Positive / Negative / Neutral Delta

[BobOD]

That's OK. It's a lot of tissue.

Originally Posted by HeliBenj

Question is, why do the majority of FBL heads around are set for 0 delta? Is it just for cost reasons?

Most things often come down to cost...yes. Not only the cost to produce, but also the cost to develope.
As I mentioned earlier, I beleive the main reason is that early developments, which is often done by ametuers with limitations in their abilities. I'm not knocking ametuers at all BTW...they drive a lot of new ideas. But, it was concluded early on that delta was not good. And everything since is just copy, copy, copy.

I honestly do not know if negative delta would help the servo heat. Makes sense that it would but there are too many variables there and I would not want to say without more evidence.

[g-bru]

Hi Bob

Great thread, and I do like your FBL head!

I was wondering if you could take a look at the attached diagram of a Gaui X5 FBL Head and answer a couple of questions, if you don't mind.

Fig 1. Is the stock setup.

Fig 2. I have installed shorter ball links to the swash simply because the longer ball links as in the stock picture only have around 2-3mm of thread the shorter ball links have 3-4mm of thread.
This has changed the angle of the connecting rod slightly (indicated in red), will this have a negative effect on the FBL system?

Fig 3. If the washout arms (indicated in red) where installed pointing the same direction as the blades leading edge, what negative effect could this have had on a FBL system?

Many thanks

Grant

[BobOD]

Moving the balls in on the inner swash will increase cyclic resolution (swash tilts more for a given pitch). This can be a good thing actually. The inner diameter to outer diameter ratio is related to your cyclic to collective mix ratios. What is better depends on too many variables.
As far as the angle of the links is concerned, if your sketching is to scale, it doesn't look too concerning. Depending on the maximum angle of the swash.

Regarding the direction of the driver arms, I don't see it matters much.

[g-bru]

Hi Bob!

Many thanks for popping in to answer my questions, I had some concern regarding these issues as I thought it would have some sort of negative effect on my setup.

I have recently converted from FB to FBL and have alot to learn!

Kind regards

Grant

[kaon]

Just came across this thread, from what I understand, it's got to do with the feathering shaft tilting within the head block.
If I am not wrong, my DIY set up (as in the photos below) is positive delta because it is trailing-edge control, and because the balls on the blade holder are too short. Yes?





It flies OK, not much different from stock, I think, but I haven't flown that many helis so I might not be sensitive to the delta characteristics.
I would like to try to make mine slightly negative delta.

Am I right that I can do this by simply finding longer balls for the blade-holders?
This seems to be much simpler than converting to leading-edge control.

[BobOD]

There isn't much delta in that. The links are not very far off center.
I wouldn't go any longer with the balls than that. They look quite long already and must have a lot of twisting on the grip arms.

[kaon]

Originally Posted by BobOD

There isn't much delta in that. The links are not very far off center.
I wouldn't go any longer with the balls than that. They look quite long already and must have a lot of twisting on the grip arms.

Ah, I understand.
Those are the stock grip arm balls of the Trex 600 ESP.
They are about 8mm short of getting to the center.
If you think that's a small amount of delta, then I will leave it alone.