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Old Aug 29, 2009, 10:16 AM
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45 Degree Flybar Conversion on a Walkera 4#3 V1 BELL HILLER head

With so much "hype" i'm seeing with the 45 degree flybar head these past few weeks, i decided to create my own 45 degree flybar experimental platform and see what this is really all about ...





I am still using the original 4#3 V1 blade grip which from the stock shaft;




to 45 degree shifted head using a "dremmeled" plastic 4#3 A/B shaft.



The head is drilled across on a 45 degree angle and a small plastic rod is inserted;



the blade grip bearings are then attached;



This is how she will look like with the blade grip in place;



and here is she now with the rest of parts in place;



and short flight demo. No fancy flight stunts yet (those will follow);

Walkera V1 4#3 Bell Hiller Head 45 degree flybar conversion (1 min 20 sec)
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Old Aug 29, 2009, 11:08 PM
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if in case you may have noticed from this config, its actually the main blades that have shifted "ahead" by 45 degrees instead of the flybar.
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Old Aug 29, 2009, 11:42 PM
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Can you do that with a 43b head? Can you shift the 43b blades ahead 45 degrees?
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Old Aug 30, 2009, 06:30 PM
inventor of flames decals.
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hi mon,

nice!
so the paddles do pitch? in your vid i see they still get input from the swash directly (via the dogbones/rotor head ring), or are they only conected to the mixerarms? looks like you have a decent amount of positive fixed-pitch on the paddles as well?

rob
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Old Aug 30, 2009, 06:39 PM
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Quote:
Originally Posted by robZulu
hi mon,

nice!
so the paddles do pitch? in your vid i see they still get input from the swash directly (via the dogbones/rotor head ring), or are they only conected to the mixerarms? looks like you have a decent amount of positive fixed-pitch on the paddles as well?

rob

Yes. they do pitch as the dogbones are retained and are directly mounted on the swash.

And i noticed one fundamental thing - they are very sensitive to cylic data when making helis very light with the same rotor head size. As such, the head speed is pretty much lower on the same amount of lift force thus the sensitivity.
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Old Aug 30, 2009, 07:05 PM
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whats the weight? 50g?
my bell head setup is about 60g auw.
i dont get why you put the positive fixed pitch on the paddles - you have an imbalance when the head rotates and you give stick input. example: lets say both are +5 fixed. now you give cylic input of lets say +5: one paddle +10 other 0. give cylcic of +10: get +15 on one and -5 on the other.
so relative to the air / plane of rotation you do not have equal forces on both end of the flybar (ie the same amount of force up on one end and down on the other). it will still fly (and with no cylclics applied you even get more lift), but for precise controll you really need equal forces.
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Old Aug 30, 2009, 07:13 PM
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Weight is roughly abut 45 grams with the newly installed brushless motor(inclusive of lipo)

yes there is an amount of positive pitch on the paddles.

Why is this so ? - It helps in reducing the gyro lag time for the flybar to neutralize itself after a cyclic input. A positive pitch on both ends induce a constant down wash creating a contstant upward force on each padle.

Once a cyclic input is induced, one side of the flybar paddle will have more pitch than the other side. In fact the other side will have either 0 or negative pitch depending on the cyclic input thus creating a big difference which amplifies the flybar clyclic data. Once the sticks are released, the paddle will 'quickly' go to its neutral state less of the gyro neutralization lag as both positive pitched paddles will push the flybar at its normal horizontal state faster than the 0 pitched paddles.

The 0 pitched paddles will simply rely on the natural gyroscopic forces to neutralized itself.


Walkera 4#3 Bell Hiller Mod : Addressing Flybar lag using Positive pitched paddles and weights (0 min 47 sec)


Isolating the effects of the gyro lag;

Flybar Gyroscopic Lag Simulation (0 min 46 sec)
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Last edited by EQMOD; Aug 30, 2009 at 07:20 PM.
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Old Aug 30, 2009, 07:52 PM
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Quote:
Originally Posted by EQMOD
yes there is an amount of positive pitch on the paddles.
Justa comment about pitch in the paddles.

The paddles are airfoils. If the heli is in fast forward flight (or in wind), the advancing paddle has a faster airspeed than the retreating paddle.

Because lift is proportional to the square of the velocity, if there is pitch in the paddles, the advancing paddle gains more lift than the retreating paddle loses. When this occurs in the main blades there is excess lift (translational lift).

If there is pitch in the paddles, it puts a differential force on the paddles.

Positive pitch on the paddles when flying into the wind or fast forward dlight will put forces on the paddles which will try and keep the heli in one place, similar to pushing the stick in the opposite direction of the forward flight or wind, which is useful in helping beginners to maintain a hover.

