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HelicopterFlybarless Rotor Head SystemsOther › Correct Delta for Freya Head Conversion
11-27-2007 10:01 PM  9 years agoPost 1
JKos

rrProfessor

Redondo Beach, CA

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I plan to convert my upcoming e-Avant to flybarless after collecting good power data with the flybar head. In thinking of the head conversion, I was wondering how one would properly configure the delta on the Freya type head since the spindle does not pivot about its center like most heads. I'm not sure that true zero delta can be achieved on this type of head.

Thoughts? Get the ball centered and run with it? If one must choose, what's better, a touch of negative delta or a touch of positive delta?

Thanks,
John

RR rules!

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11-27-2007 10:30 PM  9 years agoPost 2
Royrex

rrApprentice

TN USA

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With trailing pitch arms, the delta will go more toward the
negative side as tilt is increased. Might try a little positive
delta to start with. Any play in the grip/spindle bearings will
add to this effect. Any thought on changing to leading pitch
arms?

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11-28-2007 12:07 AM  9 years agoPost 3
Super-Hornet

rrVeteran

Singapore

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Most teetered head has the O rings damper on each side of the spindle shaft. Even though it is arrange in that way, it still have the center of teeter point at the center of the hub (Virtually).

Thus by having a leading edge control, you should have -ve delta (or is it +ve delta? I got confused). Bottom line is that if u have leading edge control, as the blade flap upward the pitch of the blades (due to delta) will automatically reduce.

I find that having leading edge control is much better (stable) control than the trailing edge.

Note that in real heli, there do exist some heli with trailing edge control. I think Bo-105 is one of them. Cobra is another one.

SH

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11-28-2007 12:22 AM  9 years agoPost 4
JKos

rrProfessor

Redondo Beach, CA

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> Most teetered head has the O rings damper on each side of the
> spindle shaft. Even though it is arrange in that way, it still have
> the center of teeter point at the center of the hub (Virtually).

That's where the Freya head is different. The "axis of teeter", if you will, is above the spindle shaft. Take a look at some pictures of Freyas and you'll see what I mean.

- John

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11-28-2007 12:26 AM  9 years agoPost 5
Super-Hornet

rrVeteran

Singapore

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So sorry I do not have Freyas heli. Can you show us some picture?
Are u referring to something like an under slung teetering?

SH

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11-28-2007 02:52 AM  9 years agoPost 6
JKos

rrProfessor

Redondo Beach, CA

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SH,
Here you go.

- John

RR rules!

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11-28-2007 02:58 AM  9 years agoPost 7
rcadd1ct

rrElite Veteran

Richardson, Texas

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Depending on your flying style, you could put the hardest dampeners in and effectively lock out the teeter.

Might be rough on autos, though.

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

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11-28-2007 03:36 AM  9 years agoPost 8
Super-Hornet

rrVeteran

Singapore

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Hi JKos

Thanks for the photo.

Yup! It is an under slung teeter design. The top allen screw (without white O ring) is the teeter point. The bottom screw is just to hold the white O ring. The White O ring act as the teeter damper. I not sure whether does your heli (Freyas) has O ring on the spindle or not. If yes, then that O ring on spindle is just a damper for lead/lag hinges.

Bottom line is that its teeter point is still at the center (seen from top view)

I know there is a similar 3rd party rotor head for TRex 450 before. I think it is microheli (Can't confirm)

SH

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11-28-2007 04:15 AM  9 years agoPost 9
JKos

rrProfessor

Redondo Beach, CA

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RCA,
I think the dampers in there are the hardest dampers for the Freya Evo 90 head.

SH,
No o-rings on the spindle; it only moves with the head block. From above it is still centered, but not from the side. When the head teeters, the center of the spindle actually moves slightly which means the ball position moves too which means I don't think you can have a true zero delta.

I'm probably just over-thinking this guys. But I was just wondering if anyone had already done a flybarless conversion on a Freya head with either the V-Bar or CSM setup and figured out which way it was better to go on the blade grip ball position.

Thanks,
John

RR rules!

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11-28-2007 05:35 AM  9 years agoPost 10
Super-Hornet

rrVeteran

Singapore

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In term of scale flying (more stability), it is better to have delta offset. The offset will start to take effect when it is in forward flight or the is a sudden wind blow.

I notice alot of ppl who converted his/her heli to 2 bladed flybarless using V-Bar or CSM tend to choose 0 offset. By doing so, you lost the stability of delta offset...but I guess the reason they do so is to have high cyclic response (just like 3D flyer prefer stiff O ring instead)

What u can do is just give it a shot and see how is it. U have to try and compare which one do u prefer.

SH

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11-28-2007 06:00 AM  9 years agoPost 11
"Cam"

rrKey Veteran

UK

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Delta-3

Having the teeter pivot above the spindle introduces a sideways motion of the spindle when it teeters. This mean the blade grips and block will move to the side slightly when you roll. Moving the grip ball sideways is moving it away from the ball on the lever, and since the linkage is a fixed length, it pulls the blade grip down a little. This happens for both directions.

This head design has the dampers ‘off the spindle’, unlike the TRex600 and most other helis, because it has advantages like improved tracking and ease of changing the dampers. From the explanation above, this head will reduce the collective pitch slightly, making it less positive or slightly more negative whenever you roll your heli. The result is it lowers the aerodynamic roll centre, brining it closer to the CoG, which on a tall heli will make the rolls more axial with less collective management.

That’s what the offset pivot does and I believe it is independent of the delta offset.
Having the ball in-line with the centre of the mast and pivot will be zero delta all the same.

http://www.pprune.org/forums/archiv...hp/t-97416.html

Few model helis seem to have perfectly vertical pitch links.

“In addition, I can see no reason why the delta-3 angle and the reduction in the phase angle need be the same, other than that of keeping the pitch link vertical”.

“Delta-3 'softens' the response of the rotor to the cyclic control”. So I would be bias to have a touch of positive delta. Negative delta (gives more pitch with flap) would only be used on a heli that was too stable / or unresponsive to cyclic inputs - I don’t think flybarless models have that problem!

DSX9
EMax V2
http://runryder.com/helicopter/gallery/37491/

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11-28-2007 07:30 PM  9 years agoPost 12
scoobydooo

rrNovice

Towcester U.K.

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Hi

Although i haven't converted my freya i have been playing with different delta offsets on my flybarless raptor and so far i have found that it has made little difference and the electronic setup seems to be the overiding factor.
Because the gyro tries to achieve a given rate of movement for a given stick position the gyro just gives more input to the swash to achieve the desired rate, and with how much we constrain flapping by using very hard dampers in most cases the delta offset actually seems to only apply very small changeswhich are easily masked by the electronics.

So overall i don't think your offset teeter hinge will affect the performance

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