to be complete for anything more than forward/backward flight. Fact is that the ol'e mechanical flybar has no such speed sensor and if the gyros are dialed in properly, you shouldn't need one there either.

Wolfgang

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
11-24-2006 04:24 PM  11 years agoPost 23
Colin Mill

rrVeteran

England

My Posts: All  Forum  Topic

Hi Wolfgang

Some nice work you have done on your site! Did you try putting the blade grips reversed to give leading edge control or was it fine with trailing edge control?

Colin

PM  EMAIL  Attn:RR  Quote
11-24-2006 04:39 PM  11 years agoPost 24
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

No, I didn't. The trailing link didn't have any problems.

In the case of leading links, you likely will not see much advantage in the event of sloppy links. The typical head design wants to have the center of pressure and mass at the blade pivot axis anyway.

Comment ; one thing I found is that the gain on the roll gyro needs to be a bit less because the moment of inertia on the roll axis is less than the pitch axis.

Wolfgang

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
11-24-2006 04:52 PM  11 years agoPost 25
Krunder

rrNovice

Denmark

My Posts: All  Forum  Topic

Dosen´t the flybar and paddels work as a kind of speedsensor?

PM  EMAIL  GALLERY  Attn:RR  Quote
11-24-2006 04:57 PM  11 years agoPost 26
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

No, they don't.
They act only as a free gyro with command inputs from the swash and outputs to the main blades, regardless of speed.

The amount of command to the main blades is strictly a function of the angular difference between the main rotor disk and the flybar disk. When the two disks are parallel, there is no command to the main blades. In forward flight, there will be an angular difference. The faster you fly, the greater the angular difference in order to maintain level flight. (more lift from the advancing blade to be compensated for and all that stuff)

Electronic gyros still have a way to go.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
11-24-2006 05:00 PM  11 years agoPost 27
Krunder

rrNovice

Denmark

My Posts: All  Forum  Topic

Ok I just figured that the function of the paddels was affected by the airspeed....

PM  EMAIL  GALLERY  Attn:RR  Quote
11-24-2006 05:15 PM  11 years agoPost 28
Colin Mill

rrVeteran

England

My Posts: All  Forum  Topic

Hi

Somewhere in the back issues of Model Helicopter World there is an article I wrote about the effect of forward flight on the flybar (and I think I should look it up sometime to refresh my memory!) however, the downflow onto the top of the flybar in the forward flight attitude causes the flybar to want to tip down at the front (a consequence of the advancing paddle producing more downforce than the retreating one added to the gyroscopic precession of the flybar treated as a flywheel)

Anyway, this acts in opposition to the nose-up pitching tendency of the main rotor by feeding in some forward cyclic trim. Very useful! However, there are a number of snags. The balance depends on the mixing ratio on the head and the advance ratio of the main rotor and flybar. Because the flybar is not full span of the rotor disk the advance ratio of the flybar is different to that of the main rotor causing the balance to shift as the forward speed changes. Also, when you lift the nose into an autorotative attitude both the flybar and the main rotor try to pitch nose up.

Colin (CSM)

PM  EMAIL  Attn:RR  Quote
11-24-2006 05:25 PM  11 years agoPost 29
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

the downflow onto the top of the flybar in the forward flight attitude causes the flybar to want to tip down at the front (a consequence of the advancing paddle producing more downforce than the retreating one addid to the gyroscopic precession if the flybar treated as a flywheel)

Anyway, this acts in opposition to the nose-up pitching tendency of the main rotor by feeding in some forward cyclic trim.
Yes, quite, there does look to be some "speed sensing" going on there, but only if the flybar disk is "commanded" to tilt forward in the first place.

It remains that in order to maintain forward flight, the advancing main blade must have less pitch than the retreating blade and for that to happen, the flybar disk must have more "nose down" than the main rotor disk. The down wash through the flybar disk helps maintain that flight condition but doesn't cause it.

Wolfgang

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
11-24-2006 05:39 PM  11 years agoPost 30
Colin Mill

rrVeteran

England

My Posts: All  Forum  Topic

Hi Wolfgang

Yes, I'm sure we can ultimately do a better job with electronics. The big thing the flybar has going for it is its immediate coupling to the main blade pitch while an electronic system has to convey its control via the servos. However, servo performance has now reached a stage where this is not the disadvantage it once was. I believe there are a number of measures we could take in the design of the rotor head that could considerably reduce the cyclic control forces and help us to use still faster servos.

Colin

PM  EMAIL  Attn:RR  Quote
11-24-2006 05:45 PM  11 years agoPost 31
Yug

rrMaster

UK. Herts

My Posts: All  Forum  Topic

Crikey, I've only just come across this thread - been busy
This is something I've always been interested in having a go with. I love the idea of all that energy not being lost in the flybar system but have always had concerns over the extra loading on the servos. The best solution I've come up with is to use longer balls on the swash so as to reduce the swash to grip ratio with respect to servo horn travel. Could use shorter horns, but this does not alleviate the loading the horns are subject to. For a good while now, I've been on the lookout for a suitable load cell that could be incorporated in a linkage and data logged. Yes, one could measure the srvo current but I fear this would provide complex information and would be hard to extract the true loading information. Just how much force is going through the blade grip links? I'd love to know.
With regard to using longer balls on the swash and with a view to issues surrounding swash interaction in an eCCPM system, I've always thought it best to go through a calibration proceedure so as to linearise the whole system, but there agin, if one is using a dual axis gyro, then you have a closed feedback loop so calibration becomes unnecessary.
He he, looks like we're getting a step closer to the design of swashless solid state head.
Keep up the good work Colin