Negative pitch in the paddles is useful in windy conditions. Negative pitch in the paddles when flying in wind puts forces on the paddles which automatically force the rotor system into the wind thus minimizing ballooning.
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Old Aug 30, 2009, 10:02 PM
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Quote:
Originally Posted by Martyn McKinney
Justa comment about pitch in the paddles.

The paddles are airfoils. If the heli is in fast forward flight (or in wind), the advancing paddle has a faster airspeed than the retreating paddle.

Because lift is proportional to the square of the velocity, if there is pitch in the paddles, the advancing paddle gains more lift than the retreating paddle loses. When this occurs in the main blades there is excess lift (translational lift).

If there is pitch in the paddles, it puts a differential force on the paddles.

Positive pitch on the paddles when flying into the wind or fast forward dlight will put forces on the paddles which will try and keep the heli in one place, similar to pushing the stick in the opposite direction of the forward flight or wind, which is useful in helping beginners to maintain a hover.

Negative pitch in the paddles is useful in windy conditions. Negative pitch in the paddles when flying in wind puts forces on the paddles which automatically force the rotor system into the wind thus minimizing ballooning.
true. The main rotor blades are encountering them as well and still we achieve forward flight. Considering the ratio of the paddles vs the blades, i think it wouldnt have much effect on the current config plus the fact they are already pitched heavily on forward flight. That is helis with 0 pitched or positive pitched paddles would encounter them anyway at forward flight.
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Old Aug 31, 2009, 01:14 PM
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ok some more 45 degree flybar config flight tests. I had to re-sit the ball-links and mixer arm links to eliminate some binding caused by shifting the flybar by 45 degrees with reference to the main blade grip;

Flight test:

Walkera 4#3 45 degree flybar Bell Hiller Head - Flying around (2 min 59 sec)


Flying around the pole;

Walkera 4#3 45 degree flybar Bell Hiller Head - Around the Pole (0 min 42 sec)
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Old Aug 31, 2009, 01:26 PM
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Hi all,
Question. How degrees of flybar travel is required to let a B/H work? It seems to me less travel than a Hiller, correct? exact figures aren't needed ~50` or less?

thanks,
Bill
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Old Aug 31, 2009, 05:53 PM
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Hi Bill,

Yes. It depends on the mixing arm ratio. Mine is roughly 70% to 80% as i gave more priority on the flybar than on the swash which is close to preserving the original hiller only config of the V1 4#3 head.

Mon
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Old Sep 01, 2009, 07:15 AM
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just to let you know, this is the first time i've been flying circles in such a small space with this heli, most of the time i just do tail-ins
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Old Sep 02, 2009, 12:15 AM
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Ok. After some tests between 90 degrees and 45 degrees on a Walkera 4#3 rotor head, below are the results;


I dont see much a of a difference in terms of stability - this using the identical config (paddles, grips, links, etc.) except for the 45 degree shift between flybar and blades. Occasionally during flight TBE occurs.

In terms of controllability - same.


So where does the 45 degree stability come from ? I dont know yet

It may be from other factors;

- Weight of the heli (mine is heavily lightened including servos)
- Lower Head speed. Because heli is lightened, head speed is much slower

* I tried adding weights to increase headspeed and not much improvement
on stability

- Flybar weights (mine uses the stock paddles plus some small bearing weights). Others may have tried much heavier flybar weights on the 45 degree head.

- Flybar mixing ratio - my setup has mixing ratios giving more priority on the flybar than on the swash

Walkera 4#3 Head is originally designed for a 90 degree cyclic control.

If you notice, the Walkera 4#3 servos are directly in line with the aileron and elevator axis respectively. Which means if you flip the swash plate to the right, heli will go right. If you flip the swashplate forward, the heli will move forward.

So technically speaking with a Walkera 4#3 head, flybar should be in right angles with the blade (90 degrees not 45) to induce any "aligned" shaft shift correction on a specific axis (either left/rght roll , fore/aft, or a combination).


If you notice, heads with 45 degree cyclics have BOTH the flybar shifted by 45 degrees and the servo's input point also shifted by 45 degrees. I think this is true for the MSR and Walkera CB180.

So technically speaking, if the servos are in-line with with the aileron and elevator axis, the head is designed for a 90 degree flybar setup. If the servo inputs are shifted by 45 degrees, the head is designed for a 45 degree flybar setup. This is also true for the other way around; 90 degree flybar, servos also 90 degrees, 45 degree flybar, servos are also 45 degrees.
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