PM  EMAIL  GALLERY  Attn:RR  Quote
11-24-2006 05:57 PM  11 years agoPost 32
Colin Mill

rrVeteran

England

My Posts: All  Forum  Topic

Hi Yug
looks like we're getting a step closer to the design of swashless solid state head.
I read about the idea of a 'control rotor' in one of the full-size textbooks some years back with the idea that each blade has its own pitch servo that is fast enough to do the cyclic commands. Very interesting stuff with the possibility of higher harmonic control leading to higher flight speeds. As it happens I have some "servos" that are plenty fast enough to do it so in principle it's 'on' but the servos are not exactly convenient so I would have a major mechanical job to do it.

Colin

PM  EMAIL  Attn:RR  Quote
11-24-2006 06:08 PM  11 years agoPost 33
Yug

rrMaster

UK. Herts

My Posts: All  Forum  Topic

I've been investigating several methods. Prefferred would be a piezo motor, either stack, bender or helix. Unfortunately they all fall short of the mark one way or the other. Phenumatic is a possibility, but a voice coil currently seems the most doable. will need a small generator mounted between the upper bearing and main shaft.

PM  EMAIL  GALLERY  Attn:RR  Quote
11-24-2006 06:16 PM  11 years agoPost 34
Colin Mill

rrVeteran

England

My Posts: All  Forum  Topic

Yes, voice coil is promising. Lucas research used this technique to produce electronically controlled valves on a petrol engine (synthetic cam profile and timing - nice!!) However, it was far from straightforward I believe.

Colin

PM  EMAIL  Attn:RR  Quote
11-24-2006 08:00 PM  11 years agoPost 35
Yug

rrMaster

UK. Herts

My Posts: All  Forum  Topic

It would be good to explore this further in this lifetime. One aspect of this that I find most interesting is the fact that with a conventional system, we are limited to a sinusoidal input to the grips. I can't help thinking that use of a different transfer funcation could well enhance the performance characteristics in ways not yet dreampt of. I also love the idea that one could completely do away with all the conventional mechanics currently associated with the head except of course the hub and grips. Just think what that would do for the CG let alone knife edge flight.
Sorry if I've gone off tipic, but when don't I

PM  EMAIL  GALLERY  Attn:RR  Quote
11-24-2006 08:06 PM  11 years agoPost 36
Colin Mill

rrVeteran

England

My Posts: All  Forum  Topic

Hi Yug - do a Google on Higher Harmonic Control. The ideas have been around since 1953 waiting for the technology. Can give almost a 30% increase in rotor thrust by increasing the pitch at front and back of the rotor - a sort of collective that comes on twice per rev!

Colin

PM  EMAIL  Attn:RR  Quote
11-24-2006 08:10 PM  11 years agoPost 37
Yug

rrMaster

UK. Herts

My Posts: All  Forum  Topic

Yup. Wouldn't it be fun to be in a position to actualy try this stuff.

PM  EMAIL  GALLERY  Attn:RR  Quote
11-24-2006 08:27 PM  11 years agoPost 38
Dood

rrProfessor

Wescanson

My Posts: All  Forum  Topic

AirwolfRC,

I read the article on your website http://airwolfrc.com/ about the Flybar-less helicopter where you (or someone else) modded a Raptor with Gyro's at the pitch and roll axis's. Also, it looks like it can be done for $200.
I was really surprised when I saw that, since I built a helicopter on RealFlight G3. Just like that Raptor design, It has no flybar and gyros at the pitch and roll axis's. I can post the g3x file here (after I find it) if anyone wants to try it out. It actually fly's quite well.
Can you discuss that system? The idea sounds really neat for some scale models. It just doesnt sound nearly as efficient as a real flybar.

  ▲
▲ ▲

PM  EMAIL  GALLERY  Attn:RR  Quote
11-24-2006 08:36 PM  11 years agoPost 39
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

Let's see, 1800 rpm on the head is 33ms per revolution leading to a servo responce time of no more than about 10ms. That's a tough one.

I'm thinking more along the lines of piezo in the blades along the length of the blade with an anti torque rod from root to tip inside the blade and the root free to rotate. Progressive pitch from out to in under piezo control and the rod can be used for collective. Build the in-blade actuator so the resonant frequency is about equal to the head speed and off you go.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
11-24-2006 08:42 PM  11 years agoPost 40
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

DJB78,
I built that head shortly after I first got into helis just to see what would happen. I also tried the FMA Co-Pilot when it first came out just to satisfy my curiosity. I have since had the Co-Pilot upgraded to the current version.

Wolfgang

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
WATCH
 5 pages [ <<    <     1     ( 2 )     3      4     NEXT    >> ] 7417 views POST REPLY
HomeAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › Virtual Flybar - what would you like to have?
 Print TOPIC  Make Suggestion 

 26  Topic Subscribe

Monday, June 25 - 6:51 pm - Copyright © 2000-2018 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online